A Couple Newbie CMM Questions

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!!!

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Rich P over 4 years ago

Start by doing the courses offered through this site, start at the beginning Try to get into a class (Hexagon) or better yet see if the company will pony up to bring in a consultant / contractor for 1 on 1, if you do this put a big "DO Not Disturb" sign up and honor it. A circle can be used in an alignment, but a circle is a 2D feature, is work plane dependent and for alignment purposes you are using the center point (location) of that circle as the element used in the alignment. there are times when a datum simulator makes sense and when it does not, that will come with experience and practicality of what your trying to measure, correlation of results is huge to having bye in on the CMM accuracy and results. If you have some experience here great, if you do not find the crotchety old grey haired dude that is the toolmaker or reasonable facsimile and find out what kind of coffee he likes and plan on buying him a few dozen and hope he eventually becomes willing to share some "good fundamentals" and then some of his wisdom. Most people on this forum started where you are today, enjoy a chuckle, try to find what works for you and gives you results that can be repeated
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Rich P over 4 years ago

Start by doing the courses offered through this site, start at the beginning Try to get into a class (Hexagon) or better yet see if the company will pony up to bring in a consultant / contractor for 1 on 1, if you do this put a big "DO Not Disturb" sign up and honor it. A circle can be used in an alignment, but a circle is a 2D feature, is work plane dependent and for alignment purposes you are using the center point (location) of that circle as the element used in the alignment. there are times when a datum simulator makes sense and when it does not, that will come with experience and practicality of what your trying to measure, correlation of results is huge to having bye in on the CMM accuracy and results. If you have some experience here great, if you do not find the crotchety old grey haired dude that is the toolmaker or reasonable facsimile and find out what kind of coffee he likes and plan on buying him a few dozen and hope he eventually becomes willing to share some "good fundamentals" and then some of his wisdom. Most people on this forum started where you are today, enjoy a chuckle, try to find what works for you and gives you results that can be repeated
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