Tag Archives: 3D printing

To a man with a hammer, …

Posted 17 March 2018,

To paraphrase the saying, “to a man with a hammer, every problem looks like a nail”, “to a man with a 3D printer, every problem looks like a 3D printing opportunity”.  And that’s pretty much what happened when I ran across the problem of adapting some 80mm wheels to my Wall E-2 robot, which came originally with 65mm versions.  The extra 15mm diameter/7.5mm radius doesn’t sound like much, but it makes a huge difference when navigating over carpet or other small obstacles (like my wife’s slippers).

After a lot of work, I finally was able to print four reasonable quality adaptors, and thought I was home free.  Unfortunately, I soon learned that despite my best efforts, the printed adaptors were no match for physics; the wheel eventually worked its way off the motor shaft, just as before – it just took a little longer ;-).

After the usual number of curses, imprecations, and woe-is-me’s, I finally decided to use whatever was left of my engineering brain to actually look at the physics of the situation.  When I did so, I realized that my adaptor idea was never going to work.  While the adaptor did indeed (after the aforementioned ‘lot of work’) provide for a better fit between the 80mm wheel receptacle and the motor shaft, it also moved the wheel another 9mm or so away from the robot chassis, which put the wheel center of pressure (CP) well outside the adaptor-to-motor shaft parting plane.  This meant that the wheel would always be trying to pry the the adaptor off the shaft, and it didn’t take all that long for it to succeed :-(.  The following photo illustrates the problem

80mm wheel with 3D-printed adaptor on the left, same wheel directly attached to motor shaft on the right

So, contemplating this problem while drifting off to sleep I was struck by a solution; I could use a small roll pin inserted through the wheel and motor shafts to literally pin them together.  The geometrical physics would still cause the wheel to flex the shaft, but the forces wouldn’t be able to overcome the strength of the metal roll pin.  Because I knew I would forget this insight if I left it until morning, I staggered out of bed and jumped onto the McMaster-Carr site (they have everything!) to look for an appropriately sized roll pin.  I found a 1 x 6mm roll pin that would be perfect for the job, and if I ordered them now they would probably already be on my doorstep when I woke up in the morning.

McMaster-Carr metric roll pins

However, while I was doing the necessary measurements on the motor shaft, I noticed the motor shaft had a axial hole in it, and so did the wheel; hmm, maybe I could simply run the roll pin through the axial hole, instead of cross-wise?  Then I thought – wait that hole looks to be slightly smaller than 3mm – maybe I could simply drill/tap it for 3mm and use a 3mm screw (of which I had plenty in different lengths) instead of a roll pin?

So, in just a few minutes I had drilled & tapped the axial hole in the motor shaft of one of my spare motors, drilled out the wheel hole for 3mm clearance, and firmly screwed the wheel to the shaft (the right-hand wheel in the first photo above) – cool!

Now all I have to do is modify all four wheel shafts for 3mm clearance, and all four motor shafts to accept a 3mm screw – piece of cake!

As can be seen in the above photos, the 80mm wheels are now much closer to the chassis.  The wheel guards are now much too wide, but I may keep them that way for the moment, as I have already adjusted the charging station lead-in rails to accommodate the (now unnecessary) greater wheelbase – oh well 😉

So, the moral of this little story is:  Just because you have a 3-D printer doesn’t mean the solution to every problem is a new 3-D printed piece; and maybe to keep one’s eyes/brain open for even better solutions as they might come along when least expected!

Stay tuned,









Printing an ABS Shaft Adaptor for 80mm Wheel

Posted 25 January 2018

Over the last few days I have been struggling with a project to 3D print a small adaptor to allow me to mount some 80mm wheels I bought some time ago to my Wall-E2 autonomous wall-following 4-wheel drive robot.

The original robot came with 56mm wheels and this gave Wall-E2 very little ground clearance.  I found some 80mm wheels that I thought would do the trick nicely, but when I tried them, it quickly became apparent that the shaft receptacle on the wheel was significantly larger than the motor shaft, leading to a very bad wobble and catastrophic wheel departures – oops!

Lightweight 4WD Drive Aluminum Mobile Dolly Car Robot Platform for Arduino


original 56mm wheel and companion motor

Ebay ‘Arduino Robot’ motor dimensions

80mm wheel

After some troubleshooting, I discovered that the new 80mm wheels have a shaft receptacle that measures 5.9mm long and 3.6mm wide, while the motor shafts are 5.4mm long and 3.5mm wide.  The width is OK, but the longer length is causing the problem.

After thinking (and cursing) a bit, I decided to try printing an adaptor.  The larger diameter wheels are also considerably thinner (20mm or so vs 30mm), so there should be room for an adaptor part, as shown below

shaft adaptor for 80mm wheel

And threw it on my PowerSpec 3D PRO (Flashforge Creator Pro knockoff).  After just a little fiddling, I got some nice parts, and thought I was done.  A couple of days later, I noticed one of the parts was just a little loose on its shaft, so I said to myself – “I’ll just print off another one”.  Unfortunately, what came off the printer was really ugly, and completely unusable, even though that same printer had produced nice parts just a few days ago – WTF!?  Clearly I had forgotten what magic I had wrought the first time, so now I had to go back and recreate it – bummer.  As part of my penance for this crime, I am writing this post so the next time I want to do this, I’ll have the print settings recorded.

Print Settings for ABS

The significant factors in how to get good prints with ABS on this printer appear to be

  • Print speed
  • Extrusion factor

The first thing I did was slow the print speed down, but this had only a minor effect on print quality.  Going slower helped, but even very slow speeds (like 10mm/sec) didn’t result in clean edges on the male part of the adapter. However, the female portion was very clean, which left me a bit puzzled – why one part but not the other?  I finally realized that the difference was that the female piece was perfect because the hole perimeter was the first thing laid down at each slice, then the outside perimeter, and finally the fill material was added last.  This meant that the hole perimeter had a chance to cool and solidify before the fill material impinged on its outer surface, and this meant that the perimeter stayed in the same shape as originally laid down.  When printing the male part, however, the outer perimeter was laid down first, and then the fill material was immediately added, before the outer perimeter had a chance to cool and solidify, even at the slower speeds.  The material making up the fill was pushing the outer perimeter out of shape.

This led me to focus on the extrusion factor.  Reducing the extrusion factor from 1.00 to 0.95 had a significant positive impact on the print quality of the male portion of the adaptor.  Reducing it again to 0.90 resulted in an even better print, as did a further reduction to 0.85.  However, at the 0.85 value, I started to see some degradation in the quality of the female portion, so I backed off to 0.90 as the final value.  The following image shows the last seven prints.  All were printed at either 20mm/sec or 10mm/sec, and the last three on the right were printed with 10mm/sec and extrusion factors of 0.95, 0.90, and 0.85 respectively.

The last seven prints. the last three on the right were printed at 10mm/sec and with extrusion factors of 0.95, 0.90, and 0.85 respectively

Original and new wheels, with completed adaptor shown

Bottom Line (PowerSpec 3D Pro, Simplify3D):

  • Material: Gray ABS
  • Extruder temp: 230 (not critical 220-240 should be OK)
  • Bed temp: 110 (not critical, 100 should do too)
  • Speed: 20 or 10mm/sec (maybe faster would be OK, but not much)
  • Extrusion factor: 0.95 or 0.90





A New Chassis For Wall-E2, Part II

Posted 17 November 2017

In my ongoing quest to give Wall-E2 a bigger/roomier ride, I am continuing the process of moving all Wall-E2’s stuff to the new chassis, and modifying the charging station to work properly with the new wide-body model.

Second Deck Sensors:

Even with the wider footprint, there’s not enough real estate to easily mount the three distance sensors (LIDAR for forward distance, and acoustic for left/right distance).  I could shoe-horn it all in, but it would look messy and would leave all Wall-E2’s electronics exposed to potential damage from furniture, cats, careless humans, etc.  So I decided to transplant the second deck, complete with all the sensors, to the new chassis.  This looked to be a real PITA, until I let go of the notion that the 60mm stand-offs had to remain in the same locations. Once I did that, things got a lot easier 😉

IR Homing Module:

This was a straightforward transplant, especially since all the detection/demodulation is being

3D printed spacers for the motor controller PCBs

done by a Teensy 3.2 physically attached to the sunshade. All I had to do was drill the mounting  holes, add two more press-fit nuts, and screw on the module.

Arduino Mega Processor and Motor Controllers:

These two items came over as a group, as that way I didn’t have to disconnect anything – my kind of transplant!  However, while I was at it, I decided to neaten things up a bit by printing spacers for the motor controllers; this isolates the underside of the PCBs from the metal chassis, and provides a nice flat surface for mounting the controllers to the chassis with double-sided tape – a win-win-win (the last ‘win’ was because I got to use my 3D printer some more!)

Arduino Mega processor, motor controllers, rear taillight assembly, and IR homing module transplanted

Charging Station Modifications:

I was not looking forward to modifying the charging station to work with the new wider chassis.  The charging station electronics assembly is non-trivial, and it would be a real PITA If I had to reprint the frame and transfer all the electronics. Fortunately for me, this turned out not to be the case.   By a happy coincidence, the distance from the right-hand guide rail to the center of the power receptacle was exactly the same for the new chassis as for the old one, so all I had to do was re-position the left-hand rail to accommodate the wider tread spacing. Well, there was one minor glitch – the charging station has two physical stops, and the one that mated with the left-hand wheel guard on the old chassis now didn’t hit anything, so I had to print a small 5mm thick spacer and double-sided tape it to the front of the existing stop.

Closeup of the spacer for the right-hand charging station stop

Front view showing left and right charging station stops (with spacer added to right one)

18 November 2017 Update:

I’ve got almost everything transplanted over now, as shown in the following photos:

Side view without the sensor deck, showing that all modules are in place

Side view showing the sensor deck in place.

end-on view showing the difference between the old and new chassis dimensions

There’s still a ton of work to be done; The latest version of the charger PCB still hasn’t arrived from Bay Area Circuits, so I still need to do all that, and then wire the finished module into the battery compartment. Also, I’m having to redo the front bumper guards, as I have found they are somewhat fragile due to the way in which they were printed – bummer!  However, it shouldn’t be too long before I can take the new model out for a spin! ;-).

Stay tuned!





A New Chassis For Wall-E2, Part I

Posted 06 November 2017

Back in May of this year I came to the conclusion that I was never going to get my new four-cell battery pack (4ea 18650 3600mAH 3.7V LiPo cells connected as 2ea 7400mAH 3.7V stacks) and its companion charger module to comfortably fit into Wall-E2’s current chassis.  It all fits, but only with a considerable amount of pushing and shoving which has invariably resulted in damage to something – a connector, a wire, or something else vital.

Bottom side view of 4WD robot showing battery packs and charging module

Bottom rear view of 4WD robot showing battery packs and charging module

So, I spent some quality time online looking for a new, larger home for Wall-E2, and found this chassis

Lightweight 4WD Drive Aluminum Mobile Dolly Car Robot Platform for Arduino

This chassis has an internal cavity width of about 14cm compared to 10.5cm for Wall-E2’s current ride.  This extra inch or so make all the difference in the world for comfortable installation of the battery pack and charger.

After getting this chassis on order, I basically forgot about it while I was working on the square-wave modulated IR homing project.  Then when my grandson Danny and his family visited in August, we dug out the kit and assembled it.  Danny wasn’t all that impressed with the quality (well, neither was I, but I didn’t expect all that much for $30 either).  After looking at both chassis (Wall-E2’s current ride and the new one), Danny suggested that maybe we could transplant the motors from the new chassis into the old one and get enough additional space from the different form factors to solve the battery problem.  At the time I pooh-poohed the idea, and put the new chassis back on the shelf to be forgotten again.

However, after finishing up the IR homing project last month, I decided I would actually try this trick and see what happened.  So, I laboriously swapped all four right-angle motors from the new chassis to the old one, and … RATS!!  As the photos below show, no real change in the available room for the charger/battery pack combination.  Well, at least I tried ;-).

So, now I’m back to swapping chassis (wow – plural form of ‘chassis’ is ‘chassis’ – go figure) instead of motors.

One of the major shortcomings in the new model was the cheapness of the threaded holes in the frame components.  The frame metal is so thin that instead of drilling and tapping the material, the holes were punched in a way that left the punched-out metal in the hole, and this material was tapped with the machine thread.  Needless to say, this lasted for about one (or fewer) screw/unscrew cycle before stripping out – bad design!.  Fortunately I knew how to fix this problem, with the help of McMaster-Carr.  I went to their site and ordered a bunch of press-fit nuts (also called PEM-nuts for historical reasons)

Press-fit nuts for my new robot chassis

In case you have never dealt with McMaster-Carr, they are incredibly quick.  I normally tell people that once I click on the ‘order’ button, I get up, walk to my front door, open it, and get hit in the chest by the shipped order! ;-).

Once I got the nuts, I replaced all the threaded holes on the new chassis with these wonderful little gadgets.  I used a #16 number drill to drill out the holes, and pressed the nuts in the new holes with a pair of cheap gas pliers – done!

As seen below, there is a lot more room in the new model

In fact, there is so much room that now I have to figure out how to keep the batteries and charging module from sloshing around in there.  Fortunately I have a fertile imagination, TinkerCad, and a 3D printer – so I designed and printed up a battery box, and a prototype stand-off design for the PCB, as shown below.

The next part of the puzzle will be to figure out how all that stuff (IR Homing Module, laser and ultra-sonic distance sensors, motor controllers and the main controller) is going to fit on the new chassis.

Stay tuned!





IR Homing Module Integration, Part III

Posted 20 August 2017

I’m writing this post from our Kids’ place in St. Louis, which just happens to be in the path of totality for the upcoming solar eclipse.  As usual, I brought my project stuff with me so I can work in the off moments, but this trip has a bonus in that I have managed to suck my 14 year-old grandson Danny into helping me with the robot project.  He also has my old PrintrBot ‘Simple Metal’ 3D printer, so he is able to print up new IR detector holders as required.

So, the first thing we did was to print up a new holder with a 30º angular offset for the detectors; this is something I forgot to do with the previous model.  With this setup, we got the following results from an azimuth scan.

Azimuth scan for 2-detector model with 30-deg angular offset and center divider

meanwhile, my friend and mentor John Jenkins came up with a set of simulated azimuth response curves (shown below) that showed that the center divider (apparently originally intended to make steering more responsive) was more of a liability than an asset.  Turns out (at least according to John’s results) that removing the divider makes the (diff/sum) ratio curve smoother and more linear in the critical boresight region.

So, we printed up a new holder with the center divider removed (and in the process made the walls thicker to block IR transmission through the material), and took some more measurements.


Charging Station System Integration – Part III

Posted 15 April 2017

In my previous post on this subject, I described some IR homing tests with and without the overhead incandescent lights, and the development of a ‘sunshade’ to block out enough of the IR energy from the overhead lamps to allow Wall-E2 to successfully home in on the IR beam from the charging station.  At the conclusion of that post, I had made a couple of successful runs using a temporary cardboard sunshade, and thought that a permanent sunshade would be all that I needed.

However, after installing the sunshade (shown below), I discovered that the homing performance in the presence of overhead IR lamps was marginal when the robot’s offset distance from the wall was more than about 50 cm.

Sunshade, oblique view

Sunshade, side view

Sunshade, front view

Apparently the IR interference was causing the robot to not respond to the IR beam until too close to miss the outer lead-in rail.  This issue was explored in an earlier post, but I have repeated the relevant drawings here as well.


Tilted gate option. The tilt decreases the minimum required IR beam capture distance from about 1.7m to about 1.0m

Capture parameters for the robot approaching a charging station

When the robot is ‘cruising’ at more than about 50 cm from the tracked wall,  the IR interference from the overhead lamps prevents the robot from acquiring the charging station IR beam until too late to avoid the outer lead-in rail, even in the 13º tilted rail arrangement in the first drawing above.


So, what to do?  I am already running the IR LED at close to the upper limit of the normal operating current, so I can’t significantly increase the IR beam intensity – at least not directly.  I can’t really increase the size of the ‘sunshade’ dramatically without also significantly affecting the IR beam detection performance.  What I really needed was a way of increasing the IR beam intensity without increasing the LED current.  As it turns out, I spent over a decade as a research scientist at The Ohio State University ElectroScience Lab, where I helped design reflector antenna systems for spacecraft.  Spacecraft are power and weight limited, so anything that can be done to improve link margins without increasing weight and/or power is a good thing, and it turns out you can do just that by using well-designed reflector dishes to focus the microwave communications energy much like a flashlight. You get more power where you want it, but you don’t have to pay for it with more power input; the only ‘cost’ is the insignificant added weight of the reflector structure itself – almost free!  In any case, I needed something similar for my design, and I happened to have a small flashlight reflector hanging around from a previous project – maybe I could use that to focus and narrow the IR beam along the charging station centerline.

LED flashlight reflector

So, using my trusty PowerSpec PRO 3D printer and TinkerCad, I whipped up an experimental holder for the above reflector, as shown below

Experimental 3D-printed flashlight reflector holder

Reflector mounted on experimental holder

IR LED mounted on reflector

A couple of quick bench-top tests convinced me I was on the right track; At 1m separation between the IR LED/reflector combination and the robot, I was able to drive the robot’s phototransistors into saturation (i.e. an analog input reading of about 20 out of 1024 max), where before I was lucky to get it down to 100 or so.  However, this only happened when I got the LED positioned at the reflector focal point, which was tricky to do by hand, but not too bad for a first try!

Next, I tried incorporating the reflector idea into the current charging station IR LED/charging probe fixture, as shown in the following photo. This was much closer to what I wanted, but it still was too difficult to get the IR LED positioned correctly, and this was made even more difficult by the fact that I literally could not see what I was doing – it’s IR after all!

New reflector and old charging station fixture designs

However, the reflector focusing performance should be (mostly) the same for IR and visible wavelengths, so I should be able to use a visible-wavelength LED for initial testing, at least.  So, I set up a small white screen 15-20 cm away from the reflector, and used a regular visible LED to investigate focus point position effects.  As the following photos show, the reflector makes quite a difference in energy density.

Green visible LED, hand-positioned near the focal point

Pattern without the reflector

Next, I used my Canon PowerShot SX260HS digital camera as an IR visualizer so I could see the IR beam pattern. As shown below, the reflector does an excellent job of focusing the available IR energy into a tight beam

IR beam visualized using my Canon PowerShot SX260HS digital camera

IR LED, without reflector

Next, I made another version of the reflector holder, but this time with a way of mounting the LED more firmly at (or as near as I could eyeball) the reflector focal point.

Reflector holder modified for more accurate LED mounting

With this modification, I was able to get pretty good focusing without having to fiddle with the LED location, so I set up some range tests on the floor of my lab.  With LED overhead lighting (not incandescent), I was able to get excellent homing performance all the way out to 2m, as shown in the following photos and plots

Range testing the IR reflector in the lab. Distance 2m

IR Detector response vs orientation at 2m from reflector, in the lab

IR reflector beam pattern at 2m, visualized using digital CCD camera

After this, I decided to try my luck again out in our entry hallway, with the dreaded IR interference from the overhead lighting and/or sunlight.   I installed the lead-in rails in the ’tilted’ arrangement, and then performed a response vs orientation test with the robot situated about 2.5m from the IR LED/reflector assembly, in natural daylight illumination with the overhead incandescents OFF.  This produced the curves shown in the plot below.

Robot response vs orientation test setup, 2.5 m from tilted lead-in rails & LED/reflector assembly

IR detector response vs orientation test, 2.5 m from IR LED/Reflector assembly

In the above Excel plot, the individual detector response minimums can be clearly seen, with minimum values in the 200-300 range, and off-axis responses in the 800-1000 range.  This should be more than enough for successful IR homing.

After seeing these positive responses, I ran some homing tests starting from this same general position.  In each run, the robot started off tracking the right-hand wall at about 50 cm offset.  One run was in daylight with the overhead lights OFF, and another was in daylight with the overhead lights ON.  As can be seen in the videos below.

Both of the above test runs were successful.  The robot started homing on the IR beam almost immediately, and was successfully captured by the lead-in rails.

So, it is clear the reflector idea is a winner – it allows the robot to detect and home in on the IR beam from far enough away to not miss the capture aperture, even in the presence of IR interference from daylight and/or overhead incandescent lighting.

Next step – reprint the IR LED reflector holder with the charging probe holder included (I managed to leave it out of the model the last time), and verify that the robot will indeed connect and start charging.















PowerSpec 3D PRO Build Plate LED Lamps

Posted 03 April 2017

In the year or so since I started printing with my trusty PowerSpec 3D PRO (Microcenter clone of the FlashForge Creator PRO), I have struggled to see what was happening in the first few layers of problem prints.  The extruder/feed motor assembly is so big that it blocks most of the sight line to the build surface.  What is left is a very shallow viewing angle, which is mostly shadowed by the print assembly.  Over time, I have found that hanging one of my goose-neck LED bench lamps over the top edge of the cabinet on either the left or the right side gave me a much better view – the restricted viewing angle was unchanged, but a lot more light was thrown on the subject, literally.  However, this was an inelegant solution to say the least, as the lamp was apt to fall off the printer at the most inopportune times.

As usual, I kept thinking of ways to improve this situation, and finally came up with the idea of seeing if I could find some small LED work lights that I could permanently attach to the printer.  After some Googling around, I came up with a 2-lamp LED Auxiliary Light Kit (p/n DRL-CW3-SM-9) offered by superbrightleds.com for $24.95/pair – nice!

DRL-NW3-SM 12-24V 9W Auxiliary LED Light Kit (2 lamps)

After some fiddling around and some goofs, I arrived at an arrangement I liked.  The lamps are mounted at the top of the cabinet and are pointed down so they illuminate the entire build surface, but are physically offset enough so the plastic top closure assembly can still be removed and put back on without problems (this was one of the goofs – the first arrangement I tried made removing/replacing this piece very tedious).  The shots below show the setup.

To power the lamps, I used a ‘Mean Well’ APC-25-1050 24VDC constant-current LED driver supply from ledsupply.com.  This is an incredibly cheap switch-mode power supply that delivers 1.05A constant current, with an output voltage from 12-24V.  This matched well with the 12-24V input spec for the LED auxiliary lamp, so I was in good shape.   I had a couple of these hanging around from a previous project where I converted a crappy Lowe’s LED clip-lamp to a robust high-power LED lamp, so I got a two-fer (didn’t have to research/buy a power supply, and used up some of my excess stock – yay!).

For control, I decided to use individual power switches, mounted at the rear left & right of the cabinet.  I had some small SPDT power switches available, so I printed up a nice little housing with integrated zip-tie anchor points for cable strain relief, and then ran a common power run down the back center of the cabinet to the power supply mounted on the back of the cabinet, below the right filament spool.

The following photos show the arrangement, and the build plate illumination during the first few layers of a test print.  Enjoy

Old vs New. Hanging bench lamp in foreground, new permanently mounted LED lamp in background

New LED lamps in action. Note the build plate illumination.

View from back of printer showing both LED lamps and ON/OFF switches

Mean Well APC-25-1050 1A constant-current LED power supply mounted at rear bottom of the cabinet

Build plate illumination with both LED lamps ON

Test print with both LED lamps ON

Test print with both LEDs OFF

View from top during test print, both LED lamps ON



Coffee pot filter holder handle repair with CFPETG

Posted 2 April 2017

No, this is not an April Fools prank – but an actual geek-type 3D printer project using 3DXTECH’s carbon fiber impregnated PETG filament.

A day or so ago I was preparing my morning coffee as usual, when I discovered the little plastic ‘milk pail handle’ handle on the coffee filter holder had somehow gotten broken, as shown in the following photos

broken handle – note the missing tip on the left side

broken handle in action (or in this case, INaction)

So, since I hate defective products like this, and since I happened to have a 3D printer and some CF-PETG handy, I decided to see if I could 3D print a replacement.  Designing the replacement in TinkerCad turned out to be pretty straightforward, using a rectangular cross-section for the handle rather than the original circular design.  The two retainer tips are cylinder sections (actually they are the ends of the same cylinder – with the middle removed along with the center of the disk making up the handle.  The TinkerCad design is shown in the following screenshots

Finished design

exploded view

After the usual 2-3 tries to get the printing parameters tuned up (seems they change slightly for every job), I got a very good print, as shown in the following photo

Broken handle and CF-PETG replacement. I only went through about 4 iterations over a few hours to get this right

When installed on the coffee pot filter holder, it seemed to work very well – it allows me to pick up the holder by the ‘milk pail handle’ and it also stows away just like the original – yay!!

Replacement handle in action – lifting the filter holder as intended

Replacement handle in stowed position

B3DP (Before 3D Printers), it would basically have been impossible to repair this part.  Now, that’s not really a disaster, as it is perfectly feasible to use the holder forever without the little ‘milk pail handle’ but if you are a guy like me who hates defective equipment, this would have been a burr under my saddle every time I used the coffee pot.  I might have been able to find a replacement part somewhere, at some exorbitant cost (probably more than the entire coffee brewer) with a 6 week delivery lag time, but that would just be a choice between two bad options; deal with a broken system every day, or just buy another brewer because of the failure of some 10-cent part 🙁

However, with my new 3D printer super power, the cost to repair is a few pennies of filament and a few hours of my time in my lab, which I love to do anyway – such a deal! 😉

Stay tuned!



Printing with 3DXTech Carbon-Fiber PETG – Solved!

A couple of months ago, I got some 3DXTech carbon fiber PETG filament to play with, and I have been having mixed success printing with it on my PowerSpec 3D PRO (FlashForge Creator PRO clone) dual-extruder machine.  My first few prints were pretty nice, but lately I’ve been having problems.  The prints turn out messy and stringy, with almost no strength – as if the layers aren’t fusing at all. I can easily snap pieces apart, where before they were quite robust.

In an effort to troubleshoot the problem, I have done the following:

  • Replaced both nozzles with 3DxTech hardened steel models
  • Re-leveled the build plate
  • Gone through the excellent XYZFABS PETG printing tips here.
  • Set the z-axis offset to 0.02mm in S3D gcode
  • Set the filament feed multiplier to 0.88 as recommended
  • Set the extruder temp to 220, bed temp to 100

With the above settings, I tried a 20mm cal cube, but it started ‘air-printing’ after about 15mm from the base (filament under feeding?).

  • Set the filament feed multiplier to 1.20 and tried again.  This time I got a nicer print, but it still failed at 15mm with a feed jam and obvious gear tooth wear on the filament – clearly over-feeding.
  • Set feed multiplier back to 1.10 and tried again.  This time it started ‘air-printing’ at about 4mm up.
  • Changed extruder temp to 230 and tried again.  This time it failed to adhere 1st layer to print bed.  This caused a ‘blob’ on the extruder tip, which resulted in sidewalls that were over-printed and ragged.
  • Changed print multiplier to 1.00 and tried again.  This time the print didn’t adhere to the print bed at all
  • Changed z-axis offset back to 0.00.  This resulted in an almost perfect print.  Sidewalls were very nice, and although there was some ‘globbing’ during bridging on the top, the final top layer was almost perfect.

So, the final settings for a good print are: Feed multiplier = 1.00, Bed temp = 100, extruder temp 230, z-axis offset 0.00, unused extruder temp set to 25 (can’t set to 0, as this gets overwritten by printer), as shown below in the S3D process settings screenshots

23 March Update:

Last night I printed a second 20mm cal cube using the same settings as above, and this time the bottom layers did not print correctly (sides and top did OK).  So I tried again this morning, with the following change:

  • Changed z-axis offset from 0.00 to +0.01mm, and changed the unused extruder temp from 25 to 75 (this last settings change is an attempt to fool the printer into showing percentage completion as normal. With an unused extruder setting of 25, the top line of the display shows ‘heating’ continuously)

With the above changes, I got an essentially perfect cal cube print, *and* the top line of the display showed percentage completion instead of just ‘heating’ (the right extruder temp display showed 75/75, so that pretty much confirms my theory about the printer having to match actual and requested temps in order to progress to the ‘percentage completion’ display mode)

Essentially perfect 20mm cal cube print with 3DXTech Carbon Fiber PETG filament

Unfortunately, when I tried to print the TinkerCad model shown below (it’s the front right wheel bumper for my robot), I could not get a decent print no matter what I did.  Either the first layer wouldn’t adhere, or the filament feed failed partway through the print, or the finished print was way to fragile for use.  I finally had to give up on the 3DXTech filament entirely and print the bumper using ABS (which printed perfectly the first time!).  This was very disappointing to me, as I had previously successfully printed two of these wheelguards using the 3DXTech filament – so I’m not sure what changed to make it difficult/impossible to do it now 🙁

Right wheel guard for Wall-E2 (blue material is support). Printed perfectly the first time with ABS, but not with 3DXTech Carbon Fiber

ABS with ABS support printed perfectly on the first try


25 March Update:

Yesterday I did what I should have done when I first started having problems with the filament, namely shooting off an email to 3DXTECH.  I quickly got a response back from Matt Howlett, the company’s founder, with a what looks like their stock reply for people having problems.  Most of the stuff in the list I had already covered, but there were a couple I hadn’t tried, and one of them was raising the extruder temp from 230 to 240-245.

So, I reloaded the carbon fiber PETG on my printer, and printed a 20 mm cal cube with Matt’s recommended settings, except for a bed temp of 90 vs 65 (because I have a PEI bed and don’t want to use hairspray, and print speed of 3000mm/min vs 4000.  This time the cal cube printed perfectly, and I could not damage the finished cube with finger pressure like I could before.

Next, I tried a full print of my right wheel guard model for Wall-E2.  To simplify things, I used the carbon fiber PETG filament for both the model and the support material (I was having trouble before getting the support material to stick at the bed temperature I was using for the carbon fiber PETG material), and lo-and-behold, this print also turned out perfectly, as shown in the following shots.

Just starting the print

About 1/4 the way through, printing nicely

About 2/3 of the way. Note how well both the model and the support area adhered to the bed

Finished print!

Finished product – and quite strong.

When I made this one change, all of a sudden I was getting almost perfect prints!  Now I feel like an idiot for going through all this wailing and gnashing of teeth when all I needed to do was raise the extruder temp 10 deg!  Now I have been forced to ‘eat my hat’ (and my complaints to 3DXTECH!) – OOPS!!  However, since I am now back to being able to make strong carbon fiber prints, I’m more than willing to accept the trade-off! ;-))))

Stay tuned,





Twisted Heart 3D Print Using Magenta PETG

A little over a year ago, in December 2015, I printed a ‘twisted heart’ vase for my wife, using  Gyrobot’s ‘Twisted_Heart_Vase_Hollow_-_Hi_Res.stl’ file from Thingiverse (http://www.thingiverse.com/thing:42570/#files).  At the time, I had been 3D printing for about a year using a Printrbot Simple Metal and I had just purchased some bright Magenta PETG 3D filament.  As usual I printed several versions to get the one I (actually, my wife) wanted, and wound up with a small 30% scale model that my wife used as her daily pill cup.

As it happens, this model wound up in the hands of a grand-daughter, so my wife asked me to print her a new one.  “Piece of cake” I thought; after all, I have a better printer – a dual extruder PowerSpec 3DPRO (FlashForge 3D Creator Pro knockoff) with enclosed build space and a heated print bed with PEI, the top-of-the-line Simplify3D plater/slicer, and plenty of PETG magenta filament remaining – what could go wrong? 😉

So, I tracked down the print file I used last time, threw it into S3D, scaled it down to 30%, and voila – NOTHING – WTF!!??  After some experimentation, I found that any time I scaled the print below 50%, the sidewalls disappeared – ugh!  After some due-diligence Googling, I finally gave up and posted to the S3D support forum, and in very short order I had a couple of replies. Turns out the answer was that the sidewall thickness was getting scaled with everything else, and once it got below about 1/2 extruder thickness – it got rounded down to zero thickness – duh!  Fortunately, poster Brian had the answer – tell S3D to make the object a solid model, and then set the infill to 0% and the sidewalls to 1 perimeter width – yay!

So, this got me to the point where I could actually slice the model and send it off to the printer, where I discovered an entirely different set of problems.  I don’t remember having any real problems with my old trusty Printrbot, but I sure was having them with the PowerSpec.  The PETG filament was sometimes refusing to stick to my PEI print bed surface, and when it did stick, it had a tendency to stick to itself and ball up in to a huge blob after several to many layers.  When it didn’t do any of these bad things, I would get ugly inclusions and/or voids in the sidewalls – not the kind of thing I wanted to show my wife – yuk!!

So, back to Google, looking for advice on printing with PETG.  Fortunately, after just a short hunt I came across a very detailed treatment for PETG printing by ‘Jules’ at XYZFabs.  The good news – it was very detailed and thorough, so it was very likely to cover my problem; the bad news – it was very detailed and thorough, and so required a lot of concentrated study to follow.

In my case, the problem resolution was to do the following, as suggested in the above article

  • Modified the Z-axis calibration in S3D’s G-code section to move the extruder another 0.02mm away from the print bed, to accommodate PETG’s enhanced stickiness.
  • Enabled the ‘wiping’ feature, and confirmed that I had ‘retraction’ enabled
  • Set the extrusion multiplier to 0.88 to significantly under-extrude.  Before reading this article, I had had other occasions to over-extrude slightly with others filaments, but this was the first time I had a reason to under-extrude.
  • Switched back from ‘high resolution’ (0.1mm layer height) to ‘medium’ (0.2mm layer height).  Not sure this was really necessary, but it seemed that the theme for PETG was ‘keep the layer separation as high as possible without actually air-printing’, so…
  • Slowed the print speeds down slightly.  Again, not sure this was absolutely necessary, but the combination of this and all the above were definitely going in the right direction.

As a result of these changes, print quality improved dramatically, to the point where my next 30% scale print was a ‘winner’  – one that I could proudly present to my wife and accept my reward (“well, it’s not as good as the one I had before, but I guess it’ll have to do”) ;-).  Hey, after almost 50 years of marriage, that’s about as good as it gets!!

I have included some photos of some of the failed versions, and a couple of the successful one.

The twisted-heart menagerie. The successful print is shown on the far right

Successful 30% scale twisted heart print, using magenta PETG

Successful 30% scale twisted heart print, using magenta PETG

I have also included screenshots from my S3D setup for the successful print.