Editing Mastercam Post Processors

[Piperion Giles]

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I've been using Mastercam to program CNC Machines since 1997. By far the most important skill I've picked up along the way is the ability to make edits to a Post Processor. But what is a Post Processor? A Post Processor is a software script that is used to convert the generic CAM program into NC code that is formatted with the proper Syntax for your machine. Understanding how to make the post processor output the proper code for your machine is a critical part of the program creation process. I've met so many different CNC Programmers over the years. The "best" of them have one thing in common; they know something about how to edit the post processor to get proper NC code for their machine.

The Post Processor is the fundamental link between the work you do inside your CAM system, and the machine that is removing the metal. Without a properly formatted post processor, you must resort to making hand-edits to your NC code. This is an error-prone and dangerous process. Making hand-edits to your NC code breaks the link between the CAM program, and the code being run on the machine. Without having a properly configured post processor, your company is playing with fire. It is a matter of "when", not "if" there will be an error introduced into your NC code.

I've seen many companies over the years that rely on their Reseller or a 3rd-Party Post Builder to obtain their posts. In reality, there is nothing wrong with using this business practice. There are many honest and reliable Post Developers in the CAM business, but I'd also provide a word of caution. Post Development is not "easy". You've got to know the CAM System itself (how the data is created in the "generic" format), the Post Language that is used by the post processor, and the proper syntax for the NC code that will be run on the machine. A break in this chain can spell a headache, or in some cases a disaster. There are many CNC Programmers that "hack" the post processor, to get the code they need "right now!". On the face, there is nothing wrong with this method.

The programmer makes an edit, and then posts the NC code for the current job they are running. Because the edit they made worked (in this case), they go on about their day, not realizing that they have broken some of the code that may be needed for a different job later on. They only discover their issue down the road, when a new job comes in that differs in the code needed, and they end up hacking away at their post, to get this new job done. I've seen shops that have dozens of Post Processors created for the same machine. This is not only inefficient, it is dangerous. There should really only be a single post for each machine in the shop, and this post should be modified for the way your company produces its parts.

Post Development is not easy. Most CAM Systems on the market today are quite complex, and the script that is used to generate your NC code can be even more daunting. But at the end of the day, an investment must be made to produce reliable NC code. I can't tell you the number of shops I've been in where the Post Processor is basically an afterthought. They will spend hundreds of thousand, if not millions of dollars on high-end CNC equipment, but expect the post to be free, or nearly free. In many cases, a quality Post Processor (purchased from a reputable company, that stands behind their work), costs between 1-3% of the purchase price of the machine. That's right, one to three percent, sometimes less than 1%.

Take a high-end 5 Axis Japanese machine, that might cost $500,000 fully equipped. The cost of a typical 5X Post, that has been properly modified to support the advanced features and functions of this machine might cost in the range of $3,000 to $7,000, depending on the level of customization required. While $5,000 certainly sounds like a lot of money, that pales in comparison to how much time your CNC Programmer might waste on a yearly basis, making the same hand-edits, over and over again. In addition, the right code, put in the wrong place, can easily crash your half-million dollar machine, and could possibly damage your spindle, to the tune of $20-60K for a replacement. (Not to mention the wasted time waiting for the necessary repairs.)

Besides the potential downtime from a crash, making hand-edits takes valuable time away from your Programmer, and increases their stress level. Let's assume that you are a CNC Programmer, and you create an average of 20 programs per week. And that you spend an average of 15 minutes making hand-edits to those programs. That is 5 hours per week that you would spend on hand editing your code. I think that is probably a very low estimate for the average programmer making hand-edits, but it serves as a good example for now, so let's stick with it. Based on an average of 50 weeks per year (can't forget vacation), that would equate to 250 hours per year of time spent hand editing the NC code. If we assume a fairly low "burdened rate" of $40 per hour (hourly wage, plus the cost of benefits and taxes), that equates to $10,000 per year of wages paid, just to hand-edit NC code. Now, most 5 Axis Programmers that I know probably have a burdened rate that is easily twice that amount, factoring in their higher hourly or salaried rate, plus the benefits and taxes. This isn't a one year cost either. This is an ongoing expense, day after day, year after year.

In addition to the costs of hand-editing the code itself, making these edits is a scary proposition for all but the most foolhardy of CNC Programmers. Every shop where I've been forced to hand-edit NC code has always left me with a bad feeling in the pit of my stomach, when running a new program for the first time. It produces anxiety when you can't trust your NC Program to run the machine without error. Nobody wants to crash a machine. Well, maybe I shouldn't use absolutes like that, but let's just say that I've never met anyone that wanted too. Unless you've got an offline Simulation and Verification package like Vericut at your disposal, it can be nerve-wracking to prove out a program with hand-edits, and costs more time at the machine, since you'll most likely turn down both the rapid override, and the feed override knobs while running the new program.

When you make a hand-edit to a NC Program, you have broken the direct link between the CAM Program that produced the motion, and the NC code that is producing your part. All of a sudden, you have introduced the necessity of "tribal knowledge" needed to make NC code. What happens when the original programmer leaves your company, is out sick, or (God-forbid) gets into a car accident? Now you've got to get someone inside your company to take over the reins, or you must hire someone new, and they are stuck trying to figure out the process that was used by the old programmer to produce the NC code. This is a recipe for disaster, and can be avoided by having a properly configured Post Processor in the first place.

Fortunately, there are many options when it comes to post processors. There is really no "one size fits all" solution, and will depend on your shop's work-flow, personnel, and capital resources. But some suggestions for addressing the issue are:

I know simple edits can be easy if one knows what they're doing. But if someone were to want to create their own post or edit a sizable portion of a post, is this actually possible or is there often information that only the machine/CAM software manufacturer knows that isn't attainable? I'd assume all the information one would ever need is in the manual but often posts will cost a few hundred/thousand USD per pop from a CAM company so I'm assuming this isn't always the case.

Also, a side question. Let's say I have a post for Fusion 360 CAM that works for 99% of what I need it to but lets say I can't get canned drilling cycles to work or something similarly minor. Instead of being charged full price, do you guys do quick edits at a reduced cost?

The biggest thing with the posts is just knowing where stuff goes and where to look I have done some big edits to posts that were just copy and paste, some edits I have done have taken all day to do and prove out.

The real question is do you have the time to do it your self sometimes 2K for a post will save you 2K of your time so you can be doing other work when the post is being done and make money so has it cost 2K no maybe $500 as you did $1500 worth of work during the time the post was being done, and if it is bang on you start making money on it straight away.

This is a great tool! For hard core developers to hackers like me. I just started using it a few days ago and it is life changing for editing posts. It's great to be able to make a change and have the posted code instantly appear (or break). Click on a line in the post and see the section of code that generated it. Such a time saver over editing, loading to Fusion, posting, editing, etc.

When editing a post in Mastercam you must and i will repeat must always save the original. So that any changes you make, you can and will always be able to go back to the original. Mastercam will supply generic post's and will also modify a post to your specific requirements on request.

I would not recommend editing the post to extensively because this may be detrimental to your machine function. But after you are EXPERIENCED with the system, you can then SURF the code to determine what line and post code to change/turn off/turn on to suit your machine function or preference.

Post processors are like the bridge between your simulation package and your physical machine. They automatically turn the graphical simulation into code that your robot or CNC machine can understand.

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