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Z Axis Calibration for Disc Stylus

MatthewHaines
We have recently purchased a 6-way module and I want to experiment with a custom disc probe (bore too small for a star probe). Is it possible to measure undercut widths using a disc probe? (touch down, take a point, pull up, take a point, distance between them etc)

If so, how do you calibrate it in the Z axis so it calculates the maths correctly?

I received an email from Hexagon saying to try turning off probe compensation, doing the features, then add on the disc thickness to the distance result as an assignment. However, I haven't quite got the hang of doing assignments in all my youthfully ignorant glory, so can someone talk me through that?

Even if the undercut widths can't be measured, at least I can learn how to do the assignments (correctly) out of all of this.

We have PCDMIS 2013.

Our programmer left the company, and the 'people upstairs' decided to make me take over. Slight problem with this... I have zero engineering or even programming experience (which they knew). I actually started here as a labourer after Uni, so either this is one h*ll of a lucky break or a worst nightmare. So don't pull any punches, I need to learn and learn fast.
  • We have recently purchased a 6-way module and I want to experiment with a custom disc probe (bore too small for a star probe). Is it possible to measure undercut widths using a disc probe? (touch down, take a point, pull up, take a point, distance between them etc)
    Nope, sorry.


    I received an email from Hexagon saying to try turning off probe compensation, doing the features, then add on the disc thickness to the distance result as an assignment. However, I haven't quite got the hang of doing assignments in all my youthfully ignorant glory, so can someone talk me through that?
    PM sent. Also, investigate Metrology Putty. The CMM isn't the only way to measure stuff and sometimes not the best.


    Our programmer left the company, and the 'people upstairs' decided to make me take over. Slight problem with this... I have zero engineering or even programming experience (which they knew). I actually started here as a labourer after Uni, so either this is one h*ll of a lucky break or a worst nightmare. So don't pull any punches, I need to learn and learn fast.
    Welcome to CMM world! This is how most of us start. I'm not a real engineer either, but thanks to many years at The School of Hard Knocks I am nearly a competent CMM-er.

    You need these three basic skills:
    1) Spatial Relations - think in 3D.
    2) Desktop computer operation - files, folders, saving, backups, and garbage-in-garbage-out.
    3) Problem Solving - because all we do all day is 3D computerized problems!

    If you are weak in any of the three, practice and good attitude will allow you to grow in strength.

    We have also found that near-paranoid levels of OCD and attention-to-detail are beneficial.

    First and foremost, GET TO TRAINING. You need at least Level 1 class from Hexagon. I teach these classes, and the difference between people on Monday and on Friday is huge.

    Good luck!
  • We had some putty, but our components seem to be too complicated for it to work. We are measuring bores with undercuts and holes all over the place. Once we put the putty in (on one side of the bore) it gets trapped in the holes and we can't get it out. We are looking into some technology from Germany that might be able to measure internally using interferometry, and best of all it only costs £100,000 *cough*.

    I am self taught so far, been spending every waking hour just reading up on basics of metrology and engineering. Used the empty office on christmas day to come in and practice programming. I do have training lined up, but I am having to alternate between CMM, vision systems, surface measurer's, interferometry, SPC and overlooking shopfloor inspection (All this with a Philosophy degree). Hopefully this forum can help me in-between training.

    Any help on the assignments aspect? Maybe someone could link me to another thread I have overlooked elsewhere?
  • We had some putty, but our components seem to be too complicated for it to work. We are measuring bores with undercuts and holes all over the place. Once we put the putty in (on one side of the bore) it gets trapped in the holes and we can't get it out. We are looking into some technology from Germany that might be able to measure internally using interferometry, and best of all it only costs £100,000 *cough*.

    I am self taught so far, been spending every waking hour just reading up on basics of metrology and engineering. Used the empty office on christmas day to come in and practice programming. I do have training lined up, but I am having to alternate between CMM, vision systems, surface measurer's, interferometry, SPC and overlooking shopfloor inspection (All this with a Philosophy degree). Hopefully this forum can help me in-between training.

    Any help on the assignments aspect? Maybe someone could link me to another thread I have overlooked elsewhere?

    Wow good luck to you sir and welcome to the forum. A philosiphy degree?? How did you end up in inspection. I suggest start with as much training as they can give you. Luckily for me I was a general machinist before I came into the cmm/ inspection side of it, and I still struggled and sometimes still do. Some people may disagree and are quick learners but I feel this is not something you learn over night. There are lots of aspects to learn eg. navigating the software, good measuring practices and one of the most important understanding the results and how you got them. Welcome to the world of pcdmis.
  • We had some putty, but our components seem to be too complicated for it to work. We are measuring bores with undercuts and holes all over the place. Once we put the putty in (on one side of the bore) it gets trapped in the holes and we can't get it out. We are looking into some technology from Germany that might be able to measure internally using interferometry, and best of all it only costs £100,000 *cough*.
    You may want to investigate having custom probes made. I have seen a 4-tipped star setup with four 0.5mm dia balls arranged in a 10mm dia pattern circle, it's smaller than common discs and can easily measure how you need.

    I am self taught so far, been spending every waking hour just reading up on basics of metrology and engineering. Used the empty office on christmas day to come in and practice programming. I do have training lined up, but I am having to alternate between CMM, vision systems, surface measurer's, interferometry, SPC and overlooking shopfloor inspection (All this with a Philosophy degree). Hopefully this forum can help me in-between training.
     I think maintaining a philosophical outlook will help you immensely! My brain would explode if I had to learn all that at once.
    Yes, this forum is helpful. We try to keep this a positive-attitude and knowledge-sharing community.

    Any help on the assignments aspect? Maybe someone could link me to another thread I have overlooked elsewhere?
    Assignment is a simple function, it assigns a new current value to a variable. It automatically declares (creates) the variable if it hadn't already been assigned.
    Edit drop-down menu, Assign brings up the Assignment Builder dialog box.

    One important thing to keep in mind is PC-DMIS's inspection plan program code in the Edit Window is unique in two ways:
    1) Time-traveling cursor. Where your cursor is clicked is where the software is "thinking", stuff below the cursor (such as assignments) has not yet happened. Click the cursor down further to travel forward in program time, or back to the beginning to travel back to before things happen.
    2) Live updates - propagation of changes based on dependencies. Change the name of a feature and see it instantly change in any dimensions that reference it.

    One thing that is often overlooked is the PC-DMIS is very sensitive to special characters. For each and every item the you get to choose a name for: programs, features, alignments, dimensions, and variables, be sure and use LETTERS_NUMBERS_UNDERSCORES_ONLY. You can get away with spaces sometimes, but decimal points and slashes will corrupt your program in unexpected ways.

    For assignment examples of doing math, I must direct you to the Search function in the upper right hand corner.
  • We had some putty, but our components seem to be too complicated for it to work. We are measuring bores with undercuts and holes all over the place. Once we put the putty in (on one side of the bore) it gets trapped in the holes and we can't get it out. We are looking into some technology from Germany that might be able to measure internally using interferometry, and best of all it only costs £100,000 *cough*.

    I am self taught so far, been spending every waking hour just reading up on basics of metrology and engineering. Used the empty office on christmas day to come in and practice programming. I do have training lined up, but I am having to alternate between CMM, vision systems, surface measurer's, interferometry, SPC and overlooking shopfloor inspection (All this with a Philosophy degree). Hopefully this forum can help me in-between training.

    Any help on the assignments aspect? Maybe someone could link me to another thread I have overlooked elsewhere?

    Welcome to the world of the "demon". With a degree in Philosophy you are poised for success in this position. You are a student of philosophos, a lover of learning. I likewise have a double degree in Psychology and Foreign Language. How did that get me here? As a fellow philosopher it allowed me to adapt and expand my thinking. I loved every subject that I took in college and could have majored in any one of them. Psychology served me well for a while; counseling, psychological assessment, behavior modification programs, etc. all moved me toward customer service and therefore to quality assurance. The winds of change would have me move from the public service domain to the private one. What a shock in income potential. I had an opportunity to join a local company as a receiving inspector because a close neighbor was the Quality Manager there and asked me to consider. Things moved rather rapidly from there. That was 14 years ago. Our company purchased a manual CMM and was looking for someone to learn how to use it. I jumped at the chance. This was the beginning of my still continuing learning experience. I got a brief, maybe 3 day intro to pcdmis as a complimentary to our purchase of the CMM. Like you, all else has been self taught throughout the years. I now program exclusively offline from CAD files as well as run the CMM to inspect these parts. I moved from receiving inspector to Quality Manager, back to my current position because of my philosophical nature. I make no public secret of the fact that I love what I do, that's what it is all about. For me, offline programming is like playing a video game. I am constantly challenged, no so much by the software as by the interpretation of engineering intent as presented on blueprint. As you learn you will no doubt face the same questions. What do they really want? Pcdmis is really quite awesome and overwhelming sometimes, but I hate when I try to tell it something the engineer wants in his drawing that I know can't be done. It always alerts me to something that I already know. That will be your main challenge.

    The love of learning the interrelationships of all aspects of existence will go far for you. Measurement is all about geometry, and yes, Pythagoras is my hero. Know cubic geometry and you are in the driver's seat here. Our very perception of existence is based upon a premise of level, plumb, and square. That is how we perceive existence amongst the muck that comprises the universe. Locating an inspection part is understanding the 6 degrees of freedom that any object has in the universe. I always tell my machinists that I'm going to put it in a box, that way I know where it is. A box always has a corner. With X (left to right), Y (front to back), and Z (bottom to top) we can define where that corner is. As the stand alone anyone of these three can move up and down and they can spin in any direction. A point, absolute zero, with no mass can spin in infinite directions. 2 points joined together by a common spin can create a vector line segment. 3 points sharing a common vector angle create stability and a plane is born. It can no longer move up and down or back and forth but it can still wobble. We have leveled something. We still need plumb which allows us to stand up straight. Pythagoras and my body tell me so. A right angle, a perpendicularity is what we need to stop the wobble. 2 points create a vector line segment that will stop the wobble as well as any shift left to right or front to back. Finally we need to stop the spin by focusing on a point. This is analogous to square, a focal point for our perception of reality. We engineer technology as well as we are physically equipped to do so. Our software now knows where 0,0,0 is and we can let the magic begin. Its a wonderful world and a wonderful life.

    Welcome again and Happy New Year to you and yours,

    Jim

    p.s.: Try using some dental putty, the kind that you mix for getting into those non reachable features. It pulls out well but you likely will need to measure with a vision system. Touch probe is not real conducive to gel like substances. Assignments rely on an understanding of Visual Basics terminology and I am not the expert on that yet, though I try to learn each and every day.


  • I received an email from Hexagon saying to try turning off probe compensation, doing the features, then add on the disc thickness to the distance result as an assignment. However, I haven't quite got the hang of doing assignments in all my youthfully ignorant glory, so can someone talk me through that?

    Even if the undercut widths can't be measured, at least I can learn how to do the assignments (correctly) out of all of this.

    Welcome Matthew.

    1) if your distance is dist1
    2) if your disk thickness is 2.0

    then in the edit window,
    place the cursor at the end of a line,
    hit the enter key,
    and type assign

    assign/v1=dist1.meas + 2.0
  • Welcome Matthew.

    1) if your distance is dist1
    2) if your disk thickness is 2.0

    then in the edit window,
    place the cursor at the end of a line,
    hit the enter key,
    and type assign

    assign/v1=dist1.meas + 2.0

    Thank you, I shall have a practice. This could come in handy elsewhere.
  • I had an opportunity to join a local company as a receiving inspector because a close neighbor was the Quality Manager there and asked me to consider. Things moved rather rapidly from there. That was 14 years ago. Our company purchased a manual CMM and was looking for someone to learn how to use it. I jumped at the chance.

    Short sighted economics has meant our government shut down most of our skills schools decades ago. Trying to get someone under the age of 50 that knows how to set a machine (for example) is near on impossible. We can give you 1000 bankers at the click of a finger, but an engineer? Good luck with that. Because of this our company has an ageing workforce. It's so bad we could lose 3/4 of our staff within 10 years. Luckily this means I am being given every opportunity to learn whatever necessary to take over. I started Uni just before the big recession started. I was all set to become an Officer in the Royal Marines, but with the recession came a massive hole in public finances and before I knew it they had put off my enlistment so often I found myself at graduation. I took any job I could to pay the bills until the Navy reopened enlistment. Hence why I started as a labourer. The boss made me an offer which had better financial benefits than the military and meant I could spend more time with my then new born son. Shall see where this path takes me.

    As for the dental putty, I will give it a go. No harm in trying.
  • You may want to investigate having custom probes made. I have seen a 4-tipped star setup with four 0.5mm dia balls arranged in a 10mm dia pattern circle, it's smaller than common discs and can easily measure how you need.

    We are using a custom probe as we speak. The issue we had was that most of the bores we measure are less than 8mm. The world leading TTP company (not sure if allowed to say their name on here) that rhymes with Any Shore said no to a star probe of 6mm dia. The best they could do was a disc probe. Have I been spun a yarn here? (although it works quite well for 90% of our jobs). Our custom disc is 6x0.5mm.
  • I also had to calculate the difference in the Z and add it via Variables. Could not find a simpler way
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