Why CNC Routers Crash

CNC owners list the programming errors, operator errors, and other snafus that can crash your CNC router. May 14, 2006

Several people have said that everyone-sooner or later crashes their router. What causes the crashes, human error or computer or what?

Forum Responses
(CNC Forum)
From contributor A:
All of the above and then some! As much as manufacturers try you can never truly eliminate human error from the equation. And not just at the interface (operatorís) level. Sometimes the programmer makes a mistake, sometimes the draftsman did not create a clean drawing which was posted and sent to the machine with errant code ( now you have two in house entities affecting the code). Sometimes the CAM manufacturer "tweeked" the post instead of "tweaked" it ( but usually they say theirs with a disclaimer that the machine control should have caught it) and letís not forget the machine control who's motherboard was beginning to show signs of failure and failed to recognize a legitimate tool offset. I know, I went to the extreme, but I think often we forget that all of the high production, and all of the convenience of CNC comes with a price - the price is simply learning the inherent complexity of the system you have and understanding as much as possible, if only to insure past mistakes are not repeated. Failure is succeeding in proving that the failed technique wonít work! Can I program, tool, and set up a CNC machine and not crash? Yes. Can I do it 99 out of 100 times? Probably. Can I guarantee it to never crash? No. To me, the key will always be to understand as much as possible about all of the systems within my manufacturing application, including the machine, the control, the tooling, the offline software, etc.

From contributor B:
Let me count the ways: Cad man error, tool library error, tooling not set in tool holder correctly, locating pin failed to lower all the way, clamp in wrong place, panel thickness set at 7.5" instead of .75", 1-1/2" panel on table but programmed for .75", programmed for .75" but entered as -.75", operator decided to edit code at the machine but got on the wrong line. And several others I can't remember.

From the original questioner:
I knew I would be over my head for awhile. I will give it all Iíve got but I guess itís like anything else - pay attention.

From contributor C:
Buy the top end Mastercam Router Pro and ensure that the reseller programs in the anti- crash barriers, in other words where the machine limits are, and you should have a very uneventful day, unless you get bored and overide the post. I have only had a crash because I forgot to program the length of the tool and thatís just sloppy machine minding.

From contributor D:
The last post was not very helpful. No CAM program can eliminate machine crashes. Parameters can be built in for machine limits, but that is an extremely narrow cause of machine crashes. Most of them are caused by sloppy programming, like the poster admitted or operator error. You don't have to spend many thousands of dollars on a CAM program wrongfully thinking that is insurance against crashes. Know the machine, know the code, understand how the machine operates and under what parameters machine movement takes place and you will be a happy owner and operator.

From contributor E:
If you add up he total cost of a crash - damaged stock, broken cutters, machine damage and downtime, buying software such as Vericut or Predator may be a good investment. It won't eliminate crashes caused by failing to update a tool library or the machine going crazy if there is an electrical supply problem. It will definitely tilt the odds in the machinistís favor as far as proving that the program should execute correctly. You can spend the time earning or spend it learning to evaluate the program and checking the setup. With parts of any complexity and their correspondingly large files, a computer will check more reliably than a human. It will catch those glitches in a program generated by a new or modified post-processor.

From contributor C:
To contributor D: Have you ever heard of Verify, and Backplot and Stop On Collision - these are all included in Mastercam and, if used properly, will ensure that the toolpath looks on paper as it will on the final product and warn you of potential crashes.

Posted by: Fred 12/31 [ #9 -- Re: CNC Router crash, why? ]

To contributor C: Yes I have, because I have used some on a tryout basis. The Stop On Collision feature was not one I found helpful. There were other goodies that interested me more. In the last 16 years I can not remember a machine crash caused by programming issues. I have caught a few by examining code, but they never ran at the machine. Almost all of the bad things happen by bad set up or operator error or inattentiveness. Anyway, I guess my point is, with 3 or 4 axis machines, those sorts of programming issues that can cause crashes are found during initial debugging of the post when the machine is new. Unless we are talking about 5 axis machines or specialized machines with elaborate fixturing, verification software is nice to have, but not necessary in most applications. Again, if you know the code and the machine the average guy can be trouble free. If you only want to draw product and apply toolpaths without going near the machine, then you probably will benefit from toolpath verification software. I didn't mean my original post to sound as if the software is a waste of money because it isn't in certain applications.