Tuesday, August 26, 2008

Best Laid Plans

Tried printing the "motor-holder" model. From left to right: 1) Y belt slipped a bit, 2) Y belt slipped a lot, 3) actually printed reasonably well.

This a first attempt at "gear-bush-holder", which I modified (hopefully correctly) to print without support. About 1/3 of the way through, the Y motor coupler came loose.

Monday, August 25, 2008

Mod Squad

Some modifications I've made...

Blobs of polymorph on the X and Y carriages to keep them from wobbling so much...

A bent paperclip to keep the filament out of the way...

A piece of plastic tubing clamped to a bookcase to feed the filament...

Saturday, August 23, 2008

Growing a Part

Tightened up the X and Y axes a bit to keep the head from wobbling. Started on a motor bracket...

After a few layers, the Y axis skewed and I had to stop the build. Two things seem to be happening here:

1. I've set the layer height too small. After a few layers, the nozzle is dragging through the work.
2. The Y belts are too loose, causing them to skip off their drive pulleys under load.

The net effect is that the build runs fine for a few layers, then slips in the Y direction.

Tightened the belts and adjusted ExtrusionHeight. Will try again in the morning.

Saturday, August 16, 2008

Supply and Demand

I tried printing off Vik's RepRap ring today...

...which the kids thought was really cool...

...so, to avoid sibling infighting, I had to make a second one. I imported the STL into Art of Illusion, converted it to a triangle mesh, scaled the mesh by 0.75 and exported the model as a new STL. This gave me a new ring at 3/4 size...

...for little hands...

Thursday, August 14, 2008

The Ascent of Mug

Some attempts at the minimug model.

Wednesday, August 13, 2008


Found that my Y axis was slipping on one side. Tightened the Y belts, X belt and all of the pulleys. Realigned the Y axis. Adjusted the infill width from 1mm to .8mm.

Melted some ShapeLock and made a 3mm-thick raft, attached it to the print bed. Started a new build.

Got most of the way done and realized I was running out of filament. Did an "in-flight refueling" by patiently holding a new piece in place until the drive screw grabbed it.

Waited for it to finish printing (about 1 1/2 hours). Soaked in hot water and peeled off the raft.

Cleaned up the lumps and threads with a Dremel.

Here's the result. It may not be pretty but it holds water. Or, more to the point, it holds single malt. Cheers.

Zeroing In

After months of trying to get the original extruder working, I finally gave up and got a new one. Someone (I won't mention who, to avoid them being inundated with requests) took pity on me and sent me a fully-assembled and tested extruder. This one has a number of refinements over the original:
- the drive screw is straight, no flexible shaft
- the motor is geared down to improve torque
- the nozzle is smaller, machined from brass stock instead of an acorn nut
- all wires are soldered to a 15-pin D-sub connector

Another thing I noticed is that the springs are much heavier on this extruder. I'm not sure how important this is to the operation of the extruder but I suspect it's responsible for at least some of the problems I had.

I haven't opened it up yet but I suspect the bearings are done better than I managed as well.

Once I wired in the new extruder (I had to get my hands on a female 15-pin D-sub), I tried a few extruder tests, calibrated the heater and measured the extrusion rate.

The extra gearing makes a huge difference. The motor isn't under as much strain and the flow is much smoother. I'm currently extruding ABS (from McMaster) at a leisurely 3mm/s. I could probably go faster but I don't want to strain the PTFE barrel.

I need to update the PIC firmware and host software at some point but I want to print a complete model first. Trying not to change too many variables at a time.

Last night, I managed to get an entire shot glass printed. My infill is a bit too loose, so it leaks. It also looks like the Y axis slipped a bit part way through the build.

It's close, though. I suppose I should pick up some scotch at the liquor store, just in case.