Changing probe angle mid program

[brodonn]

Hi All,
My use of PC-DMIS has been very limited to date, but now I am trying to digitize a component and I want to change the probe angle at a certain point in the program. When I insert the new probe command the angle changes, but the points digitized at the new angle are offset to the set of points that were taken at the previous angle. Just judging by looking at the points on the screen, they look like they are off by as much as 150mm in both X and Y.
I would appreciate it if somebody could tell me what I am doing wrong, or what exactly I should be doing.
Many thanks.

Brian

[neil.challinor]

It sounds like a probe calibration problem. You need to calibrate all of the tip angles that you are going to use in your program. The crucial thing is that they must be calibrated on the same calibration sphere and that sphere must not have moved between calibrating one tip and the next. A common mistake that people make is to calibrate each tip individually and to answer YES each time to the question that asks if the calibration sphere has moved. If you do this, you essentially remove any relationship between the different tip angles.

[DAN_M]

In order to use multiple angles in a program, you need to create a "master" and "slave" relationship with your probe files.

1) Qualify a short stubby probe that gets very low STDDEV in A0B0 (I use a 4X20). Say "YES" the sphere has moved.

2) Qualify all of your other tip angles you want to use, Say "NO" the sphere has not moved to ALL of them.

The above two steps above set the A0B0 of your accurate probe to be your MASTER (because you said YES) and all of the other angles will be slaves TO THAT master (because you said NO)(which means all of your tip angles will be related and should work).

[brodonn]

Many thanks for the reply, Neil.
I have just created a short program, doing as you say, and the points are now correct.
However, when executing the program in DCC, when it comes to the point where I have inserted a new "Load probe" command and typed in the new angle, the probe moves vertically downwards until it makes contact with the table. Perhaps I am inserting the wrong command. Could you advise me on that, please.

[neil.challinor]

You shouldn't need a new LOADPROBE command unless you are physically changing to a different probe build, you should only need the tip command.
With regards to the probe driving down into the table, It may be that the machine is trying to drive to the probechanger mountpoint which, if it hasn't been defined, will be X=0, Y=0, Z=0. The other thing to check is whether you have a clear plane active - it could be trying to move to the clearplane prior to indexing the tip.

[Roberto]

If you post your code would be easier for others to help.

[brodonn]

Ah! That sounds like my problem.
So I presume I find that command under 'Insert - Parameter change - Probe - Active tip'.
I'll try that and see how it goes.

[Matthew D. Hoedeman]

Ah! That sounds like my problem.
So I presume I find that command under 'Insert - Parameter change - Probe - Active tip'.
I'll try that and see how it goes.

There SHOULD be a drop-down at the top of the Pcdmis window that shows what your current probe file is and one for what the current probe angle is, you simply use the dropdown for the angle to select the angle you want. No need at all to go through a bunch of menus.

[brodonn]

Problem solved.
Many thanks indeed to Neil, DAN_M and Roberto.
I really appreciate the help.

Brian