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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!!!
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  • Good evening everyone!
    Hi!!

    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. Welcome! I started my CMM programming career in a similar fashion 10 years ago. It get easier with time. You're in the right place to get help.

    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. Hexagon is holding courses. Suggest you look into it. Going to Hexagon has been better then the vast majority of my college courses. .

    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.
    When you're writing a CMM program, you're using rules of geometry to physically define where a part is for a machine. The machine has no brain. It only understands the mathematic implications of the commands that you tell it. PC DMIS will understand that a circle is an ORIGIN (imagine yourself standing at the center of a circle.. you can because that has definite location!) A circle CAN'T control rotation (imagine yourself standing at the center of that circle again..you know where the center is but it can still spin!) Telling PCD a circle is an origin makes sense but telling the software that it controls rotation is mathematically illogical. One circle rotated TO another will force the software to view that as working with a LINE..but thats a lesson for another day. It is time to start thinking in the TWO AND THREE DIMENSIONAL worlds. You're a programmer now! We REALLY need you to understand the SIX DEGREES OF FREEDOM and how making an alignment in PC DMIS works with those rules.

    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? I work in aircraft. Everything is regulated. For me, Datum Simulators are an acceptable method of measuring a part as long as is it is called out by the design authority of the part itself. I have some parts where -A- is a casting and that face bolts to an inspection fixture. Prior to measuring the part itself, the operator puts the fixture on the table and allows the CMM to measure it and create a plane that I use as my Datum -A- simulator. As ling as the APPROPRIATE people are telling you to use a Datum Simulator, it is a widely used industry norm and in a lot of cases WILL improve your results.

    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? Legit training at Hex is the best. Followed by working directly along side a senior programmer that wants to help you. Third best option..you're already here. Hope I helped, feel free to reach out if you ever need anything.

    Thanks for any help and I’m sorry this post is super lengthy!!!
Reply


  • Good evening everyone!
    Hi!!

    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. Welcome! I started my CMM programming career in a similar fashion 10 years ago. It get easier with time. You're in the right place to get help.

    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. Hexagon is holding courses. Suggest you look into it. Going to Hexagon has been better then the vast majority of my college courses. .

    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.
    When you're writing a CMM program, you're using rules of geometry to physically define where a part is for a machine. The machine has no brain. It only understands the mathematic implications of the commands that you tell it. PC DMIS will understand that a circle is an ORIGIN (imagine yourself standing at the center of a circle.. you can because that has definite location!) A circle CAN'T control rotation (imagine yourself standing at the center of that circle again..you know where the center is but it can still spin!) Telling PCD a circle is an origin makes sense but telling the software that it controls rotation is mathematically illogical. One circle rotated TO another will force the software to view that as working with a LINE..but thats a lesson for another day. It is time to start thinking in the TWO AND THREE DIMENSIONAL worlds. You're a programmer now! We REALLY need you to understand the SIX DEGREES OF FREEDOM and how making an alignment in PC DMIS works with those rules.

    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? I work in aircraft. Everything is regulated. For me, Datum Simulators are an acceptable method of measuring a part as long as is it is called out by the design authority of the part itself. I have some parts where -A- is a casting and that face bolts to an inspection fixture. Prior to measuring the part itself, the operator puts the fixture on the table and allows the CMM to measure it and create a plane that I use as my Datum -A- simulator. As ling as the APPROPRIATE people are telling you to use a Datum Simulator, it is a widely used industry norm and in a lot of cases WILL improve your results.

    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? Legit training at Hex is the best. Followed by working directly along side a senior programmer that wants to help you. Third best option..you're already here. Hope I helped, feel free to reach out if you ever need anything.

    Thanks for any help and I’m sorry this post is super lengthy!!!
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