Monthly Archives: January 2010

Thing 2: Axis Tensioner – Y Axis

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Y Axis Tensioner

Y Axis Tensioner

Tightening the Y axis pulley is pain since you basically have to pull the entire Y stage off the X axis rods.  I suppose this isn’t a bad thing since it forces me to tighten down bolts and oil the various rods.

I designed this Axis Tensioner for the Y Axis last night.  Both parts are included in the STL file.  I’ve included the Google Sketchup file for anyone who wants to help improve the part.  It may be a little disorienting as one of the parts is laid on it’s side to be printable.

  • The larger part fits around the edge of the Y axis stage.
  • The smaller part fits under the Y axis pulley, around the M6 nut.
  • Drop an M3 nut into the slot in the smaller part.
  • Insert an M3 x 16 bolt (preferably with a washer) through the slot in the larger part.  Rotate to tighten/loosen.

Here’s the Axis Tensioner Y on Thingiverse.  Thanks to unrepentantgeek for his Sketchup version of the Cupcake CNC which allowed me to create the screenshot.

Let me know how this works for you.

Google Sketchup STL import plugin tip

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I had previously noticed that the Google Sketchup STL import plugins were very hit or miss.  They probably only imported fully about 60% of the time – with more failures on complex models.  I’ve just discovered a little trick that helps tremendously.

When you are importing, you are given a several different measurement options.  I have been choosing millimeter by default.  But, if that fails to import the entire model, try again using a different measurement!  I just imported a hugely complex model by trying millimeters, centimeters, and finally meters.

Printing between prints

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Sometimes after I finish a print I know I’m going to print something else in a few minutes.  In those cases I want to keep the heater warm rather than waiting to cool it down, warm it back up, and then start printing.  Here’s my new idea – I use the in between print time to print something quick, simple, useful, and relatively worry-free.

Insulator retainer rings.  I’m guessing you just can’t have too many of these.  As suggested by Cathal Garvey, this should be a high priority print.

New print: Dalek

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InnovationByLayers has done it again.  As soon as I saw he had uploaded a dalek STL, I downloaded, skeinforged it, and started printing.  1 hour and 28 minutes with a 50% infill:

Dalek operational

Dalek operational

Obviously you can’t print it with the arms and eye stalk as part of the body due to overhang issues.  However, I wrapped the unsharp end of my smallest drill bit (1/16″) in a thick rubber band to give it grip and drilled three holes for the arms and eye stalk.  I then used pieces of discarded filament that had been stretched as I backed it out of the extruder for the arms and eye stalk.  I wrapped the arms/eye stalk in small pieces of black electrical tape to finish the look.  Here’s what it looked like before I augmented it:

Dalek

Dalek

In fact, I was so pleased with this build that I printed up a second with a 0% infill.  FYI, that took 52 minutes and apparently had no affect on the final product.  Although, it does sound hollow.

How to update your Plastruder/Extruder firmware for the 1mm thermistor

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Disclaimer:  This is only for Windows XP.  It worked for me and may not work for you.  I’m a complete novice, so use at your own risk.  That said, this procedure completely fixed the “avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x51” errors I was getting in the Arduino environment.

  1. Download and install the Arduino IDE
  2. Download the Sanguino patch
  3. Apply the Sanguino patch to the Ardunio IDE (Directions copied from this page)
    1. Copy “\sanguino-software-1.x\cores\sanguino” to “\arduino-0017\hardware\cores\sanguino“
    2. Copy “\sanguino-software-1.x\bootloaders\atmega644p” to “\arduino-0017\hardware\bootloaders\atmega644p“
    3. Copy all the folders in “\sanguino-software-1.x\libraries\” to “\arduino-0017\hardware\libraries\” overwriting the existing libraries.
    4. Open the Arduino file located at “\arduino-0012\hardware\boards.txt” and append the text from “\sanguino-software-1.x\boards.txt“
  4. Edit the “\reprap-gen3-firmware-1.6\ArduinoSlaveExtruder\ThermistorTable.cpp” file so that it reflects the new table information for the 1mm thermistor. (New table data courtesy of Jet)
  5. Copy the entire contents of “\reprap-gen3-firmware-1.6\libraries\” into “\arduino-0017\hardware\libraries\”
  6. Run the Arduino IDE
  7. Tools -> Board -> “Arduino Diecimila, Duemilanove, or Nano w/ ATmega168“
  8. Open “\reprap-gen3-firmware-1.6\ArduinoSlaveExtruder\ArduinoSlaveExtruder.pde“
  9. Sketch -> Verify/ Compile
  10. Wait for “Done compiling.“
  11. Hold down the reset button on your extruder board.
  12. Click “Upload“
  13. Wait for 3 seconds after you’ve clicked “Upload” and then let go of the reset button.

Congratulations!

A huge thank you to Jet and Rick Pollack for walking me through this procedure step by step.

How to diagnose and fix a burned out thermistor

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Unfortunately, Bender just stopped working.  As I was keeping the nozzle warm while I was working on a new model, I looked up to see a flash of fire/spark shoot out from the nozzle area, ricochet off the build platform, and disappear.  Looking at the RepG control panel I discovered that I wasn’t getting any readings from the thermistor.  Not good.

The RepG control panel showed 0.0 as the temperature, so I shut the plastruder down, not wanting the heater to burn out of control.  I restarted Bender and RepG – but I discovered that while I could control all three axes very slugishly, I could not move the extruder motor or detect temperature.  I’m guess I couldn’t have increased the temperature either, but I didn’t want to try it since I couldn’t monitor the temperature.  That about covers the symptoms.

In order to diagnose the problem I tried to isolate the various parts.  I pulled all of the wires out of the extruder board.  Then, while the wires were still out I tested the nichrome for resistance – still around 6ohms.  Then I tested the thermistor – no connectivity.  Again, not good.  I tested the  motor for continuity, and it was fine.  Since the nichrome and motor seemed fine, that left the thermistor and extruder board.  I popped a random resistor into the thermistor ports, but still couldn’t get a reading on it.  Unfortunately, after several resets of the motherboard and extruder board, I still couldn’t get the motor to move or a reading from the thermistor.  Also, I was getting an error message that the Payload was not big enough.

Rick Pollack of MakerGear suggested on the MakerBot Operators group that I reflash the extruder firmware.  After several failed attempts, I finally figured out how to flash my extruder firmware from the Arduino environment by holding down the extruder reset button.  This got rid of the payload error message as well as the avrdude errors and let me reflash the extruder.

I pulled the entire extruder apart and did a little maintenance.  I flossed the extruder pulley teeth, pulled all the stray bits of plastic out of the idler pulley wheel area, removed the old thermistor, unwrapped the nichrome (which was wound down and then doubled over itself as the original pictures in the wiki suggested) and rewrapped the nichrome (a single layer from the nozzle up the barrel following closely in the threads to make good contact everywhere) as suggested by several people in the MakerBot operators group.  I then tested the nichrome again once it had been taped down for the proper resistance, check.

Once I pulled the thermistor out of the heater assembly, I tested the thermistor at its own leads, rather than at the wires soldered to it (in case the thermistor had come apart from the wires).  Still nothing.  I plugged a random resistor into the thermistor ports and was now able to get a reading off the extruder (as well as move the extruder motor). Concluding my problem was the thermistor, I forged ahead with a plan to replace it.

Luckily, I had placed an order for some PLA and nearly every single part needed for a secondary extruder (or what would be needed to fix a broken extruder) including a new thermistor.  If you haven’t picked up backup parts, I highly recommend it.

I clipped the old thermistor off the wires, pulled out the new thermistor and taped it to a white piece of paper immediately, putting the tape across the leads just below the bead.  I then bent the leads upwards, tinned them, soldered them to the wires, taped down the wires, pulled up the original piece of tape, and then sandwiched the thermistor in tape as per the instructions.  I then plugged the heater, the motor, and the thermistor back into the extruder board – and was able to get a temperature reading, apply a little heat to the barrel, and move the extruder motor.  I also noticed that this removed the sluggishness from the 3 axes stepper motors.

With the heater, motor, and thermistor working separately I put everything back together and reassembled the plastruder, plugged it back into the board and tested it again – readings, heat, and extruder motor working.  I then popped it back into the dinos, did a test extrusion, and starting printing again.

“Rock on completely with some brand new components”

On second thought…

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After seeing the dramatic difference printing from the SD card made, I think I’ll try my hand at printing the replacement insulator retainer ring again.  I think I’ll end up with a much better result on the small screw holes by doing this.

Sooo…  if you break your acrylic (or ABS) insulator retainer ring, drop me a line.

New print: Legos!!!

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THIS is what I’ve been dying to print.

Printed Legos

Printed Legos

How did I achieve such a feat?  Printing from the SD chip.  For those of you who aren’t sure how to do this, it’s a lot easier than you think.  I was wondering if there was some complicated kind of upload/buffering command.  I just wasn’t seeing instructions or a how-to anywhere.  Well, that’s because its pretty freaking easy.  I printed to a file, popped an SD chip into my laptop, copied the file to the chip, popped the chip into the ‘bot, and then chose to print from SD card option in ReplicatorG.

My first attempt to upload code to the chip was through the USB cable.  While this is certainly feasible, it’s painfully slow.  It took about two minutes to upload 200k through the USB cable versus less than two seconds worth of writing to the chip.

Admittedly, this wasn’t what I had tried first.  I discovered that by moving the extuder board to the same side as the motherboard, I had blocked the SD chip port.  Bummer.  To solve this problem I unbolted the motherboard, rotated it 90 degrees counter-clockwise, put two more holes into the side of my MakerBot, and bolted it back on. 1

Now that I’ve printed up my first lego, I’m going to want to print:

  • More legos, natch
  • Wacky brand new legos
  • Construx
  • Replacement construx
  • Wacky brand new construx
  1. I did this using the drill bit plus rubber band method described earlier. [↩]

PLA on the way!

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I just saw MakerBot’s blog post saying they finally got in a batch of MakerBot approved PLA.  This is supposed to be nigh magical stuff.  It prints at a cooler temperature than ABS, it has a low shrinkage factor meaning it won’t warp much if at all, it will stick to blue masking/drafter’s tape not requiring the use of an acrylic build platform, and it’s very clear.

While I was at it, I also ordered an extra brass nozzle, brass barrel, PTFE insulator, ceramic tape, nichrome wire, thermistor, and I asked for some MakerBot stickers to adorn my laptop.  :)