### Parameter Settings: Clearance Plane tab

Parameter Settings dialog box-Clearance Plane tab

The Clearance Plane tab provides the means to define and add clearance planes. Clearance planes, in essence, create an envelope around a part where the probe will always travel when moving from one feature to another. PC-DMIS will move the probe out from the part a predetermined distance, relative to the coordinate system in which it was defined. After the last hit on the feature is measured, the probe will stay at probe depth until called to the next feature. This helps to reduce programming time because the need to define intermediate moves is minimized. In addition, using properly defined clearance planes can help protect your probe from accidental collisions with the part.

A sample part with an imaginary envelope from clearance planes

To use clearance planes:

1. Access the Parameter Settings dialog box (Edit | Preferences | Parameters), then select the Clearance Plane tab.

2. Select the clearance plane using the Active Plane and Pass Through Plane areas, and specify the clearance distances using the respective Value boxes.

3. Click OK to finish defining the clearance plane. PC-DMIS inserts a CLEARP command containing the clearance plane information into the Edit window. The finished command will look something like this:

CLEARP/ACTIVE_PLANE, n, PASS_THROUGH_PLANE, n,TOG1

ACTIVE_PLANE and PASS_THROUGH_PLANE refer to the axes selected. n refers to the offset distances specified. TOG1 is an ON/OFF toggle field determining whether or not the clearance plane is active and automatically used for newly created Measured and Auto Features.

3. You can then insert MOVE/CLEARPLANE commands into your part program. A MOVE/CLEARPLANE command does not in itself create motion to move the probe to the clearance plane. Rather, when PC-DMIS encounters a MOVE/CLEARPLANE command during execution, that command essentially gives permission to move to the predefined clearance plane on the next move, measure, tip selection, or auto feature command. When one of those motion commands is about to be executed, the probe will move to the specified distance away from the selected Active plane.

3. If a new CLEARP command is defined, the very next MOVE/CLEARPLANE will move first to the old clearance plane, then to the Pass Through plane, and then to the new clearance plane.

Hint: You can easily display the current clearance plane as a translucent image in the Graphics Display window by selecting the Toggle Clearance Plane Items icon from the Graphic Items toolbar. See "Viewing Clearance Planes" in the "Editing the CAD Display" section.

Active Plane Area

The Active Plane area defines the plane (or axis) in which features lie when they are measured. The Value box defines the clearance plane as an offset distance in the current units of measurement away from the specified plane. To define a clearance plane, select the plane from the Axis list, then enter a new value in the Value box.

Pass Through Plane Area

The Pass Through Plane defines a clearance plane that the probe will move to and then pass through to get to the next active clearance plane following a probe's TIP command. The new CLEARP definition command must immediately follow the TIP command to properly define the pass through plane. When PC-DMIS encounters the next MOVE/CLEARPLANE command, it will move to the pass through plane and remain at that offset distance until it reaches the next active clearance plane.

Clearance Plane Active (ON) Check Box

If you select the Clearance Plane Active (ON) check box PC-DMIS will automatically insert a MOVE/CLEARPLANE command before any Measured Features or Auto Features inserted into the Edit window from that point on.

Notes on Clearance Planes

Be aware of the sign of a clearance plane when entering its distance value. The sign must correspond to the positive or negative end of the normal axis defining the plane. For example, to define a top clearance plane, enter a positive value, and to define a bottom clearance plane, enter a negative value.

Movement from one clearance plane to another affects the position of the probe. Make sure that the set clearance plane is sufficient to clear the part.

A clearance plane is defined relative to the current coordinate system and part origin. Therefore, you must be careful when defining a clearance plane to ensure adequate clearance around the part.

Clearance Plane Example

Using the above drawing, suppose your part is ten inches long, and it is lined up close to the machine axes with the X origin at the bottom left-hand corner. You can set a one inch clearance from the right side of the part by setting the XPLUS clearance plane to 11 inches.

Always define clearance planes relative to the current coordinate system. When you create a new coordinate system, the clearance planes still relate to the first alignment. If you wish to associate the clearance planes with the new coordinate system, they must be redefined.

Clearance planes are not used when taking sample hits. It is therefore important when measuring pins to set the spacer value to a distance that will allow the probe to move around the pin.

Code Example

Consider this example:

TIP/T1A0B0, SHANKIJK=0, 0, 1, ANGLE=0

CLEARP/ZPLUS,2,ZPLUS,0,ON (New clearance plane defined)

PLN1 =FEAT/PLANE,CARTESIAN,TRIANGLE

THEO/<0.3597,0.3544,-0.8268>,<0,0,1>

ACTL/<0.3597,0.3544,-0.8268>,<0,0,1>

MEAS/PLANE,3

MOVE/CLEARPLANE (Probe moves to the defined clearance plane)

HIT/BASIC,NORMAL,<0.2346,0.6411,-0.8268>,<0,0,1>,<0.2346,0.6411,-0.8268>,USE THEO = YES

HIT/BASIC,NORMAL,<0.2034,0.2502,-0.8268>,<0,0,1>,<0.2034,0.2502,-0.8268>,USE THEO = YES

HIT/BASIC,NORMAL,<0.6412,0.172,-0.8268>,<0,0,1>,<0.6412,0.172,-0.8268>,USE THEO = YES

ENDMEAS/

CON2 =FEAT/CONE,CARTESIAN,IN,LENG

THEO/<8.9134,0.4921,-0.9193>,<0,0,-1>,0.3964,0.5906,0.5906

ACTL/<8.9134,0.4921,-0.9193>,<0,0,-1>,0.3964,0.5906,0.5906

MEAS/CONE,8

MOVE/CLEARPLANE (Probe moves to the defined clearance plane)

HIT/BASIC,NORMAL,<9.2087,0.4921,-0.9193>,<-1,0,0>,<9.2087,0.4921,-0.9193>,USE THEO = YES

HIT/BASIC,NORMAL,<8.9134,0.7874,-0.9193>,<0,-1,0>,<8.9134,0.7874,-0.9193>,USE THEO = YES

HIT/BASIC,NORMAL,<8.6181,0.4921,-0.9193>,<1,0,0>,<8.6181,0.4921,-0.9193>,USE THEO = YES

HIT/BASIC,NORMAL,<8.9134,0.1969,-0.9193>,<0,1,0>,<8.9134,0.1969,-0.9193>,USE THEO = YES

HIT/BASIC,NORMAL,<9.2087,0.4921,-1.3158>,<-1,0,0>,<9.2087,0.4921,-1.3158>,USE THEO = YES

HIT/BASIC,NORMAL,<8.9134,0.7874,-1.3158>,<0,-1,0>,<8.9134,0.7874,-1.3158>,USE THEO = YES

HIT/BASIC,NORMAL,<8.6181,0.4921,-1.3158>,<1,0,0>,<8.6181,0.4921,-1.3158>,USE THEO = YES

HIT/BASIC,NORMAL,<8.9134,0.1969,-1.3158>,<0,1,0>,<8.9134,0.1969,-1.3158>,USE THEO = YES

ENDMEAS/

CIR1 =FEAT/CIRCLE,CARTESIAN,IN,LEAST_SQR

THEO/<6.0827,3.1693,-0.012>,<0,0,1>,0.5906

ACTL/<6.0827,3.1693,-0.012>,<0,0,1>,0.5906

MEAS/CIRCLE,4,WORKPLANE

MOVE/CLEARPLANE (Probe moves to the defined clearance plane)

HIT/BASIC,NORMAL,<6.378,3.1693,-0.012>,<-1,0,0>,<6.378,3.1693,-0.012>,USE THEO = YES

HIT/BASIC,NORMAL,<6.0827,3.4646,-0.012>,<0,-1,0>,<6.0827,3.4646,-0.012>,USE THEO = YES

HIT/BASIC,NORMAL,<5.7874,3.1693,-0.012>,<1,0,0>,<5.7874,3.1693,-0.012>,USE THEO = YES

HIT/BASIC,NORMAL,<6.0827,2.874,-0.012>,<0,1,0>,<6.0827,2.874,-0.012>,USE THEO = YES

ENDMEAS/

CLEARP/YMINUS,-3,ZPLUS,2,ON (New clearance plane defined, this time with a pass through plane)

TIP/T1A90B-180, SHANKIJK=0, -1, 0, ANGLE=180

CIR2 =FEAT/CIRCLE,CARTESIAN,IN,LEAST_SQR

THEO/<4.8819,0,-0.5906>,<0,1,0>,1.2362

ACTL/<4.9445,15.8342,-0.5906>,<0,0,1>,31.4282

MEAS/CIRCLE,4,WORKPLANE

MOVE/CLEARPLANE (Probe travels through the Pass Through Plane in ZPLUS to the YMINUS clearance plane)

HIT/BASIC,NORMAL,<4.8819,0.0623,-0.8406>,<-0.9999185,-0.012768,0>,<4.8224,0.0025,-0.8406>,USE THEO = YES

MOVE/CIRCULAR

HIT/BASIC,NORMAL,<5.1319,0.0623,-0.5906>,<-0.9999279,-0.012008,0>,<5.0733,0.0026,-0.5906>,USE THEO = YES

MOVE/CIRCULAR

HIT/BASIC,NORMAL,<4.8819,0.0623,-0.3406>,<-0.9999185,-0.012768,0>,<4.8224,0.0025,-0.3406>,USE THEO = YES

HIT/BASIC,NORMAL,<4.6319,0.0623,-0.5906>,<0.9999071,0.0136308,0>,<4.69,0.0041,-0.5906>,USE THEO = YES

ENDMEAS/

MOVE/CLEARPLANE

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