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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!!!
Parents
  • Hi,
    I like this: "2. What is the benefits of having a datum simulator?". Maybe this good sounds in a books or at least from lips of expert who would have tricky ides, but when beginner asking like this is not easy understand whats going on. I think if there is no expert who can tech is the best go to courses. Forums and books are ok with good background otherwise could be that after gaining experience appears that all programs are wrong.
  • at some point you will come across a time when a datum simulator is the way to measure a feature and get good results. I've measured some small parts where datum A was a small hole, a gage pin inserted into the hole was the only way we could get correct and repeatable results because of poor form and/or lack of PREHIT/RETRACT distance. I've also used parallels or a 1-2-3 block or an angle plate for datum features because the part was not flat or straight enough for reliable measurement
Reply
  • at some point you will come across a time when a datum simulator is the way to measure a feature and get good results. I've measured some small parts where datum A was a small hole, a gage pin inserted into the hole was the only way we could get correct and repeatable results because of poor form and/or lack of PREHIT/RETRACT distance. I've also used parallels or a 1-2-3 block or an angle plate for datum features because the part was not flat or straight enough for reliable measurement
Children
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