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Spindle tram on a CNC

Donkey Hotey

Stainless
Joined
Dec 22, 2007
Searched around and nothing quite covering this. Subject is Haas but, could be applied to any CNC where the spindle is screwed to a machined face. Could be vertical or horizontal. The basics apply.

On the four Haas verticals I've dealt with, the spindle cartridge was shimmed at the factory using plastic sheet shim stock. In the two I tried to tram (more than ten years ago), we ordered a plastic shim assortment from McMaster.

To adjust: loosen the screws attaching the spindle, remove and replace the plastic shims already in there, torque the fasteners, measure the results. It was hours of trial and error to get a 3-5" sweep to be below 0.001" run-out.

Even 0.0005" will leave undesireable witness marks and wavyness when using large face mills. I would like to get to around 0.0002" in 4-5". This works out to the bolt circle of the mounting flange or a 1:1 relationship between shims and results.

The problem is not being able to find shim stock in less than 0.0005" increments. Say you picked 0.003" as the nominal thickness. 0.0025 and 0.0035 are available. That will get you to splitting a quarter thou (0.00025") one way or the other. That's great for the back and the front of the tilt but, what do you do to fill in the smaller gaps around the spindle? I ran into this the last time and we had to settle on 'good enough' and move on. Wondering what others have done.
 
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Does the spindle not fit up into a "cartridge" bore on a Haas?


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Think Snow Eh!
Ox
 
I have never had the spindle out of any of these machines. This is a picture from ebay.

Haas Spindle.jpg

From the O ring and the short flange, it looks like it probably does engage a short bore in the casting. Semi-circular, precut plastic shims are used between the screw holes to achieve squareness.
 
Looks to me like it fits in a bore for at least 6".

What does cocking shims under the flange doo - other than test the ductility of the flange it'self?


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Think Snow Eh!
Ox
 
Have you checked that the z axis is perpendicular to x and y before you start shimming the spindle? Maybe the column is out of square, similar results when taking a facing cut.
 
I promise you all that I have seen and done this to two, brand new Haas verticals from 2010. There are plastic, sheet-stock shims in there that accomplish the final orientation of the spindle. They're in there from the factory, nicely die-cut and everything. They are different thicknesses and they interchange them to get it into final spec.

 
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The video attached to that procedure....
View attachment 398054
That only addresses the casting squarness and not the spindle tram. Column squareness to the table is a different thing than having the cutter true to the table. That video assumes it was once trammed and remains correct.

Maybe I'm not communicating clearly: I know how to measure and shim the spindle. What do people use for shims when the minimum jump between shims that I've found is only half a thou? If I use a half thou increment shim on one side, I'm going to need a 0.0001-0.0002 jump for the first bolt position in between and a 0.0002-0.0003 for the next shim behind that.

If those shims aren't available, what are people doing to correct it?
 
I would be putting shims between the headstock casting and the "truck/skate" that rides on the linear rail, before trying to shim a cartridge spindle's flange.

That's assuming the Z travel is square to the table.

We have machines with "head sag", z travel is very square but spindle tram is not. On one machine, we shimmed it, at the skate/truck/guide, whatever you wanna call it, to correct it.

Plus if you only need to shim for a .002" error over 10" and the skates are 20" apart, you only need about .004" shim on the bottom skates. Much easier to shim with larger shims than trying to get gradually decreasing thickness shims around a flange.


This only works with linear ways, by the way.

If you had a similar issue with a box way machine, I wouldn't be looking at the spindle, I'd be looking at how worn the turcite is. That'd be the biggest contributor to head sag on a box way.





I agree with Ox that you're just cocking and warping the flange more than anything. You might get some sort of improvement but it surely isn't the way I would do it.

How much clearance is standard for the bore that a cartridge spindle goes in? The only time we removed one for a rebuild, seemed to be a pretty close fit, and that was on a taiwanese machine.
 
I agree with Ox that you're just cocking and warping the flange more than anything. You might get some sort of improvement but it surely isn't the way I would do it.

Again, the understanding is not clear: I am not the person making the decision to use this method. Haas engineering made that decision. They all come this way. That's how they're built and aligned. Whether I change the shims or not does not alter the fact that they're in there and are varying thicknesses to achieve alignment.
How much clearance is standard for the bore that a cartridge spindle goes in? The only time we removed one for a rebuild, seemed to be a pretty close fit, and that was on a taiwanese machine.

I have no idea on the clearance or the fit but, if their service procedure calls out this method, one has to assume the clearance allows for it.

If you want to compare to shimming linear guides, the same would apply and I'm very interested. I shared elsewhere that my TL-1 Lathe has about 0.003" of bed twist in 30" that will not come out with leveling. I plan to shim the front guide to correct that. The screws are something like 4" spacing and will need incremental shimming along the way. 0.001" per foot means 0.0005" increment at the 6" mark is the only shim I can use without introducing steps.
 
Again, the understanding is not clear: I am not the person making the decision to use this method. Haas engineering made that decision. They all come this way. That's how they're built and aligned. Whether I change the shims or not does not alter the fact that they're in there and are varying thicknesses to achieve alignment.


I have no idea on the clearance or the fit but, if their service procedure calls out this method, one has to assume the clearance allows for it.

If you want to compare to shimming linear guides, the same would apply and I'm very interested. I shared elsewhere that my TL-1 Lathe has about 0.003" of bed twist in 30" that will not come out with leveling. I plan to shim the front guide to correct that. The screws are something like 4" spacing and will need incremental shimming along the way. 0.001" per foot means 0.0005" increment at the 6" mark is the only shim I can use without introducing steps.

Sorry, I somehow missed the link.

Seems dumb to me. But I guess if thats how they do it, then thats how they do it.

I guess they'd have more than a thou or two clearance in one of those.
 
Fadal also used shims under the spindle flange to achieve a decent tram. That they and Haas use similar methods says much.

On a linear guide machine the shims are typically plates ~2mm thick that are ground to thickness as needed to achieve accurate geometry. All one needs is a decent grinder and operator and adjustments of .0001” are not a problem.
 
You fella's can open that vid link?

Looks like a pic to me.

???


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Think Snow Eh!
Ox
 
That doesn't have anything about shimming the spindle cartridge FLANGE.

???


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Think Snow Eh!
Ox
 
On a linear guide machine the shims are typically plates ~2mm thick that are ground to thickness as needed to achieve accurate geometry. All one needs is a decent grinder and operator and adjustments of .0001” are not a problem.

This sounds like a good solution. Grinding a custom shim is a better and more sturdy answer than the plastic shims. I'm not opposed to doing that. I wanted to ask here because I hate reinventing the wheel and later discovering there was a $50 solution that could have done the job.

This thread was part of what also got me chasing this:

 
That only addresses the casting squarness and not the spindle tram. Column squareness to the table is a different thing than having the cutter true to the table. That video assumes it was once trammed and remains correct.

Maybe I'm not communicating clearly: I know how to measure and shim the spindle. What do people use for shims when the minimum jump between shims that I've found is only half a thou? If I use a half thou increment shim on one side, I'm going to need a 0.0001-0.0002 jump for the first bolt position in between and a 0.0002-0.0003 for the next shim behind that.

If those shims aren't available, what are people doing to correct it?
Oh no I'm sorry I was just pointing out how funny it was that they linked a video with "DO NOT PUBLISH" in all caps in the name.
 








 
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