PDA

View Full Version : It could have been a Lot worse at work yesterday



Howdy
11-22-2012, 08:36 AM
For those who don't know I am a Presision Grinder at my Job. I grind and Polish Hydralic Rams for Fork lifts. The rams vary from 1" to 3 3/8" in diameter and from 12 inches long to over 28 feet long. We have a tollerance of + / - .0003 ( 3/10ths of a thousands ) from end to end.
Started my day at work yesterday running our big Cincinnati centerless Grinder ( over 28,000 lb machine ). This grinder uses a grinding wheel 24" in diameter and 20" wide and runs at 1064 RPM. The aprox weight of the wheel is 400-600 lbs.
I started out the day running 1 3/4" material and everything was running great. The 8th part of the day was 1/2 way through the machine and all of a sudden "KABOOM!!!!!!!". The part stopped and a error message came up on the computer screen. Upon opening up the guards and the mist rags ( to contain the coolant spray ) I found the center part of the Grinding wheel ( 3 part wheel ) had violently exploded. The explosion and resulting carnage was VERY loud. The boss and group leader came running to see what happened. None of us could believe what we found. The boss took some pictures and printed a few out for me. It took almost 7 hours to replace the wheel and to fix the damage enough to get it back up and running. I ended up working over 4 hours just to try and get caught up on production. We run a on time delivery style set up.

In these pictures. The main cover that protects the wheel / operator is 1/2 thick steel with a 3" lip on it ( 1/2 thick ). You can see in the one picture that in less than a blink of an eye the cover was bent. Oh, and the grinder went from 1064 rpm to dead stop in less than a sec.

The Picture of the whole machine is a machine that is Very simular to the one we have at work. It's just the basic machine ( same model ), It don't have the outriggers, rollers, control panel, and such.

I am VERY Thankfull today as things could have been a lot worse yesterday.
Howdy

Scootertrash
11-22-2012, 09:20 AM
Thank goodness for those guards, eh? I never did any centerless grinding, but back in my machine shop days I ran a surface good sized surface grinder and had a wheel shatter. Scary stuff.

remsandpets
11-22-2012, 09:42 AM
We have several centerless Grinders as well, Blanchard, and surface grinders. Always scarry when things go wrong. Se also have several cnc lathes and mills with assorted manual equipment as well.
Glad you are OK Howdy.

El Camexican
11-22-2012, 10:14 AM
Scary stuff! I've been in close proximity to a number of broken wheels and disks over the years and it never fails to scare the livin bejesus out of me. Glad to see you lived to tell a story instead of being the lead character in one that everyone else in the shop was telling today.

Howdy
11-22-2012, 10:24 AM
I was Lucky as I was about 15-20ft from the machine when she blew. Had I been by the control panel I probably would have had a heart attack. I don't scare easily, but this shook me up pretty good for 2-3 hours. After putting the new wheels in and getting ready to restart it for the first time I was shaking. I looked around and everyone else was sorta hiding waiting for it to go KABOOM again. Luckily it started up fine and ran great afterwards. But The old wheel was just installed Monday and ran fine for 1 1/2 days before it exploded. Next 2-3 work days will be stressful.
Howdy

coolpool
11-22-2012, 10:36 AM
Holy crap that could have caused some serious damage if the guards were'nt in place. Will it even run with the guards open? Does the machine have on board vibration monitors that would shut it down if something is detected? Seems weird to me that something that can grind to such close tolerances can fail so dramatically without warning. Glad everyone is OK.

dustrunner
11-22-2012, 10:44 AM
glad your ok.. wow.

Howdy
11-22-2012, 10:55 AM
Holy crap that could have caused some serious damage if the guards were'nt in place. Will it even run with the guards open? Does the machine have on board vibration monitors that would shut it down if something is detected? Seems weird to me that something that can grind to such close tolerances can fail so dramatically without warning. Glad everyone is OK.

Yea, it will run with no problem without the guards. This is a 35+ year old machine. It has been rebuilt and upgraded over the years though. It's computer adjusted and has a Lazer mic on it as well. The lazer mic measures to within .00001 ( 1/10th of a 1/10th ). There is no vibration shut off, but if it sences too much pressure it will alarm out and depending on the alarm it will shut down. We do have a Electric harmonic balancer on the wheel arbor. The meter is old skool but is digital. It was running very well with very minimal vibration. There was NO warning what so ever, spinning at 1064 RPM it wouldn't have mattered any how. It normally takes 4-5 minutes for it to stop when you shut it down ( arbor and grinding wheel combined is around 1800- 2000lbs ). The only thing slowing the wheel down is the 40-60 HP drive motor.

Howdy