[BrendanDixon]

Hi All,

Looking on advice on the norms and expertise in calibration of milling machines. This seems to be an grey area in my company so I would like advice on who and how this should be done. We have 2 of 5 axis Zayer milling machines with a Heidenhain control system and 3 interchangeable heads, a direct head, a L head and a 45deg head which has the 5th axis. We have been having issues with mechanics on the heads so then they want to change the heads between the machines. The problem is that the heads do not have 100% identical dimensions so then the head geometry on the head then needs to be calibrated. There are tables for the heads to setup the geometry but no one knows how to do this and what value is for what. There re labels but honestly they do not make sense to me. We also having issues with the one machine in that the geometry of the L head keeps going out after about a month. When we speak to the heidenhain person they are not sure over the phone how to set the geometry. But then we get him on site and with trial and error he eventually get the machine working, but can never really tell what value does what.

This comes down to the maintenance managers wanting this to be done internally. They expect the electronics Technicians to learn what to do but they spend time with the Heidenhain guy buy do not understand what he is doing. the next time The managers expect the electronics technicians to phone the heidenhain guy. so that he can tell them what to do but this always ends up in confusion as no one knows what is going on. and we end up getting the heidenhain guy out.

The staff we have is as follows

Electronics Technicians. These guys have been to university studying electronics.they have no other training and anything else they learn how to do from experience from other people.

Mechanics. These are artisans that have done a 3 year apprenticeship of which 80% is mechanical and 20% electrical. No other training and learn from experience.

Electricians. These are artisans that have done a 3 year apprenticeship of which 90% is electrical and 10% mechanical. No other training and learn from experience.

Operators. The operators know how to operate the machines. Are trained turner machinist artisans. They can operate, write programs and test the machine, change settings for tools. and do measurements with the machines as it has a measuring probe they they can install on the machine. etc So the operators know the most about the machine.

From the technicians they know the electrical/electronics, but do not know anything about mechanical or operation.

Honestly our mechanics and electricians know nothing. They battle to connect wires and mechanics can loosen mechanical things and re assemble basics.

The operators are a mixed batch. We have one operator who was trained by the machine manufacturer and knows the most about the machine.and can you the full operation of the machine. He knows how to write programs and get to the head geometry but is not sure what all the values are for. The rest of the operators know how to operate all the common functions of the machines and basics of programming.

The maintenance management expect that the electronics technicians must know everything about the machine, how to setup the geometry, how to operate the machine, how to program the machine. basically anything that no one knows how to do then it is expected that the electronics technician must know how to do it. From the electronics side they have no mechanical training and do not wish to learn mechanical and they were employed for electronics so have no interest to suddenly have to learn how to do a mechanics or operators job. We also have hundreds of different machinery they they need to work on. for our province we have 2 electronic technicians and about 30 electricians and about 40 mechanics.

My question is what type of expertise are needed to do the geometry calibration of the heads and who should be doing this type of calibrations? because the managers think it should be the electronics technicians that need to be trained and I am thinking it should be someone who comes from a mechanical/measurement background.

[awerby]

It sounds like you need to assign your best, most all-around qualified person to figuring this out. Since the issues involve measurement and setup more than electronics, I think you're correct in thinking that a person with background in that would be most qualified, but try to find someone who's enthusiastic about solving problems and willing to dedicate some time and energy to this process, whatever their background. Compensate them accordingly. Have you tried reaching out to Zayer? On their site, they claim that "Our customers are safe in the knowledge that immediate, effective, professional technical support is available to them at all times, for each and every one of the products that we supply." https://www.zayer.com/en/company#sec...service_policy

If that's not true, and they refuse to help, please let us know.

[joeavaerage]

Hi,
one of the classic tests for a mill is a ball-bar test. There are plenty of videos about this test on Ytube. It is a simple way to get a good and realistic
impression of your machine. Downside is that the test gear is not cheap.....many thousands.

This is a second hand cheapy ($1900USD):

https://www.ebay.com/itm/40514771805...3ABFBM7vDvvLhk

And this one looks the part but costs more ($$6895USD):

https://www.ebay.com/itm/23565968965...Bk9SR-7w77y4ZA

Looks like depending on where you buy that the Reinshaw ball-bar kit new is about $10,500USD.

https://willrich.com/product/renisha...allbar-system/

You might in the first instance get a company whom specialise in this sort of measurement and characterisation.

Once you have the machine sorted ....then start looking at equipment like a ball-bar test etc to maintain it and check it every once in a while.

Craig

[peteeng]

Hi Brendan - Look at ASME B5.54 for ideas. You will need someone who is mechanically trained or has some mechanical sypatico. Then you need to look at geometric laser systems to do the measurements so the machines can be corrected. These are not cheap but worth the effort as otherwise there is no real way to check machines other then CMM of the parts which sort of works but is not a direct method.

heres an example - https://easylaser.com/en-us/products...e920-geometric

Regards Peter

[joeavaerage]

Hi,
I disagree with peteeng here.

The systems he has linked to are NOT laser interferometers, just laser beams, and largely incoherent beams at that.

Laser interferometry is the GOLD standard for machine metrology, but is a specialist occupation. Laser interferometry requires a coherent laser. For CNC machinery a coherence length of
several metres is required, and tens of meters if you can afford it.

Aside from anything else a complete laser interferometric setup and software could cost $80k upwards, and if you want an iodine stabilised laser, and lets face it.....who does not want an iodine
stabilised laser?, then it will cost more again.

The operator of such a piece of equipment is usually scientifically trained. That is not to say that any intelligent person could learn but its not easy either.

I think the cost and the technical complexity all but preclude laser interferometry as a 'small shop' solution. It is the sort of thing that is done by companies whom specialise in metrology.

Even if you were to engage such a company they would (Ytube videos) typically do a ball-bar test right from the outset. Then, and only then, and if indicated would you bring out
the interferometer.....and that's when you really start to pay!!!!

May I suggest that if you are interested in laser metrology then take a look at the Hewlett Packard Zeeman stabilised dual mode laser system. Despite being 40 years old you can still but them
second hand for $2k-$5k. The Zeeman splitting results in an orthogonally polarised dual mode (He-Neon laser) separated by 3.25Mhz. This allows for differential measurements which much increase
the capability WITHOUT some of the most (mega MEGA dollar) expensive optics. Even still such a dual mode laser, interferometer and required optics, but not including an optical square will still cost $20k,
and add another $10k for the optical square. An HP laser of this description has a coherence length of somewhere between 7m and say 15m on a good day, which I think you'll agree is damn good for a sub $10k laser.
If you want more coherence then buy an iodine stabilised laser....and they start at $20k second hand!!!

https://www.ebay.com/itm/36509526294...Bk9SR7z628O4ZA

I'd dearly love to get into this, but have yet to find any bunch of souls whom might be prepared to collaborate. I live in New Zealand, so I imagine both Kiwi and Aussie hobbyists CNCers could benefit
from such a collaboration.

One piece of equipment that you might consider, and very useful for establishing a linear axis for smoothness and straightness is an Autocollimator. This is an example.
There are tons of videos about how they work and how they are used on Ytube. In the hands of a good operator they are truly superb despite being simple.

https://www.ebay.com/itm/17644689521...Bk9SR4bA8cO4ZA

Such a device would also benefit by being a collaborative purchase.......any Kiwi or Aussie takers???

Craig

[peteeng]

Hi Joe et al - The easylaser and similar machines give direct readings. No particular skill required just good trade skills understanding of what is required and respect for the equipment. A machinist would have no problem understand the set up. The easy laser (and similar systems) starts at $30k USD so if you need to keep very expensive machines in spec its not really a great cost. Peter

[joeavaerage]

Hi peteeng,
an Autocollimator can do all that and more and cost a small fraction of the geometric laser system you linked to.

If you want to go laser then you need to get into interferometry....and that is an order of magnitude more expensive again.

Craig

[peteeng]

Hi Craig - I appreciate that but I want a tool that's easy to use, suitable for the task and is well supported. And I expect a machine shop will be the same. Peter

[joeavaerage]

Hi,
it does not come much simpler than an autocollimator and a mirror.

Craig

[BrendanDixon]

Hi All,

Thanks for the Replies. I have just sent an email to Zayer asking for advice and awaiting their reply. The operators have a rectangular bar they the put on the bed of the machine and measure this, I am not a mechanical person and am involved in electronics but i generally have a good mechanical understanding although I no training just what I learn as I go along and work things out. some of the things you have mentioned I have no idea what these are, but for interest I will do some research.

It gets annoying that the maintenance manager expects the electronics technicians to be trained to do this work. but in my opinion, these are the least suitable people that we have to learn this. The problem also is that they are the most enthusiastic staff we have but that is only i the electronics field, they are not interested in learning mechanical. and all the other staff are not enthusiastic and just come to work to do the minimum and get a paycheck. most cases mechanical work is outsourced as the mechanical people cannot repair the problems.