Giving the Mostly Printed CNC a try (MPCNC)

Declan had the good idea to make a CNC machine. There is a popular plan available here

A Doge

The really cute part of it is using electrical conduit as rails, which are shockingly inexpensive. Like a couple bucks for 4 feet! Holy shnikes!

We’ve been printing up a storm for the last couple weeks. A ton of parts!

We already had a lot of motors and stuff lying around. Declan bought a lot of stuff too just for this. Assorted bearings and bolts. The plans have a bill of materials.

Repetier host seemed to work pretty well for controlling the board

Used the RAMPS branch of the mpcnc marlin repo

Edited the header files as described in this post so that we could use both extruders as extra x and y motor drivers. It did not seem like driving two motors from the same driver board was acceptable. Our bearings are gripping the rails a little too tight. It is tough to move.

Some useful links on the thingiverse version of the mpccnc

He suggests using this program Seem like windows only? ugh.

The mpcnc plans don’t contain actual tool mounts but here are some examples

A pen holder:

A dewalt mount:

This is an interesting web based g-code maker. Ultimately a little to janky though. It works good enough to get started . Not entirely clear what pocket vs interior vs whatever is. engrave sort of seemed like what I wanted. Went into inkscape with a reasonable png and traced bitmapped it, then object to path. It’s also nice to just find an svg on the internet

The following code was needed to zero repetier and the RAMPS at the touch off point. We added it as a macro. It is doing some confusing behavior though.

G92 X0 Y0 Z0

pycam is the best I can find for 3d machining. Haven’t actually tried it yet

We should probably upgrade the thing to have limit switches. It pains me every time we slam it into the edge.

All in all, a very satisfying project. Hope we build something cool with it.

A horsie

3d Printed Soda Can Stirling Engine


After a very disappointing day trying to use hand twisted wire crankshafts and bottle cap piston tops, we shifted over to 3d printing to make a well dimensioned soda can Stirling engine. We found that the crankshaft sizes has to be really surprisingly small. Remember that things more twice that radial distance over a full revolution.

Things that may have helped: We got those Sterno heat things. Actually it was too aggressive. The steel wool displacer was nearly the width of the.

We kept the floss hole pretty tight, by poking it with a small object and threading the floss through with a needle and running it back and forth until the steel wool weight is enough. It is basically air tight and a little too sticky, but it works.

The files can be found here

Mostly everything is 3d printed, with some 3mm screws and 1/8in home depot steel rod for axles.

Currently we hot glued the crankshaft together. A better idea possibly is to print them a little tight and then head the shaft with a lighter and sort of melt it through a bit. Might make for easier assembly.

The free wheeling floss pulley is clutch. We had a lot of problems with binding on our crappy version.

The displacer and piston rod are 90 degrees out of phase. Checkout the assembly in the Onshape document to see.

We do have difficulty with melting parts. The stand in particular keeps melting. We’re thinking about it.