Aligning ball screws?

[jgourlay]

Gents, this is off topic, but I'm posting it because this is the only place on the web where I think folks have the expertise. So, please forgive the bunny trail.

I have a Dewalt D735 thickness planer. Basically, it's a large box with a long rotating cutter supported over a flat surface by four stationary ball screws. There is a drive belt that goes around all 4 ball screw nuts. This belt is driven by a handwheel on the outside of the upper box and the nuts are in the box.

Turning the handwheel drives the belt. The belt drives the ball-screw nuts, which makes the box go up and down. It's critical to note that the function of this arrangement to allow the box to ascend and descend in in perfectly coplanarity with the base plate.

Friday, I went to fixing something that caused me to have to take off the base plate. While considering another issue, my evil left hand started brainlessly twaddling with one of the posts. So, note now that I have the box upside down with all four posts sticking up--something like a dead armadillo. Because the posts are not now in the base plate, they are free to turn.

And, of course, as soon as I turned this post the distance between the bottom of that post and the bottom of the other three posts is not what it's suppose to be. So I put it all back together and it's immediately obvious something very wrong because that hand wheel won't turn without a lot of force and I can see the box is now out of parallel with the base plate.

What makes this harder is that the post go into holes in the base plate and you really have hammer to drive them home: it's a very tight fit. Which means I can't just flip it over and hand rotate the ballscrews down until the touch a registered surface.

Now, I thought about putting a gauge bar onto the cutter head and stacking the base plate on that and threading the ballscrews to location. But that turned out badly because there was simply no way to hold everything together to allow the alignment: it was frustrating and ugly.

Do you have some high-speed/low-drag methodology to solve this kind of issue on your machine tools? Any suggestions beyond "take it back to Dewalt and fess up?"

[davidh]

their web site sez 1 year free service. boy are they proud of those 4 ball screw screw shafts. . . . near $90 each/ by the way, the model is a
dw735. would it help if you had a parts breakdown ? i have serviced and repaired many planers but none had 4 corner screws. . . your gonna need to call them and see if they have anyone that can give you advice.

davidh

[Paul Alciatore]

I don't know what tools you have to work with, but perhaps four equal length (+/- a few thousanths) spacers to allow you to align it as the screws engage. Or if the nuts are on the screws, just use a caliper or depth gauge to set them to the same distance above the base and then assemble it. Heck, a length of threaded rod and some nuts may work as a gauge if you can move from one screw to another.

Or call DeWalt and ask how. I assume you have read the instructions and searched their web site for any possible help.

[Rich Carlstedt]

I am not familiar with your machine , but have a thought.
Get 4 precison spacers, as mentioned earlier, like 4 hardwood blocks all cut at the same time on a table saw,
or one big block, sliced into 4 pcs.
Use them to prop up the cutter base
See if the ball screws are fastened with a screw from the top
If so, by loosening the one ball screw, it will turn and allign itself to the nut.
Because the blocks are all parallel, the assembly should regain allignment.
If the ballscrews are rigid, then you have to remove the belt for the nuts to move into a normal position....in my opinion
Rich

[kc5ezc]

I have a similiar problem with my WOODMASTER 18" planer. It has 4 posts driven by a chain and sprocket arrangement. It is 'almost' (depending on your definition of almost) right, but varies a few thou from side to side on wide pieces. No instructions provided. I have been trying to use a DI, but now you guys have lit up the light bulb. I am going to use 123 blocks and adjust to them and see how it goes.
Thanks for the help.

[outback]

The 4 ballnuts need to be in perfect time with each other to keep the table level.

Either the ballnuts have an adjustment or the ballscrews do. There has to be a way to rotate the ballnut or screw and lock it in place when adjusted. Keep the dial indicator handy. You should be able to make it better than new.

Outback

[RobbieKnobbie]

Outback's got it... ballscrew assemblies almost always have a method of turning the nut (or in this case one nut relative to the other three) for adjustment. I'm sure DeWalt made some compromises in their design to bring the price down, but I can't imagine they would have gotten rid of that adjustment.

Outback: considering your expertise, and the location you list, is it safe to assume you have a professional connection?

[jgourlay]

Gents, imagine the look you would have on your face if a guy brought a lathe to you for repair, after HE had tried to 'level the high spots on the ways with an angle grinder'.

That's the look I got when I took it into for repair. For half the price of a new one, they fixed it. It works perfectly now. It had me completely defeated.