Stl tools

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 I have started working on some stl manipulation programs. I don’t want to give too much away at the moment but the people I have talked to have been encouraging. Also if I never get anywhere then it is nicer to be able to fail quietly.

I have been able to load a binary stl file and render it to screen - it was actually easier than I thought. The way I am calculating the vertex normals is waaaay toooo sloooow. I will try using vertex data as an index of sorts to try and speed things up.

New plastic

After some more printing I am happy with the abs from repraper.com (using some tweaks), but the results with pla is very varied. The black pla goes well at 220 deg, while the blue works best at 177. The green is the most difficult, it burns and warps if too hot but has major splitting problems if too low. I still haven’t found a usable temperature for it yet.  To test plastics I have been printing many 4cm hollow Stanford bunnies. I figure it’s a reasonable model with walls and overhangs. I still have many more to print yet I think.

The PLA splitting problems have been problematic, especially for my new printer like when pushed by a screw or a nyloc nut. I have had to repair parts welding them using a soldering iron.

Compared to the PLA the ABS prints with thin streams of extruded plastic. Tracks around tight areas are also sparse. To get round this I have adjusted slicer decreasing the nozzle size and increased the plastic multiplier. For a better solution I need to take a look at the firmware settings and adjust them to reflect my setup.

Bed tape

Getting a print to stick to the bed is difficult. Currently I have settled on a cold bed and painters tape for PLA and a hot bed with Kapton tape for ABS both on glass.

Surtape - painters green ~$12

Can be difficult to get off without destroying the tape, but sticks well

Kapton tape ~$15

Minimum temp woes

I have been having the most annoying problems printing. During a print, part way through it just stops. I have tracked this down to two causes. The first was dodgy connectors supplied with my original printer and the second appears to be the dodgy power supply that came with my original printer.

The faulty connections would break contact with the hot end thermistor. This would make it think that the thermistor was cold and stop extruding plastic reporting “cold extrusion prevented”. At other times it would report something like “Min temp exceeded, Kill();”. This motivated me to replace all the connectors and re-wire my printer which was a big job.

The power supply had no evidence I have observed other than changing it makes prints finish. After a while I gave it another shot and sure enough it failed again. 

Mendel90 Parts

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I am missing some m3 screws that did not appear in the materials list. I found a mixed pack of m3 4 5 6 screws and nuts for $2.50 at Coles, though I found the same set for $2.25 at SuperBarn. The m3 screws in the pack where a bit longer than I needed, I was thinking that I could cut them to the right size.

I cut the screws and used them. By putting a nut on the screw before cutting it, once cut I undid the nut which forced the thread back into a usable state. However on screwing them into the steeper motors I found that at least one screw destroyed the thread and stripped it with no effort at all. I have stopped using cut screws and bought some 10mm M3s from Jaycar. If I ever need to cut screws again I will gently saw and file them, rather than the crushing – side cutter method I used.

At Bunnings I bought two cans of black spray paint (~$4 ea), a plastic drop cloth ($1), and well as a mixed box of springs. Springs seam soo expensive ~$3 ea. Even though I only needed 3 springs I bought a $20 mixed pack as it was cheaper per spring in bulk, and I like having spares. It also didn’t help that I wanted to finish having to hunt for parts, found it hard to locate springs, and am still confused what exactly the numbers mean (12 x 0.75 x 10, and 7 x 1 x 10).