How to take my z apart?

[knight_toolworks]

I have a PRT alpha and there is some slop in the z. well vertical play really. I have had a little of this for most of the time I had the machine a little over a year. But right now it is about .05 slop. When I push down on the z there is no give and it will snap back. But I can lift it up that tiny amount freely.
I got a allen wrench on the pinion and it seems tight so it must be somewhere else. I am nto sure the best way to remove it to check the parts since you can’t access it otherwise. I hate having to take it all apart and getting it all aligned again.

[ljdm]

Is there an adjustment for backlash between pinion and rack?

[knight_toolworks]

thats what I am wondering but getting too it is the issue.

[scottcox]

Steve,

I think the only adjustment for that is the position of the v-rollers for that side of the z. Get those v-rollers set right relative to the pinion and perpendicular to the table, and then snug up the other side.

[knight_toolworks]

I checked the rack today and one screw was loose but not the other. tightened them up and still the issue. I think it has to be the pinion gear I will get another one tomorrow.

[paco]

Is it the rail (T rail) or the pinion to rack that is loose?

[knight_toolworks]

it is all vertical so it has to be the pinion. there is no side to side slop only when you lift up on the z there is a little free movement. I just tightened the one loose screw on the rack and that did not fix it.

[paco]

-Set screw on the pinion could be loose.

-The pinion could be badly worn.

-The motor, which is not spring load from the factory, could be not fully engaged; the pinion is not engaged correctly in the rack. It may have to do with the previous point. I had this problem with my tool; the pinion would engage in about half of the rack but not on the other half no matter what. I made a spring load pivot for the Z motor.

-The motor mounting bolts are getting loose.

-The motor gear box (if there's one) is worn out or damaged.

-The rack is getting loose (very not probable).

-All of the above.

Do you still wonder how to take the Z apart (if required) or are you Ok with that? Most of the above can be troubleshoot (and fix) without removing the Z. Work slow to get the job done quicker!

[knight_toolworks]

I took the motor off the pinion was only about 1/2 on the track fixed that. I put it back on put a clamp on the motor so I could pull it tight and tightened the bolts I have exactly the same vertical slop. the pinion does not move when I move the z up and down the tiny bit it does. so it seems the pinion is sloppy. I ordered a new one.

[paco]

Those are consumables; I suggest you order a complete new set (4).

[knight_toolworks]

Ok time to chew out shopbot. got the new pinion and no go still got the slop. I found out the pinion is not engaging the rack fully. but I found that the rack had a loose screw on top and I was thinking the foam was collapsed because I used a spray lube. but nope it was a missing washer behind the rack. one was there on the bottom but gone on top. so someone forgot to install it.