Thank you for the extensive feedback. Where to begin...
ahaer wrote:The motor shaft is 7mm to short. That is if the motor shaft were 7mm longer it would go through the entire gear.
You could pick up 3mm moving the bearings/gear/belt 3mm closer to the wood. That would leave you with 0.2mm space between the back gear flange and the wood. It is 3.9mm from wood to the back of the 608's
That's great, I show the shaft is 12mm short in the model, and only 1.5mm clearance behind the plate and flange in the model, so I can certainly shorten the plate by a couple mm to help.
ahaer wrote:The only modification I made to the existing wood was to cut this notch. Using this notch I was able to put and the bearing on AFTER the y-axis was re-installed and tighten the set screw by inserting a normal allen key at a ~30 degree angle. Given the large flange on the GT2 gear from PrintrBot it is NOT possible to install the bearings after the gear because they overlap soo much. This would mean if I installed the GT2 and bearings before the re-installing the y-axis the clearance hole would have had to be big enough for the GT2 PLUS BOTH bearings..
Love the notch for access the set screws after assembly to adjust the pulley position, or simply tighten the set screws. Good suggestion!
If you install the gear with bearings to get the position on the shaft, remove the bearings, insert the pulley thru the Y-axis plate, and re-attach the Y-axis plate you should then be able to drop the bearings in from the top into position and insert the screw to anchor them. I used the same method on the MXL setup where the bearings sit inside the flanges, and I can install/remove the bearings after complete assembly.
Now for the X-axis:
ahaer wrote:One very important point if you try this mod - your printer must be calibrated for you to have any hope of the main part fitting! I think my z-axis was a little "long" so I had to spend a while filing the tabs to get the part to fit with the wood parts.
I have to admit, I made the part thicker after making the one on my machine. Mine came out way too thin, but maybe my Z-axis is off calibration the other direction. I made them 1/4" thick to match the wood, but I'll adjust the thickness to allow for some calibration error on the Z. A little thin works, but a little thick adds lots of cleanup. The X & Y still have to be calibrated fairly well to minimize rework.
ahaer wrote:A undocumented modification to a wood part is required to make this work. With the printrbot GT2 gear the large flange (17.75) mm would rub against the bottom. I had previously cut out this hole so that I could see the motor shaft shaft from the bottom. You may need to do the same. IMHO this is worthwhile thing to do in any case so that you can see what is going on.
The 17.75mm flange is larger than the pulley I had on hand which only measured 16mm. With the 17.75mm flange you should theoretically 1mm clearance between the flange and bottom wood piece, but as we have seen reality rarely follows theory. I can move the motor pulley up to allow for more clearance. The lower motor position is a carry over from the MXL design and not necessary here.
ahaer wrote:There is one problem with this modification as it currently stands: There is a significant reduction in y travel (30mm) when the belt support pieces hit the bearings. Note the amount of unused rod to the left of the bearings
The fix for this problem is to rotate the y-axis rod plate 180 degrees so that the tabs are in front and make new belt support tabs. In this configuration the plate AND the bed move forward enough that the bed doesn't have to be raised over the bearings. This means less wobble and less new parts required! Now that I've got things back together I'll work new x-belt supports
I believe it is obvious, but there is a typo, there is a reduction in the "X" travel. Extensive write-up, great pictures, we can overlook this one...
I missed the reduction of travel in the X axis altogether. Took a long look at the Y axis to make sure the bearings did not hit the end supports, but then completely neglected the X.
Great suggestion on turning the X base plate around. It looks like if you turn the base plate 180 degrees, keep the top plate orientation the same (it's not symmetric), and come up with new belt ends, the 608 bearings will sit just behind the top plate, the GT2 pulley flange will fall under the top plate, and the Y axis limit is 1.2mm from the back edge of the plate. It's tight, but certainly possible. Also, if you use a glass plate on top, it can overhang the bearings and belt with ease.
Ahaer, thank you again for the extensive feedback.
Anybody else with success / failure please let me know.
In the mean time I will get going on Revision A to correct all the above.