jccaclimber
Stainless
- Joined
- Nov 22, 2015
- Location
- San Francisco
I have a part the size and shape of a margarine tub. I need to measure the roundness at a few different heights on both the ID and OD. Some of the parts are transparent and others are very shiny so my usual laser ranging device isn't getting a good reading. I do have a Tesa gauge head that is consistent around 0.1 to 0.2 microns, assuming very good fixturing. I suspect I'm looking for form error in the range of 1 to 3 microns, so I started by taking a practice measurement on a class X ring gauge. What I found is that my rotary table (small, normally used for rotating optics) has >20 microns of X/Y position error.
I mounted the ring gauge, rotate the table a full revolution, and my measurement differs by 20 microns. Rotate again and it's anywhere in between. The plan was to measure the gauge in a few different orientations to back out error in the table, master ring, etc., but I'm not there yet.
This is something I'm going to be doing many times for a month or two, then infrequently after that. A manual method is ok as I do want to do it in house vs. send to an inspection house with a CMM if at all possible. If I end up needing to send it out I will, but I've had issues with external CMM work not being accurate to this level in the past.
Rotation isn't critical, even 1/4 degree error would probably be ok, but staying centered is important. Would a standard rotary table work for this? If not, does anyone have recommendations on how this would normally be done? I have a good X/Y stage, so getting a part centered to 1 micron for measuring is easy, but spinning it seems to be causing heartburn.
Every place I've ever worked has had a rotary table for mounting on a Bridgeport.....except this one, so I can't just clamp my ring gauge to that and try that out.
I mounted the ring gauge, rotate the table a full revolution, and my measurement differs by 20 microns. Rotate again and it's anywhere in between. The plan was to measure the gauge in a few different orientations to back out error in the table, master ring, etc., but I'm not there yet.
This is something I'm going to be doing many times for a month or two, then infrequently after that. A manual method is ok as I do want to do it in house vs. send to an inspection house with a CMM if at all possible. If I end up needing to send it out I will, but I've had issues with external CMM work not being accurate to this level in the past.
Rotation isn't critical, even 1/4 degree error would probably be ok, but staying centered is important. Would a standard rotary table work for this? If not, does anyone have recommendations on how this would normally be done? I have a good X/Y stage, so getting a part centered to 1 micron for measuring is easy, but spinning it seems to be causing heartburn.
Every place I've ever worked has had a rotary table for mounting on a Bridgeport.....except this one, so I can't just clamp my ring gauge to that and try that out.