We will start by qualifying a single probe setup. To begin, the PROBE UTILITIES window must be accessed. To do this, go to |INSERT|HARDWARE DEFINITION|PROBE|. Once the PROBE UTILITIES window has been accessed, a name has to be given to the probe that is going to be created.

The probe has to be described via the pulldown menu below “Probe Description:” For this article we will build a probe that consists of a PH10MQ, PAA adapter (keyed locking mechanism), TP20 probe module, and a 3mmX20mm stylus.

Once the desired probe has been built, any desired tip angles need to be added to the probe. For ease of description we will add five tip angles other than A0B0.

To add angles to the probe, click on the “ADD ANGLES” button…
A listing of all available tip angles will appear…

Notice that the tip T1A0B0 is grayed out. It is grayed out because T1A0B0 is a critical tip angle. When the probe is initially qualified T1A0B0 is the default angle that PC-DMIS requires to be used to create the relationship between the probe and the CMM. This relationship is between the probe and the CMM’s coordinate system. The A0B0 tip will be g rayed out in any probe build because it is necessary for all probes to have that tip in its active tip list. Once all the tips are added that are required to inspect the part, the next step in the qualification process is to go on to describe the sphere that we are going to use to relate the probe to the CMM. This is referred to as the “Qual Sphere” by people in the industry.

Once the “MEASURE” button is clicked…
…the MEASURE PROBE window pops up

The settings of these parameters are user specific. The values displayed are the most commonly used values. The main focus of this article is related to the relationship that is built around the probe and CMM during qualification, so except for the “LIST OF AVAILABLE TOOLS” area, these parameters will be lightly touched upon. If a “TOOL” or qual sphere is not already built and chosen in the drop down list, one must be built, and a description of the qual spheres’ attributes must be completed.

Click on the “ADD TOOL” button and the ADD TOOL window pops up.

From this window the qual sphere is created. In this particular case the most typical sphere has been described. The sphere is a ceramic sphere that has a diameter of .9839” and is sitting parallel to the Z axis. (See the picture for clarification).

The shank vectors should be familiar as they are the same as found when creating features in PC-DMIS; I = X axis, J = Y axis, and K = Z axis. Hence, the tool that has been built has a vector of 0,0,1. The SEARCH OVERRIDE values are set such that the software will look for and use T1A0B0 as the default first tip. This is true for all probes measured using this qual sphere.
Now that the set up has been taken care of it is time to describe the actual probe qualification process. To begin the qualification process, highlight the line in the window *T1A0B0 BALL.., click on the MEASURE button and the MEASURE PROBE window opens. When the MEASURE button is clicked, a query to the programmer presents itself, “Has the qualification tool been moved or has the Machine zero point changed?”, this is the most important part of the entire qualification process.

For the initial probe angle being measured the question must be answered “Yes”. This is the point at which the entire relationship between machine and probe is realized. What occurs after the question is answered yes is that yet another window will appear…

Answer “ok” to that query (this window will be addressed at length later).
At this point the programmer is prompted to load the probe…

That means, replace whatever probe is attached to the PH10MQ with the CMM_PROBE that was just created.  The programmer is then prompted to take a measurement point on the qual sphere. Though it is not explicitly stated, it is assumed that the programmer knows to take this point as close to perfectly centered on the sphere as possible. Once the point has been taken, the programmer then pushes the “DONE” button on the jogbox, this will set in motion the CMM to begin a “find” mode. The CMM probes three points on the top surface of the sphere such that it has a gross sense of where the sphere is located. The CMM then begins the qualification process taking nine points at three levels.  Once the initial probe qualification is completed, it is now time to qualify the other probe angles. Highlight the remaining probe angles and choose the MEASURE button found within the MEASURE PROBE window.

As with the initial qualification, the query, “Has the qualification tool been moved or has the Machine zero point changed?” pops up. This is the second most important part of the entire qualification process.

The answer to this question is “NO”. The reason for answering “No” is that this is how the relationship between tip angles (and eventually multiple probes) is developed. With the initial T1A0B0 probe angle having been qualified and the question “Has the qualification tool been moved or has the Machine zero point changed?” answered “Yes”, that has set the known zero point of the sphere. To measure all subsequent angles and other probe builds, each set of angles or probes need to have the question “Has the qualification tool been moved or has the Machine zero point changed?”  answered “No”.

Once the probe is finished qualifying, the PROBE UTILITIES window is visible again. If the programmer clicks on the RESULTS button…

….another window pops up called CALIBRATION RESULTS. This window describes the results of the qualification. Note that the results shown below have another name, these results are shown only for descriptive purposes and they do not reflect the actual qualification of the CMM_PROBE setup.

(This is a results window from a metric program; until now inches has been the units used)

Generally, the programmer should be concerned with the standard deviation (StdDev) results and the diameter of the stylus. The parameters for these items are set in the SETUP area…

This is what the setup window looks like

Standard deviation is typically set at 0.0003936996” (.010mm) and the stylus size is typically set at .020” (0.508mm). These parameters may be tighter or looser dependant on the industry using the software. If either the standard deviation or the probe diameter is out of the assigned tolerances, then some investigation will have to be undertaken. With regards to the standard deviation surpassing the allotted tolerance, the programmer needs to look at a number of things. The root cause could be dirt, loose equipment, or faulty equipment (TP20, PAA etc etc). If the stylus diameter is out of tolerance, the diameter can be verified by the use of a caliper. If the caliper check verifies that the probe diameter is correct the next place to look would be to look at the physical make up of the stylus, there may be a chip in the material.

It may become necessary to remove the sphere from its’ original location on the CMM to fit a large part on the table. If the sphere is removed, but another tip angle is needed that wasn’t originally measured while the sphere was at its’ original location, all is not lost.

As long as the probe that is being used had its’ T1A0B0 tip angle measured at the original position, the new angle can be qualified such that the relationship between all the tips remains intact.

The warning that is given in the above window is what was just explained. It states, “In order for the tips calibrated on the new position to relate to tips on the prior tool position, T1A0B0 must have been calibrated on the prior tool position”.