Tag Archives: printrbot

Glass Print Bed for Printrbot Simple Metal – Part V

Posted 12/17/15

In my last post on this subject I described my (ultimately successful) efforts to level my new glass print bed and disable Printrbot’s ‘auto leveling’ feature so I could get decent prints everywhere on my print bed.

During this project I had been posting results and questions on the ‘PrintrbotTalk’ forum (see this post), and one responder suggested the use of a cheap dial indicator from Harbor Freight to level the bed, independent of Printrbot’s Z-axis probe.  After some initial missteps I was able to get one (item #623 on Harbor Freight’s website) and figure out a way to mount it on the extruder carriage. The following photos show the mounting arrangement, using the handy mounting tab on the back of the dial indicator.

Dial indicator mounted to the extruder carriage. Note ground-down portion of the carriage .

Dial indicator mounted to the extruder carriage. Note ground-down portion of the carriage .

1/4" by 1/4" bushing fit nicely inside the 1/4" I.D. mounting hole.

1/4″ by 1/4″ bushing fit nicely inside the 1/4″ I.D. mounting hole.

Dial indicator mounting tab and mounting screw/bushing

Dial indicator mounting tab and mounting screw/bushing

Dial indicator mounted, with carriage height adjusted to achieve a zero reading

Dial indicator mounted, with carriage height adjusted to achieve a zero reading

With this arrangement, I was able to simply move the carriage around by hand, noting the needle excursions from zero.  Then painter’s tape was added to the low side (or removed from the high side) to minimize the differential across the printing area.  A 1mm height difference equates to about 40 small divisions on the indicator, and after shimming I was able to achieve a height differential of  +/- 5 small divisions (about 0.125mm) across the print area.

After getting the glass plate all shimmed up, I decided that because I was no longer using the ‘auto-leveling’ (actually more like ’tilt correction’) feature, I could now remove the copper foil layer from beneath the painter’s tape – BIG MISTAKE!!  On the very first test print after doing this, I realized to my horror that the Printrbot still needed to find the Z-axis ‘home’ position, and the only way to do that was with the Z-axis metal-sensing probe.  Fortunately I was able to pull the power plug before the extruder tip had a chance to shatter my nice new glass plate!

After beating myself up for a while over such a bonehead move, I realized I had just two choices; I could laboriously replace the copper foil layer (one quarter-inch strip at a time), or I would have to find some way of replacing the metal-sensing probe with something else.  I did not want to go through the agony of replacing the foil layer, so I was left (I thought) with option 2.  Someone on PrinterbotTalk had mentioned a mechanical switch replacement for the Z-axis probe, and said there was at least one Thingiverse design for a bracket that mounted to one of the vertical carriage posts.  I took a look at this and decided I could adapt it for one of the normally-open pushbutton switches I had in my electronics parts bins.  After some further Googling, I realized that the replacement project might be a bit more involved than I originally thought, as there was an issue with later rev motherboards requiring a pullup resistor and some extra wiring to make the mechanical switch idea work.

Then I had an uncharacteristically brilliant idea, if I do say so myself.  Rather than removing the Z-axis probe and replacing it with a mechanical switch mounted on the vertical slide assembly, why not combine the two ideas and simply mount the Z-axis probe itself on the vertical slide assembly?  Then I get the best of both worlds – I don’t have to screw with the wiring at all, and the metal carriage base is perfect for the Z-axis probe to sense – voila!

Looking around a bit, I found that if I mounted the probe on the rear vertical slide post bushing, it would have a clear shot at a nice, flat open spot on the carriage base.  All I needed was a right-angle bracket to attach the probe to the bushing.  A few minutes in TinkerCad produced a printable design, and after a few minutes more I had the bracket printed up (I had to fake the Z-home a bit to get the bracket printed, but who’s counting).  I super-glued the bracket to the slide bushing as shown in the following photo, and simply adjusted the height of the probe in the bracket so the extruder just ‘grabbed’ a sheet of printer paper when the Z axis was ‘homed’.

Z-axis probe relocated to the rear vertical post bushing

Z-axis probe relocated to the rear vertical post bushing

OK, so now I have a really cool glass print bed, with no ugly copper foil layer, and the Printerbot is no longer trying to murder my glass plate.   I’ve only done a couple of test prints so far, mostly to figure out what M212 offset is required now with all the changes.  However, I am looking forward to consistent prints with the new setup.

Stay tuned!

Frank

 

 

Glass Print Bed for Printrbot Simple Metal – Part IV

Posted 11/25/2015

In my last episode of “The Perils of Pauline” (aka Printrbot Simple Metal Glass Print Bed Issues), I described a set of measurements and print tests that ultimately led exactly nowhere, except maybe to the conclusion that Printrbot’s vaunted ‘Auto-leveling’ (more accurately ‘bed tilt correction’) wasn’t all that effective, and might even be part of the problem rather than part of the solution.

So, in this episode, I decided to manually level the glass print bed with painter’s tape shims, to see if I could get better prints that way.  To do this, I used the existing Z-axis probe, the G29 ‘auto-level’ command, and the G30 ‘Z-axis probe here’ command.  The G29 command tells the Printrbot to probe the Z-axis at three pre-configured points ( (10, 150), (10,10) and (150,10) in my case), and the G30 command tells it to probe the Z-axis wherever it happens to be (I used this to probe the bed at (150,10) – the rear right corner).  Between these two commands, I could measure the print bed surface height at all 4 corners and adjust accordingly.

From previous measurements I knew that the bed tilted upwards from the rear to the front, and from left to right.  Therefore I started out by moving the single layer tape shim from the front edge, and adding a single layer shim along the left edge.  After three or four iterations, I wound up with two tape layers on the left and rear edges, and the resulting probe measurements were within 0.2mm everywhere. It’s hard to get much closer than that, due to variations in the probe results.

Initial painter's tape shim layout

Initial painter’s tape shim layout

After getting the bed as level as I could, I ran another set of test prints.  As shown in the photo below, all 5 positions printed successfully.  I also noticed that the Z-axis worm gear moved noticeably less during print operations, providing an additional indication that the print bed was in fact pretty darned level.

 

All positions printed successfully

All positions printed successfully, although the front right (Position 5) print was very lightly attached

When I removed the test prints from the bed, I noticed that the near-right (Position 5) print was less well attached than the others, and in fact the attachment quality improved as I went from Position 5 to 4 and then to 3.  Positions 3, 2, and 1 (all in the same vertical line) seemed to all be nicely attached.  So, the actual print results indicate that the extruder tip is getting farther away from the print bed as it progresses to the right, but the Z-axis probe measurements indicate the exact opposite situation – the print bed actually gets higher as it goes from left to right!  How can this be?  Well, based on everything I have learned to date, I now strongly suspect that the answer is that the tilt correction algorithm is correcting the wrong way somehow.  Maybe the fact that the Printrbot’s ‘home’ position is at (Xmin, Ymax) rather than (Xmin, Ymin) is causing a sign error somewhere, and this is causing the Printrbot to correct the Z-axis up for movements in the positive X and negative Y directions when it should be correcting it down.  This theory tracks with what I have experienced so far, as it would imply that the closer I can get the plate to absolute level, the smaller the error would be, ultimately going to zero error for a perfectly flat plate. Of course, if I’m right, I should be able to somehow track down and correct this sign issue, and therefore convert what is now a force for evil into a force for good – arggghhhh!!!!

Late addition:  After posting this to the ‘Printrbot Talk’ forum, I got a note from ‘Retiree Jay’ to the effect that I could disable the tilt correction function entirely by omitting the ‘G29’ command from the startup script, leaving only the ‘G28 X0 Y0 Z0’ command. So, I did this and ran another series of test prints as shown in the following photo.  As you can see, all prints were successful, even the added Position at the right rear of the print bed.  And even better, Retiree Jay was correct in that the Z-axis motor did not run at all (up or down) during prints of a specific layer (since I printed only one layer for each position, this means that the Z-axis motor didn’t run at all during the entire print series.  This pretty much proves that my new glass plate is flat across the entire print area; “Tilt Correction?  We don’t need no stinkin Tilt Correction!” ;-))

Print series with tilt correction disabled.  "Tilt Correction?  We don't need no stinkin Tilt Correction!"

Print series with tilt correction disabled. “Tilt Correction? We don’t need no stinkin Tilt Correction!”

Stay tuned,

Frank

 

 

Glass Print Bed for Printrbot Simple Metal – Part III

Posted 11/24/2015

A few days ago I posted a long account of my attempt to add a glass plate printing surface to my Printrbot Simple Metal, to address printing problems due to non-planar warping issues with the original print bed.  As described in the post, I was able to satisfy myself that the glass plate was much flatter than the original bed, but I still couldn’t get consistent prints except in a very small area – printing the same part at the same Z-axis offset resulted in either a print that wouldn’t adhere, or gouges in the painter’s tape.  My conclusion at the time was that maybe the vaunted ‘auto-leveling’ feature (actually just 3-point tilt correction) has been inadvertently disabled in my firmware version, or maybe it wasn’t ever functional in the first place.

So, in this post I describe my efforts to manually level the glass plate print bed.  Based on the results from the previous post, I know that the bed must slope downward from the back to the front, as the print was more or less OK at the back, but became separated from the bed as the print positions progressed toward the front.  So, I put down a layer of painter’s tape underneath the glass plate at the front edge of the original print bed, and then ran the same series of prints, starting at the rear right corner as before.

The following two photos show the painter’s tape shim installation

Painter's tape shim installation

Painter’s tape shim installation

Painter's tape shim installation

Painter’s tape shim installation

With this setup, I started by printing the 20mm cal cube at the extreme left rear corner of the print area, what I’m calling ‘Position 1’.  The first print failed partway through when the piece detached from the bed, indicating the Z-axis offset was too high, at Z = -1.1.  This was interesting all by itself, as Z = -1.1 was the offset I used for the entire first experiment a few days ago; I speculate that the addition of the painter’s tape shim may have lowered the plate very slightly at the back corner.  I changed the offset to Z = -1.2, and this gave me a good Position 1 print, as shown below.

Position 1 print with Z = -1.1. Note the detachment

Position 1 print with Z = -1.1. Note the detachment

Position 1 print with Z = -1.2

Position 1 print with Z = -1.2

Then I moved on to Position 2 (still at extreme left edge, but midway from back to front) and tried again.  As shown in the following photo, I got a good print here as well.

Position 2 print with Z = -1.2

Position 2 print with Z = -1.2

From there I moved on to Position 3 (extreme front left corner of the print area), and Position 4 (front edge, midway from left to right).  As shown in the following photo, I got a very good print at Position 3, but the Position 4 print detached immediately.

Positions 3 and 4. Position 3 printed OK, but Position 4 detached immediately

Positions 3 and 4. Position 3 printed OK, but Position 4 detached immediately

So, it appears at the moment like I have the plate leveled in the front-to-back direction, but not in the left-to-right direction.  Next I’m going to try adding a layer of tape from front to back at the extreme right edge and see what this does.  Note in all this that Printrbot’s ‘Auto-level’ feature should already be compensating, but it appears to be AWOL.

With one layer of tape added, I was still getting very poor results in the X (left to right) direction, so I added a second layer of tape.  After this, I was able to get all 5 prints to stick, although as the photo below shows,  the last two were ‘iffy’

With two layers of tape front to back at the extreme right edge

With two layers of tape front to back at the extreme right edge

So, I added a third layer of tape, and ran another print series, and got almost identical results!  How can this be?  I’ve added three layers of tape, and I’m still not able to print in the near right-hand corner – this just doesn’t make any sense.

OK, the only possible way it could make any sense at all, is if the Printrbot ’tilt-correction’ algorithm IS enabled, but not functioning correctly, either due to the algorithm itself, or due to incorrect Z-axis sensor readings from the probe.  So did another test print, but this time I concentrated solely on the Z-axis servo worm gear.  At first I simply put my fingers on the worm gear so I could feel if there was any Z-axis movement during lateral head moves, and sure-nuff, there was some!  Then I put a painter’s tape ‘flag’ on the worm gear and I can easily see Z-axis movement during even small lateral head moves.  The clear indication is that the tilt-correction algorithm is working, but for prints near the right-hand edge of the print bed, the correction is wrong.  I wonder if the errors are due to scaling based on inaccurate print bed dimensions in the printer setup dialogs; this would seem inconceivable, but what do I know?

On a recent print at the near right edge, with 3 layers of tape, the probe measurements were:

(10,143,1.46), (10,10,1.79), (143,10,2.32)

with the tape removed, the measurements are

(10,143,1.35), (10,10,1.59), (143,10,1.94).

This seems to indicate that positive Z is ‘up’ and that lower positive Z values indicate a surface that is actually closer to the bottom of the printrbot.  This, in turn, should mean that I could achieve what I want by putting tape under the left edge, not the right, even though the print performance indicated just the opposite! Oh, I have a headache!

with the right-edge 3-layer tape shim removed entirely, I re-ran the original test print series.  Instead of the mess I got the first time, printing at all 5 positions succeeded as shown in the following photo – huh?????

All three tape shim layers removed from the right edge

All three tape shim layers removed from the right edge

OK, so this just should not be happening!  When I started this post, with no shimming at all, I could print to position 1, 2 & 3 (along the left edge, from rear to front), but not positions 4 or 5 (along the front edge, from left to right).  This behavior is what led me to shim along the right edge, but although I thought I was making the situation better, increasing the shim height from 2 to 3 layers didn’t help at all, and now I find that with no shim layers I get really nice prints at all 5 positions – what gives?

Thinking back through everything I did this evening, I realized there was one thing I did that could maybe have affected the situation – I changed the printer extents via the Repetier ‘Printer Settings’ dialog.  This should not affect tilt correction calculations at all, since the Printrbot already knows the absolute coordinates for all three Z-axis probe points, so why would it care (or even know) what extents have been set in Repetier?

As a test of this wild and zany idea, I set the Y-Max value in Repetier to 350, basically twice what it should be, and set up for another print series.  When the probe results came in, they were:

(10,143,-1.06), (10,10,-0.85), (143,10,-0.5) – whoa!  How can that possibly be?  Clearly there is some coupling from the values set in Repetier’s Printer Settings dialog, but why?

For position 2, the Z-axis probe reports (10,143,1.42), (10,10,1.56), (143,10,1.90)

– Oh, now I have an even bigger headache!  How can this be?  Negative values one time, and positive values the next – with exactly the same hardware and software configuration (including the same – bogus – Y Max value)??

For position 3, I get:  (10,143,1.46), (10,10,1.72), (143,10,2.03) – print was fully successful

For position 4, I get:  (10,143,1.44), (10,10,1.70), (143,10,2.02) – print was successful, but marginal

For position 5, I get:  (10,143,1.44), (10,10,1.71), (143,10,2.02) – print fully successful

All three tape shim layers removed from the right edge

All three tape shim layers removed from the right edge

OK, I give up – I’m officially baffled.  Everything I have done has had either no effect, or an effect opposite to what I expected.  Then returning the experimental setup to its baseline condition did not restore baseline results – WTFO@!!@#$%^&*(

Frank

 

Glass Print Bed for Printrbot Simple Metal – Part II

Posted 11/19/2015

A week or so ago I posted an account of my attempt to add a glass plate to my Printrbot Simple Metal print bed.  I thought I had a great idea – place patches of copper foil tape on top of the glass plate at the three points where the Z-axis probe sensor checks for print bed tilt (it’s called auto-leveling, but it is actually more like auto-tilt correction), and everything should be groovy.  Unfortunately, what I thought would happen and what actually happened were two different things.  It appeared that either tilt correction wasn’t being applied at all, or it was being applied, but in the wrong direction (which doesn’t make any sense either, because I didn’t change anything except adding the glass plate).

So, I decided to make another run at the problem.  My new approach was three-fold; first, I took some time to thoroughly investigate the flatness of the original Printrbot print bed, and the flatness of the glass plate.  Second, I decided to cover the entire glass plate with copper foil, not just the small areas used by the Z-axis sensor.  Third, I figured out a way (the ‘G30’ command) to take Z-axis sensor reading at multiple spots on the print plate, rather than just the 3 points used in normal printing, so I could really determine how well the Z-axis sensor itself behaved.

Printrbot print bed and glass plate flatness investigation:

I used two different techniques to evaluate the flatness of both the original Printerbot print bed and the glass plate addition.  The first technique was to place a light source so that it illuminated the bed from the side, and look for light leakage under a straight-edge placed on the bed.  The second technique was to use a piece of printer paper (approx 0.09 mm thickness) to see if there were any areas where the paper would slide freely under the straight edge.  The photos below show the result for both the original print bed and the glass plate.  The first image shows the setup, with an LED flashlight placed so it shines light parallel to the surface, with a steel straight-edge blocking the beam except where the bed is warped.  Subsequent photos show warped areas.

151119 PrintrbotBed1

Flashlight shining along surface of print bed, with steel straight-edge blocking light except where the bed is warped.

151119 PrintrbotBed8 151119 PrintrbotBed7 151119 PrintrbotBed6 151119 PrintrbotBed5 151119 PrintrbotBed4 151119 PrintrbotBed3 151119 PrintrbotBed2

 

Next I did the same thing with the glass plate, as shown in the following images.

151119 GlassPlate8 151119 GlassPlate5 151119 GlassPlate6 151119 GlassPlate7

The glass plate is clearly much flatter than the original print bed.  I verified this using the paper technique – I was able to easily slide a piece of 0.09 mm paper under the straight-edge on the original print bed, but not on the glass plate.  So, as far as flatness is concerned, the glass plate is a clear winner.

Z-Axis Probe Measurements

Since I was now convinced that the glass plate was much flatter than the original print bed, this issue could not be the reason I was having so much trouble trying to get reliable prints at different points on the print bed.  So, I turned my attention to the only other possible factor, the Z-axis probe itself.  If it was somehow producing aberrant readings, maybe that would explain why the Z-axis offset required for printing at the near right corner was wildly inappropriate for the same print in the back left corner.  To acquire the data I made use of the G-code ‘G30’ command, which causes a Z-axis probe operation at the current X/Y location.  I recorded Z-axis probe readings at 12 locations on the glass plate, and plotted the results using Excel’s ‘Surface’ plot feature

Z-axis probe sensor readings for glass plate

Z-axis probe sensor readings for glass plate

11/20/15 Glass Plate Z-axis probe sensor results

11/20/15 Glass Plate Z-axis probe sensor results

As can be seen in both the data and the surface plot, the glass plate is pretty flat – with only a 0.42 mm deviation from one extreme from the other.

 

The same set of measurements were performed on the original Printrbot metal print bed, with the following results:

11/20/15 Original print bed Z-axis probe results

11/20/15 Original print bed Z-axis probe results

11/20/15 Original print bed Z-axis probe results

11/20/15 Original print bed Z-axis probe results

The data shows that the original print bed is pretty flat too, even though the illumination experiment showed that it exhibits significant warping.  I suspect that the probe measurement locations were too widely spaced to capture the low spots.  In any case, all that can be said for sure at this point is that both surfaces (original print bed and glass plate) are pretty flat, and both exhibit some tilt, with Z-axis probe measurements consistently rising from the left rear corner (0,153) to the front right corner (130,3).

 

Print Trials:

After convincing myself that the glass plate was indeed flat, and that any residual tilt should be well within the Printrbot’s correction range, I decided to do a series of test prints – starting at the rear left corner and moving toward the near right corner.  For the first print, I adjusted the Z-offset for optimum printing – not too close, not too far away.  Then I kept this same Z-offset for all the other prints.  The following photos tell the story.

20mm cal cube printed at the rear left corner (0,153)

20mm cal cube printed at the rear left corner (0,153)

20mm cal cube printed at (0,103)

20mm cal cube printed at (0,103)

First try at printing 20mm cal cube at the third position (0,53). Note the blob attached to the extruder!

First try at printing 20mm cal cube at the third position (0,53). Note the blob attached to the extruder!

2nd try at printing 20mm cal cube at the third position (0,53). Note the raised corner

2nd try at printing 20mm cal cube at the third position (0,53). Note the raised corner

20mm cal cube printed attempt at the near right corner

20mm cal cube printed attempt at the near right corner.  Part is separated from the bed and ‘blobbed’ to extruder and

20mm cal cube printed at the rear edge, midway toward the right

20mm cal cube printed at the rear edge, midway toward the right

20mm cal cube print attempt at the rear right corner

20mm cal cube print attempt at the rear right corner.  Part has separated from bed and is ‘blobbed’ to extruder.

So, at this point I’m pretty sure of three things:

  1. The glass plate print bed is pretty darned flat
  2. The Z-axis probe seems to be working correctly
  3. The Printrbot tilt correction feature does not appear to be working properly.

Stay tuned,

Frank

 

 

Glass Print Bed for Printrbot Simple Metal

Posted 11/08/2015

I’ve been having some problems lately getting good prints on my Printrbot Simple Metal 3D printer, and after a lot of inet research I concluded the problem was a warped print bed.  The bed that comes with the Simple is pretty nice, but just not thick enough IMHO to avoid some warping. And once the bed becomes even a little bit non-planar, then the very nice ‘auto-leveling’ (more accurately ‘bed tilt compensation’) ceases to be very useful.

There was some discussion about putting a glass plate down over the original bed, which takes care of the non-planar issue, but then the Hall-effect metal bed sensor can’t ‘see’ the metal print bed through the glass plate, unless the glass plate is too thin to do any good.  What to do?

I’m a long-time Electrical Engineer and antenna researcher, and so it occurred to me that I might be able to fake out the bed sensor by applying some adhesive-backed metal tape to the top of a glass plate, thereby establishing a new ‘zero’ reference at the top surface of the glass plate.  I ran some simple experiments, and found that the bed sensor worked fine with even very thin strips of just about any metal, including copper.  Since I knew I could get copper tape in various thicknesses and widths, I thought this idea might be worth a try.

The glass plate:

I remembered seeing a post somewhere that someone had found that a popular picture frame size worked just great for the Printrbot Simple Metal print bed, so I headed over to my local JoAnne’s fabric to see what was available.  I found lots of cheap picture frames in various sizes, but nothing that even remotely approached a good size for my print bed – bummer.  So, I decided to go the custom route, and, after carefully measuring my bed, got a piece of 3/32″ (~2.3mm) glass cut to 9.5 x 6.5″.  I brought the piece home and carefully smoothed the edges with my belt sander (a sander drum attachment for a drill would work also).  Unfortunately, when I laid the piece on my print bed, I discovered I had screwed up – the 9.5″ dimension was slightly too large, and the pieced didn’t quite fit between the two sets of mounting screws.  I was really bummed out, until I realized I might be able to recover from this disaster by simply grinding cutouts for the screwheads, thereby converting a ‘bug’ into a feature! ;-).  Indeed I was able to do this with a Dremel tool and a small grinding bit, and when I was finished I had a nice, self-registering glass plate for my Printrbot!

Screw head cutouts ground with Dremel tool and small grinding bit

Screw head cutouts ground with Dremel tool and small grinding bit

The Sensor Tape:

I didn’t have any adhesive backed copper tape handy (I used this stuff by the roll in my prior life as a research scientist, but didn’t think to take any with me into retirement), so I tolled the net for a while for sources.  I finally wound up ordering a 10′ roll of 1/4″ adhesive-backed copper tape from eBay

CopperTape

Assembling the new Print Bed:

I used heavy-duty document clips to hold the glass plate down on the original print bed, and then placed copper tape patches at the X/Y home location and the two ‘slope compensation’ sensing points, and then covered the entire thing with blue painter’s tape to provide the same first-layer adhesion as before.

151108_PrintBed2 151108_PrintBed4 151108_PrintBed5

151108_PrintBed1

Testing:

I used a 20mm hollow cal cube as my test object, starting at a point near the X/Y home position.  As expected, I had to adjust the Z offset some, and wound up with a Z offset of about -0.8 to get a decent print.

151108_20mmCube1 151108_20mmCube2

Then I tried moving the cube around on the print bed, and found that I had to keep moving the Z offset further negative as I moved the print position away from the X/Y home position.  To get the cube to print properly, I would up with a Z offset of -2.0mm, way more than I had expected, and then when I tried to move the print back to near the X/Y origin with the same Z offset, I got the extrusion drag marking shown – bummer!

151108_PrintBedSlopeProb1

After seeing the above problem occur, I tried to figure out what was going wrong, and having a heck of a time with it.  Here’s what I know:

  • The Z offset required to get decent first-layer adhesion gets markedly more negative the further away the print position is from the X/Y home position
  • Trying to print near the X/Y home position with the Z offset required for a position far away from X/Y home causes extrusion head dragging.
  • However, in a somewhat contradictory finding, if I manually move the extrusion head position arm (the Y axis, I think) toward the outer edge of the print bed, it starts to drag about halfway across for X values near home, and this condition becomes more marked when the bed is manually moved in the positive X direction (to the left looking at the front of the printer).  In other words, when moving the extrusion head in manual mode, it appears the print bed has a marked upward slope as X & Y increase, causing significant head drag.  However, when printing, the opposite effect seems to occur, where the print bed appears to have a  marked downward slope as X/Y increase.  This makes no sense at all!

So, at the moment I’m officially baffled. In manual mode, the printrbot behaves as if the bed is sloped upward as X & Y increase, but in printing mode (where I assume the ’tilt compensation’ is in effect), the printrbot behaves as if the bed is sloped in the opposite direction.  What gives!?

More to come (I hope)

 

 

 

ClearNav Joystick Part 2 – From TinkerCad to Finished Print

At the conclusion of ‘Part 1 – From Clay Model to TinkerCad’, I had finally managed to get a decent 3D model into TinkerCad as a binary STL file.  Now the challenge would be to transform that blank template into something that could actually be printed on my PrintrBot and used in a real glider aircraft.  To get from where I was to where I wanted to go required the following steps:

 

  • Modify the joystick top to accept a ClearNav remote controller
  • Design in the the ability to install a separate switch, for use either as a ‘climb/cruise’ vario switch or as a separate ‘push-to-talk’ (PTT) switch (the ClearNav stick-top remote controller accessory has it’s own integral PTT switch, but…).
  • Create a 1″ diameter hole to mount the joystick onto the glider joystick handle/tube
  • Create a wiring passageway up to the top of the joystick
  • Print it out on my PrintrBot Simple Metal.

 

Modify the top to accept a ClearNav remote controller

This step appeared to be the hardest and most critical part of the design, so I decided to tackle it first.

Of course, a fundamental part of this step required that I have precise dimensions for the ClearNav stick-top remote controller, and this turned out to be rather more problematic than I had expected.  ClearNav, Inc didn’t have any technical specifications for the part on its website, and the support crew there couldn’t provide anything either.  The president of the company promised to send me a 3D design of a blank controller part as an STL file, but never delivered anything, even after multiple inquiries.  Fortunately, I had a hand-held remote controller left over from my previous life as a glider pilot, and I happened to know that the outside dimensions of the stick-top and hand-held controllers were identical.  The difference was that the stick-top remote has an extra button to replace the normal PTT button, and the hand-held controller does not.  Another non-relevant difference is that the hand-held remote has a telephone-style RJ-45 connector, while the stick-top version uses a wire pigtail.

So, I was able to use my hand-held controller to produce a blank 3D model for sizing the stick-top cavity.  I started out with a blank that was as precise as I could make it, and then oversized it by about 1mm in all dimensions to use as a ‘hole’ in the design.

Disassembled Hand-held ClearNav Remote

Disassembled Hand-held ClearNav Remote

Slightly oversized blank for joystick ClearNav remote cavity

Slightly oversized blank for joystick ClearNav remote cavity

Then I started trying to fit the blank into the top of the joystick, with very limited success initially.

First attempt at fitting the ClearNav remote into the top of the joystick

First attempt at fitting the ClearNav remote into the top of the joystick

The thickness of the 3D representation of the clay model just wasn’t sufficient to contain the volume of the ClearNav remote, no matter how I moved it around.  So, back to the drawing board (literally!).

I did some more research, and taught myself how to use MeshMixer’s ‘Inflate’ sculpting brush to add some bulk to the top of the joystick, and the ‘Flatten’ brush to slim and smooth the neck area.  After several back-and-forths between MeshMixer and TinkerCad, I arrived at a version that would indeed contain the remote.

Close, but no cigar!

Close, but no cigar!

Remote is completely contained now in the joystick, so this one is very close to final

Remote is completely contained now in the joystick.  Note the neck has been slimmed down as well

Design in the the ability to install a separate switch.

The typical cross-country glider uses a boom microphone and a stick-mounted push-to-talk (PTT) switch for radio communications, and there is often at least one more switch (typically a SPDT toggle) mounted on the forward surface of the stick top.  The stick-top ClearNav takes over the real estate used by the original PTT pushbutton, but cleverly replaces it with an integrated PTT switch on the remote itself (this integrated PTT button isn’t on the handheld version).  However, I still needed to make room for the front-mounted SPDT switch.

The first step in this portion of the design was to create a 3D model of a ‘subminiature’ SPDT switch.  Fortunately I happened to have one in my design shop, left over from an even earlier lifetime as an electrical design engineer.  Now that I have my high-quality Fowler calipers from McMaster-Carr, it was a snap to measure the switch and create a fairly accurate 3D model in TinkerCad.

Subminiature SPDT switch model

Subminiature SPDT switch model

Once I had the switch, I was able to figure out how to shoehorn it into the top of the joystick, in a forward-facing orientation.  This took a while, and involved creating a smaller ‘sub-basement’ cavity under the one created to accommodate the ClearNav remote.

MountedSPDTSwitch2 MountedSPDTSwitch1

Create the 1″ diameter mounting hole and wiring passages

You’d think this would be the simple part – just a couple of cylindrical ‘holes’ added to the part and we’re done.  Unfortunately, life (or joystick design) just ain’t that simple, and what I thought would be a ’10 minutes tops’ job turned into a multi-day headache, and finally into a fun piece of creative work.  The initial 1″ diameter hole wasn’t too bad, but since the joystick body isn’t particularly symmetric, it wasn’t (and still isn’t really) clear where the hole should go.  I finally opted for the placement that would allow the hole to penetrate the farthest up into the joystick body, as that would result in the widest range of mounting options in the actual aircraft.  Then I created a smaller diameter angled cylinder to connect the vertical hole to the top cavity, to act as passage for the necessary wiring.

This seemed to be working really well, until I printed a couple of half-scale models and discovered that both the vertical and slanted cylinders poked through the side of the joystick, even thought the TinkerCad model showed some material thickness all the way around.  I was trying (and failing) to figure out how this could possibly happen when my wife, who knows nothing about 3D printing, pointed out that the minimum printable wall thickness stays the same regardless of scale, so something that shows 2-3 min thickness walls at full scale might not be even one min wall thickness at half-scale – oops!

OK, back to the drawing board.  I played around with this forever, but finally concluded that I was going to have to give up on the linear passageway idea, and go with something curved if I wanted to have decent wall thickness all the way around the passageway for its entire length from the top of the 1″ mounting hole to the cavity at the top of the joystick.  To make this work, I used TinkerCad’s ‘Torus’ primitive, and adjusted the torus diameter and cross-section to get what I wanted.  When everything looked right, I used several rectangular ‘holes’ to cut off the sections I didn’t need.

Final version, showing the 1" vertical cylinder for joystick handle mounting, and the curved wiring passageway

Final version, showing the 1″ vertical cylinder for joystick handle mounting, and the curved wiring passageway

Printing on my PrintrBot Simple Metal

After verifying this hole structure via a half-scale model, I was ready to step up to full scale testing.  However, I really really did not want to pay the time and filament cost for multiple full scale prints, so I decided I would just print the top of the model to verify all the cavities at full scale.  Since none of the hole structures poked though anymore at half scale, I was pretty confident they wouldn’t at full scale.  So, I made a series of full scale prints of just the top portion, and these caused me to make some adjustments in the auxiliary SPDT switch cavity and mounting arrangements.  With these partial full scale prints, I was able to use the actual full scale real-world parts (ClearNav remote and subminiature SPDT switch) to check for fit and clearances.

First full scale print of just the top cavity structure.  Note the top part of the cavity is incorrect.

First full scale print of just the top cavity structure. Note the top part of the cavity is incorrect.

Second full scale print of the top cavity structure.  Note the top portion of the cavity has been corrected.

Second full scale print of the top cavity structure. Note the top portion of the cavity has been corrected.

Final version of the joystick top cavity structure

Final version of the joystick top cavity structure.  This just required a slight resizing of the cavity to accommodate the actual full scale ClearNav remote, and the actual full scale SPDT switch.

After the full scale partial printouts, I was ready to go for a full scale print.  The overall height of the joystick (121.6 mm or 4.8″) would be close to the 6″ maximum for my PrintrBot, so I was a bit worried that bad things were going to happen.  Also, since this was to be such a long duration print, I was worried about filament jams and all the other things that could go wrong on a long print.  As it happened, the print went off without a hitch, and produced a near-perfect model.

 Summary and Lessons Learned

  • Although I much prefer to have a ‘real’ project as a motivator when learning a new software package or skill, I probably overreached a bit with such a complex project so early in the learning curve.  Learning how to capture a 3D model from photos, how to use MeshMixer’s sculpting tools, advanced TinkerCad techniques, and a challenging print size and overhang configuration all rolled into one project!
  • The combination of the Autodesk suite of 3D applications (123d Catch, 123d Design, MeshMixer, and TinkerCad) forms a very complete and rich design suite for capturing a 3D object in a form suitable for further development and eventual 3D printing.  The fact that all of these applications are (at least for the moment) entirely free is amazing!
  • the 3D capture and design application world is changing and evolving at warp speed. All of the above apps have serious bugs, deficiencies, and internal inconsistencies, so staying light one’s feet is an absolute necessity.  If it doesn’t work right now, check back tomorrow!  In my case the 123 Catch application literally changed overnight – on day 1 I couldn’t seem to get my capture to stitch at all, and on the next it was all done automagically!  The downside of all this is that skills and/or workarounds learned today may be irrelevant tomorrow, so the need for constant retraining is going to be a fact of life.
  • As in other endeavors, success is 1% inspiration and 99% perspiration.  I just kept banging away at the problem until it gave up and rolled over.  It didn’t matter to me whether my progress was due to my brilliance or just sheer doggedness – either one was fine with me ;-).

 

ClearNav Joystick Part 1 – From Clay Model to TinkerCad

In a previous lifetime I was a cross-country glider pilot.  This means I would regularly fly an aircraft with no engine up to six or seven hours and cover hundreds of miles without landing.  Expert glider pilots can do this at average speeds approaching or exceeding interstate speed limits.  Since gliders must stop occasionally to regain lost altitude in rising air currents (called thermals), their inter-thermal speed has to be significantly higher than the average, meaning a glider flying along an interstate will easily outpace the cars and trucks below.

Anyway, a friend from that previous life showed me a clay model of a custom joystick handle he was working on.  The model was intended to incorporate a complex instrument remote control panel in the top of the joystick, where the push-to-talk (PTT) switch would normally go.  When he first showed it to me, I was just thinking about getting into 3D printing and in my ignorance I thought this would be a perfect 3D printing project (little did I know at the time!).  Later on when I had just ordered (but not yet received) my PrintrBot Simple Metal Kit I asked him to send me his clay model, and promised him I would at least make the effort to turn his clay model into a finished 3D printed product.  This is the story of how I went from 3D ignoramus to Joystick hero in a few short weeks.

 

07/28/14 Capture using Autodesk’s Catch/123d:  I’ve gone through this now a couple of times with BZ’s joystick, and I am now starting to get some clues.

  • The first time through was with just some painter’s tape patches placed on the joystick surface to give some reference points.  This worked, but not very well.  The patches didn’t stick very well due to the oil in the clay, and I got a number of unstitched photos.  Also, I couldn’t manually stitch photos together – just never worked

    Joystick with blue painter's tape 'stickies'

    Joystick with blue painter’s tape ‘stickies’

  • Next time through I used narrow strips of painter’s tape, wound around the joystick in several places.  This worked MUCH better, and in fact I had zero unstitched photos, and was eventually able to generate a full 3D STL file editable in 123d Design and TinkerCad (see below).  However, the only fly in the ointment was that the painter’s tape wasn’t completely conformal with the joystick surface in several places, and this came through on the model as raised ridges.
Joystick wound with strips of  blue painter's tape

Joystick wound with strips of blue painter’s tape

  • The third try was to replace the painter’s tape with felt-tipped marker markings. The thought was that this would be more conformal to the surface, and if done properly would also be appropriate for automatic stitching.  However, what actually happened was that the model came through OK, but with many unstitched photos.  Then when I laboriously manually stitched a number of photos into the model, the re-submission crashed – ouch!  This problem continued even if I re-submitted after stitching only one photo.  This was all done with the PC version, so I tried again with the online version.

    Joystick with Sharpie pen markings for surface contrast

    Joystick with Sharpie pen markings for surface contrast

  • In the online version, I see that I have a number of projects that appear to be ‘In processing’, even though they are older (as in days older) versions of the joystick process, and there doesn’t appear to be any way to remove them!.  The ‘Sharpie’ version is shown to be complete, and when I open it in the online version it looks great, but in the online version there is no ‘lasso’ tool for removing all the background elements.

 

08/07/14:  Working with a newer version of 123 Catch

  • A newer version of 123 Catch became available in the last few days, so I decided to try a new capture using my photos from the ‘Sharpie’ version of BZ’s joystick.  This time when I  uploaded the photos, I didn’t get any unstitched images – yay!!
  • I discovered the ‘mesh resolution’ setting in Catch, and was able to change the mesh resolution from ‘Mobile’ to ‘Maximum’.  This also takes a selection area as a parameter, and re-meshes only the portion of the capture within the selection, so it takes much less time than doing the entire scene.  Remeshing took only a few minutes with the selection limited to just the area around the joystick.

 

08/09/14 – Still working on the ‘Sharpie’ joystick:  I was able to print a ½ scale model of the joystick, but I discovered it was all solid inside, notwithstanding the ‘hollow’ attribute advertised by the Catch/3D Print operations above.  Also, I wasn’t able to figure out how to undo the ‘minimum support’ setting that left the joystick on its side.  So, I’m making another try at this from scratch and will try to document the steps more rigorously.

  • Started a ‘New Capture’ in 123 Catch, using the 07/28/14 Sharpie photos.  This took a long time to process.  Catch asked for a Capture file name, and suggested ‘Capture_2014_08_09_06_17_31’ (date and time).  When it completed, I was presented with the constructed model as shown below.

    First successful capture of the 'Sharpie' model

    First successful capture of the ‘Sharpie’ model

  • I did an immediate ‘Save As…’ at this point, and noticed I already had a ‘Capture_2014_08_09_06_17_31’ folder and .3dp file saved in the same folder as the original Sharpie photos (140728_Sharpie Photos).  I have seen this before, but AFAICT, this folder and file aren’t usable later – can’t figure that out.  I cancelled the ‘Save As…’ operation.
  • I found a 2011 tutorial at http://aucache.autodesk.com/au2011/sessions/4056/class_handouts/v1_AC4056%20-%20It%E2%80%99s%20a%20Snap!%20Take%20a%20photograph%20and%20create%20a%203D%20Model.pdf.  This was apparently a presentation at an AutoDesk conference.  This tutorial explained things like the ‘photo lock’ mode (constrains the scene view to just the available discrete camera locations), but wasn’t all that helpful for my purposes.
  • I somehow got into ‘Photo Lock’ (PL) mode and now I can’t get out again!  If I disable PL, I get a blank screen with just the camera locations and the coordinate axes shown.  Hmm, I clicked on ‘show mesh’ and now I have the scene back – weird.  Yep – confirmed that you have to have ‘show mesh’ checked to get *anything*!
  • OK, selected the lasso selection tool and deleted everything around the joystick.  Shit!  I deleted a small section of the mesh, and *then* got a dialog warning me that I needed to make sure I was in the correct mesh quality setting, or edits might be lost.  So I tried to undo the mesh edit, only to find there’s no UNDO function!
  • Used the rectangle selection tool to select just a small area around the joystick for re-meshing (including part of the deleted area from the previous bullet) as shown.  Note that I rotated the view to a fairly high angle so that my selection was restricted to just the newspaper around the joystick – omitting any of the office background.

    Remeshing a selection of the original Sharpie model

    Remeshing a selection of the original Sharpie model

  • Selected the Remesh icon and selected ‘Maximum Quality’.  This produced a dialog with the original capture name (Capture_2014_08_09_06_17_31) which I assume is a reference to the previously uploaded photos.  Curiously, this field is editable, giving the impression I could have used another name – maybe then it would have saved the re-mesh into a different capture structure?
  • OK, the remesh finished successfully, leaving me with a rectangular patch from the original scene.

    Sharpie model after remeshing a selected portion of the original scene

    Sharpie model after remeshing a selected portion of the original scene

  • I saved this result as ‘140809 Sharpie Capture After Remesh.3dp’.  I don’t really know if this will actually save anything or be useful later, but I thought it couldn’t hurt.  I also saved it as an .OBJ file, which might actually be more useful/permanent.  By default, both these files were saved in the same folder as the original capture photos, i.e. ‘F:\3D Projects\Joystick\140728_Joystick Sharpie Photos’.  The .3dp file is only 5.3KB, indicating that (as noted in the 2011 presentation) it only contains references to the online location of the Capture files, not the files themselves).  The .OBJ file is a more respectable 4 MB.
  • Back in Catch, I used the lasso tool to further refine the mesh to just the joystick, and saved this in both .3dp and .OBJ format.  Even after being very careful with the lasso operation, I wound up with a big hole on the right side of the joystick base.  I saw this before on a previous run through, but found that the 123d Print application was able to ‘repair’ the hole – strange.

    After the 'lasso and delete' operation, I have a big hole in the bottom of the joystick!

    After the ‘lasso and delete’ operation, I have a big hole in the bottom of the joystick!

  • Saved this as ‘140809 Sharpie Capture After Remesh And Lasso’ .3dp and .obj.
  • Clicked on the ‘3D Print…’ button to launch the AutoDesk MeshMixer app.  By default, this opens with the joystick in the ‘minimum support’ orientation – no idea how to change it back to the upright orientation (note – as it turns out, this isn’t the ‘minimum support’ orientation – it just looks like it).
  • Clicked on the ‘Modify’ icon and got a warning message about losing unsaved changes.  Clicked OK, and got the following:
  • After fooling around in the MeshMixer for an hour or so, I finally gave up on this model.  I couldn’t figure out a way to add surface material to repair the hole.   Still fooling around, I selected ‘Edits’ and ‘Overhangs’ and MeshMixer crashed – oops!
  • Back in Catch, I opened the file ‘140809 Sharpie Capture After Remesh.3dp’, and it indeed opened the correct project, as shown.
  • This time I used this model to go to ‘3D Print…’, (which launches Autodesk’s MeshMixer app) and got the following default layout.MeshMixerDefault2
  • This is actually a bit nicer to work with, as the section of newsprint gives me a decent X-Y plane to work with for transforming the joystick to the upright position.  After rotating 270 deg around X axis, and then ‘Move to Platform’ to move the base down to the Z = 0 level, I got the following.

    After a 270 degree rotation around the X axis and then 'Move to Platform'

    After a 270 degree rotation around the X axis and then ‘Move to Platform’

  • Hmm, I tried to go back to the ‘Modify’ mode in MM and discovered you can’t do that.  Apparently there are two distinct MM modes – ‘Modify’ and ‘Print’ and they aren’t integrated.  Transforms/Translations in ‘Print’ mode don’t flow back into ‘Modify’ mode – bummer!  To get to ‘Print’ mode, click on ‘Send to Print’.  To get back to ‘Modify’ mode, click on ‘Modify’.
  • OK, finally figured out Rot/Translate in ‘Modify’ view.  The center ‘box’ is for linear scaling for all axes.  The colored arcs are for rotating about the various axes, and the triangles are for translating.  After figuring this out, I was able to rotate the joystick to an upright orientation, as shown.  I still have no idea what the ‘L’, ‘S’, ‘A’, and ‘W’ labels are for.
  • Exported the model as ‘140809_MeshMixer_Rev3.stl’ in Ascii STL format and tried to import it into TinkerCad, but it doesn’t seem to want to import at all.  Imports easily into 123D Design, however.  Tried this trick again with the binary formatted STL file.  The binary version does import into TinkerCad (and 123d Design) OK – yay!!
  • OK, figured out how to use the Select tools to delete the newsprint mesh, leaving only the joystick (hopefully), as shown.

    Joystick after newsprint removal

    Joystick after newsprint removal

  • After this I was able to use the transform tools in ‘Modify’ mode to rotate/translate the joystick into a more understandable orientation, and saved the model as ‘140809_MM_Rev5_RotXlt_bin.stl’.
  • Next I tried using the Edit/Plane Cut tool to cut off the garbage at the bottom of the joystick, as shown below.  I accepted the transform, which gave me just a disk – oops!
  • Tried again, with the cut plane rotated 180 degrees.  This time things worked out much better.  The selection and the result are shown below.

    Plan cut operation with the plane rotated 180 degrees from the original

    Plan cut operation with the plane rotated 180 degrees from the original

  • After proper plane cut selection, the joystick bottom is nice and flat

    After proper plane cut selection, the joystick bottom is nice and flat

Saved this as 140809_MM_Rev6_PlaneCut_bin.stl.  Then I opened it in TinkerCad successfully, as shown below.  Note that the joystick in TinkerCad is still laying on its side, so  maybe the transformations in MM aren’t getting into the export file?

 

TinkerCad model after successful Plane Cut operation.  Note that the model is on its side

TinkerCad model after successful Plane Cut operation. Note that the model is on its side

  • Tried undoing the rotation transformation in MM and re-exporting.  OK, this worked!  Apparently, the coordinate systems in MM and the rest of the world are defined differently – so if going from Catch to MM to TinkerCad, don’t have to rotate in Meshmixer.

    After undoing the rotations & translations

    After undoing the rotations & translations

  • After this, I went back into MM and used the ‘Flatten’ brush to smooth out some of the rough spots, saved it as Rev8Flattened, and imported that back into TC

Summarizing lessons learned so far:

  • MeshMixer can be used to remove the newsprint background from the Catch export
  • No need to rotate/translate in MM when going from Catch to MM to TinkerCad
  • Probably need to establish a scale in Catch, as the resulting model winds up being very small in MM and TC (3.5 x 6 mm).  OTOH, I can just as easily establish the scale in TC (this is what I wound up doing).

08/09/14:  Starting from ‘140809 Sharpie Capture After Remesh.3dp:

  • Click on ‘3DPrint…’ to launch MeshMixer and load the file:  Opens as ‘2014-08-09-13-06-47_8466_41.obj’ in MM, with the ‘Print’ mode active.
  • Click on ‘Modify’ to get into that mode.
  • In ‘Modify’ mode:

o   Analysis/Inspector/Auto Repair All

o   Edit/Plane Cut & adjust as low as possible with a solid bottom.  This should also remove much of the newsprint area.

o   Choose Select tool with Unwrap Brush active and double-click anywhere in the remaining newsprint area to select it all.  Then hit DELETE to delete it all.  Save this state as a .MIX file, and export it as a binary STL.  Check in TC to make sure it can be imported properly (140809_MeshMixer_Rev4_JoystickOnly_binary.stl)

o   Choose ‘Sculpt’ and the ‘Flatten’ brush.  Run the brush over the entire surface, flattening out minor bumps and wiggles.  Spent some quality time on the top surface, flattening it out for future work.  Went through a bunch of revisions, but saved the last one as 140809_MM_Rev9_Flattened_bin.stl.

08/09/14  – in TinkerCad:

  • Imported 140809_MM_Rev9_Flattened_bin.stl.  This was very small, but it was properly oriented with the joystick upright – yay!
  • Found the ‘all axis scale’ function – Alt-Shift-Corner resizer.  This allowed me to scale all axes until the vertical dimension matched the measured 121.5mm from the original clay model.  Saved this in TinkerCad to ‘140809 Rev 9 Scaled to Clay Model’

Next up – Modifying the basic model in TinkerCad to incorporate the mounting hole for the joystick, wiring passage to the joystick head, and mounting arrangements for an auxiliary switch and the ClearNav remote  head.  Stay tuned!

 

Mounting Clamp

Clamp for Bicycle Aux Instrument Holder

Just as I was contemplating the dive into 3D printing, a friend came to me with an interesting problem.  Ray is an avid bicycler, and he has a number of auxiliary gadgets attached to his bicycle.  One of these gadgets is an auxiliary instrument holder that clamps onto the horizontal tube from the vertical fork tube to the handlebars, and provides its own small ‘handlebar’ for more instruments, as shown in the following picture

Side view

Side view showing aux instrument bar holder clamped to horizontal fork tube

20140812_061016_resized

Side view of aux instrument holder

Unfortunately, after a short time the strap that holds the instrument holder to the bicycle broke, rendering the whole thing useless.  The first time he thought it was maybe it was just a random manufacturing defect, but after going through several that all exhibited the same failure mode, he basically gave up on that model.  When I mentioned that I might be able to help out with my brand-new PrintrBot 3D printer, he brought me the parts.

When Ray brought the broken clamp in, it quickly became obvious what the problem was, and why it was breaking so quickly.  the system uses a metal band that is drawn down into a cavity by an adjustment screw, and this action requires the clamp band to make a right-angle turn right at the nut on the screw.  The band metal is thin steel, and quickly develops fatigue cracks right at the bend.

Mounting Clamp

Mounting clamp interior view showing the capture nut

Mounting Clamp

Mounting clamp and steel strap. Note the break occurs right at the right-angle bend

capture bolt

Capture bolt/nut. Notice the strap residue still on the nut

After some thought, I decided that the solution was not to try and reproduce the system exactly, but to redesign the clamping system to use a standard pipe clamp instead of the steel strap.  The trick would be to ‘cut’ a slot through the body of the plastic clamp in such a way as to still allow the mounting bolt to attach the clamp to the rest of the system, while still leaving enough thickness to prevent the pipe clamp from breaking through the plastic part under load.

After going through a number of revisions and downright mistakes, I finally got a product that worked.  One of the mistakes I made was trying to create the part without a decent set of calipers for precision measurements, resulting in a part that was about 10% undersized in one dimension, and about 10% oversized in the other.  I remedied this problem by getting a very nice Fowler digital caliper from McMaster-Carr.  Another minor problem was that the capture screw was too long, and interfered with the pipe clamp band.  I solved this problem by simply cutting down the bolt a bit with a hacksaw, as the extra length was no longer needed.  Also, as this was my first real 3D printing project, the print quality left something to be desired.  Since this project, I have figured out how to get much higher quality prints.

Bike Clamp Versions

Original clamp on left, mis-sized version in center, final version on left. Note slots for pipe clamp band

After action reporting:  Ray reported that the new clamp worked perfectly on his bike, and seems to be holding up very well.

20140812_071325_resized 20140812_071224_resized 20140812_071253_resized 20140812_071317_resized

 

PrintrBot Metal Extrusion Problems

Had my first round of extrusion problems on my PrintrBot Simple Metal, and now I’m older and wiser (well, older anyway).  Turns out the problem ultimately was as simple as adjusting the filament feeder gear tension, but I didn’t know that at the time.  So, I carefully cleaned out the extruder and hot-end tip, using some tips I picked up on the net.  A couple of things that weren’t on other posts, but worked well for me:

  1. After removing the extruder tip from the extruder assembly, I temporarily remounted the extruder on the Y-axis arm and reconnected the heater and thermocouple plugs, and then ran the temp up to 200 or so. With the extruder tip missing, any extra filament material came out the bottom in a fairly large drop.
  2. With the particular extruder assembly I had with my recent version (July 2014) PrintrBot Simple Metal, the top (filament feed) end of the assembly is cool enough to blow into, pressurizing the filament channel.  This allowed me to simply blow extra molten filament material out and confirm that there was a complete, open passage through the extruder assembly (minus the 0.4mm tip at this point).
  3. After blowing out the extruder tube, I screwed the extruder tip back on the (still hot) assembly, and let it heat up.  Then I stripped a length of 30 gauge wirewrap wire I had laying around from a previous lifetime (30 gauge is about 0.3mm) and used it to clean out the now-hot tip.  This take a bit of fiddling, as solid wirewrap wire isn’t very stiff, but it did the job nicely.  In fact, I was able to strip a 4″ length and push it through the assembly from the hot-tip end all the way up through the top, verifying that the passage was completely clear.

After doing all this, I made some test prints, only to discover that the filament was still not feeding properly.  Eventually I tracked this back to an improperly tensioned feed roller bearing assembly.  When I added some more tension, the filament started feeding perfectly.