Measuring a hole

[Big Jeffers]

I am quite new to PCDMIS programming(using v 3.5 CAD++) and I am trying to set up a programme to measure the hole postion on a panel which is'nt constant.It has a tolerance of ±2.0mm,but when i change the part over , the machine keeps stopping and i get a message "read new probe postion".I am using the find hole function when constructing the hole.I have tried changing the Target value within the programme,the spacer with the Auto feature screen and the Check distance/percent with in the parameters.Is there a way of working out the best settings for this problem.The probe stops before it hits the part or it dosn't manage to find the hole.

[cmmcaliguy]

Can you post a sample of your part program so that we can get a better idea of what your trying to do?

[Big Jeffers]

How

How do i insert a sample of my programme and what format would it be best saved as(JPEG/BITMAP).

[Wes Cisco]

The easiest way to post some code is just to copy and paste into your reply. Open your program in the edit window. Highlight the portion you need and right click on the highlighted portion, choose "copy" from the contextual menu, then come to the forum and click post reply, when the window opens up, left click in the top left corner of the text window then right click and choose "paste" from the contextual menu. That should do it, then click submit reply at the bottom of the reply window.

As for your problem, is this a sheet metal part? If it is not you may not need sample hits. Find hole usually works quite well. Have you tried changing the value for how far it will look from center to find the hole? I am at home now and do not recall the exact labels for the boxes, but if you open autocircle or autocylinder in your program and hit the F1 key it will pull up the section of the help files covering that autofeature and you should find an explaination of of the findhole feature and it's settings there. When help shows you the autocircle window you can click on a portion of it and hit F1 again for more specfic information. F1 is useful for all portions of pc-dmis when you are a novice. There are some places the help menus are weak, but by and large they can help you solve a lot of your own problems.HTH

[Big Jeffers]

I have inserted part of my programme showing 1 x hole.With reference to is this a sheet metal part ,it is.The main problem is the probe is stopping before it reaches the part.


MOVE/POINT,605.445,-68.892,485.591
CHECK/ 3,0.25
PREHIT/ 15
BURR HOLE =AUTO/CIRCLE, SHOWALLPARAMS=YES, SHOWHITS=YES
THEO/557.4,-62.04,439.788,1,0,0,8.5
ACTL/554.025,-61.301,437.995,0.9979167,-0.0111134,-0.0635518,4.623
TARG/556.4,-62.04,439.788,1,0,0
THEO_THICKNESS = 0, RECT, IN, CIRCULAR, LEAST_SQR, ONERROR = NO ,$
AUTO MOVE = YES, DISTANCE = 10, RMEAS = None, READ POS = NO, FIND HOLE = CENTER, REMEASURE = NO ,$
NUMHITS = 3, INIT = 3, PERM = 3, SPACER = 1.5, PITCH = 0 ,$
START ANG = 90, END ANG = 450, DEPTH = 2 ,$
ANGLE VEC = 0,0,-1
MEAS/CIRCLE
HIT/BASIC,552.095,-56.98,438.397,-0.0111359,-0.999938,0,552.126,-59.004,438.424
HIT/BASIC,552.258,-63.358,442.07,-0.0494661,0.5005819,-0.8642748,552.131,-62.271,440.202
HIT/BASIC,551.79,-63.352,434.724,0.060602,0.4993561,0.8642748,551.90 1,-62.467,436.144
ENDMEAS/
DIM LOC8= LOCATION OF CIRCLE BURR HOLE UNITS=MM ,$
GRAPH=OFF TEXT=OFF MULT=1.00 OUTPUT=BOTH
AX NOMINAL +TOL -TOL MEAS DEV OUTTOL
X 557.400 2.000 2.000 554.025 -3.375 1.375 <--------
Y -62.040 2.000 2.000 -61.301 0.739 0.000 ------#--
Z 439.788 2.000 2.000 437.995 -1.793 0.000 #--------
END OF DIMENSION LOC8

[Matthew D. Hoedeman]

If the probe stops before it reaches the part, increase your PREHIT and RETRACT values.

[Paul Barriage]

Do you have a repeating alignment?

2.0 mm should not be too much variation to measure.

Make sure the parts are set on fixture, or holding plate consistently. Not only have a manual alignment, but a DCC as well

[cmmguy]

Won't the prehit violate the diameter. with a prehit of 15 how will it measure the diameter of 8.5

[#2#]

Won't the prehit violate the diameter. with a prehit of 15 how will it measure the diameter of 8.5

I believe when the prehit is larger than the diameter it will prehit from the center of the hole.

[Matthew D. Hoedeman]

Yep, if the prehit is larger than the radius, it will start from the center of the hole, but the prehit and retract WILL determine how far beyond nominal the CMM will travel looking for a touch before it wil stop for a non-touch. The higher these values are, the farther it will travel BEYOND nominal.

[#2#]

Yep, if the prehit is larger than the radius, it will start from the center of the hole, but the prehit and retract WILL determine how far beyond nominal the CMM will travel looking for a touch before it wil stop for a non-touch. The higher these values are, the farther it will travel BEYOND nominal.

Get those bambies out of your head. It's not tomorrow yet. CHECK distance determines how far beyond nominal the CMM will go searching for hit.

[Matthew D. Hoedeman]

Get those bambies out of your head. It's not tomorrow yet. CHECK distance determines how far beyond nominal the CMM will go searching for hit.

NOT only check distance. If you are using a prehit and retract of 5mm, it will travle about 7mm beyond nominal before it STOPS and says it can't find the part. If you are using 10mm prehit and retract, it will go about 15mm beyond nominal. The bigger these values are, the farther it will go beyond nominal before it stops and says, HEY, AIN'T NOTHING THERE!

Check distance will STOP the machine from traveling beyond the nominal more than the check distance value, so you can set it to a very small amount without setting the prehit and retract to a small value, thus possibly causing more crashes (part too close to probe) and non-touches (part to far from probe).

[Dannyrl]

May want to change the check percent. 25% of 3 may not be enough

[#2#]

NOT only check distance. If you are using a prehit and retract of 5mm, it will travle about 7mm beyond nominal before it STOPS and says it can't find the part. If you are using 10mm prehit and retract, it will go about 15mm beyond nominal. The bigger these values are, the farther it will go beyond nominal before it stops and says, HEY, AIN'T NOTHING THERE!

Check distance will STOP the machine from traveling beyond the nominal more than the check distance value, so you can set it to a very small amount without setting the prehit and retract to a small value, thus possibly causing more crashes (part too close to probe) and non-touches (part to far from probe).

OK, wait a minute??? Lets run through a few scenarios here.

If you have your prehit retract set to 10mm... and you set the check to 2mm, it will move to nominal and then check 2mm beyond nominal. Correct?

Now, if prehit retract is set to 10mm and you set the check to 20mm, it will move to nominal and then check 20mm beyond nominal. Is that correct also?

If both of the above are true how do you get it checking to 15mm using only the prehit and retract? Set check to zero?

[Dannyrl]

Using autocircle PCdmis sets the Prehit/retract itself on the diameter hits. the prehit/retract you have set works on the surface hits only. If the tolerance is +/-2mm tell it to measure the smallest hole possible with a check distance of at least 4mm. CHECK/4.0,1