Tree Journeyman 310 - Terrible Z-Axis Backlash

Hi everyone,

I've got a Journeyman 310 that I am working on. Everything seems to be okay except for some terrible backlash on the Z (vertical) Axis. Terrible like 1/4". There is a side panel that can be removed to see the Z-Axis leadscrew (or is it a ball screw?) and when jogging up and down, the screw itself lifts up and down a little while turning (the spindle not moving vertically), then as I continue to jog, the up/down motion of the screw stops and the spindle begins to move vertically as expected.

My theory is that the Z-Axis screw is not being retained properly. I see from looking at videos and manuals for the Journeyman 325 (couldn't find one for the 310) that these screws are supported at the top by a pair of bearings. I am guessing that's the case here, and that the bearings aren't tight, or one is worn, or even missing.

Does this sound like correct reasoning?

I don't have the manual for the machine, and I don't want to take too much apart without knowing what I am doing. In particular because it looks like I'm going to have to move/remove the spindle motor/transmission assembly to get access to what I need access to.

I see that a few people here have the 310. Could someone give me some basic instructions for how to access this part of the machine? Maybe part numbers for the bearings and where to get them (compatible parts are fine if they work). I'd also love to get a picture of that part of the diagram from the manual. If someone really wants to be my hero, a video of how to disassemble and replace/adjust those bearings would be amazing!

Thank you so much for any help or feedback (including if I have made any forum faux pas, as I am new here)

If pictures or video of the problem would be helpful, please let me know and I will provide it.

Hi

I don't know anything specific to a Tree mill. Most of the CNC converted knee mills whether factory or retrofit attached the Z axis ball nut to the quill with single bolt and a stud. Many times excessive Z axis (quill) backlash is cause by this bolt coming loose or failing. You will need to remove any cover that is over this area to get to it.

John

Hi John, thanks for the tip. I just checked and ball nut is attached to the quill with two bolts that appear to be solidly attached. There doesn't seem to be any play between the ball nut and the quill, but I can see the ball screw move up and down a little bit in addition to turning, which is what makes me think the screw is not being held properly.

Hi Michael,

I have a J310 built in 1986 and I was lucky to get the owners/maintenance manual when I bought the machine. Find attached photos of the drawings I have for the Z-axis lower head assemble.

Attachment 321066
Attachment 321068

Hope these help! If they are not useful I can scan them and attach better images...

Mike

Mike! That's awesome, thank you! If it's not a lot of trouble, scanned images would be great, but it's cool either way. I really appreciate it!

I think I can see in there a double bearing arrangement to capture the Z-Axis ball-screw, which is what I was expecting. I think that's where my problem lies. This gives me some more confidence to move forward.

I still need to figure out how to actually get in there. The spindle motor/transmission assembly is kinda in the way, and it looks like the bolts for that are inside, so maybe I would have to actually take it apart to get it off? I might be able to get what I need without removing it, not sure yet. I've removed the covers on the top and side of the Z screw, removed the bolts from the pulley, but the pulley doesn't seem to want to come off (I haven't applied leverage yet) maybe the little key needs to be removed first?

It's a little unfortunate that the manual gives names for the parts, but not part numbers or dimensions or anything like that.... where do people go to find parts for old machines like this?

Michael,

Find attached better scans of the diagrams you need. I also attached the instructions for removing the entire head which seems to be very simple other than working out how to sling the head... Hope this helps!

Good luck!

Mike

Well you are officially my hero (sorry Dad!) thank you very much for doing this for me!

Including the instructions was especially helpful. For example, I didn't know the front panel was anything other than decorative. Also helpful is the description of the parts, now I have something to google. I didn't know what a split taper hub was and what the additional threaded holes on it were for, now I do. That right there has already saved me a lot of frustration.

Okay. With a herculean effort, and a few new tools, I was able to lift the spindle assembly off the top, remove the split taper hub, and pulley. I kept disassembling and found I was able to remove the lock nut on the Z-Axis ball-screw with hardly any effort. I did it with my bear hands without even holding the ball-screw in place. In other words, the lock nut was super loose. Upon further inspection and a little googling, it became clear that the lock washer was supposed to have (at least) one of its tabs folded up into the lock nut to keep it from coming loose. This either wasn't done, or the tab that was bent up had since broken off. I think that explains the backlash I was seeing. I was happy to see that the bearings appear to be in good shape.

So the repair seems pretty straightforward at this point: tighten the lock nut back down, fold up one of the remaining lock washer tabs and put the whole thing back together.

My question now (mikecolee, maybe you'd be so kind as to see if the manual is any help on this) is how tight do I need to make it? Is there a torque rating? Or just hand tight? I'd like to avoid guessing, putting it all back together, and finding I guessed wrong. Even if I guess, I'm sure the machine will be tons better than it has been. I'm very excited to have it usable again!

Thanks again for all your help!

Michael,

I am away from home presently and will not return until Sunday the 12th... I am happy to check the manual then. Perhaps someone else will have advice for you regarding how tight this nut should be. Happy to hear you have made progress! Must have been a PITA to sling the head off the machine.

Mike

Thank you, I'd appreciate that.

Yes it was a bit of a pain to get the spindle motor assembly off. It required securing webbing to the rafters (in a big triangle as the spot just above the machine was blocked by a large heater) strapping the assembly, buying a chain block, and using that to carefully hoist the whole thing up. Also, I had no really good way to determine where the center of gravity would be, so it tilted back as it came off (thankfully it was secured well enough that it didn't fall.)

If you are able to take a look at the manual for me, I'd appreciate it. Work on the machine is going slow because I don't actually have much time to work on it. Right now I am trying to figure out where to buy, or how to fabricate a tool to tighten that nut...

I've got the machine partially reassembled now and I think I've got it right now. I still need to tighten everything down and run a few parts to be sure.

So many times I've been searching a forum for help, and I find someone who has the same problem, but they never report back how they got it to work, so I am going to try to do that here.

First, it was helpful to be able to see the problem. I was able to do this by removing the cutting head, and bringing up the table to support the Z-axis (I had some firm plastic between the two so there was just a little give and less risk of forcing or breaking anything.) with the Z-axis thus supported, I found I could turn the Z-pulley by hand and it would turn a little either way with very little resistance and without any corresponding vertical movement from the Z-axis. This was easier than my previous method of turning the pulley with the Z unsupported and trying to watch for a certain tell-tale drooping. So now that I could see clearly that there was some play, I tried tightening down the lock nut to make that go away. It improved, but did not eliminate the problem.

At this point it was clear there was something else going on. I had originally assumed that the part that I call the "Bottom housing" in my drawing was attached to the frame of the machine, and so, had tried to install it from underneath. That's really awkward, and I had put the part I call the "Bottom conical bearing surface" in at an angle without realizing it. Now I lifted that whole assembly (labeled "assemble in one piece...." in my drawing) out and saw my mistake. I took that apart, cleaned everything, put it back together as one piece and put it back on the ball screw. One thing I did notice is that if I tightened the bottom housing down all the way, the bearings would jam, so my compromise was backing them off just a little. That's not ideal, but we'll see how it works for now. Thread locker might be a good idea there, or maybe I need new bearings? I anchored that to the machine, and now went back to tightening down the lock nut.

Success! Now I can turn the pulley back and forth with no apparent play, and an immediate movement from the Z. I lined the lock nut up to the nearest lockwasher tab and bent that up to retain it. Running it with the servo seems to respond as I'd expect, without the backlash visible before.

Thanks everyone for your help. In particular, thanks Mikecolee!

Attachment 324372

Ran some parts last night. So far so good! Did not see any obvious issues with the Z! (though these were not precision parts)

I'm not sure if it's in my head or not, but the spindle motor sounds a little noisier than before.

Also there seemed to be some weird sensation (bumpiness) on the spindle break, but when I went back just now to check, it seemed smooth.

I might take the spindle motor and transmission assembly apart too to make sure I didn't mess something up in there.