Saturday, June 23, 2012

Unexpected speed -> first tests of the modified printrbot parts...

Before we get to the new part tests, someone asked about bed leveling.  I prefer not to shim between the heatedbed and/or the glass.  What I like is to put the heated bed directly on the platform, place the glass directly on it held in place by tape and not clips (expansion will cause problems).  To level the bed I place a few mm of silicone tubing designed for peristaltic pumps (really springy) between the y-axis bed mounts.  This way 1/4 to 1/2 a turn will cause abount a sheet of paper's thickness change in that corner of the bed.  It's very very stable (no adjustments for hundreds of prints) -> simple, quick, just works (remember to level the bed when it's at temperature).

When I got the three modified parts (see the last post) swapped out and installed I wasn't happy with the way I planned to mount the cooling fan.  While there was a conflict with the standard extruder (there won't be in my upcoming one) making it difficult to put in a nut -> din't matter since the m3 bolts will thread the holes nicely -> I felt it still wouldn't be stable over time...

So I just drilled two quick diagonal holes into the cooling duct through the front two upper holes in my modified extruder mount and fed in two additional m2 bolts -> this solution works really well -> sometime later I will work on updating the design once I finish analyzing the function.

While the fan does work really well for printing small details (I did a bunch of test pieces), once I did the herringbones (came out wonderfully - much better uniformity of detail and alignment) I moved onto speed tests.

Usually I don't print over 25mm/sec but I couldn't find any flex in the new parts (there was a lot in the original parts) I wanted to see what happens whan I increased the speed.  From left to right 50mm/sec, 100mm/sec, 150mm/sec, 200mm/sec and 250mm/sec.  One interesting thing is that above 50mm/sec I have to turn down the fan speed or I get a bit of lift at the edges of some prints -> 50% max speed worked at all the test speeds today -> no lifting.

I really wasn't expecting this to work at all... but it looks like the new designs are better than I expected.  Normally I have slic3r setup for different speeds for lare perimeters/small perimiters/inflil/movement and so on... here I just changed every number at once to the new speed to see where things fall apart.

It seems from the quick tests that I can go to 250mm per second for most parameters but perhaps ought to drop back to 100-150ish for small perimeters.

Over the next days I'll start teasing out what the limits are for the different parameters.

It's such a good feeling to see the little printrbot going at these speeds...