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Move Points vs. Incremental Moves

FIRST POST EVER! Ive been programming for a little over a year. A company we make parts for is in a pickle. They have asked if we could make a few CMM programs for them. I guess there programmer has left the company on bad terms, and the replacement is now swamped with work and needs programs made for him. Now, I have completed a couple programs for them, and they ran successfully with no crashes (I rarely program without having the actual part on my table, so I was a bit nervous).
Now here is my question. The programmer at the other company was happy with the programs I sent. But he told me he would prefer if I used Incremental Moves instead of Move Points. What is the reasoning for this? I don't understand why one is better than the other? Can someone please explain for me.
  • IMO, incremental moves are generally less useful.

    Move/incremental moves a given distance from WHEREVER the probe happens to be.

    Move/Point moves the probe to a specified place.

    I would certainly not substitute move points for incremental moves en masse. While there is no right/wrong in this case, one is superior to the other.

    Also, do a forum search, there are some past discussions on this topic.
  • I don't like incremental moves for one 'major' reason. If an incremental move is interrupted (false trigger) when you tell it to continue, it will move the entire incremental move, not just what was left to move. An absolute move will always move to an absolute XYZ location.

    ABSOLUTE MOVE: moves to an exact XYZ location based on the current alignmnet
    INCREMENTAL MOVE: moves each axis by the value (and direction based on it being a positive or negative value), no matter where the probe happens to be.

    ABSOLUTE move to X500,Y300,Z250 will move to that location (based on the current alignment) from no matter where the probe happens to be
    INCREMENTAL move X500,Y300,Z250 will move 500 in X, 300 in Y and 250 in Z, no TO X500 Y300 Z250.

    So, for an example, you need to move up and over 'something' on the part. So, you could incremental move X0Y0Z25, then X-50Y0Z0 and it will move up 25 then left 50. Which sounds fine, until it gets a false trigger when moving the 50 left. You hit continue (since it was a false trigger) it will then try to move 50 to the left. If it have moved 25 of that 50 before the false trigger, when you continue it will now be 75 to the left of where it moved up, and that could be a CRASH!!!!!!!!!
  • Good to hear. Sounds like I'm doing something right.
  • I use both tbh. Sometimes you are in a limited space within the part and you know you have to move a few millimeters on a given direction, then on another and finally pull out. For this purpose the incremental move is so much more convenient to program imo than carrying over the exact coordinates each time.

    Another advantage is with using star probes and constantly changing tips. Putting exact coordinates can be a pain and easy to mess up when you want your arm to clear within tip changing and probing. With incremental moves, clearing is much easier imo
  • I feel I haven't said this in a long time...... clear-planes on offline programming are the way to go !!
  • One of the applications engineers from Hexagon once told me "Use all the tool in the toolbox". Good advice.
    Move points
    move incremental
    clearance planes or cubes
    avoidance moves in autofeatures
    Whatever you are comfortable with.
    another trick he showed me was with a move point is that if you don't put values in some of the fields it won't do anything
    MOVE/POINT, NORMAL,<,,5>
    doesn't move X or Y but goes to 5mm from current alignment Z zero.
  • that only works in the 'newer' versions of Pcdmis. If you don't have the < > surrounding the move info, then it won't work. Without a number for all 3, you get 'invalid number entered' error.
  • Nice! I didn't know that trick about leaving fields blank to move in just one or two axis'. It always bothered me that you could do that in ancient g-code but not PCD. Glad to see that they added that at some point.