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

dwade over 4 years ago
1. A circle can’t be used for rotation because there’s nothing to grab hold of. Use a plane, a line or a cylinder.

Why not? First example is with 2 circles second example is with a circle and a point. The software shows circle but that is how the DEMON shows it.

AUTO =ALIGNMENT/START,RECALL:STARTUP,LIST=YES ALIGNMENT/LEVEL,YMINUS,A_DATUM ALIGNMENT/[B]ROTATE_CIRCLE[/B],ZPLUS,TO,D_PIN,AND,F_PIN,ABOUT,YPLUS ALIGNMENT/TRANS,XAXIS,F_PIN ALIGNMENT/TRANS,ZAXIS,F_PIN ALIGNMENT/TRANS,YAXIS,A_DATUM ALIGNMENT/END

AUTO =ALIGNMENT/START,RECALL:STARTUP,LIST=YES ALIGNMENT/LEVEL,YMINUS,A_DATUM ALIGNMENT/[B]ROTATE_CIRCLE[/B],XPLUS,TO,D_PIN,AND,140_G_PNT,ABOUT,Y PLUS ALIGNMENT/TRANS,XAXIS,F_PIN ALIGNMENT/TRANS,ZAXIS,F_PIN ALIGNMENT/TRANS,YAXIS,A_DATUM ALIGNMENT/END

2. Explain Datum Simulator? Do you mean using a CAD model to program with? A datum simulator is a perfect geometric feature such as a surface plate, precision gage pins, angle plate. sine bar/plate, master ring. Anything that is known to be as near perfect as possible, see 1.3.17 (page 3 of the 2009 release) see 4.5.2 for datum simulator requirements, (page 53 of the 2009 release) of the GD&T standard

3. Please get the training. It’s not that expensive and it’s much better than watching a video or asking one of us. We will help you all we can but only when we have time.
Tec-Ease is one of the better places for GD&T training in regards to using it with CMMs. It is cheap considering the world of knowledge Don Day has in his head and resources he has.
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dwade over 4 years ago
1. A circle can’t be used for rotation because there’s nothing to grab hold of. Use a plane, a line or a cylinder.

Why not? First example is with 2 circles second example is with a circle and a point. The software shows circle but that is how the DEMON shows it.

AUTO =ALIGNMENT/START,RECALL:STARTUP,LIST=YES ALIGNMENT/LEVEL,YMINUS,A_DATUM ALIGNMENT/[B]ROTATE_CIRCLE[/B],ZPLUS,TO,D_PIN,AND,F_PIN,ABOUT,YPLUS ALIGNMENT/TRANS,XAXIS,F_PIN ALIGNMENT/TRANS,ZAXIS,F_PIN ALIGNMENT/TRANS,YAXIS,A_DATUM ALIGNMENT/END

AUTO =ALIGNMENT/START,RECALL:STARTUP,LIST=YES ALIGNMENT/LEVEL,YMINUS,A_DATUM ALIGNMENT/[B]ROTATE_CIRCLE[/B],XPLUS,TO,D_PIN,AND,140_G_PNT,ABOUT,Y PLUS ALIGNMENT/TRANS,XAXIS,F_PIN ALIGNMENT/TRANS,ZAXIS,F_PIN ALIGNMENT/TRANS,YAXIS,A_DATUM ALIGNMENT/END

2. Explain Datum Simulator? Do you mean using a CAD model to program with? A datum simulator is a perfect geometric feature such as a surface plate, precision gage pins, angle plate. sine bar/plate, master ring. Anything that is known to be as near perfect as possible, see 1.3.17 (page 3 of the 2009 release) see 4.5.2 for datum simulator requirements, (page 53 of the 2009 release) of the GD&T standard

3. Please get the training. It’s not that expensive and it’s much better than watching a video or asking one of us. We will help you all we can but only when we have time.
Tec-Ease is one of the better places for GD&T training in regards to using it with CMMs. It is cheap considering the world of knowledge Don Day has in his head and resources he has.
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