Probe Calibration In Polyworks

Published by CMMXYZ on February 3, 2022

PC-DMIS Tech Tip: This video tutorial shows how to calibrate a probe/tool starting from creating and locating a reference sphere using Polyworks. The video also explains the steps for manual calibration as well as CNC calibration of the tool along with the steps to create different tool orientations.

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Welcome to a new Tech Tips video by CMMXYZ. Today, let's calibrate the CMM probe using PolyWorks. To calibrate the probe, first, build the probe components in PolyWorks. The video tutorial on CMM probe building in PolyWorks can be found in our channel. After building the probe, we have to build a reference sphere that is used for calibration. To build a reference sphere, go to Probe Device Properties. In here, go to Reference Sphere tab, and click on Create Reference Sphere icon. In this dialog box, enter the diameter of the reference sphere. Usually, the diameter can be found labeled to the reference sphere. I'm entering the value of the reference sphere on my CMM, and then the approximate stem diameter, which is the portion under the sphere. Next, check the orientation of the sphere. The sphere is pointing in Z plus direction, so the orientation will be 0,0,1. In Configuration tab, we can set the clearance distance after the calibration of the tool orientation. I've set a clearance of 20 millimeters along Reference Sphere Stem.

Next, set the name of the reference sphere. Here I can set an automatic name given by the software or a specific name, and then click on Create. Now in the list of reference spheres, we can find our reference tool. But next to the tool, there is a warning symbol warning us that the reference sphere hasn't been located. We have to locate the sphere using the probe that we've built. Click on Apply and OK to save the changes. Next, choose the tool orientation from the dropdown, that is A0, B0, which will be created when we build the probe. There's a warning sign next to the tool orientation warning us that the tool orientation is not calibrated. If we try to locate the sphere using this tool orientation, we'll end up getting a message that the tool orientation is not calibrated and will not be able to locate the sphere.

We'll have to use a manually calibrated tool orientation to locate the sphere so that we can CNC Probe for the calibration of the other tool orientations. To calibrate the tool orientation manually, in Tools and Tools Orientation dialog, select the orientation and click on Calibrate Orientation icon on the right. In the Calibration dialog, select the Probe as the method to manually calibrate the probe, and set five hits to calibrate the A0, B0 orientation. Select the reference tool and click on Probe. Then take five hits on the reference tool, with four hits at the equator and one hit at the top.

After calibration, you can see that there's no warning sign, and A0, B0 has been calibrated. Now, with the calibrated tool orientation, let's go ahead and locate the sphere. Go to Locate Reference Sphere icon. In the dialog zone, we can choose Probe or CNC Probe method. In Probe method, we have to select the reference sphere and manually take hits to locate the sphere. And in CNC Probe method, we have to take one hit at the top of the sphere and the remaining hits will be taken automatically. In CNC probing method, select the reference sphere, and select Probe Point on Top option to locate the sphere with one hit. Then choose the number of circles and the number of points per circles. Highest angle will be the angle from the top of the sphere, and the lowest angle will be the angle from the equator of the sphere. You can control the approach distance and search distance in the CNC parameters section, then click on CNC Probe. Take one hit at the top of the sphere and click on Continue. The probe will take four hits on two levels or circles as set, and the locating process will be completed.

Now, I can calibrate A0, B0 orientation in CNC mode. Select the orientation, click on Calibrate Orientation icon, and keep all the parameters at default value. Select CNC Probe as the method, and click on CNC Probe to calibrate A0, B0. A warning message shows up warning us that the machine is about to move and to check for any possible collisions. Click OK and the orientation will be calibrated. To add more orientations, go to Add on the right side of the Tools and Tool Orientation dialog, and in the dialog box, we can enter the A and B angle. And then click on Create. Now, because the reference sphere is located, I can add more orientation and calibrate those orientations in CNC mode.

This was a video on probe calibration in PolyWorks. Thank you for watching the video.

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