TP20 / MCR20 Probe Change Setup
The Following article explains the correct process
for setting up a TP20 probe changer rack.
First you will need to locate the MCR20 rack in a
suitable position on the surface of the machine.
This is normally to the rear or the side of the
granite surface. It doesn't matter if the rack is
facing towards the Y or X-axis, as long as it is
easily accessible and away from any potential
obstruction. It is best if the rack can be located in
a permanent position so that you don't have to
keep moving it around.
Once the rack is secured to the surface in the desired location, it is then
necessary to square it up to the machines axis; this has to be within 0.25mm.
The following instructions will guide you through this process:
1. Create a new part program, then calibrate a 20mm long tip to A0B0, a
good tip for this would be 2mm by 20mm styli. For this example I will
named the probe file SL-1, meaning (Slot 1), as later I will store this
profile in Slot 1 of the changer.
2. The next stage is to take a single point measurement on the far left
vertical metal face of the rack and create an origin in X or Y depending
on the direction of the rack, for example my rack is at the back of the
machine facing towards me, so my origin will be in Y, this may vary
depending on the axis convention of your machine.
3. Now take another single hit on the vertical face at the other end of the
rack and output the location in Y, making a note of the dimension. This
will show the error in the squareness of the rack to the machine axis.
4. It is now time to adjust the rack so that it is within the required 0.25mm
squareness tolerance. The easiest way to do this is to carefully twist
the changer and re-measure the second hit until the deviation is
approximately half of the original measured output. For example, if you
measured 2mm error, then you need to adjust the changer to read
1mm+/- 0.25. This procedure requires a delicate touch and is one of
trial and error.
5. With the adjustment complete, re-measure the datum point and set the
origin, then confirm the other end is within 0.25mm. The manual
adjustment is now complete.
Defining and Calibrating The Probe Changer.
In this section I will guide you through selection and calibration of the MCR20
rack.
1. Go to Edit, Preferences, Probe Changer. This will open the probe
changer dialogue.
2. Under "probe changer type", select TP20 and click apply. Then click
on the Calibrate tab. Active Probe File should be set to SL-1 and
Active tip should be set to T1A0B0.
3. Next click the calibrate button and follow the simple on-screen
instructions. It is advisable before continuing in DCC mode, to set the
speed control on the jog box to about 25-30% for safety.
4. Now the machine should have finished calibrating the changer in DCC
mode.
Mount Point
The next stage is to define a mount point. A mount point is where the
machine will move to just after picking up a new tip from the changer. If you
decide not to select a mount point, the CMM will move to its home position
upon picking a new tip, which can be dangerous if the surface of the machine
has obstructions.
Click the Mount Point tab and you will see that under CMM Position the X, Y,
Z coordinates are set to zero, unless previously defined.
To define a suitable mount point, you can either key-in the required X, Y, Z
coordinates or alternatively you can position the tip in a suitable position and
click on the Read CMM button, I chose the latter, so my mount point is about
50mm in front and 300mm above the changer, this is a safe distance. When
done click ‘Apply’.
Slot – Tip Assignment
The next and final stage of set-up is to define what tip goes in which slot, as I
stated earlier in this article, my currently active tip is SL-1 or (Slot1), so we will
default this tip to slot 1.
Click on the "+" symbol next to slot 1 and then double click on (no probe), this
will display a list of all probe files available on your machine. From the list
select SL-1 and click Apply. Assuming you have more probes already precalibrated i.e. SL-2, SL3, SL4, SL5 & SL6, repeat this procedure for the
respective slots.
Now For The Test.
Ensure that tip SL-1 is fitted and active in PC-DMIS.
Ensure that all other modules are located in the rack and that the lids of the
rack are closed. Note: the orientation of each individual module in the rack
should line up as best as possible by eye with the corresponding symbols on
the main TP20 body, some minor adjustment by hand may need to be made
once each module is picked up from the rack for the first time.
In PC-DMIS go to Insert, Hardware Definition, Probe, and under probe file
select SL-2, then press OK. This will insert a new load probe command into
your program.
Next, go to Operation, Load Active Probe. Note: Ensure the speed on the jog
box is down low for this. The machine will move into slot 1 and drop off
module SL-1 and then come out and into slot 2 and pick up SL-2. Repeat this
procedure for the remaining modules in slots 3 to 6.