Backlash micron clocks

[Seekingknowledge]

I'm Using 1 Micron plunger style clocks but having repeatability issues getting it to return to the same reading when setting, the clock has a fine adjustment wheel on it which feels more responsive in a certain direction than it is in the other so I assume this is some backlash in the rack and pinion which controls the reading? If not this any suggestions what it may be? Everything is thoroughly cleaned. Thanks

 

[Bakafish]

Is there a reason you don't mention the make and model(s) of what you are using? And why no pictures or descriptions of your setup? You also don't specify what material you are measuring or the environmental conditions. Microns are small, there are a million things that could be affecting what you are doing, thermal effects are significant at that scale. Isolating errors requires a methodical and scientific approach, I wouldn't assume anything until the low hanging fruit of improper setup has been picked.

 

[ballen]

Consider trying a Johansson Mikrokator. They have no backlash: https://en.wikipedia.org/wiki/Johansson_Mikrokator

 

[Seekingknowledge]

Is there a reason you don't mention the make and model(s) of what you are using? And why no pictures or descriptions of your setup? You also don't specify what material you are measuring or the environmental conditions. Microns are small, there are a million things that could be affecting what you are doing, thermal effects are significant at that scale. Isolating errors requires a methodical and scientific approach, I wouldn't assume anything until the low hanging fruit of improper setup has been picked.

Sorry it was my first on here and it did lack detail, I work for one of the major CNC machine manufacturers who I cannot name and cannot upload photos of my setup etc as I may be in violation of some part of my contract? The setup however is tried and tested by many people over the years, the temperature is controlled in the work areas to maintain accuracy and the problem occurs when measuring a variety of things on the machine during the various build and test processes we go through (test bars, straight edges, ground faces on spindles, turrets etc) the accuracy of the readings are OK but it takes a long time to get repeatable readings such as a zero starting point when moving on and off the measured face the clock often jumps (obviously moving on and off as carefully as possible) eventually after constant adjusting and resetting it will settle and repeat constantly to zero then we can begin measuring but it seems to me we waste a lot of time doing this and my instant thoughts were that the clocks have backlash and may need to be fixed or calibrated (we have a calibration department who I will bring this up with but I wanted to find out if anyone else has had any issues similar? I am also trying to get the company to order some new clocks so it will be more evident if it is a wear related issue? The particular clocks for these particular tests are MAHR MILLIMESS 1um plunger style

 

[Seekingknowledge]

Consider trying a Johansson Mikrokator. They have no backlash: https://en.wikipedia.org/wiki/Johansson_Mikrokator

Thanks I will have a look into those and see if we can get one ordered to compare.

 

[Screwmachine]

Are you using the cable (or whatever it's called) with plunger to retract the tip? If so, and the setup is rigid and tested as you say, sounds like the indicator could use a service. These are actually quite easy to work on- but I'm a watchmaker; maybe get a new one to see how it stacks up against what you're using. They really aren't expensive considering what they do.

 

[Bakafish]

The particular clocks for these particular tests are MAHR MILLIMESS 1um plunger style

I suspected it might be a Mahr since you said it had a dial adjuster. I don't really see how backlash is an issue for repeatability if you are approaching the measurement from the same direction each time. Magnetism or congealed lubricant would be my first guesses, leaning towards the lubricant as repeatedly moving the dial to the same spot may be wiping a clear area that frees it up.

Create and document the simplest test case that repeatably shows the issue. Document what you expect, and what it is actually showing. Determine if some of them are better than others and then take the worst performing instrument to your service department and provide them the test case so they can validate what you are seeing. Confirm it is fixed using your test case after they have serviced it, if the worst one is fixed it is likely they can fix the others. If it is not satisfactory, try to get them to give you a new one to see how it responds to the same conditions.

 

[TGTool]

This is a long shot but I've often found on setups that are hard to get repeatability on, that the problems is often with the linkage rather than the indicator itself. Of course I've got that one indicator .....