And could anyone explain what tramming is please?
If the ballscrews are bent then you will get a periodic tightening as you rotate it, especially at either end of travel.
If the ballscrews / mounts / nuts are all mis-aligned then it will have a constant tightening at either / both ends.
Assuming the ballscrew is fairly straight then looking at the design the ballscrew supports and ballnut bracket are probably not completely in line. It doesn't look like you can adjust in the plane away from the sides of the machine, only up and down.
Try moving the machine to the driven end, loosen the 6 bolts holding the ballnut to the ballnut bracket, and remove the floating end bearing. This should allow the ballnut to sit in an unloaded position.
Nip the bolts back up and move the gantry over to the other end. Gently slide the floating bearing back on - it should sit snug onto the mounting block on the side of the gantry. If it is out, fit a shim. If it is tight you need to machine a bit off the mounting block.
Tramming is related to getting the spindle motor normal to the bed so that the side of the cuts are 90deg to the top surface. You can get close by putting a bar in the spindle and using an engineers square to check the spindle is 90deg to the surface on all sides / angles. You can also get a twin DTI block which gives a much better indication of tram condition. Have a read . . .
Last edited by routercnc; 12-03-2016 at 09:52 PM.
I think I've solved the ballscrew problem, re-made one of the BF mounting blocks and shimmed it a little. How hard should it be to push the gantry back and forth on the machine? It takes quite a lot of force to get it going then it still requires a far amount of force to push it...
The mechanical build is nearly complete, just got the back gantry cover to finish!
My one slides fairly easy with the belts off.
Did you try loosening the bolts on the BK & BF then moving the motion to the bK end and nipping them up then move to opposite end and nip the bolts up - there should be no tension on the screw when the bolts pull up.
This worked wonders on my build.
If it is hard to move and stops as soon as you stop pushing then either bearings are faulty (unlikely if new) or more likely is they are misaligned relative to each other.
They are very intolerant of misalignment in any plane. This is why epoxy is popular. One side could be higher than the other side, or they could be the same height but twisted, or they could not be parallel etc. etc. I does not take much to make them bind.
Did you set the first rail against a known straight edge?
Did you then use a DTI to set the other rail parallel to it?
Are they at the same level as each other (use straight edge across bearings and check with feeler gauge)
Loosen the bolts connecting the gantry to the bearings on one side, then see if it improves. If it does you have misalignment.
Time spent getting this smooth will pay dividends in the long run.
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