RepRap: Blog

Just for kicks, I printed out a couple of belt clamps and a pulley. Oh, and about 95% of an X-axis restraint (software crash, blue-tinged air etc.) but it looks like we're on our way to starting an X-axis here.

I've switched to a 0.78mm nozzle now, and the new shape is an improvement in preventing strings - or at least shedding them quickly - but not much so. Also having a few problems with PLA not adhering to my new machine bed so well. Hopefully a good wipe-down with acetone and a scrape with a wire brush (for the Reprap, not me) will improve things.

Vik :v)

Labels: pla, x-axis

OK, here's the tidied up version. I had to ream out the vertical holes by hand, the horizontal holes were fine and just needed de-stringing. I have seen how threads of molten plastic climb up the curved surface of an acorn nut nozzle and I'm modifying one to see if I can reduce the stringing. The holes in general were smeared somewhat, mostly due to a soon-to-be-fixed software bug which resulted in the extruder not being turned off at appropriate moments.

In the previous post, you can see the part starting to curl like a king-size mattress being stuffed into a queen-size fitted sheet. The curl is not very pronounced, but did distort the 8mm holes making the insertion of an 8mm rod very tight indeed - you can see shavings on the end closest to the camera. The nuts fitted into the rectangular slots at the top without a problem. The other holes were a little tight and required gentle persuasion to drive the nuts home - a bolt and very large washer was used to winch them in.

What didn't fit was the nut down the channel in the 8mm hole. My reaming didn't clean that out enough and I had to resort to a dremmel tool.

It near enough works and I'll be building it into a Reprap as soon as I can.

I'm extruding in 0.55mm layers, 1.62mm outline size and 0.73mm infill size from a 0.86mm nozzle. Max x-y movement speed is set to 238. This gives fat outlines, but because of the jerky movement between points by the head, curved lines are fatter than straight lines and the slow speed minimises the difference in width.

A very respectable 0.5mm width wall was printed by mistake during a buggy phase of this printout when the nozzle moved without being turned off, but this is good as it shows what the hardware is actually capable of - even with a 0.86mm nozzle.

Vik :v)

Labels: bracket, idler, pla, x-axis

Here's the pretty side of 11 1/2 hours of Reprapping. You can see that the PLA started to curl - I'm not cooling layers here so I might have to get that working again.

The paper tube is because I realised half way through that the hole for the axle was not Reprap-friendly as it was not pointed. So I quickly rolled up a bit of the nearest thing to hand (a Catalyst compliments slip as it happens) and poked it in the 3/4 complete hole. I had to roll it around a bit of 6mm rod as a guide to slip it in.

The Reprap-friendly hole shape is quite clear in the top right corner. The loops on the left edge are caused by the nozzle erroneously seeking warmth in its corner due to temperature reading bugs.

Anyway, I'll tidy it up and take some pretty photos tomorrow. Kinda tired right now.

Vik :v)

Labels: bracket, idler, x-axis

Appologies, this has been a bit slow coming - I've had the lurg. The final repeatability test for Darwin: here we're looking at the performance of the x-axis after mouding a gear diectly on to the motor (see the previous "Darwin's X-axis toothed pulley" post). Results are, again, looking promising with repeatability to ±0.025. Again, a further test is needed at a later date to understand how asymptotic the trends are, but as with the other two axes, we're in the right ball park here.



Next on Darwin's todo list.. home sensors, wiring & documentation.

Labels: darwin, gear, performance, repeatability, reprap, x-axis

The last gear problem for Darwin, casting a 12 mm gear to fit on a 6.35 mm motor shaft. A flat was needed to ensure no slippage on such a thin shaft. Final solution was to use the same kit used to make the Y gears (see previous post). The collar was prepacked again, but this time, becasue there was a bit more wall thickness, the hole was simply started by working a screwdriver into the capa. The collar was then put into the pot with a new blade part which fitted the motor shaft profile. The motor shaft was then poked in from the back. Worked first time.

This was then complemented with Vik's superb idea of a washer + bit of capa for the second lip.



Next: a repeatabiltiy test for the X. Though I need to solder up a universal PCB first...

Labels: casting, darwin, gear, toothed pulley, x-axis