What is a Post Processor?
A Post Processor, also simply known as a “Post”, is a necessary component for anyone running a CNC machine. Before we further discuss what a post is, it is important to understand the various steps in the typical process of programming a part to cut on a CNC machine. The process generally starts with design software (CAD) to create the design for the specific part you want to make in the form of geometry. The design can consist of a combination of wireframe, surfaces, or solid objects. All Mastercam and SOLIDWORKS licenses include design capabilities, and often the design is provided by a customer or designer.
Programming software (CAM) generates the tool motion necessary to cut a specific part on a CNC machine. CAM software allows the user to reference the specific part geometry to create a machining plan that incorporates the preferred materials, tools, cutting styles, and process parameters. These toolpaths are usually generic across all machines and controls but are designed to fit within the operational capabilities of the specified machine, such as the maximum speeds and cutting envelope.
A Post Processor is an application that converts the generic tool motion from a CAM system into NC code that is designed for a specific CNC Machine and Control. The final NC code consists of a series of individual instructions that drive every action on the machine, and not all machines speak the same language or have the same options. The machine follows the instructions exactly as written, so the success of the program relies completely on the NC code being correct. G-Codes are often movement codes created by CAM and are usually generic across most machines, while M-Codes are usually special commands that control things like the spindle, clamps, air, and additional related actions. I say usually because machines can be modified from their original configuration or reprogrammed for unique applications, so the Post Processor might need to be customized for a completely custom machine configuration. With a properly configured Post you should be able to generate NC code from your CAM project that is ready to use on your machine with no manual intervention required.
What does a Post do?
A Post Processor creates the final instructions that are properly configured to match your machine’s kinematics, capabilities, instruction set, and options. Many aspects are controlled or configurated by the Post, but it would be helpful to narrow our scope to just one topic for illustration, so let’s focus on coolant. Coolant keeps the tool and the part cool, as well as extending the life of the tool and removing chips to improve surface finish. When the first NC codes were originally developed there were a very limited number of coolant types, so, for example, M08 turns the flood coolant on, and M09 turns the coolant off. As long as all machine makers re-use the same codes in the same way across all machines and machine types then this is easy, however as new technologies expand it hasn’t been possible to stay consistent. New coolant options are available such as thru-tool coolant, air blast, or even nozzles that can be rotated to specific angles to achieve targeted cooling or coolant pumps that can be configured at user-specified pressure. Keep in mind, with multi-spindle machines the number of variables to control can become confusing quickly and cannot possibly match-up exactly across all machines. So while the CAM tool is generic and allows the user to choose which coolant to turn on for a given program, it is the Post Processor that writes the correct code for your specific machine.
The Post Processor is specific to the CAM tool you are using and the machine for which it is creating NC code. If you create NC code for the same CAM program using two different Post Processors, at a minimum you will see variations in which M-codes are called and how they are formatted. It is possible to manually edit the code after it has been posted, but this approach is very prone to error on creation and re-creation and is never recommended for production environments. In a worst-case scenario, an improperly configured or edited Post Processor can send a command incorrectly that will cause the machine to stop, scrap parts, or crash.
How Do I Buy a Post Processor?
The Post Processor is a critical component in any successful CNC machining operation, so be ready to discuss which machines you plan to use when evaluating CAM software and look for it on the quote. You will need a Post Processor for each machine type to make it run, possibly even for different releases of the same machine. Similarly, keep this in mind when buying new equipment, although the cost for a new Post should be a very small fraction of the total machine cost. Common or simple machines may have free Post Processors available, while more complex machines such as 5-axis or multi-spindle mill-turn machines will often need to be customized to your specific needs or even configured on-site with custom training. Considering the complexity involved in creating a Post, companies almost always purchase them from a professional post programmer who is familiar with the CAM software you use instead of learning how to create the Posts themselves.
How do I Request a Post Processor?
Contact your local MLC CAD representative or fill out the Post Processor Request form to get pricing information for a Mastercam or SOLIDWORKS CAM Post. The Post Processor Request form will help you gather the standard information necessary to generate or customize a post to meet your needs. If additional edits are required, create an example program that illustrates the behavior that needs to change, along with details of the changes that are needed or an example of the modified NC code output. Use Zip2Go in Mastercam or Pack and Go in SOLIDWORKS CAM to save the project and Post Processor for review. Post Processors for some software can be easily configured for small changes by the end-user or by a MLC Application Expert, but not all, so make sure you understand how they work for your CAM tool. Given the variety of machine types and customizations required we need to review each situation to provide pricing and availability.
With a good Post Processor configured to your specific machines requirements, you can generate edit free code to load into your machine’s controller and run parts.
About the author
While Marcus has been a SOLIDWORKS Applications Expert with MLC CAD Systems for over a decade, his knowledge extends into all 3 product lines MLC offers. More than once, he has held the prestigious title of the world’s most certified SOLIDWORKS AE. He actively supports the user group community and is known for his improv comedy tips and tricks session. Connect with Marcus on Twitter to discuss your project.