Reply with QuoteThe pictures are a little fuzzy, but it looks like your gib is way too high to me.
Make sure you follow the prcedures in the manual to adjust the gib or you could have a serious problem.
Mike
Z axis gib
could anyone tell me if this z axis gib is situated properly? it doesnt look right to me, and i'm having some binding issues with the head.
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The pictures are a little fuzzy, but it looks like your gib is way too high to me.
Make sure you follow the prcedures in the manual to adjust the gib or you could have a serious problem.
Mike
yeah sorry about the picture quality, i grabbed some quick pictures while in the shop this morning. thats how the machine was sent to me, so i'm just getting input before i adjust it to where i think it should be, which is think its about an inch and a half to high atm.
Mine is a fairly early machine, so the design might be different, but the top adjusting nut sits on top of the gib.
I also found that it was possible to get the adjusting nut to pass down the side of the gib, without being engaged, if the gib was not correctly positioned in the slot.
With the gib that far out the head/slide should be very loose on the z-axis ways, try rocking the head.
Phil
Originally Posted by 905CustomFab
So, is that where the put that oil fitting now... the one on the side of there used to be in that hole that is right behind the gib screw...
Like Phil, I have one of the early mills (S/N 14 actually.) I've been having problems replacing my Z axis gib recently and posted on the Yahoo group looking for photos such as yours but of a correctly installed gib. I've now pulled and replaced the gib about 4-5 times so I can almost do it with my eyes closed...
Provided that the gib design hasn't changed, the large washer-like part of the gib screw should sit on top of the gib and keep it from coming out like yours is. The gib should be pushed as far forward as possible in the slot otherwise you'll end up with the problem that Phil described where the screw will ride down the side of the gib, and force it even further back. I didn't notice my lower gib screw was doing this until it had thoroughly torn up the bottom corner of my gib. As far as keeping the gib to the front of the slot, I now insert a small plastic tube in the back of the slot before inserting the gib. Works perfectly! The tube is the outside of a plastic push-pull linkage for R/C airplanes, maybe .20" OD or so I would guess...
If you're having binding issues it's quite possibly that the gib is now lodged in there diagonally and is rubbing along the back side of the ways and creating a good bit of friction.
Take a look at the top gib screw and see if the gib is riding along side it.
Take a look at the bottom gib screw and see if it's actually contacting the gib, keeping it up that high.
My z axis has been nothing but a pain to me... It's now looking like the ballscrew is shot. When I wipe the screw with a clean white paper towel it comes away with all sorts of little beautiful sparkly pieces on it... This is just the latest in a long string of issues with my Z axis... When I finally replace the ballscrew the machine will be better than new!!
Sorry, didn't mean to ramble on about my problems on your thread...
Dave
Hi Dave,
It was I that promised you photos of the z-axis gib and didn't do it. Do you still need the photos?
I also had your problem with the z-axis sparkly bits. I replaced the screw under warranty.
I subsequently disassembled the z-axis ball/crew and could see no obvious galling or damage, so it was a mystery.
The x and y-axis screw showed/show a similar but less severe problem but still perform within spec. I don't do that many hours on the machine.
Phil
Here is photo of my Z-axis gib arrangement.
Hey Phil,
I meant to write back to let you know I think I have the gib situation under control now. But thanks for the photo you posted on the yahoo group! I've at least verified that mine is correct now.(Duh... just noticed that you posted it here too... thanks!)
This is the first I've heard of anyone having problems with their Z-axis ballscrew. Guess that's similar to no one hearing of the problems I've had with mine...
So, can I ask the procedure you used to replace the screw? I imagine you blocked the head up as close to the top as possible, then removed the motor, backed the preload bearings out, then pulled off the motor mount box (not sure of the correct name for this part.) I'm hoping after that you should have access to the screws that hold the nut to the back of the Z axis saddle?
Did someone at Tormach provide you with support for this or did you just jump into it? I ask because when I was speaking with Greg a few weeks back he wasn't exactly sure how to get in there to pull the old screw. I'm sure with the people he's got working for him he's got his head into other parts of the business these days and lets someone else deal with these type of issues...
How far out of spec was your z axis? I'm seeing .0035" of backlash, and I've covered every other possible cause. I was able to get the backlash down to .0015" which is within spec, but to do that I had to loosen the gib to the point that it was sticking out over .25" from the top. This caused the gib screw to block the oil fitting there - and also allowed the head to shift back and forth a bit. I've tightened it back up for now and I'm going to live with the backlash until I feel like springing for the $525 for the new screw.
FWIW, my machine has seen maybe 30 Hrs. of use over the past 2.1 years at most so I don't see it as being a normal wear issue. Had I noticed the metal dust on the screw earlier I suppose I could have taken care of it under warranty... Greg was nice enough to send me a new VFD under warranty just recently due to a spindle problem that's been there from the beginning and just kept getting worse...
Thanks,
Dave
Last edited by dammachines; 11-28-2007 at 11:45 PM. Reason: because I'm a dummy...
Hi Dave,
You have to break the head from the z-axis slide to gain access to the z nut carrier bolts. The following procedure worked a treat:
- Raise the head all the way up and disconnect the lube system.
- Mount a threaded stud (see pic) in the table front T slot and a drill chuck in the spindle.
- Lower the head/chuck onto the stud.
- Support the head from the table with wooden blocks just behind the spindle
- Lower the head onto the blocks and lightly clamp the chuck to the stud.
- Remove the 2 dowel pins pinning the head to the z-axis slide.(the dowel pins are threaded)
- Remove 4 of the 6 bolts attaching the head to the z-axis slide and replace with 4 long threaded studs (for stability)
- Remove the remaining two bolts and use the y-axis to move the head away from the z-axis slide.
- Now you have access to the bolts that attach the Z nut carrier to the z-axis slide.
- Disconnect the z-axis motor coupling
- Remove the stepper motor.
- Unlock the lock-washer and undo the preload nuts with C spanners (see pic)
- Press out the ball-screw from the housing bearing using the adapter plate and a threaded bar with nut. (see pic for adapter plate) Actually mine would have tapped out with a wooden dowel.
- Remove the ball screw from the machine.
Tormach gave me a generic procedure for the preloaded bearing mount plus spare bearings, c spanners, lock washers and of course ball-screws. I didn’t need anything else.
My backlash was within spec but the z-axis was sounding a bit “crunchy”. While the screw was mounted it looked like a groove had started to form in the high use area of the ballscrew thread and the assumption was that this was the source of the shiny bits. However after very close inspection (under a microscope) after removal the loaded area on the ballscrew appeared shiny but not worn. My current best guess is that the shiny bits are small particles of cast iron left over from manufacturing (my machine had lots in all the hard to get to places) that have been picked up by the oil on the screw and have then been rolled by the ball/screw.
So if you are not under warranty I would recommend you remove the z-axis screw thwen very carefully clean/flush it and the nut. If there is no visible galling then replace it in the machine and see how it goes. If necessary do the same with the x and y/axis also.
I also removed the gib and slide for inspection as mine had an out of spec forward lean. I stoned the head/slide mating faces and fiddled with the gib to get it within spec on reassembly.
As I don’t use my machine in a production environment I didn’t use the new bearing mount preload nut lock washer on reassembly as it interfered too much with the very fiddly preload procedure.
Regards
Phil
Hey Phil,
I meant to write back to let you know I think I have the gib situation under control now. But thanks for the photo you posted on the yahoo group! I've at least verified that mine is correct now.
This is the first I've heard of anyone having problems with their Z-axis ballscrew. Guess that's similar to no one hearing of the problems I've had with mine...
So, can I ask the procedure you used to replace the screw? I imagine you blocked the head up as close to the top as possible, then removed the motor, backed the preload bearings out, then pulled off the motor mount box (not sure of the correct name for this part.) I'm hoping after that you should have access to the screws that hold the nut to the back of the Z axis saddle?
Did someone at Tormach provide you with support for this or did you just jump into it? I ask because when I was speaking with Greg a few weeks back he wasn't exactly sure how to get in there to pull the old screw. I'm sure with the people he's got working for him he's got his head into other parts of the business these days and lets someone else deal with these type of issues...
How far out of spec was your z axis? I'm seeing .0035" of backlash, and I've covered every other possible cause. I was able to get the backlash down to .0015" which is within spec, but to do that I had to loosen the gib to the point that it was sticking out over .25" from the top. This caused the gib screw to block the oil fitting there - and also allowed the head to shift back and forth a bit. I've tightened it back up for now and I'm going to live with the backlash until I feel like springing for the $525 for the new screw.
FWIW, my machine has seen maybe 30 Hrs. of use over the past 2.1 years at most so I don't see it as being a normal wear issue. Had I noticed the metal dust on the screw earlier I suppose I could have taken care of it under warranty... Greg was nice enough to send me a new VFD under warranty just recently due to a spindle problem that's been there from the beginning and just kept getting worse...
Thanks,
Dave
Last edited by philbur; 12-03-2007 at 06:21 PM.
Hi Dave and Phil,
I have serial #13... still out in the carport waiting to get moved inside the shop. I appreciate you guys posting your Z axis issues so I can inspect mine before putting it to work this winter. I might have 3 hours on mine. Phil beat me to getting his machine on line.
MikeAber
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
hey guys, sorry it took so long for me to get back to you. the pictures i linked before are correct, a guy at tormach told me the new machines are coming with a longer gib in the z axis to give room for more adjustment, so now i just need to figure out why it still randomly binds up. the x axis is starting to do it as well.
