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Worst crash ever?


Bob W.
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Lathe- I was making 3" dia wafer thin parts: Turn, drill, part off. Incrementally move in Z -.500, turn, drill, part off. Incrementally move in Z -.500, turn drill part off....parts are running great and I'm all proud of myself......of course the turret is getting closer to the chuck with each part....until a tool change caught the chuck at about 3,000 rpm.  Spun the turret, sheard all sorts of stuff, exploded 8" chuck. 12,000lb machine jumped.

 

Took it apart myself and fixed for about 2k. . Learned what a curvic coupling is and what a cool piece of engineering it is.  Ever wonder how a turret withstands cutting forces, yet indexes with perfect repeatability? Curvic coupling.

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We have 25 foot ceilings with skylights; one operator decided he wasn't getting enough sunlight and launched a 3" diameter bar out of a big-bore Okuma lathe, straight up through the skylight. It landed on the roof.

 

Before I started working here, the story goes that the same guy, same machine, indexed the turret into the chuck. Shop hears a explosion like sound, and they turn to see the guy look into the machine, shake his head, head to the time clock and punch out and walk out the door. When they went to investigate they fount the turret laying in the chip conveyor on the bottom.

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operator decided to polish a 5 ft long by 3\4 in rod in spindle and it was taking to long he jacked spindle up to 1200 rpm maybe (it was a long time ago) any way that bar went bent grabed him threw him 5 or 6 ft up and sideways ripped his arse wide open. He was allright after some stiches and embarisment. the worse part was two days later he had to go about 75 miles north of Pittsburgh Pa to have a DUI hearing so he drove on one cheek the whole there and back LOL

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Well was not there, but the owner of a company I worked for years ago would come in Friday we worked 4 days a week and run parts.
We had cut some brass up into 13" long pieces to run in the CNC lathe at 5k. He ran one piece and wanted to run some more. He took a 13' yes 13 foot long bar and stuck in the back of the machine and hit cycle start. We come in Monday to what looks the world come to the end. Hydraulic fluid, sheet metal and debris everywhere. He come in about 3 hours after we start and I asked him point blank when did he change his underwear at work or the house. He was like no no it didn't scare him and I called him a lair and said you are lucky you are not dead. He didn't say anything and walked away. He never did go back in the shop after that day.

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Well was not there, but the owner of a company I worked for years ago would come in Friday we worked 4 days a week and run parts.

We had cut some brass up into 13" long pieces to run in the CNC lathe at 5k. He ran one piece and wanted to run some more. He took a 13' yes 13 foot long bar and stuck in the back of the machine and hit cycle start. We come in Monday to what looks the world come to the end. Hydraulic fluid, sheet metal and debris everywhere. He come in about 3 hours after we start and I asked him point blank when did he change his underwear at work or the house. He was like no no it didn't scare him and I called him a lair and said you are lucky you are not dead. He didn't say anything and walked away. He never did go back in the shop after that day.

I had a similar wasn't there story from an old friend that ended far worse. 

 

With some of the machines you guys run, I'm impressed anyone hits cycle start.

 

Worst that's happened around me is someone ran a $60k laser scanner on the end of a robot through a casting when they sent it home

 

or I had a robot running a program over and over... on one run it just up and rook off and wrecked the part, and cut the safety guarding with the diamond tools, jammed the spindle.. etc. fun times  never trusted a machine after that

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You hear the stories of tools, material, inserts, etc going through multiple guards/walls during those extreme accidents, but just the normal insert snap or endmill break can have the ability to kill or mame. One heavy stringy chip off a lathe could do serious damage and yet people still override the safety switches on their machines. I would rather take the extra 30 second sit takes to safely interrupt the machine properly than have a piece of a broken endmill with nothing slowing it down as it hurls towards me.

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We had a machine (an old Kitamura Mycenter 5) that had a short in the tool changer.  When it would change tools, it would randomly invert the spindle and tool pot numbers making for some interesting crashes.  It never seemed to grab the shorter of the two tools first during a mix up. Always the long one.

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2014-02-21_09-43-39_806_zps311abdc1.jpg

I have seen the aftermath of several being in repair... one of my favorites and I never did find out how it happened was all the bearings inside a spindle were either blue or broken and I have several that were sheared in half these this was a low speed spindle so steel balls.... 

 

I have seen the whole shaft to long for lathe thing too NL 2000sy cut it about a foot to long and it whipped around destroying the back half of the spindle and all the couplings.  

 

witnessed someone not lock the chuck on a surface grinder... that was exciting.  

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Not all human error. We had a lathe running off a barfeeder, an old Okuma Cadet, that lost the ability to communicate with the chuck mid run. Chuck opens to feed out, then never closes but the machine thought it did. Bar sticking out four feet into the machine, and it ramps up to 2k. Ripped the door open and smacked the side of the control on the outside, right where the operator was standing. Sucky coincidence that it happened when we were running hex stock so it drove the bar even though the chuck was open. Had it been round stock it would have just spun.

 

Nothing bad happened to the machine, and after replacing all the prox. switches the machine ran for several more years.

 

Totally unrelated, but the guy that almost got hit quit and then got arrested for robbing a bank on a bicycle.

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Not a very good one, but kind of funny. Years ago, when I first started working with CNC lathes, the shop owner I worked for bought a puny little Sharp lathe. I indexed the turret too close to the part with a 3/8 jobber drill sticking out of the turret. When the turret indexed, the drill didn't break, but the turret moved! Owner had to fly in a tech from California to align everything again. I think the wedge was attached with something like six M6 cap screws!

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Plywood reminded of a dumb thing an engineer did one time. I was still a teenager working in a plant in the machine shop. I also helped out on maintenance of machines and Eddie was the senior guy called me over mad as all get up. Eddie was about 70 and he didn't get mad, but he was ready to skin this engineer alive. He is cussing and asking for this guy's job. We get over to the metal shear and it is all busted up; broke the main top casting on this 40 year old metal shear. The engineer wanted to cut up some plywood and thought it was a good idea to take some 3/8" thick plywood and try to shear it to length. We pulled the machine apart, but there was not fixing it the machine it was a total lost.

 

Old Job shop was inside of a 100 year old building and we had a Betts 48" VTL. The shop foreman the owners son was cutting some SS rings on a 2" thick 42" diameter fixture plate. I was running some production work on the CNC lathe and happen to look at the same time he rammed the tool block into one of the jaws. He jumps to the side and how the plate missed him I still don't know. Came flying off the machine and hit the floor taking out a chuck of concrete. I watched it come down the isle between my machines and some Bridgeports. It came to rest like a quarter on the floor about 15 feet past my machine.

 

Same shop the other CNC guy was doing some very thin walled parts and thought it would be a good idea to hold .1 of a 14" long part without a tail stock and try to turn some material off the parts. I told him not a good idea, but I was just some stupid kid and he went charging ahead. About 30 minutes later sounds like the end of the world. Here is the part laying in the chip bin, him white as a ghost and dings and marks all inside of the machine where it bounced around like a pinball.

 

Different shop, the owner thought it was a good idea to take a 1" dia x 6" loc HSS finish endmill and remove 1" wide by 4" deep worth of material in one pass. 2500 rpms and about 40 ipm. I told the shop foreman that would not work. Again shut up and do your job you stupid kid. I was like no this is dangerous and he was asking are you not going to do your job? The owner programmed this in Teksoft our CAM Software and it looks great on the computer screen. I said okay I will set it up and you hit the green button once I am a safe distance from the machine. He said yes you coward he would show me the owner was right and how dare I doubt the owner he had been a machinist 40 years. Machine is all ready and I get a safe distance away from the machine and say go for it. Yes sounds like the world is coming to the end as it rips the material, 3 jaw chuck, holder and flings them around inside of the machine like a pinball. People come a running and are gathered around the machine. Shop foreman is white as ghost and the owner is asking me why I was not in front of he machine. I repeat my story to him and he is dumbfounded because the CAM system showed it would work. I said for a finish pass it might, but you have not roughed the material for that finish tool. Machining 101 use a finish tool for finishing and a roughing tool for roughing. Why didn't you rough off the material? You would never attempt such a thing on any conventional machine would you? Well It took me 3 weeks to make this CAM program and we need to delivery parts. I said I could make this program by hand in less than an hour and get this job down in a few hours no problem. He got mad at me and say okay kid do it then. I fixed all the damage of the machine and did just that. Part turned like I said it would. I got promoted to CNC Mill Programmer. My review after that, and I still have says " Employee needs to slow down to see the unforeseeable" and "Employee is to quick to say what is on his mind." They refused to give me a $.5 an hour raise. I went and found another job and gave my 2 weeks notice. Shop foreman was like why are you leaving? Some of us have not got raises in 7 years what do you think you are special? No, but I bring value to this company and that is worth something and when this place goes out of business you remember you said that. Sure enough it went out of business about 6 year later.

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2nd  week on a new job

 

the part is 58" dia x 32" tall, 5000 pounds of out of balance cast iron on a brand new  vtl

I program 450 sfm and G50 S80

the machine has a max rpm of 400

first move is G0 X10.

the operator didn't know what G50 S100 was so he deleted that line.

I'm in the office and hear a what sounds like a jet engine spooling up.. maybe 3 seconds worth,

followed by a lifetime's worth of crashing and banging.

The part came loose at 400rpm, and blew through the doors.

The operator, a guy in is late 50's was on a step stool and got away a half step ahead of it.

It clipped him on the hip laying him open to the bone.. 60 stiches and 4 months worth of stress leave.

The part demolished a double door tool cabinet, an employee's roll away and the coolant tank to an HBM

It stopped after slamming  into the back of a small VTL, shearing the foundation bolts, moving it 6"

The employee parking lot was the next stop had it missed the vtl.

I was lined up for a firing squad, but the time stamped print out of the program, included G50 S80

which was missing from the machine's program.

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This one I only saw the aftermath :rofl: ( I know, I know.... bad juju, but I laugh because... well I'll get to that later)

 

I was working for Mori in the mid-90's. A certain US Machine Tool Builder had a CL-200. I get a call and the person at the end of the phone calls an tells us he's having trouble moving the X-Axis. It moves about 50mm from home then it gets a servo load alarm. So I go through the normal questions, fluid levels ok, ways look shiny, do the way covers have chips in them and finally anything unusual happen to the machine etc... "No, no, everything was fine, it looks normal, nothing unusual happened to the machine". So, I say we'll schedule someone from Service to go and take a look. Long story short, there was a 6mm crack in the casting along the X-Axis. Nobody knew anything, nobody heard anything, nobody saw anything. :yes: Yeah right. ( :rofl: ) We did some calculations and figured to get that type of crack, the spindle needed to be running near full throttle, and slammed a boring bar into the chuck jaws. Speaking of Chuck Jaws, "mysteriously" ( :rofl: ) there was no chuck on the machine.

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