rfrink
08-27-2009, 09:20 AM
It's a fairly normal day here in the shop. The phone is a little slow and I'm setting up a new job in our CNC turning center. This part is a brass button about 3/4" dia.
I'm running this part from bar and using a bar puller to index the raw material through the lathe chuck for the next part. Once setup, it runs by itself.
This CNC program has 2 parts..a main and sub program. The sub program does all the machine work. The main program just keeps count of the number of parts and tells when a new bar of material is needed.
Late yesterday, I finished debugging the sub program and ran a small bucket full of buttons in a semi manual mode. Today, I was going to run it in full auto from the main program...so I wrote the code, down loaded it to the machine, jogged everything into position for the first time..it looked good..so I punched the run button and were were off to the races!
The first length of bar was pulled into the chuck, the spindle started...and in the blink of an eye, I knew something was wrong...but I was a fraction of a second behind the action while my brain was trying to process everything. Suddenly the shop exploded with a thunderous racket. Everything in the shop shook and rattled. The deafening roar reverberated through my guts as my brain tried to catch up with what was happening. Everything seemed to be in slow motion as the 5500 lb CNC lathe started jumping in the air and walking across the floor. Finally, my frantic hands found the E-stop and there was silence giving my brain some time to regain the split second delay and realize what just happened.
My main program came from another part that we make..I just cut and pasted a few lines of it into this new job. One of those line was a "G96" command which keeps the cutting tool at a constant surface speed regardless of the part's diameter. So as the part gets smaller in diameter the spindle speed gets faster so that the surface speed is the same. It's a neat feature for some applications...but not today!! not for this job, not when everything else is program differently..and not on Bar jobs with bar hanging out of the back of the spindle.
When the spindle started, it reved up to an un-godly speed. I had about 12" of bar sticking out of the back of the spindle which flung around from the centrifigal force, bent at 90 degrees and tore the bejeezus out of the machine's enclosure. I have no idea how fast the spindle got to...
I knew better than this!! Holy smokes..how did I let it happen. I dunno...my knees are still banging together and my hands are quivering on the key board.
In the end, there is no blood...no foul. Just a torn-up cabinet panel and a bent rod of brass.
I'm going home for the day.
Be safe in your shop!!
-Rob
I'm running this part from bar and using a bar puller to index the raw material through the lathe chuck for the next part. Once setup, it runs by itself.
This CNC program has 2 parts..a main and sub program. The sub program does all the machine work. The main program just keeps count of the number of parts and tells when a new bar of material is needed.
Late yesterday, I finished debugging the sub program and ran a small bucket full of buttons in a semi manual mode. Today, I was going to run it in full auto from the main program...so I wrote the code, down loaded it to the machine, jogged everything into position for the first time..it looked good..so I punched the run button and were were off to the races!
The first length of bar was pulled into the chuck, the spindle started...and in the blink of an eye, I knew something was wrong...but I was a fraction of a second behind the action while my brain was trying to process everything. Suddenly the shop exploded with a thunderous racket. Everything in the shop shook and rattled. The deafening roar reverberated through my guts as my brain tried to catch up with what was happening. Everything seemed to be in slow motion as the 5500 lb CNC lathe started jumping in the air and walking across the floor. Finally, my frantic hands found the E-stop and there was silence giving my brain some time to regain the split second delay and realize what just happened.
My main program came from another part that we make..I just cut and pasted a few lines of it into this new job. One of those line was a "G96" command which keeps the cutting tool at a constant surface speed regardless of the part's diameter. So as the part gets smaller in diameter the spindle speed gets faster so that the surface speed is the same. It's a neat feature for some applications...but not today!! not for this job, not when everything else is program differently..and not on Bar jobs with bar hanging out of the back of the spindle.
When the spindle started, it reved up to an un-godly speed. I had about 12" of bar sticking out of the back of the spindle which flung around from the centrifigal force, bent at 90 degrees and tore the bejeezus out of the machine's enclosure. I have no idea how fast the spindle got to...
I knew better than this!! Holy smokes..how did I let it happen. I dunno...my knees are still banging together and my hands are quivering on the key board.
In the end, there is no blood...no foul. Just a torn-up cabinet panel and a bent rod of brass.
I'm going home for the day.
Be safe in your shop!!
-Rob