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Run out issue on indexer

qrovin

Aluminum
Joined
Jul 28, 2015
We have a fairly new indexer.
No major crashes except broken taps a few months back.
The problem is the body of the indexer is at zero but the part is out of zero by .008.

I have cleaned rechecked the adapter .(its mounted to a 4th axis cnc mill)
Im about to change careers if i dont figure this out soon ...jk (ehh)
 
What type of workholding do you have on there? When you say out, is it runout? Or is it an axis squareness issue? When you say the body, you are saying the outer diameter of the 4th spindle face? What about face runout? You aren't painting a very descriptive picture of you issues here.

In general, when setting up a 4th, you have to make sure it's rotational axis is parallel to the axis you want it to be parallel to (in general the face runout doesn't matter as long as it is low), once that is done, you can then go about setting up and indicating your tooling on the faceplate, and determining the center of rotation location for the work offset. If your foundation (4th) isn't good, you will always be chasing your tail when you put tooling on the thing.

Tip #1, don't just indicate across the face plate with an indicator (this is only good for a rough alignment), strap a joe block to the axis face and rotate the axis checking the block, this will eliminate any "face" runout on the 4th. Make sure to check for vertical nod as well.
 
My apologies for not being very clear.
We are holding mostly round parts with a 3 jaw self centering chuck mounted to the 4th axis.
The face of the chuck as well as the body are all at 0 runout but the part being held is not at zero. When u rotate the part the indicator moves .008 in total.
 
Sounds like to me your chuck isn't running true to the center of the fourth. I use and adjustable chuck on my indexer for that reason.
 
My apologies for not being very clear.
We are holding mostly round parts with a 3 jaw self centering chuck mounted to the 4th axis.
The face of the chuck as well as the body are all at 0 runout but the part being held is not at zero. When u rotate the part the indicator moves .008 in total.

Is it square to the axes? Have you indicated the chuck properly, the jaws don't necessarily hold on axis to the chuck body, clamp up a round bar and indicated the chuck in on a few different diameters.
 
Was the part indicated / adjusted to have zero run out when spinning the 4th through a few rotations?

My 4ths usually have a 3 jaw, scroll chuck adapted to the face.
The chuck body, (or adapter mount) should allow for concentricity adjustment, via 4 (+-) set screws.

**Tip** number the screws 1-4 so you will know what screw to adjust, as you take readings.
**Tip #2** If you cannot indicate the actual part when dialing in concentricity on the chuck, use a piece that is close in diameter to the part. This takes out much of the error on the scroll.

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If your chuck is indicated true to the 4th, and you part is STILL out 0.008" then you might have a flaw in the 4th itself.
A quick check of the face plate, through hole ID (when rotated) with an indicator, should reveal any issues.
 
My apologies for not being very clear.
We are holding mostly round parts with a 3 jaw self centering chuck mounted to the 4th axis.
The face of the chuck as well as the body are all at 0 runout but the part being held is not at zero. When u rotate the part the indicator moves .008 in total.

is it a 3 jaw universal scroll chuck ? scroll could be dirty, damaged or jaws not in correct slots.
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on a horizontal cnc then there is center of index of rotary table to the spindle. there are basic tests to adjust common work offsets and grid shift values on parameter screen so X0.0000 is centered to rotary table rotation axis. i use a mag base and .0001" indicator with a test bar in spindle and find the average runout spots on spindle to indicate too. hard to describe but normally tests are shown in the manuals. other test is Y.0000 even with top of pallet/table and Z.0000 end of spindle centered of rotary table rotation.
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got to check grid shift everytime maintenance work done on the machine, quite normal for it to change .002" or even change .010" at times
 
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Yes it is a universal self centering three jaw chuck with the 4 adjusting screws on the od.
The adapter is 0 runout so is the chuck body . The face is squaref.
I have cleaned the everything save for dismatling the chuck itself.

Would it be possible that the actual scrolls be damaged ?
I do remember one time i misprogrammef a drilling cycle went into at rapid speeds on z axis .
 
Yes it is a universal self centering three jaw chuck with the 4 adjusting screws on the od.
The adapter is 0 runout so is the chuck body . The face is squaref.
I have cleaned the everything save for dismatling the chuck itself.

Would it be possible that the actual scrolls be damaged ?
I do remember one time i misprogrammef a drilling cycle went into at rapid speeds on z axis .
.
.
dried grease, chips, rust can stick to scroll and require cleaning
.
some prefer soft jaws they can easily machine to true it. but if its dirt and chips it obviously can move around every time chuck used
 
You set it up so the chuck body has 0 runout? Then are expecting the jaws and scroll mechanism were machined perfectly to match the body?

The jaws aint gonna be concentric with the body. Just chuck a piece of round stock and dial (those 4 adjusting screws) in on the stock.
 
You set it up so the chuck body has 0 runout? Then are expecting the jaws and scroll mechanism were machined perfectly to match the body?

The jaws aint gonna be concentric with the body. Just chuck a piece of round stock and dial (those 4 adjusting screws) in on the stock.

.
i have often seen a damaged or dirty scroll the concentrically changes when you chuck different sizes.
 
So if i “zero the part” it doesnt matter if the chuck itself is not concentric anymore.? M
 
You set it up so the chuck body has 0 runout? Then are expecting the jaws and scroll mechanism were machined perfectly to match the body?

The jaws aint gonna be concentric with the body. Just chuck a piece of round stock and dial (those 4 adjusting screws) in on the stock.


Yeah, indicate to the part, not the body OD.


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