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A Couple Newbie CMM Questions

zoebear
Good evening everyone!

I’m extremely new to CMMs, GD&T, and pretty much anything to do with this whole world. (>4 months) My employer found themselves in a tight spot when our old CMM Operator/Programmer left for another company. The previous employee was the only one who /really/ knew how to run a CMM and program it - of course there was one “back up” who got very small amounts of training.

So I’m interested in learning and I’ve gotten the job title and was trained on what could be - due to the current situation in the real world - no one is having in class training so I’m stuck with online videos and tutorials and this lovely forum.

I have a couple of random questions I’ve compiled since getting my job - they will be newbie questions and they will probably make people mad but I checked search and couldn’t find what I’m looking for.

1. I’ve noticed that an alignment shouldn’t have a circle as a rotation. Why is this? I have noticed nearly every single program made at my company has a circle - or even circle(s) as the rotational alignment.

2. What is the benefits of having a datum simulator? I understand a simulator is the perfect datum and that it reduces chances of positional tolerances to be out - but why exactly would I use them instead of taking hits from the actual physical part? Would it help if the part were (hypothetically) .005 in out?

3. What is the best method to learning programming for PC-DMIS without any type of real training or mentor? I have watched a lot of videos and I check the forum every day just for random knowledge. Are there any book, video, website suggestions anyone may have?

Thanks for any help and I’m sorry this post is super lengthy!!!
Parents
  • Ok, I will put my two cents into the fray. First, there are lots of opinions on how to do something, as long as the results are correct at the end, that is what matters. Now, do you use prints? Do you know how to read a print? I am not trying to be insulting, but there are many cmm people that do not know how to read prints. Note your starting points, datums A, B, C, this most likely will be your starting points as many have mentioned above. Alignments are the start of any program, get it wrong, the rest follows. Program to the print and cad if available, if someone tells you different, get it in writing, you will be thrown under the bus a few times until you learn. I try to measure parts on the part fixture as a standard, if you have part fixtures, use them. As mentioned, parts are not perfect as cad, when you measure a part in freestate, that error can be introduced into the measured features. If you question a result, check it old school, height gage and or other measuring tools, all cmm operators should know how to use the tools. (showing my age) You will always learn a tip or tidbit if you pay attention, take notes, keep a folder with info, web links, what you might hear today may not be needed, but there's always tomorrow it will be needed. Good luck and always enjoy life as a programmer.
Reply
  • Ok, I will put my two cents into the fray. First, there are lots of opinions on how to do something, as long as the results are correct at the end, that is what matters. Now, do you use prints? Do you know how to read a print? I am not trying to be insulting, but there are many cmm people that do not know how to read prints. Note your starting points, datums A, B, C, this most likely will be your starting points as many have mentioned above. Alignments are the start of any program, get it wrong, the rest follows. Program to the print and cad if available, if someone tells you different, get it in writing, you will be thrown under the bus a few times until you learn. I try to measure parts on the part fixture as a standard, if you have part fixtures, use them. As mentioned, parts are not perfect as cad, when you measure a part in freestate, that error can be introduced into the measured features. If you question a result, check it old school, height gage and or other measuring tools, all cmm operators should know how to use the tools. (showing my age) You will always learn a tip or tidbit if you pay attention, take notes, keep a folder with info, web links, what you might hear today may not be needed, but there's always tomorrow it will be needed. Good luck and always enjoy life as a programmer.
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