Crashing the CNC Machine

      Accidents will happen, but damaged CNC tables can be repaired with epoxy, and new pods can be machined on the device. March 1, 2006

Question
I think I need to replace a bleeder board. Only the left side has some damage to it. How much does it cost for a new bleeder board, the table thats made out of that hard wood?

Forum Responses
(CNC Forum)
From contributor M:
I am unsure what needs replacing. Is it a spoil board that was damaged or the actual phenolic table? If it is the spoil, simply replace with spoil board of like attributes (LDF, MDF, etc) and resurface.

If the table is damaged, what is the extent of the damage? I have repaired damaged tables for customers using a "bondo" style epoxy or equivalent and simply re-machining the damaged area using the machine.



From the original questioner:
The phenolic table was damaged. There was damage all over the left side, small ones on each corner, one severe burn on the bottom and its still been working for the longest time.


From contributor T:
I agree with Contributor M. We've cut into our table several time and just bondo filled it back up, re-machined the bad spots and were back running quickly.


From contributor T:
I was taught 20 years ago that you aren't a trained operator until you crash into the table. The theory was that until you do this once, you really don't understand what can go wrong. You start getting a big head and then something dangerous could happen. Once you crash into the table, you realize that its a dangerous machine. You have a big responsibility, and then you are more careful and methodical in the future.


From contributor W:
I'll have to disagree. I've never had a crash and I'm really not expecting to have one. I agree with what was said about crashing and the fear it puts in you to not do it again. I got this fear without actually doing it. I used to run an AXYZ machine with no vacuum hold down, so basically the sheet was clamped around the outside and man and machine became one as you helped to hold the piece down at the cnc cut out the shapes.

Then I changed jobs and started to run a Biesse rover 24ATS, on the axyz. 1/2" was the biggest bit I used, they don't scare me, but on the rover running a 8" diameter panel shaper, that scared me and believe me that is a tool you do not want to crash as well as the $12,000 aggregates we have, that puts enough fear in you to never let it happen. I have cut up a few pods from misplacement, but never a crash yet, and I hope I never have to witness one, experience pays.

To the Original Questioner - you mention the worst part is when you change tools on your rover, when I set up a tool I load it, run it, check the PRF value is good, then measure the length of the tool in the holder, this way when I change to a new tool I only have to measure the new tool in the holder and whatever the difference is I change in the tooling parameters. I find if you measure the tool exactly and enter that value in the tool table it does not come out exactly right on the machine. If you do what was mentioned above it should help you out.



From contributor D:
I have a Biesse Rover 30. It has pods that move around rather than a spoil board. Probably you have the same (not sure about Rover 24). Anyway, in 5 years, through several operators (and me), I have gone through all of the pods on it. I made new ones on the machine using solid surface and they work great. So, no need to pay Biesse $90 each for the replacement ones.

Remember to mill them off to make them the same thickness as your Biesse ones so you don't get varying depths of cut. If you run into the aluminum vacuum valves, then you have to get new ones of those - or if you have a metal shop, make some. It is very disconcerting to run your router into the pads. It was worse to run it into the aluminum bars below the pads, but I even got over that when it happened. I do it way less these days.



From contributor S:
With regards to crashing a bit into the phenolic table is there not some setting that could be entered, like a limiter that would prevent any program that called for the bit going too deep to be halted? I know that the tool lengths would still need to be entered correctly and it would do nothing for hitting pods. Is there any such limiter that can be set to prevent this? If not could the manufacturers not do this?


From contributor M:
Contributor S, some manufacturers do offer what you inferred to varied degrees. The problem is tooling of different lengths, jigs and fixtures and your specific applications. Most limit the travel of machine motions in each axis by both software limits and fixed hard stops. To write the logic of the machine in a manner as to prohibit the travel based on basis of tool lengths and fixture boundaries would require additional software programming within the controller, and even at that point you are still relegated to information provided by the user outlining such boundaries as being accurate.


From contributor R:
We had a fire eat about 1/4 of a table on a machine. We chipped and ground out the affected phenolic and filled with a mixture of West System epoxy with high strength filler, with some tempera paint powder tossed in for color. We used the machine to surface the patch and cut all the grooves back into the table. Down about 2 days all in all, although the first hour after it happened seemed to last about a year. After the epoxy had cured for a couple of months we resurfaced the whole table to make sure it was all happy and flat.



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