This online help documentation contains the following sections:
Postprocessing in general
Postprocessing with Post
Developing a Post
Installing a Post
Your primary use of the Manufacturing application is to generate NX tool paths in order to manufacture parts. Generally, you cannot just send an unmodified tool path file to a machine and start cutting because there are many different types of machines. Each type of machine has unique hardware capabilities and requirements; for instance, it can have a vertical or a horizontal spindle, it can cut while moving several axes simultaneously, etc.
Furthermore, each machine is controlled by a computer (i.e., controller). The controller accepts a tool path file and directs tool motion and other machine activity (e.g., turning the coolant or air on and off). Naturally, just as each type of machine has unique hardware characteristics, controllers also differ in software characteristics. For instance, most controllers require that the instruction for turning the coolant on be given in a particular code. Some controllers also restrict the number of M codes that are allowed in one line of output. This information is not in the initial NX tool path.
The tool path file hits the controller's brick wall of incompatibility. The tool path data is not formatted for the machine.
Therefore, the tool path must be modified to suit the unique parameters of each different machine/controller combination. The modification is called postprocessing. The result is a postprocessed tool path.
Two elements are essential for postprocessing. They are:
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Tool Path Data |
This is an NX tool path. |
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A Postprocessor |
This is a program that reads the tool path data and reformats it for use with a particular machine and its accompanying controller. |
The tool path data is reformatted by the postprocessor for the machine.
Make sure the output units in NX match the Postprocessor units. If they do not match the following warning is issued:
"The output units and the units of the postprocessor do not match. The output formats may be incorrect. You should set the units to post-defined."
Stop the postprocess and correct this mismatch. If you continue the following problems may exist in your output:
1) The coordinate output will be rounded incorrectly.
2) Inch/metric codes (G70/G71 or G20/G21) will be incorrect.
3) If there is no decimal point in the coordinate output (G01 X1000 Y2000), the coordinate data will be interpreted incorrectly.
4) Dimensional output will be either 25.4 times too small or too large.
5) Feed rate limits (IPM/MMPM, IPR/MMPR) will give erroneous warning messages.
The postprocessor program is usually dedicated to a single type of machine/controller combination. You can modify postprocessor file parameters for functions of that particular type of machine/controller combination. However, you cannot modify the program for use with another type of machine/controller combination.
NX provides a generalized postprocessor program, Post, which uses NX tool path data as input, and outputs machine readable NC code. Post is highly customizable and can be used for both very simple and very complex machine tool/controller combinations.
Post Builder is the NX product that is used to customize the postprocessor for each machine tool/controller combination.
NX provides the Post postprocessor that can properly format tool paths for specific types of machine/controller combinations. The Post postprocessor requires several elements:
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Event Generator |
Is the NX core module that cycles through the events in a part file and communicates the data associated with each event to the Post postprocessor. An event is a collection of data, that when processed by Post, causes the NC machine to perform some specific action. This is activated by following the path Tools-->Operation Navigator-->Output-->Post Postprocessor, or the icon. |
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Event Handler (.tcl) |
Is a file containing a set of instructions dictating how each event type is to be processed. This is created with Postbuilder. |
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Definition File (.def) |
Is a file containing static information related to a particular machine tool/controller combination. This is created with Postbuilder. |
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Output File |
Is the file where the postprocessor puts the postprocessed NC instructions that will be read and executed by the machine tool. |
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Post User Interface file (.pui) |
This is used by Postbuilder to edit the event handler and definition files. |
The Event Generator, the Event Handler, and the Definition File are dependent upon each other. Together they transform the tool path data contained in the part file into a set of formatted instructions that they can be read and executed by a specific machine tool/controller combination.
The Post Postprocessor does the following:
Uses the Event Generator to read the events (tool path data) in the part file.
Each event is processed according to the instructions contained in the Event Handler.
The resulting instructions are formatted according to the information contained in the Definition File.
The postprocessed machine control instructions are written to the Output File.
The tool path data is postprocessed according to the instructions in the Event Handler and the formats in the Definition File.