worst crash ever


Post your worst nightmare here.
Just want to see if any were as bad as my
big mistake.
Mine was running our large CNC lathe a few years back.
I pulled up an on screen calculator and did a
program adjustment. Unfortunatly, I missed the
decimal point and instead of movoing an extra .01
rapid traverse, it went an entire 1.00. Well I was
spinning a 12 inch diameter hunk of round aluminum
in a 15 inch chuck at 800 rpm. I hit the start button, and it ran the
turning tool full force into the workpiece. The
workpiece was knocked out of concentric, and the
face of the part wedged between the tool turrent and
the chuck. The resulting force sheared the 6 10 mm
cap screws holding the ball nut to the casting and sent
the tool carrige crashing into the tailstock.
I turned several different colors before settling on
off white.
Reply to
jimz
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You mean it stayed inside the machine? Your lucky day. Mine came out. ABS plastic, 12 inches square, 2 inches thick, weighs ten pounds as it sits. Spinning on the end of a 3/4" end mill at 5000 rpm. Until the pull stud broke. Then the plastic tried to fly through me, but I'm tougher. It only knocked me down, along with almost knocking my arm off below the elbow. I thank God it wasn't a boring bar. If you need some serious medical attention, it helps to live where the best in the world teach medicine. After having some leg parts moved up to replace some pureed arm parts, I'm almost good as new. Still working, walking, riding motorcycles, etc. The plastic justs hides in a box. Maybe someone still has a link to pictures.
Later,
Charlie
Reply to
Charlie Gary
Well it wasn't MY crash but... Several years ago we purchased a new CNC mill (dyna 4322). They were selling it with a PC based control of their own design, damn thing never did work properly so they eventually had to take it back, anyway on one of many visits to our shop I explained to the factory service "engineer". that the machine really did have a mind of its own and would sometimes just take off and do really weird shit. IMPOSSIBLE! says he, you must be doing something strange in the program to cause it, (stock answer whenever we had an un-explainable problem). Well Mr. wizard is working away running programs with no tools in spindle when the machine decides (on its own) to do a tool change, 1) z axis goes up to TC position 2) magazine comes under spindle 3) z axis goes down....and keeps on goin' !!! 4) magazine breaks in half 5) x and y axis are now going nuts, movig all over while z axis is zooming up and down bashing the spindle into the tops of 5 brand new 6" kurt double lock vises thus marring the livin' shit out of them. 6) machine FINALLY blows and overload and stops. 7) Mr. Genius the "engineer" looks at me and sez....Why'd it do that? 8) I sez, how the f**k would I know? ,yer the rocket scientist that said I was doing something wrong what happend to THAT theory???
Anyhow it was REAL fun to watch, lots of fun to talk about and we got a new machine with a mits control and 5 new vises. and all is well.
George
Reply to
George
Well, mine wasn't really a crash but it was a butt clincher.
I had just started at a new job running a Mori Seiki MV40/45 that apparently had a problem with the draw bar. I was one of my first setups at this shop and the first time running this particular machine. You would think that someone would have told me about the problem. Anyway, I started into my first cut. It was a 1" endmill buried about an inch deep doing about 4500 rpm. Right before it was about to exit the cut the machine decided to just let go of the tool holder and send it flying around the inside of the machine like a top. Luckily it stayed in the machine. I didnt even bother hitting the red button. I just hit the floor as soon as I saw it come out. The Mori I was running didnt even have full guards. It had the guards that were only about 12" tall. I thought for sure that tool was coming out of there.
Reply to
Dave
"jimz" wrote in news:Eg0dg.38792$Lm5.34602 @newssvr12.news.prodigy.com:
I didn't do it...but I was there when it happened... 1 week old Cinncinati Milcron 250 4 axis lathe. Thought Z zero was behind chuck.. Result was the lower SLIDE broken off the ways among much other major damage, machine was ruined, they hauled it back out.
Reply to
Anthony
Anthony wrote in news:Xns97CDB2CC045F1acziparle3sp835@216.77.188.18:
Back in '81 kid went to work for me who had just come out of a Baker-Hughes plant in Round Rock. Second week he was at B-H. Offline programming of the lathes. The programmers loaded a program in the machine, helped him set the tools and said go for it. They missed a decimal point. Turret broke off the cross slide and came thru the doors. The 12 inch chuck went thru the roof of the building (25 feet) after bouncing off the floor. He showed me pictures of the damage.
Reply to
alphonso
One of my mills runs the spindle up upon startup. I've left stuff in the spindle that shouldn't be spun on a couple occasions with various results...
My only emergency room visit was about ten years ago for a steel splinter in my eyeball that I just couldn't get out by myself. It was inside of the clear bit (cornea?), so it just looked like is was floating in there. They dug it out with a needle, which didn't hurt, but it still sucked. But Charlie Gary? He was "degloved". Damn...
Reply to
Polymer Man
Hey guys, Worst crash ever for me in my 9 years of owning my own cnc shop was on my beloved Mazak SQT15. Machine was running parts from barstock...I went to change the retract dimension of the cut-off tool before stocking out for the next part. Well, with Mazatrol, all program dimensions are "+ Z, but, when using TPC to control approach and escape points, you must remember to use "- Z" to get the tool off the right, or clearance side, of the part. Shithead me wanted to shorten the distance the cut-off tool moved off the right side of the part from 6" to 5". I mistakingly input "+5" in TPC instead of "-5". Machine drove cut-off tool into chuck at 1,181 inches per minute (full rapid). Not only do the chuck jaws break off the 8 inch Kitagawa chuck, but the master jaws inside the chuck body are broken and ripped from the chuck as well. Kitagawa chuck body looks like a small nuke was set off inside of it. The VDI-style Mazak cut-off tool holder broke cleanly in half at the shank. Machine turret was knocked 1/8" off center. Turret was knocked out of square on its linear guideways. Spindle was knocked out of line. Spindle bearings were brinelled, forever giving the machine an obnoxious whine with the spindle turning. Figuring $3K for Kitagawa chuck, $10K for rebuilt integral spindle from Mazak, $500 for cut-off toolholder, and about $3K in repair/rebuild labor, plus a weeks lost production, it was a pretty lousy stinkin' mistake!!!
Greg
Reply to
cnctool
snipped-for-privacy@naxs.com wrote in news:1148516418.940945.206260 @i39g2000cwa.googlegroups.com:
The only bad thing about a Mazak SQT (have a bunch of them)..you aren't fast enough, even if you KNOW you've f*cked up immediately upon 'cycle start' to get it stopped in time to avoid a crash. That big red button is an 'it's too late' button..
Reply to
Anthony
This isn't CNC, but was more like a launch. Some of our group were running RTM trials in a 250 ton press. Reactant resins and catalysts are injected into a closed mold after reinforcement is placed in the mold and the mold closed.
One day I heard a bang, then the supervisor came in and got all of us to go out hunting for the launched cylinder which appeared to have left the building through the roof, judging by the sunlight streaming in. As it turned out, the guys had air in the peroxide injector, and it dieseled. The engineer thought they had a leak because he thought he saw a mist from one of the armored hoses. The technician hollered "That ain't a leak, it's smoke! RUN!" as the reaction front ran down the hose like a fuse in about 5 seconds. When it got to the cylinder, there was a big bang, then the sun was streaming in. Nobody saw it because they were going the other way fast. The catalyst pump cylinder as well as the actuator cylinder were gone.
We couldn't find it outside. We were afraid it might have scored a hit on the open dome of one of the tank cars being loaded on a siding about 100 yards away, but later we found the whole bent assembly up on top the 250 ton press laying on the catwalk. All the cylinder tie rods had failed in tension, then the whole assembly had knocked a big hole in the roof, then fallen back on the catwalk.
Pete Keillor
Reply to
Pete Keillor
Bet you NEVER made that mistake again! I keep a collection, right at eye level, of all the destroyed parts & tools I have created. The big goofs, I don't make twice.
ca
Reply to
clay
Everyone makes mistakes at one time or another. Even if it wasn't me and one of my employees, it would not cost them their job. Just a little less profit sharing at the end of the year.
You've got to expect this sort of thing -- it's going to happen.
Jim
Reply to
jimz
Well, I as working on a vmc and decided to send the Z axis to home while trouble shooting So I merrily go to mdi and and do a G0X0.
I used to program a ASI gantry waterjet and that was what would take the Z to home. Inside the VMC was a 12" cylindrical square and my indicator. Somehow, I missed the square, knocked the handle off of a fixture and trashed my indicator stand. Damn I felt lucky on that one. I could fix that stuff before the end of shift. I hate to think what would have happened if I had hit that square with the spindle nose.
G53 was a command I learned about that day.
I'm supposed to fix em, not break em.
Wes
Reply to
clutch
I'm really pushing my luck even saying this, but I have never directly caused a serious crash of any type. However, I was on site during three spectacular crashes over a span of 2 years at my previous employer.
#1- A Niigata HN80 HMC (huge, 60,000lb machine with 60 inches of X travel), was running a large part, about 55x48 inches. The program was in the rough facing stage, starting at the right side of the part and cutting all the way to the left side. Unfortunately, the left side X axis way cover fell off during the cut. When the machine decided to rapid at 787ipm all the way back to start the next pass, the X axis cover that had fallen off bound up and blew the whole left side of the machine out, knocking down the inspection table positioned directly outside of the machine. It sounded like two Honda Civics hitting head on at 45mph.
#2- An operator running production parts on a Niigata SPN63 high speed horizontal decided to make some program changes without asking me for help. He actually did a good job restarting the program where it left off, and he walked through the first tool approach nice and slow. Unfortunately, at the next tool change, instead of a 4 inch long chamfer tool, the ATC brought in a 12 inch long, $3,000 Tecnara boring head. It rapid traversed at 1,575ipm directly into the 90 degree face of the part. This machine is so rugged, it wasn't even phased. It sheared the six 1/2-13 bolts right off of the tombstone, sheared one of the 1/2-13 studs holding the Kurt vise, and bent the other stud. Meanwhile, the machine is in circular interpolation with half of the boring head down in the conveyer. I don't know what was worse that time, the sound of the crash, or the sound of the owner yelling.
#3- A nearby shop was running their brand new, two machine, Mori Seiki SH5000 FMS, Somehow one of the setup guys rammed a 4 inch face mill into the tombstone at full rapid, either 1968ipm or 1654ipm. He basically destroyed the whole machine. Tens of thousands of dollars in damage to the B axis just to get the machine running again, and a permanent spindle runout of .001.
Reply to
Joe788
Worst crash?...25 years ago we were carving out a large die on a VMC (Takisawa?). The program was too large for its memory, and was being drip fed by a remote tape reader next to it. I was the swing shift guy, and the cavity was basically finished. I came in, asked how everything was going & was told it was all ready..."just push the button". It turned out later that he meant the "spindle start" button because he wanted me to take a light surfacing pass on the top of the die, but he didn't explain that...so of course I hit "cycle start". The wrong tool was in the holder and it rapided into the top (not the cavity...whew!) of the die. 25 years later and I can still hear the echo in that building. (He's an occasional contributor to this forum,,,so HIYA KEV! lol)
Reply to
jmulh

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