Bolt Hole Generator

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The Bolt Hole Generator is a multi-feature routine that can create 2 or more inside diameter or radius 2D circle features. These features surround a common center point which is defined in the current Part Coordinate System.

figure 1, Bolt Hole Generator

To begin the Bolt Hole Generator, select from the main drop down menus, [Measure→Macro Routines→Bolt Hole Generator]. Geomet will display the generator as shown in figure 1.

The generator can create new features by inserting program steps during the self-teach or offline modes. It can also create and execute the all motion required. This directs the motorized CMM to measure all features associated with the Bolt Hole Pattern.

Step 1

Launch the Bolt Hole Generator. Main drop down menus; [Measure→Macro Routines→Bolt Hole Generator].

Step 2

Select the required Number of Holes, the minimum is 2.

Step 3

Choose the center of the bolt hole pattern. Example: the bolt hole pattern is centered at X=5.000", Y=4.500" in the PCS XY base plane at a Z=1.000". The Z component controls the height of the surface where the Bolt Hole Pattern is taken from. In figure 2, we show the Bolt Hole Pattern on a surface above the PCS, 1.000". 

Step 4

Choose the reporting format, Diameter or Radius.

Step 5

Set the size of the holes in either Diameter or Radius based on the chosen reporting format.

Step 6

Establish the starting hole position in angle deviation. In the example shown, the angle is set at 30° and is represented by a blue dashed line from the pattern center to the first feature.

Step 7

Choose the correct PCS Base Plane, XY, YZ or ZX.

Step 8

Set the number of hits per hole.

Step 9

Choose the depth the motion path generator will use to capture data points. In this example, the probing depth would be set at -0.100" to allow safe probing below the surface. In figure 2, we show the 4 circle Volt Hole Pattern on a block 1.000" off the XY base plane of the PCS. Our probing depth is represented by the blue line which is set at 0.900". This is the result of the nominal height (Z=1.000") adding the Probing Depth (-0.100").

Step 10

Choose a Clearance Height value which determines the safe height between holes for the CMM. In our example, the probing distance is set at 0.900", the block height is 1.000" and we will use a Clearance Height of 0.500". When the CMM moves from one feature to the next, it will move to the Clearance Height, Nominal Height (1.000") plus Clearance Height (0.500"). The CMM will move at Z=1.500" between features.

By placing a check next to this option, Geomet will attach relevant tolerance data to the feature when it is created.

When this option has been selected, all features created with the Bolt Hole Generator are linked together to form one macro feature. When they are linked together, they can be edited in the part program with the Bolt Hole Generator tool. The Bolt Hole Generator will insert a program step "Bolt Hole Variable Parameter" which contains the bolt hole pattern characteristics and links to all the features associated with the pattern.

For example, in manufacturing the bolt hole pattern consisting of 36 holes might require two operations. The first operation bores each hole at a diameter of 1.000". The second operation inserts a bushing reducing the diameter to 0.750".

Create an inspection program to measure the first operation using the Bolt Hole Generator to build the 36 holes. Place a check next to Program Step and create all features by choosing <Ok> to create the features offline, or <Execute/Close> to instruct CMM to measure the feature immediately. Save your inspection with a unique name identifying it as the first operation.

figure 3, Editing the Bolt Hole Pattern Parameters

To edit the parameters used to create the Bolt Hole Pattern operation based on the first manufacturing operation, open the file and highlight the Bolt Hole Parameter record, or any feature within the bolt hole pattern and press the right mouse button. A sub menu will appear, see figure 3.

Choose Macro Parameters which will activate the Bolt Hole Generator to allow changing the location, size and number of hits. Some details will be protected such as number of holes and PCS projection plane. Edit the size of each hole to a diameter of 0.750" and accept the change. All linked features will update with the new parameters. Save this change with a unique file name referencing operation number two.

In most applications, the use of the command <Add Entry IP> and <Add Exit IP> will ensure safe transition for your CMM. The use of these commands requires that a Clearance CS is currently set active.

The Add Entry IP command calculates an IP directly over the feature in the normal base plane. For example, in the XY circle example, the first Standoff Point is extracted and projected into the XY Base plane of the active Clearance CS. The motion will start directly over the hole and plunge to the first SO safely.

The Add Exit IP command creates an IP at the end of the motion map which use uses the last SO and calculates a transition path into the Clearance CS.

The combination of these two commands results in the CMM moving directly over the first SO, perform the measurement and exit the hole safely.

In the Bolt Hole Generator, the Clearance Height value will be used to create an entry and exit IP point for each hole. If the Add Entry IP or Add Exit IP option has been selected, then the Clearance Height will be disabled and the IP will be calculated based on the existing Clearance CS. In most applications, the Clearance Height is sufficient for safe CMM travel.

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