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Written by Stephen Horsfall
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Output: Reporting features
In previous articles I showed you how to spend a lot of time and energy creating programs to measure features. Now that we have gone to all the trouble of making and manipulating datums and creating features it is time to discuss how we report them.
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Datums: Creating Coordinate Systems |
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Written by Stephen Horsfall
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There are no direct datum measurement commands contained in the DMIS language so this article will build on the previous ones by using features we would have already measured or constructed to create them. The reason we create datums, sometimes referred to as coordinate systems, is so that we can report valid feature positions from a known origin in up to three dimensions. The orientation of the coordinate system will also have a direct effect on the shape of some features when analyzed. DMIS’ various datum statements allow us to define the orientation and position of the axes and planes that make up the coordinate system. When you create a datum you use features to define the direction and position of three scales that are square to each other. Each scale comprises an axis that will lie along the direction of the datum feature and a plane that is square to that scale, passing through the scales zero point. Because of their close relationship with CAD systems, DMIS datums are always right handed.
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Measurement: Defining and measuring features. |
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Written by Administrator
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Now that we have set the machine up and created our sensors it is time to start measuring. The DMIS language requires that the programmer use a feature based system in order to measure and this means that you have to define a feature before measuring it. The most common types of feature are:
POINT, ARC, CIRCLE, CYLNDR, SPHERE, CPARLN (slot), LINE, PLANE, CONE, GCURVE and GSURF.
Other less common types of feature like TORUS and ELLIPS are also available. Refer to the DMIS standard for all available features.
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Sensors: Defining and calibrating sensors |
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Written by Stephen Horsfall
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In the previous article we created a shell with relevant settings for our program. Now we must define and calibrate the sensor we would like to use for inspection.
Sensors are sometimes referred to as probes and usually consist of a head, trigger device and one or more styli. Depending on the manufacturer of the head it will be either fixed or have the ability to rotate. If the probe is fixed it will usually have multiple styli attached to provide access to different areas of a component. An indexing head provides a manual or automatic rotary axis allowing the user to move the head for part access with a single styli (although more styli are an option):
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Getting Started: Creating a program shell with a setup section |
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Written by Stephen Horsfall
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This article builds on the previous overview and gives you some examples of program structure along with suggestions regarding some ‘must have’ settings to get your program underway.
Most DMIS based CMM’s provide icon based tools to create DMIS programs, however a DMIS programmer does not need CMM software to create a DMIS program. DMIS programs can be created from any text editor and the program can usually be opened by or imported into the CMM software later. It should be noted however that a text editor works well when you are measuring primitive features or making simple changes using engineering drawings but will not suffice if you need data from a CAD model in order to measure complex surfaces or simulate your measurement routines. These types of tasks are best left to a professional CMM system.
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