Scribe a Line

[B. Jacobs]

Is it posible to scribe a line using the CMM. I am using a PH10m head with TP20 probe. If so how would I go about it? Tanks ahead of time

[Matthew D. Hoedeman]

Well, once upon a time, this was possible and quite easy. I still have the hard probe scribe that goes in the quill of my machine, replacing the head. At that time, there was a switch on the controller that let you move the machine, either by hand or by joystick WITHOUT a head even attached to the cord. However, with all the 'advances' that have been made, it is next to impossible with the newer controllers, no head attached to the cord, no movement. HOWEVER, there are ways around this. This is the one that I came up with:

Align the fixture/part to the machine axis (get it square, like within a couple thousandths)
Align the part using the head and probe as you normally would
Remove the head from the quill, but do NOT unhook it from the cable
Attach the head to the front cover of the Z axis cover (bridge machine) so that it will not hit anything and can move as the machine moves
Insert the scribe head in the machine
Move the scribe to a positive location, this is where HOLES come in handy as the solid carbide scribe point I have has a taper body so that it will locate in a hole for 2 dimension pickup.
Now you make a read point and set that as the origin and do the rest of the alignment you need (origin, offset, whatever)
Your scribe is now ready to go, in 2-D, and is aligned to your part/fixture.

BE VERY CAREFUL using a CMM to scribe. To get it to scribe, you will have to move it by hand, not by joystick, and the machine is NOT MADE FOR THAT (unless it is a manual machine). Gentle care is required or you could very easily wrench it out of square and out of calibration. You will generally need to unlock the Z axis and let it float. My machine has a pressure gage/valve for teh Z axis counter-weight air cylinder. I can tweak this so that the quill either falls slowly or rises slowly which can make it easier for getting those scribe lines on a part.

[Mike N.]

Is it posible to scribe a line using the CMM. I am using a PH10m head with TP20 probe. If so how would I go about it? Tanks ahead of time

In the old days I might have entertained a request for that using a manual CMM that was not nearly as accurate as the new products.

If possible set it up on the rock (granite) with a carbide scribe

[Paul Sarrach]

Depending on the brand and style, you can buy a cube and a scriber. Typically a arm cmm vs a bridge. like a vento. I have good results,

But in today times they usally just want 2 lines in each axis and to cross hair the holes. Ask you SQE whats the minimal you can get away from. My ford and gm guys usally dont want anything. But the plate is tried and true.

[Andrew Gardner]

Depending on how accurate your line needs to be, the way I have approched this is: After setting my alignment and moving where the line needs to be, I brought the probe down almost touching the workpiece. Then, scribe a small line by hand "eyeballing" the location. Using a 1mm probe, you're not going to be out much. I do that in multiple locations, and then just connect the dots. Not the most accurate way, but close enough that it always worked for me.