Chess Piece Replacement Project

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Posted 15 March 2019,

A week or so ago a family friend asked if I could print up a replacement part for a chess set.  I wasn’t sure I could, but what the heck – I told them to send it to me and I would do my best.  Some time later a package arrived with the piece (shown below) to be duplicated – a pawn I think.

Chess piece to be duplicated

Chess piece to be duplicated

The piece is about 43 x 20 x 20 mm, and as can be seen in the above photos, has a LOT of detail.  I didn’t know how close I could come, but I was determined to give it the old college try!

3D Scanning:

The first step was to create a 3D model of the piece.  I was semi-successful in doing something similar with an aircraft joystick about five years ago, but that piece was a lot bigger, and had a lot less detailed surface.   This previous effort was done using Autodesk Capture123, and it was a real PITA to get everything right.  Surely there were better options now?

My first thought was to utilize a professional 3D scanning service, but this turned out to be a lot harder than I thought. There is a LOT of 3D scanning hardware out there now, but most of it is oriented toward 3D scans of industrial plants, architecture installations and big machinery.  Very little to be found in the way of low-cost high-resolution 3D scanning hardware or services.  There are, of course, several hobbyist/maker 3D scanners out there, but the reviews are not very spectacular.  I did find two services that would scan my piece, but both would charge several hundred dollars for the project, and of course would require a round-trip mailing of the part itself – bummer.

Next, I started researching possibilities for creating a scan from photos – basically the same technique I used for the joystick project.  While doing this, I ran across the ‘Photogrammetry’ and ‘Photogrammetry 2’ video/articles produced by Prusa Research, the same folks who make the Prusa Mk3 printer I have in my lab – cool!  Reading through the article and watching the video convinced me that I had a shot at creating the 3D model using the Meshroom/AliceVision photogrammetry tool.

At first I tried to use my iphone 4S camera with the  chess piece sitting on a cardboard box for the input to Meshroom, but this turned out to be a disaster.  As the article mentioned, glossy objects, especially small black glossy objects, are not good candidates for 3D photogrammetry.  Predictably, the results were less than stellar.

Next I tried using my wife’s older but still quite capable Canon SX260 HX digital camera.  This worked quite a bit better, but the glossy reflectivity of the chess piece was still a problem. The wife suggested we try coating the model with baby powder, and this worked MUCH better, as shown in the following photos.  In addition, I placed the piece on a small end table covered with blue painter’s tape so I would have a consistent, non-glossy background for the photos.  I placed the end table in our kitchen so I could roll my computer chair around the table, allowing me to take good close-up photos from all angles.

End table covered with blue painter’s tape

Chess piece dusted with baby powder

Chess piece dusted with baby powder

Chess piece dusted with baby powder

Next, I had to figure out how to use Meshroom, and this was both very easy and very hard.  The UI for Meshroom is very nice, but there is next to no documentation on how to use it.  Drag and drop a folder’s worth of photos, hit the START button, and pray.

Meshroom UI

As usual (at least for me), prayer was not an effective strategy, as the process crashed or hung up multiple times in multiple places in the 11 step processing chain.  This was very frustrating as although voluminous log files are produced for each, the logs aren’t very understandable, and I wasn’t able to find much in the way of documentation to help me out.  Eventually I stumbled onto a hidden menu item in the UI that showed the ‘image ID’ for each of the images being processed, and this allowed me to figure out which photo caused the system to hang up.

Meshroom UI showing hidden ‘Display View ID’s’ menu item.

Once I figured out how to link the view ID shown in the log at the point of the crash/hangup with an actual photograph, I was able to see the problem – the image in question was blurred to the point where Meshroom/AliceVision couldn’t figure out how it fit in with the others, so it basically punted.

Photo that caused Meshroom/AliceVision to hang up

So, now that I had some idea what was going on, I went through all 100+ photos looking for blurring that might cause Meshroom to hang up.  I found  and removed five more that were questionable, and after doing this, Meshroom completed the entire process successfully – yay!!

After stumbling around a bit more, I figured out how to double-click on the ‘Texturing’ block to display the solid and/or textured result in the right-hand model window, as shown in the following photo, with the final solid model oriented to mirror the photo in the left-hand window.

textured model in the right-hand window oriented to mirror the photo in the left-hand window

So, the next step (I thought) was to import the 3D .obj or .3MF file into TinkerCad, clean up the artifacts from the scanning process, and then print it on my Prusa Mk3.  Except, as it turns out, TinkerCad has a 25MB limit on imports due to its cloud-based nature, and these files are way bigger than 25MB – oops!

Back to the drawing board; first I looked around for an app I could use to down-size the .obj file to 25MB so it would fit into TinkerCad, but I couldn’t figure out how to make anything work.  Then I stumbled across the free Microsoft suite of apps for 3D file management – 3DPrint, 3DView, and 3DBuilder.  Turns out the 3DBuilder app is just what the doctor ordered – it will inhale the 88MB texturedMesh.obj file from Meshroom without even breaking a sweat, and has the tools I needed to remove the scanning artifacts and produce a 3MF file, as shown in the following screenshots.

.OBJ file from Meshroom after drag/drop into Microsoft 3DBuilder. Note the convenient and effective ‘Repair’ operation to close off the bottom of the hollow chess piece

Side view showing all the scanning artifacts

View showing all the disconnected scanning artifacts selected – these can be deleted, but the other artifacts are all connected to the chess piece

The remaining artifacts and chess piece rotated so the base plane is parallel to the coordinate plane, so it can be sliced away

Slicing plane adjusted to slice away the base plane

After the slicing operation, the rest of the scanning artifacts can be selected and then deleted

After all the scanning artifacts have been cleared away

Chess piece reoriented to upright position

Finished object exported as a .3MF file that can be imported into Slic3r PE

Now that I had a 3D object file representing the chess piece, I simply dropped it into Slic3r Prusa Edition, and voila! I was (almost) ready to print!  In Slic3r, I made the normal printing adjustments, and started printing trial copies of the chess piece.  As usual I got the initial scale wrong, so I had to go through the process of getting this right.  In the process though, I gained some valuable information about how well (or poorly) the 3D scan-to-model process worked, and what I could maybe improve going forward.  As shown in the following photo, the first couple of trials, in orange ABS, were pretty far out of scale (original model in the middle)

I went through a bunch of trials, switching to gray and then black PLA, and narrowing the scale down to the correct-ish value in the process.

The next photo is a detail of the 4 right-most figures from the above photo; the original chess piece is second to right.  As can be seen from the photo, I’m getting close!

All of the above trials were printed on my Prusa Mk3 using either orange ABS or gray (and then black) PLA, using Prusa’s preset for 0.1mm layer height.  Some with, and some without support.

After the above trials, I went back through the whole process, starting with the original set of scan photos, through Meshroom and Microsoft 3D Builder to see if I could improve the 3D object slightly, and then reprinted it using Prusa’s 0.05mm ‘High Detail’ settings.  The result, shown in the following photos is better, but not a whole lot better than the 0.1mm regular ‘Detail’ setting.

Three of the best prints, with the original for comparison. The second from right print is the 0.05mm ‘super detail’ print

I noticed that the last model printed was missing part of the base – a side effect of the slicing process used to remove scanning artifacts.  I was able to restore some of the base in 3D Builder using the ‘extrude down’ feature, and then reprinted it. The result is shown in the photo below.

 

“Final” print using Prusa Mk3 with generic PLA, Slic3r PE with 0.1mm ‘Detail’ presets, with support

Just as an aside, it occurred to me at some point that the combination of practical 3D scanning using a common digital camera and practical 3D printing using common 3D printers is essentially the ‘replicator’ found in many Sci-Fi movies and stories.  I would never thought that I would live to see the day that sci-fi replicators became reality, but at least in some sense it has!

Stay tuned!

Frank

 

 

 

 

 

 

 

 

Better Battery Charging for Wall-E2

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Posted 08 February 2019,

After recovering from my bout with #include file hell, I’m back to working on Wall-E2, my autonomous wall-following robot.  In a previous post I described the integration of the TP5100 charger module into Wall-E2’s system, but I have lately discovered that the TP5100 end-of-charge (EOC) detection scheme isn’t very reliable in my application.  The TP5100 uses a current threshold to determine EOC, which works fine in a normal application where the battery pack isn’t simultaneously supplying current to the load, but in my application, Wall-E2 stays active and alert while it’s docked at it’s feeding station; it has to, in order to be able to respond to the EOC signal and detach itself.  So, the current going through the TP5100 never goes below the idling current for Wall-E2, which is on the order of 300mA or so.  This is enough to keep the charging current above the TP5100 EOC threshold, and so Wall-E2 hangs on to the charging station forever – not what I had in mind!

Life would be good if I somehow measure Wall-E2’s idling current while on charge and the total charging current.  Then I could subtract the two values to get the excess current, i.e. the current going into the battery but not coming out – the current actually going into increasing the battery charge level. When this current falls below an appropriate threshold, then charging could be terminated. This scenario is complicated by the need to measure the current on the high side of the charging circuit and of the +Vbatt supply to the rest of the system.

Well, as it turns out, Adafruit (and I’m sure others) makes a high-side current sensor just for this purpose, based on the 1NA219 and INA169 chips. The INA219 module reports current via an I2C connection, while the 1NA169 module provides a open-emitter current source proportional to the current through an onboard 0.1Ω resistor (see this data sheet for details).  My plan is to use two of these modules; one at the charging circuit input, and a second one at the 8.4V +VBatt supply from the battery to the rest of the system. Since Wall-E2 stays awake during charging, it should be simple to monitor both currents and decide when charging is complete (or complete enough, anyway).  As a bonus, I should be able to extend the life of Wall-E2’s battery pack by terminating the charge at less than 100% capacity. See this very informative post by François Boucher for the details.

03 March 2019 Update:

After the usual number of mistakes and setbacks, I think I have the dual current sensor feature working, and now WallE-2 charges by monitoring both the battery voltage and the actual charging current (total current measured at the charging connector minus the run current measured on WallE-2’s main power line).  As a final test, I discharged the main battery pack at about 1A for about 1 hour, and then charged it again using the two-current method. As shown in the Excel plots below, Charging terminated when the actual battery charging current fell below 50mA.

Complete charge cycle, after discharging at approx 1A for approx 1 Hr

Last 20 minutes or so of charge operation, showing detail of end-of-charge behavior

two 1NA169 high-side current sensors mounted in the battery/motor compartment.  Note the 3D-printed mounting plates.

Here is a showing the installation of the two 1NA169 sensor modules in WallE-2’s battery compartment.  The one on the left measures running current, and the one on the right measures total current (charging + running).

The following figure shows the system schematic for WallE-2, with the two new 1NA169 sensors highlighted

System schematic with locations of new current sensors highlighted

Now that I have the current sensors and the new charge algorithm working, it’s time to go back an take another look at the charge/discharge characteristics of the Panasonic 18650B cells I’m using to see if I can extend their life with a more intelligent charge/discharge scheme.  The following plot shows the charge characteristics for this cell.

Charge plot for the Panasonic 18650B LiPo cell

As noted by François Boucher, the red line above is the total energy returned to the battery during charge.  As he notes, the battery acquires about 90% of its total capacity in the first 105 minutes of the charge period, when charged at 0.5C at 25C.  My battery pack is a 2-cell parallel x 2-cell series stack, and currently I’m charging to a 50mA cutoff.  According to Boucher, this is way too low – I’m charging to almost 100% capacity and thereby limiting the cycle life of the battery pack.  Looking at the end-of-charge detail plot above (repeated below), I should probably use a charge current threshold of around 500mA charging current (250mA per cell in the parallel stack) for about 90% capacity charge.

End-of-charge detail with approximate 90% charge current highlighted

On the discharge side, Panasonic’s Discharge Characteristics plot below shows a discharge down to 2.50V/cell.  WallE-2’s typical current drain is about 1A or about 0.3 – 0.5C, and the cutoff I’m using is 3.0V cell.  From the plot, this gives about 3150mAH of the approximately 3300mAH available at 0.5C, or about 95%.  So, it looks like I should raise the discharge cutoff voltage to about 3.2V or about 3000mAH of the 3300mAH available, or about 90%.

Conclusion:

So revisiting WallE-2’s battery management seems to have paid off; I now have much better visibility into and control over charge/discharge of the 18650B battery pack, and at least some expectation that I can use WallE-2’s new found battery super powers for good rather than evil ;-).

Stay tuned!

Frank

 

Digital Tension Scale, Part IV

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Posted 25 December 2018

In my copious free time I have been refining the design for a low power battery operated tensionometer.   In my last post on the subject, I had described the components I had planned to use, and in the ensuing weeks I have been working on implementing this design.   There are several challenges in this project:

Bluetooth Link:

There are a huge number of Bluetooth products out there in the Maker-verse, with varying degrees of Arduino support, and widely varying performance characteristics.   To add to the confusion, there is ‘regular’ Bluetooth and the more recent  ‘BLE’ (Bluetooth Low Energy) which are completely incompatible with each other.   As I now understand it, BLE is synonymous with Bluetooth 4.0+ (the iPhone 4S was the first smartphone to implement the new standard).   However, the most common product in use in the Arduino world seems to be the venerable HC-05 ‘regular’ Bluetooth module, available from your local grocery store (well, not quite, but from almost everywhere else!) for not much more than a few pennies

I had no previous experience with BT modules, so this part of the project took some time, and was the last major part to be accomplished.   After receiving my HC-05 modules from China, I used this tutorial to get started.   The real challenge for this part of the project wasn’t getting the HC-05 hooked up to the microcontroller – it was sorting through all the layers of BT-related settings on my Win 10 laptop to pair with the HC-05 device and determine which serial port did what.

  • In Windows 10, I used the ‘Bluetooth and other devices settings’ panel (Settings -> Devices -> Bluetooth and other devices) to find and pair to the HC-05.   The device shows up as ‘HC-05’ and the default pairing password is “1234”.
  • When the HC-05 is paired it automatically sets up at least two serial ports that show up in device manager as ‘Standard Serial over Bluetooth’ ports, as shown below.   However, only one of these ports is actually usable for two-way communication, and it isn’t clear to me why, or how to tell which is which;   I had to experiment with each available ‘SSoB’ port to figure out which to use  (so far, it seems like the highest-numbered port is the proper one).
  • After the HC-05 is paired and the com ports are set up, then any serial terminal app (I used RealTerm) can be used to communicate between the PC and the microcontroller via the HC-05.
  • On the microcontroller (I used a Teensy 3.2 with multiple hardware serial ports), I wired the HC-05 to Serial1 leaving Serial (Serial0) available for normal communication between the Teensy and my Visual Studio 2017 Community Edition/Visual Micro add-on for Arduino development platform.

Physical Layout:

The original idea behind this project was to create a self-contained battery-operated digital weight scale that could display weight values on a local display, but could also stream the data live to a remote recording station like a laptop or smartphone. The ‘self-contained’ part requires that all the electronics be mounted on the S-shaped load cell assembly itself, and to that end I designed a housing that connects to the two bolts that hold the arms of the load cell.   The idea is that all the electronics save the LCD display and the battery will be mounted to the underside of the box lid so that servicing would be easier.   Also, by mounting everything to the lid, I can make cutouts for the charger and Teensy USB connectors for easy charging and reprogramming.   After several iterations in TinkerCad, I came up with the following design

Looking up at the underside of the box lid, showing all modules except the battery and the LCD display

Showing the top of the lid with the mounting bracket for the load cell

Isometric view with transparent box walls. The LCD display module is under the battery.   Note the cutouts for the charging and programming USB-C connections

Module Integration:

I had previously tested each module individually, but hadn’t had all of them working at the same time.   I had tested the HC-05 with an Arduino Mega, and I had tested the load cell with both a Sparkfun Pro Micro and with a Teensy 3.2, and I had tested the Nokia LCD display with a Teensy 3.2, but I hadn’t put everything together.   So I wired everything up on my half-size ASP plugboard and got it all working together with a simple program (included below) that exercised the LCD Display, the load cell, the BT module, and the battery charger, as shown in the following photos

RealTerm Serial Terminal Program showing load cell readouts collected wirelessly via the Bluetooth HC-05 modules

HC-05 Bluetooth, HX-711 Load Cell Amp, Sparkfun Charger, and Teensy Microcontroller modules integrated together. Note disconnected USB cable showing that the circuit is running on battery power. The scale is currently measuring 1.8 liters of water in the suspended plastic bag (note the ‘1.8 Kg’ reading on the LCD display)

 

Software:

The software used for the above integration tests is a reasonably complete sketch for day-to-day use of the digital weight scale.   It displays the measured weight on the LCD display, and also sends it to the USB serial port for display on a directly connected PC, and to the HC-05 Bluetooth module for display/capture via a BT-connected laptop or smartphone.   This program is shown below:

However, this program depends on the proper calibration of the load cell, which I have been doing with a separate sketch (also included below):

What I need to do now is to combine these two programs into a single sketch with ‘operating’ and ‘calibration’ modes.   My calibration program already does this to some degree, as it waits 5 seconds on startup for the operator to send the ‘y’ key via the direct-connect serial port. If the ‘y’ character is detected within this window, then the program starts the calibration sequence; otherwise it starts taking measurements as normal.   This behavior needs to be expanded somewhat in that it should accept a calibration command either through the direct-connect serial port (Serial) or via the BT port (Serial1).

Low Power Operation:

I have already done some experimentation on low-power operation of the Teensy 3.2, using Colin Duffy’s fine ‘Snooze’ library, and have determined that I can easily drop the Teensy’s operating current from around 20-30 mA to about 1-2 mA by putting it to sleep during periods of load cell inactivity.   Assuming I get the full 2500 mA hours out of the battery, then I can expect something like 1000 hours or about 40 days between recharges.   However, more work needs to be done to get the low power mode fully operational.

 

Stay Tuned!

Frank

 

Digital Tension Scale

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Posted 27 October 2018

I recently underwent rotator cuff repair surgery on my left (dominant) shoulder, and am now starting the rehab process.   My PT person was adamant that I not re-start my normal rowing routine for at least six weeks post-op, due to the possibility that I could re-tear the tendon.   This made me curious as to what the tension really was on my arms when rowing, so I decided to try and build a digital dynamic tension sensor, capable of plotting rowing strap tension in real time.

To start, I had to educate myself on the world of strain gauges and load cells, and what the differences are.   As I came to understand, what I wanted was a  load cell configured for tension measurement, with a  strain gauge as the active sensing element in the load cell.   So, I started searching for load cells, and was immediately inundated with ‘too much information’.   This deluge is certainly better than the old days where I had to search through paper (really, no internet!) magazines and catalogs, but at least you didn’t have to worry about overload headaches! ;-).

Anyway, I found this item ‘Degraw 40Kg Tension Load Cell and HX711 Combo Pack Kit‘, as shown in the screenshot below

Amazon catalog item for Degraw load cell

This looked perfect for my intended use, as I could hook one end onto my rowing machine strap, and connect some sort of handle to the other end.   Now all I had to do was figure out how to hook the thing up and get it to work.   Fortunately Degraw also provided a sketch of the hookup using an Arduino Uno, so that part was pretty easy.

Degraw-provided hookup diagram

After a bit more research, I found a nice HX711 library by bogde and some example programs, and got the whole thing to work using an Arduino Mega 2560.   Once I got a program running with some preliminary (but believable) results, I started thinking about how I was going to manage the physical aspects of hooking this assemblage to the rowing machine and recording dynamic tension.   I couldn’t really just let the HX711 board hang by the strain gauge wires while connected with jumpers to the Mega board, as the #28 strain gauge leads would surely break.   So, I came up with the idea of somehow attaching the HX711 board and a small microcontroller to the load cell assembly, and then connecting the whole thing to my laptop with a USB cable.   Hopefully the USB cable would be long enough to allow full extension of the rowing machine strap so I could collect full rowing cycle data.

After some digging around in my parts cabinets, I came up with two candidates for the ‘small microcontroller’ part of the plan; a 3.3V Teensy 3.2, and a 5V/16MHz Sparkfun Pro Micro.   I tried the Pro Micro at first, and almost immediately went down the rabbit hole (my term for getting lost in some technical wonderland without a clue how to get back) trying to figure out how to program the device – a challenge due to the way it handles com ports through the USB connector (it actually implements two different ones, depending on whether the boot loader or the user firmware is running – yowie!).   After climbing my way out of the rabbit hole, I decided to try the Teensy 3.2 instead, as I familiar with it from several other projects.   With the Teensy, I got a test program running and started taking data with known weights attached to the load cell. The way I did this was to suspend a plastic bucket from the load cell, and poured water into the bucket one liter (1Kg) at a time while recording data.   This was successful because I got good data, but unsuccessful because the data didn’t make much sense, as shown in the plot below

Results of pouring 1L (1Kg) water at a time into bucket suspended from load cell, using a 3.3VTeensy 3.2

As can be seen, the data was anything but the stairstep function I was expecting to see.   At this point I wasn’t sure if I had a hardware problem or a software problem, or something else entirely, so I sent an email to Degraw Product support with the above plot attached, asking if they had any insight into the problem.   Amazingly, they replied almost immediately, and offered to send me another load cell unit gratis so I could eliminate their hardware as the cause of the problem.   Although I was quite pleased with their offer of support, I thought maybe the 3.3V supply of the Teensy 3.2 might be causing the non-linearity (the HX711 advertises 2.7-5V operation but the lower voltage might be causing output linearity problems).   So, I tried again with the Sparkfun Pro Micro, and this time I managed to make the programming magic work. Then when I did the same test as above with the 5V Pro Micro instead of the 3.3V Teensy, I got the plot shown below.

Tension vs time plot created by pouring 1L (1Kg) of water at a time into bucket suspended from load cell, using Sparkfun 5V Pro Micro

So, now that I had the software and microcontroller problems solved, I started working on the mounting issue.   After a few minutes in TinkerCad and some quality time with my PowerSpec 3D PRO 3D printer, I had a mounting platform that clipped onto the two vertical rods in the ‘S-shaped’ tension load cell, as shown in the images below.

Reverse side of assembly, showing mounting plate clips attached to load cell vertical members

Sparkfun Pro Micro and HX711 board mounted on load cell

After getting all this set up, it was time to take some real data. Since I was still in the ‘no rowing’ zone after my surgery, I enlisted my lovely wife to do the honors while I recorded the data.   We have an Avari magnetic rowing machine, which thankfully doesn’t make much noise.   I recorded a total of 12 rowing cycles on two different ‘wave’ settings (I’m still not sure what the different ‘wave’ settings mean) at the lowest tension level, with the results shown below

As shown in the above plot, the peak tension reading was around 18Kg (about 40 lbs).    I’ve included a short video of the test below.

Dawes Lightning 1500 Stem Bracket

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Posted 13 June 2018

A friend got a new Dawes Lightning 1500 bike, and wants to install a ‘Swing Grip’ handle accessory on the piece (the ‘stem’) that connects the front fork post to the handlebars.   I had printed up a similar bracket for Ray in the past, and so he asked if I could do one for this bike too.

I had him bring the bike over so I could get a good look at the ‘stem’ shape and then built up a prototype in ABS.   I had a lot of difficulty with getting the ABS to print without lifting off the heated bed, and so eventually had to use a raft, which sucked because the raft stuck to the part too well.   When I got the part done I tried it on the bike, and of course it didn’t fit, but it did allow me to see where the design had to be changed.

Printing Notes:

I printed the PLA part with

layer height:   0.2mm

extruder temp: 205 for layer 1, 195 for 3 & up

print bed temp: 70C

speed: 30mm/sec

Z-offset: -0.05mm

I had to work a bit to get the PLA to stick to the bed, and the right combination was the above settings, plus attention to getting the bed levelled properly and the correct Z-axis offset so the first layer was ‘squished’ significantly.

 

 

Printing an ABS Shaft Adaptor for 80mm Wheel

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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

 

 

 

 

PowerSpec 3D PRO Build Plate LED Lamps

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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

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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!

Frank

 

Printing with 3DXTech Carbon-Fiber PETG – Solved!

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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

Frank

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,

Frank

 

 

 

Twisted Heart 3D Print Using Magenta PETG

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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.

Frank