Summary

GT2 belt and pulley mod for Mendel90 by nophead

Instructions

This mod is for the GT2 belt and without an belt twist.

-- UPDATE 09.08.2013 ----
Added tensioner to y axis for dibond model

You need the following vitamins:

2 GT2 pulley 20 teeth 5mm bore http://www.robotdigg.com/product/9/GT2-Pulley-20-Teeth-5mm-Bore
2 GT2 pulley 20 teeth 8mm bore http://www.robotdigg.com/product/23/GT2-Pulley-20-Teeth-8mm-Bore
663 mm + 903mm GT2 belt
http://www.robotdigg.com/product/10/Open-Ended-6mm-Width-GT2-Belt
4 M3 4mm grub screws http://www.robotdigg.com/product/17/M34-Grub-Screw-PACK-SET-for-Timing-Pulleys
4 608ZZ ball bearings http://www.robotdigg.com/product/12/608ZZ-Ball-Bearing
1 M8 cap screw x 60mm
1 M8 cap screw x 45mm
2 M8 nyloc nut
2 M8 washer
2 M3 nyloc nut
2 M3 cap screw x 40mm
2 M3 washer

INSTRUCTIONS:

X-axis mod:

Print Mendel90_gt2_x_axis.stl
Remove the raft and open the bridge layer in the ball bearing hole with a knife.
Open up the bridge layer for screw holes with a drill. (4,5 for M4, 3.3 for M3 screw holes).
Press fit the bearings in the x idler holder
Put the GT2 pulley with 8mm boring all up on the M8 x 60 cap screw - teeths are closer to the cap. Fix the pulley with the grub screws.
Insert the cap screw with pulley into the ball bearings. The pulley is on the top of the printed x idler holder.
Fix the cap screw with a washer and a nyloc nut.
Check if the pulley revolves easy - otherwise loosen up the nut a little bit.
Remove the original x idler M4 cap screw/bearing/washers and the M4 nyloc nut.
Remove the belt clamps on the x carriage
Replace the stepper motor pulley with the GT2 5mm bore pulley
Put the nyloc nut in the GT2 x idler
Press fit the GT2 x idler on the original x idler assembly and fix it with the original M4 cap screw
Insert the GT2 belt without twist and fix it with the new clamps
Adjust the belt tension with the tensioner on the x carriage

Y-axis mod:

Print Mendel90_gt2_y_axis.stl
Open the bridge layers in the ball bearing hole with a knife.
Open up the forward and upward looking part of the y idler with a knife and clean up everything.
Press fit the bearings in the y idler holder
Push the GT2 pulley in the new idler teeth closer to the right
Insert the M8 x 45 cap screw and fix it with a M8 washer and nyloc nut.
Check if the pulley revolves easy - otherwise loosen up the nut a little bit
Insert the two M3 nyloc nuts into the botton
Remove the original y idler and put the nyloc nut in the GT2 y idler
Remove both y rods and turn the heated bed over
Remove both belt clamps and belt
Insert the GT2 belt through the GT2 idler without a twist and clamp the GT2 belt to the anchors with the new GT2 clamps. The end of the belt should project enough to have five complete teeth showing.
Replace the stepper motor pulley with the GT2 5mm bore pulley
Turn over the heated bed and mount on the y rods.
Mount the GT2 idler with the original screw but just slightly tighten the screw
Put the y axis tensioner over the edge behind the GT2 idler and insert the two M3 x 40 cap screws with two washers into the tensioner and the y idler
Adjust tension of the belt and direction of the GT2 idler with the two M3 cap screws

No firmware changes needed.

I recognized some clack sounds while printing from the GT2 pulleys. These sounds came from the sligtly smaller diameter of the cap screws compared to the pulleys. I fixed this temporary with a little bit of painter tape arount the cap screws where the pulley and the bearings are. Better for now but I'll upgrade to a 8mm rod with two snap rings on both sides.

If you just wan't an upgrade to the GT2 belt but with a twist in the belt you need only 2 GT2 pulleys with 5m bore, the GT2 belts and the GT2 belt clamps.

Mendel90 GT2 mod