Process of finding center of rotation on HMC.

[?Mark]

Fairly simple task, but apparently most machinists don't know how to accomplish this.

Does anyone have an eloquently described procedure for this that they can share?

I'm thinking about writing one for all our facilities, but hoping to find one that is easy on the eyes, read: easy to understand

 

 

TIA

[jlw™]

I have a PowerPoint I did and actually did a whole class on just this. that was 2 jobs back tho, if I can find it I'll share. it'll be later tho, have to check computer at home.

[mkd]

Well, ONE way is to use a machinist's chair

 

@ b90. indicate and zero "relative" X coordinate (fanuc)

rotate to b-90 and indicate chair on same face

1/2 of the relative is centerline.

 

 

Kinda surprising that machinist wouldn't know this. Of course, i've trained people with 20+ years how to indicate-in a 5 axis head and how to find centerline of a large bore with an Interapid in a chuck.

[jlw™]

I taught a guy with "20 year eshpurance" how to read "them c thangs everbody usin".

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Micrometers, for those still wondering.

[?Mark]

ROFL, you guys a killing me here 

 

I actually like a method of cutting a blank material on a tombstone (preferably on top) and finding out/confirming the TLO of the tool as well at the same time. Even better and easier when starting with a new tombstone.

This also helps detect any (wobble) in the b axis (some think their machine is perfect), so there are no surprises later on, lol

[mkd]

ROFL, you guys a killing me here 

 

I actually like a method of cutting a blank material on a tombstone (preferably on top) and finding out/confirming the TLO of the tool as well at the same time. Even better and easier when starting with a new tombstone.

This also helps detect any (wobble) in the b axis (some think their machine is perfect), so there are no surprises later on, lol

seems that facing a tombstone any trying to confirm CoR via TLO is only fooling yourself into thinking you know where it is.

I must have misunderstood what you're trying to say.

[?Mark]

seems that facing a tombstone any trying to confirm CoR via TLO is only fooling yourself into thinking you know where it is.

I must have misunderstood what you're trying to say.

 

 

Nope, I never said that. I said that at the same time when I find my COR i can find my TLO. I'd never attempt to find COR by using tlo and facing the tombstone, lol. 

[jaydenn]

The proper way to determine center of rotation and gauge length requires a test bar of known length and known diameter. You'll also need an empty flat pallet.

 

1. Clamp test bar in spindle.

2. Move machine as close to center as you can by eye.

3. Attach Magnetic base and indicator to table. Orient indicator such that you are indicating the side(diameter) of test bar.

4. Tram the axis get the high spot on the bar.

5. Move the indicator clear and rotate the table 180 degrees and tram the opposite side of the bar.

6. Split the difference, adjust, wash, rinse, repeat until satisfied.

7. This location is the center of rotation....NOW, this is where the "known size bar" comes in handy.

8. Make note of the test bar diameter and make sure your indicator reads zero on the high spot. This value is equal to exactly half the bar diameter.

9. Clear the indicator and rotate the table back 90 degrees.

10. Approach the indicator with the end of the test bar until indicator reads zero.

11. You can now calculate the absolute exact gauge length of your machine to the center of rotation. Bar length is known, indicator zero is half the bar diameter. Add em' up!

 

J

[Matthew Hajicek - Singularity]

Ok, Google is not helping me.  What is a machinist's chair?

[GoetzInd]

Jaydenn is describing the way I do it. Requires a test bar but the most accurate way IMO. 

 

Mike

[mkd]

Ok, Google is not helping me.  What is a machinist's chair?

same here

 

like this, but different. Shaped like a chair for finding a single surface.

Mine was made by SPI

[specv]

Ok, Google is not helping me.  What is a machinist's chair?

 

http://www.flexbar.com/shop/pc/MAGNETIC-SINGLE-EDGE-FINDER-p4838.htm