Post your worst nightmare here.
Just want to see if any were as bad as my
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
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.
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
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.
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.
"jimz" wrote in news:Eg0dg.38792$Lm5.34602
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
Result was the lower SLIDE broken off the ways among much other major
damage, machine was ruined, they hauled it back out.
Anthony wrote in
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.
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
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...
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'
firstname.lastname@example.org wrote in news:1148516418.940945.206260
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..
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
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.
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.
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
G53 was a command I learned about that day.
I'm supposed to fix em, not break em.
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
#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.
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
(He's an occasional contributor to this forum,,,so HIYA KEV! lol)