So I finally have gotten around to installing the Z-Plus I bought in May, and, as the install is going ok for the most part (there were no M3x18mm cap screws for the z-proximity in the kit*), I have found a situation that maybe needs correction? Basically, the rails that the actual z-stage rides on (the part driven up and down by the screw) - those rails are not parallel. They are 0.5mm closer together at the top than they are at the bottom. Does this matter?
The distance between the inner surface of the rails at the top is 75.47mm, the distance between the rails at the bottom is 76.00mm…
Top:
Bottom:
*Oddly, M3 is one of the metric screw sizes I use frequently, so I do have M3x18mm on hand, if it were missing some M4s then I’d be SOL…
Well, I haven’t tried to power it on yet. It does move up and down by hand if I turn the screw, and it is harder to move in the up direction, but that should be expected due to the mass of the stage…
I can disassemble everything and see what I can do to make them parallel, but I don’t want to take it all apart if 0.5mm is within the tolerance expected.
I guess I should ask, if this were your machine, is this something you would try to cure? And if so, what value should the distance between the inner surfaces of the rails/guides be?
If it were mine it would bug me and I’d have a lot of trouble resisting the urge to ‘fix’ it.
However, if it moves up and down the full travel without obvious tight or loose spots and there’s no lateral play then maybe it doesn’t need anything doing to it.
If you power it up and the motor can’t move it up and down properly all that will happen is the motor will make an unhappy buzzing as it misses steps, you won’t immediately break the motor.
I don’t know what the tolerance is on the Z+, maybe some Z+ owners have measured and have some data?
I will note that calibers is not the most accurate for this (too easy to introduce error), also parallelism needs to be measured against the ground datum of the rails and blocks. Traveling/sweeping a test indicator would be a better verification.
If resistance changes when the carriage comes to this area you feel is not parallel then it could be a problem, a torque deflection wrench or digital torque adapter can help detect this as a lead screw is pretty resistant already (low efficiency).
If you have the time (for being down), and there is actually an issue (Z moment is poor/jammed) I would wait for Carbide3D support to respond. If you haven’t handled ball bearing blocks and rails before you could make travel worse, accidentally lose ball bearings from the blocks, etc. You need “ball keepers” to be able to remove the carriage/blocks or you’ll be in a world of hurt.
Loosen the rail screws, run the z from one end to the other to straighten them up (don’t loosen them a lot, just enugh to be able to get thm to move with some force). Then tighten the screws again. You can see them just above the caliper display in the “bottom” picture.
Before you do anything drastic, why don’t you wait for a response from Carbide? No need to try to fix this yourself, if in fact they are not parallel out of the box.
I appreciate the advice, thank you.
I will get it up and running today to find out if there is an issue. Like I said above, I have no idea how far out of parallel the guide rails can be and still be within tolerance for the parts, so I realize I may be making a mountain out of a molehill, that’s why I am asking here to get a larger perspective.
With that said, I would also be disappointed if I ran the machine in a state that induced excessive wear to a part not considered to be replaceable/consumable (the z-stage guides)…
Your idea sounds like it would be a straightforward and logical way to ensure there is a consistent distance between the guide rails, without fully disassembling anything. I will try to get the machine working first though and go from there…
