#### About Slot Clearance Distances

Clearance distances area

The Clearance distances area, available from the Probe Changer Slot Data dialog box, lets you define two different clearance distances from the slot that your machine can use before dropping off and picking up hardware.

Note: You can also define clearance distances and tie them instead to specific probe tips by using the Probe Setup dialog box. Any probe-specific values defined take precedence over those defined here in the Clearance distances area. See "Using Probe-Specific Slot Clearance Distances" below.

In versions prior to PC-DMIS 2009, there was only a single clearance distance that you could specify, and you had to use the Settings Editor. Now you can define these different distances directly within the PC-DMIS software. These distances affect the motion during a probe change operation.

- Before drop-off - The clearance distance used when the probe is still attached. This distance applies before dropping off a probe to the slot, but it also applies after picking up a probe from this slot.

- Before pick-up - The clearance distance used when no probe is attached yet.

The main reason for having these two distinct clearance values available to each slot is to better accommodate probe configurations that have a stylus pointing back into the rack. In the graphical example below, the star probe contains a stylus pointing towards the rack, some example clearance lines are also provided on the image to illustrate the two separate clearance distances.

Example showing Before pick-up (line A) and Before drop-off (line B) clearance distances

In these types of probe configurations, additional clearance distance may be needed to move to the clearance location without colliding with other probes stored in the rack. For example, using the sample image above, a mount point may have been defined in a central area of the rack (such as the area in front of slot 4 or 5). For a probe change that drops off the current star probe in slot 1 and picks up the new one from slot 2, when moving from the mount point to the clearance location for slot 1, a collision could occur between the star probe's stylus that points toward the rack and the probe in slot 2. In this case, a Before drop-off distance (indicated as line B) would provide the needed clearance. Yet, since that extra clearance distance is no longer needed when moving between the drop-off and pick-up slots with no probe attached, the Before pick-up distance (indicated as line A) is also beneficial.

Consider this Example

Again, using the image above, a typical probe change cycle, where the current probe is dropped off into slot 1 and a new probe is picked up from slot 2, could be described as follows:

1. The machine moves to the defined mount point for the probe changer.

2. The machine moves to the Before drop-off clearance location for slot 1 (line B)

3. The machine moves into slot 1 and drops off the current probe.

4. The machine moves back out to the Before pick-up clearance location for slot 1 (line A).

5. It moves to the Before pick-up clearance location for slot 2 (line A).

6. It moves into slot 2 and picks up the new probe.

7. It backs out to the Before drop-off clearance location for slot 2 (line B).

8. It moves back out to the defined mount point.

Affected Probe Changers

Although these clearance values can be specified for almost all tool changer types, it’s possible that they may not have any effect in some cases. For some of the machine-specific changer types, where the change cycle is handled by the particular machine interface, it’s possible that the interface has not implemented this functionality. Additionally, there may be some machine-specific changer types where the change cycle motion is handled by the machine controller itself and therefore is not under the direct control of PC-DMIS.

Initial Default Clearance Values

You can modify the initial default clearance values for specific probe changer types by modifying appropriate registry entries within the PC-DMIS Settings Editor. These entries exist within the Options section of the Settings Editor and start with the name of:

- TCDefaultClearanceBeforeDropoff_<Changer> - This is the before drop-off clearance distance in millimeters for the probe changer type referred to by <Changer>

- TCDefaultClearanceBeforePickup_<Changer> - This is the before pick-up clearance distance in millimeters for the probe changer type referred to by <Changer>

For example, a TP20 probe changer would have variable names of:

- TCDefaultClearanceBeforeDropoff_TP20 -

- TCDefaultClearanceBeforePickup_TP20

If these new variables have not been customized for a given changer type, PC-DMIS will still look for the possible existence of a customized value from the older clearance related registry setting that was available for some types. If found, it applies that value to both clearances until that older variable is deleted or the new customized values are saved using the above entries. These older clearance related registry values should be considered deprecated:

- "AutochangeClearance"

- "ACR3Clearance"

- "FCR25Clearance"

- "SCP80Clearance"

- "TESASTAR-PRClearance"

- "TESASTAR-RClearance"

- "TP20Clearance"

More:

Using Probe-Specific Slot Clearance Distances