First, two models are required: one model of the tool and one model representing the reference frame. One model is one object defined as a list of points (X,Y,Z coordinates) corresponding to the targets with respect to the model reference (tool or base reference frame).

We must follow these steps twice to define the tool and base models:

1.Connect to VXElements by selectingConnect➔Connect Creaform’s C-Track Optical CMM.

2.Select Connect and wait until the connection is Ready.
Make sure to calibrate the tracker and the HandyProbe if it is required by VXElements. Also make sure to have the VXTrack and VXModel software options provided by Creaform.

3.SelectBase referencein RoboDK. VXelements will open and will display visible positioning targets. You should select the static points. Make sure to select all points that represent the static reference. You should not include points that can move.

Robot Calibration Creaform - Image 19

Tip : Hold CTRL to select a group of targets.

Robot Calibration Creaform - Image 21

4.SelectTool referencein RoboDK and repeat this operation by selecting the points that represent the tool model.

Robot Calibration Creaform - Image 22

Note: You can optionally import or export the models as text files. We should see the targets in the text file as a list of XYZ coordinates. You can also visualize the points in RoboDK by right clicking theBase referenceorTool referencebuttons and selectDisplay points.

Tip: The reference frame of the reference or the TCP can be placed at a specific position with respect to certain features of the object. This step is optional but recommended if we need to accurately place TCP features with respect to the robot flange. For example, we could accurately place the Z axis of the tool along a reference cylinder that is used as a spindle axis.

To properly move the reference frame of the object we must use the HandyProbe and bring these features in the virtual VXelements session. The model being used must be defined as the positioning model so that the features are probed with respect to this model. It is possible to probe points, lines, planes, cylinders, cones and define reference frames with respect to these features.

Robot Calibration Creaform - Image 23

Note : If the objects being tracked are very complex, we can use the MaxShot device or photogrammetry services to properly define the object model. This procedure may give better accuracy results.

Probing reference frames