Author: Maker Block

MakerBot Is The New Duct Tape

Google Sketchup Model of Broken Window Latch
Google Sketchup Model of Broken Window Latch

This summer I discovered that one of the window latches in my home was broken.  Since the windows are so old, I didn’t even bother checking for replacement parts at the hardware store.  My repair consisted of wrapping duct tape over the broken part and fitting back inside the latch mechanism.

It worked, but was a less than ideal fix.  The part had snapped in two places, making the entire part slightly unstable even when reinforced with duct tape.   Additionally, the extra thickness of the duct tape prevented the latch from sliding smoothly and eventually started to bunch up the duct tape.

Several months ago, figuring that it was only a matter of time before I bought a MakerBot CupCake CNC, I modeled the part in Google Sketchup.

After getting my MakerBot operational yesterday, this was my second print.  It was also my fourth print – another window was missing a latch entirely.  A little light sanding and a slight use of a hacksaw blade to separate the small divide underneath the part, and it was ready for installation.  Both latches installed without fuss and work far better than the duct tape version.

Window latches, top view
Window latches, top view
Window latches, underside
Window latches, underside

Unlike the duct tape fix, this repair permanently replaces the broken part with a functionally identical part that is also far more cosmetically appealing.  Best of all, I now live in a house that is partially built by a robot I made.  :)

Print 5: Replacement toy fire engine part

Here’s another part I printed.  The original piece was from a toy fire truck.  It served as a rotating platform, hinge, and guide for the fire ladder.  The toy broke when the part was pushed laterally, shearing the axle off.  Overall, I’d say it was a poorly designed piece.  The entire toy would have been much sturdier if the axle stuck out from the body of the truck in the form of a low round stub the rotating platform fit around.  However, I’m rarely consulted in the engineering of toy fire trucks.  :)

As with the window latch, I had taken the measurements and modeled the piece in Google Sketchup several months before ever purchasing my MakerBot.  I had to make several small changes to the design of the part to reduce overhangs.

Replacement toy fire truck part, for comparison
Replacement toy fire truck part, for comparison
Replacement toy fire truck part
Replacement toy fire truck part

This wasn’t the cleanest piece I’ve printed, but it’s fine for a part that is destined to be broken all over again.  If I were printing it again I’d widen the two walls which serve as the hinge to the ladder.  The piece I printed had the same kind of unevenness in the tall thin axle that I had on the handle of the Z-axis crank. The part became so blobby that I tried to sand it down to be more even – and accidentally snapped the axle off.  Hence, the piece of round chop stick glued into the part.  I’m still fiddling with the Skeinforge settings to deal with this issue.

The process was really pretty easy:  Measure broken piece -> model in Sketchup -> export to STL file using a plugin -> Skeinforge -> ReplicatorG -> FIRE THE MAKERBOT!

MakerBot Raft Settings

I was having some trouble getting my rafts to stick to the build platform until I did the following:

  1. Switched to the acrylic build base (which I promptly pock-marked with a hot extruder)
  2. Changed the Skeinforge raft settings to those suggested on the Thingiverse blog

If you’re having raft trouble, do both of the above and don’t look back.

More calibration

Calibration is proving to be a relatively slow process. As you can see from my prior post, my prints are drifting towards the back of the MakerBot. This appears to be due to either improper tension, the power being set too low for the Y stepper motor, and/or the Y axis rods not being smooth/oiled/straight enough. Given that the first few layers are spot on, I suspect it is a stepper board power issue. The Y axis motor is easily the first quietest of the three axes. As the X axis motor is the nosiest, I could probably dial it back without an effect on performance.

To do for tonight:

  1. In the hopes of diminishing the Y axis drift problem
    1. Oil the Y (and X and Z) axis rods
    2. Check the Y (and X) axis slides
    3. Dial up the Y axis power by turning the potentiometer on the Y axis stepper board clockwise
  2. In the hopes of diminishing operational noise
    1. Dial down the X axis motor slightly
    2. Dial down the Z axis motor slightly

Heater barrel – backasswards?

Dangit.  According to the very latest changes to the MakerBot assembly wiki, I put the heater assembly together with the heater barrel upside down.  I’m not entirely sure what this means for my heater.  Clearly it was working well enough that I could extrude reasonably well.

The questions is – do I leave it as is or disassemble/reassemble?

If I leave it as is, I suppose there’s a chance I could bulge the insulator, ruining it.

I’ve already disassembled/reassembled once because of a bad thermistor connection.  If I disassemble again, I’m thinking the ceramic tape and nichrome may have had it.  Not to mention that I’m probably going to have a royal mess of plastic inside the barrel and nozzle to clean up.

First and second test prints

Well, I’m trying the traditional mini-mug!

Mini-Mug test!
Mini-Mug test!

Something tells me they’re not watertight.  The first one (left) snapped off the foam-core raft part way through the build.  The second one (right) got all gloppy and then snapped off the foam core raft part way through the build.

Except for the fact they’re not even close to done, the adhesion between the layers seems pretty good.  The raft on the second one was a little gloppy which caused me to be a little apprehensive throughout the build.  After a few layers the gloppiness evened out.  However, it cropped up again, accumulated, got super gloppy, and ruined the build.

Suggestions?

My first hack

Seeing as how I already had the heater in pieces, I figured it couldn’t really cause that much harm to move the plastruder board.  I totally get why the MakerBot guys put the board on the extruder – that way all you had to do was swap out an extruder and you can roll with a totally new print head.

I don’t really intend to do printing beyond single color plastic.  This may very well change if we see a support material extruder being offered.  But for the foreseeable future, I am really looking forward to printing away with my giant coil of black ABS.

That said, I’m not attached to the idea of having totally modular heads. 1  On the right side of the MakerBot there’s a really large area above the motherboard and to the left of the three stepper motor boards.  The only things preventing the plastruder board from being mounted right there are (1) the motor wires are too short and (2) four holes in the body.

I had dissected a piece of ethernet cable for the wires running to the nichrome wire and thermistor, so I still had four wires left.  I used another two and a bit of solder to extend the wires to the extruder motor.

Sometimes when I need to drill a small hole through soft or thin material I don’t even bother with the drill.  I used a small drill bit with a rubber band wrapped around the non-drill-bitty-end to give it a grip and rotated it into the right panel of my MakerBot.  Bolt it on and…

Presto!  Now I can see all the way through the plastruder.  :)

  1. Sorry about the pun. [↩]