Oh, that's not good...

1. It’s better not to burn a board out in the first place.  Shut off the power to the power supply unit before messing with the wires to your 3D printer.
2. If you have to burn out a part, try to make it one near the edge of the board.
3. If you have to burn out a part and it’s not near the edge, try to make it one that’s not near tall parts.
4. When trying to desolder a part, you cannot move too slowly, re-check your work too much, or be too gentle.
5. When desoldering or resoldering a surface mount electronic part, the magnifying lens headgear is super helpful.
6. Keep a toothpick handy to wipe away any solder paste between electronic leads or to apply extra solder paste to the joints.
7. Solder paste gets everywhere, plan accordingly.
8. Rubbing the soldering wick very slightly with the soldering iron seems to help. ¹
9. When you think you’re all done, check your work by testing continuity between the top of a lead that touches the electronic part and the pad where the lead is (hopefully) soldered.  If there’s no continuity, touch the solder join again with the soldering iron.  Retest.  If still no continuity, add a little solder paste with a tooth pick, wipe away any excess with another clean toothpick, touch with the soldering iron, and retest.  Repeat this until there’s a connection.
10. When you think you’re all done, check your work by testing each lead against each adjacent lead.  If there’s a connection between two leads, you might have a solder bridge between them.  I don’t think I ran into this problem, but if I had I would have tried peering into/underneath the part with the magnifying headgear, trying to wipe or break the bridge with a toothpick, then trying to heat the two leads and poking at the bridge and hoping it broke. ²  Please leave a comment on how you would fix this problem.
11. I also tested the extruder board very very slowly.  With the power off to the entire 3D printer and with the extruder board disconnected, I connected just the thermistor, plugged in the extruder board, and turned on the MakerBot.  Success.  I then powered down and disconnected the extruder board.  I then connected the leads to the power resistors/heater, reconnected everything, then turned it back on.  I was still getting a reading from the thermistor, so in the control panel for ReplicatorG I set the temperature for 5 degrees higher than what it was registering.  When I saw the temperature climb, I shut everything down and disconnected the extruder board again.  Then I connected the motor wires, connected the extruder board, then powered it all up. ³  Yay!

The extruder board has two sets of terminals where the motor connects and two sets of fiddly bits (part number “A3949SLBT”) called H Bridges by people who know what they’re talking about.  Theoretically there’s a way to switch H bridges just in the firmware.  Maybe the next firmware/ReplicatorG update will have such a feature?

Stay tuned for how I repaired my extruder board!

1. And shaking my mouse back and forth and clicking rapidly helps webpages load faster. [↩]
2. Hulk smash! [↩]
3. The first three times I went through this process I couldn’t move the extruder motor.  After the fourth time checking and resoldering some of the joints, it finally worked. [↩]

Are you rocking the Five?

When the Plastruder MK5 I ordered hadn’t arrived this last Friday I was a little disappointed because I was hoping to build it over the long weekend.  Luckily it arrived late Saturday!  Huzzah!  My weekend was saved!  I had put off soldering the Relay Board I got with my heated build platform since I haven’t gotten around to picking up a hotplate yet.  However, since the Relay Board was needed to run the Plastruder MK5, I busted out my soldering kit and got to work putting together the Relay Board and Plastruder.¹  Without further ado, here are the things I learned assembling and building my Plastruder MK5:

• When attaching the thumb wheels to the bolts, definitely use a vise.  I tapped the bolts into the thumb wheels with a hammer – and smashed the threads just enough to make the bolts useless.  :/ ²  If I did this again, I would definitely put the nut partway onto the bolt and tap the NUT rather than the bolt itself.  This would keep the force away from the threads and probably keep them from being damaged.
• When threading the nuts onto the retainer mounting plate, I found it easier to put the nuts about halfway onto the bolts – rather than almost all the way to the plate.  If you put them halfway on, it’s easier to tighten each bolt individually.  If the nut is nearly to the plate, you have to simultaneously tighten all screws or tighten them each a little at a time.
• The MK5 thermistor preparation instructions direct you to the MK4 directions for wrapping the thermistor.  The MK4 directions suggest you essentially sandwich the thermistor leads in between two long pieces of Kapton tape.  This is exactly how I built my MK4 plastruder – and it’s just not easy to trap these two thin leads in between pieces of thin sticky tape.  An easier way, and what appears to have been done in the MK5 pictures, is to separate the thermistor leads and wrap the Kapton around the leads – making sure they never touch.
• I would test the thermistor’s resistance and temperature measurement before attaching it to the plastruder.  If there’s something wrong with the thermistor, I would want to know long before I taped it to the plastruder, insulated it, and mounted everything inside the ‘bot.  Both tests are quick and easy to do before you assemble everything – just check the resistance with your multimeter then plug the unattached thermistor leads into the extruder board.  This quick sanity check could save you a lot of time and supplies by not having to undo a lot of work.  This would be a good time to test resistance on the power resistors too.
  With all the wires running from the plastruder and relay board, it can get confusing.  I picked up some heat shrink tubing the last time I was at an electronics store and am using them to color code each of the sets of wires – one small band at each end.  This helps me keep everything straight.  By just looking at the end of the wires and doing a sanity check against the bands on the motor, thermistor, or heating element I can quickly verify I’m wiring everything up correctly.
• I braid the wires together to keep them all in check.  There’s no particular reason for braiding over twist ties other than it just seems more elegant.

What did you learn while building your Plastruder MK5?

1. Photo courtesy of WoodleyWonderWorks [↩]
2. I’m just that strong. [↩]