June 9, 2011
Generally most things print pretty well… with the exception of the small RepRap pulleys which need a lot of ‘cleaning’. I could feel some backlash in both pulleys when the motors weren’t powered up. So, like other folks, I put a pencil on the nozzle and plotted an 80 mm diameter circle with fill.
I used the lash option in SF 40 to compensate but pulleys looked a bit odd. So I designed up some crude adjustable belt tensioners in openSCAD which I could fit to both y-axis and x-axis without dismantling anything (except loosening the x-axis belt to fit the tensioner!). The x-axis one fits under the prusa x-carriage onto existing bolts and the y-axis one fits under the bottom plate using the belt clamp bolts.
Y-belt tensioner (the bolt is too short so there are some other bits jammed in to raise the belt a bit more!):
Printed pulleys (left to right, original, SF40 lash, tensioner, tensioner with more tension):
It mightn’t be that obvious from the photo but there is a decent improvement, although there is a bit more tuning to do!
May 25, 2011
The repstrap I put together a few months back used laser cut gears to couple the steppers to the leadscrews. I printed some pulleys on it for the Prusa build but they weren’t precise enough. So I laser cut some instead!
Someone asked my about them so I thought I’d write it up and take some photos. I used openscad to generate dxfs of each of the three different profiles in the pulleys (3 different heights) and the gears (see GilesBathgate’s blog). The first ones weren’t strong enough so I increased the base size and used drilled holes for nails to take the strain. Here’s some photos of putting them together…
gluing the parts:
Gear glued and using screws to take the turning forces:
Gluing teeth together and using nails to take force:
Gluing and ‘nailing’ base parts:
Clamping pulleys for glue to set:
Finished pulleys with nails cut to size:
On a side note I’ve listed some printed parts for sale on eMAKERshop. Also eMAKERshop are rasinig funds to sell Huxley kits here: http://igg.me/p/26971?a=130847&i=shlk.