8530 Y Axis Problem

Richard,

First, I'm a little more familiar with the 8530 than I thought earlier. I had it temporarily confused with the horizontal mill. I don't have a manual on the 8530 but do have the 8520/8525 manual. And my understanding is that the area that we are concerned with is the same on the 8520 and the 8530 Just today, in fact, I noticed that on the last page showing the cross feed (Y-axis) screw and nut, and the knee, there is nothing shown as holding the nut to the cross slide above. The screw that holds it, 696-018, is shown on the previous page.

None of this really makes any sense. If the error were due to variable pitch due to differential wear in the screw, it would repeat. If the error were due to failure to take up slack or backlash in the cross feed screw and nut after the first slot, all of the rest of the slots would show the same error, not progressively greater. The only three things I can think of that would cause a progressively shorter slot would be that the table was getting progressively farther away from the column as it moved from right to left, the part is not held down parallel to the X-feed motion (which would also mean that the slots wouldn't be perpendicular to the edge that the cut started from) or that the part is gradually moving on the table during or between each slot.
 
Terry,

Access to that thread would be great. Please recommend a kit if you can. I appreciate your description of the differentiation between the glass and magnetic DROs. See, I'm learning something here ahead of the curve.

Looking forward.......
 
wa5cab said:
Richard,

First, I'm a little more familiar with the 8530 than I thought earlier. I had it temporarily confused with the horizontal mill. I don't have a manual on the 8530 but do have the 8520/8525 manual. And my understanding is that the area that we are concerned with is the same on the 8520 and the 8530 Just today, in fact, I noticed that on the last page showing the cross feed (Y-axis) screw and nut, and the knee, there is nothing shown as holding the nut to the cross slide above. The screw that holds it, 696-018, is shown on the previous page.

None of this really makes any sense. If the error were due to variable pitch due to differential wear in the screw, it would repeat. If the error were due to failure to take up slack or backlash in the cross feed screw and nut after the first slot, all of the rest of the slots would show the same error, not progressively greater. The only three things I can think of that would cause a progressively shorter slot would be that the table was getting progressively farther away from the column as it moved from right to left, the part is not held down parallel to the X-feed motion (which would also mean that the slots wouldn't be perpendicular to the edge that the cut started from) or that the part is gradually moving on the table during or between each slot.
Click to expand...
 
Robert,

Parallelism is not the issue. I am so careful on this, loath to change a perfect set-up of my 6" Kurt 688 vice, though occasionally I must change for some 45 degree slots. Getting perfection takes a little time on some occasions. Sometimes we get lucky the first try. I use a lighted sensor to check my work. I always work towards zero tolerance. My customers expects all like parts will be interchangeable on all like machines, and they should.

The X axis functions perfectly. This is the axis I think would be showing wear first. I am surprised by the Y axis acting up before the X, though they both do endless repetitions within a fairly small range of travel. Come to think of it, maybe the Y axis is doing the lion's share.

The travel distance between the slots I am machining is typically in a range of 2.0 mm to 4.5 mm. To lose .003 on the X axis between one slot and the next, the table would be visibly and obviously more than 10 degrees out of alignment.

Nothing gets loose in my Kurt 688. The way I machine the .030 Delrin is by laminating it to .25 " expanded PVC with 3M industrial contact adhesive. I precisely machine .591" x 6.0" strips (billets), making sure they are .591 at both ends. I stock them to make the wide variety of combs required by my customer. I clamp the strip in the vice, resting on parallels to get the required clearance above the vice jaws, the majority of the .25" PVC engaged in the jaws. I install a stop in the jaw to give further protection against the strip shifting on the X and as a backup reference in case there is a reason I might need to pull the part or change mills during the process. After machining the comb profile, I carefully pop the finished Delrin product off the PVC with my fingernail (and a little firm effort) and clean it in solvent, debur as necessary while inspecting under a magnifier. The lamination is not shifting in any way. The .o23" dia. cutter is spinning at 3250 rpm and makes negligible lateral force as it passes through the Delrin, insufficient to cause shifting of the lamination by creep of the adhesive bond.

I am going to look into the difficulties of checking whether that fastening screw for the Y screw nut has come loose. Not sure what that will entail. Back to the manuals. Meanwhile, I did still get a lot of production done yesterday. Time to head out to the shop. Coffee's done.
 
OK. I didn't know what the distance between slots was.

I think, from looking at the 8520 parts drawings, that to get at the screw holding the cross feed nut, you will have to remove the table.
 
Robert,

Big news: The access to the set screw for the Y axis screw nut is from the front of the table. There is a centrally located hole accessed through the compression plate that holds the Y axis, rubber, way scraper to the front of the X axis bed. It provides access to a 3/8" Allen set screw about three inches in.

Here is the interesting part: My set screw was backed off a full half turn. I think I have found my discrepancy. As soon as I have time, I will verify this.

Meanwhile, back to work.

Rick
 
Well, I hope so. At least you found something to "fix". :) It is still weird, though, that it seemed be so consistent.
 
Robert,

While fingers are still crossed, and I walk in from the shop at 6:58 pm, after a long day of buffing tiny PEEK dispenser parts, I am hopeful this answers my problem.

I can only thank you and Terry for encouragement and particularly that lead about the set screw for the Y axis nut.

Whew! Time to make something yummy for dinner. My sweetie just pulled in the driveway.

Rick
 
If tightening the nut hasn't fixed your problem, you might give Clausing a call. They still stock some parts for the 8520/8530. A leadscrew and/or nut (if they have them) will likely be ridiculously expensive, but it sounds like they'd pay for themselves in your case.
 
I never gave a thought to the setscrew! Hope it helps to resolve your problem.

Richard Melloh said:
Terry,

Access to that thread would be great. Please recommend a kit if you can. I appreciate your description of the differentiation between the glass and magnetic DROs. See, I'm learning something here ahead of the curve.

Looking forward.......
Click to expand...

The link to that thread was in the post where I brought it up. All you need to do is click on it and it will open in a new window.

Sorry I was't more on the ball on this thread this week - I was out of town for work so ended up falling behind, so to speak.

Looking forward to seeing how this all plays out.
 
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