Cylindrical Grinder Question

[rdh88]

I recently started a job running a grinder. I grind 10x50 inch rolls that crush wheat and stuff like that, they then get corrugated. The problem is that the grinder I run is old, I mean really old, I don't even think the drive motor welded on to the table is the original one, the journals of the rolls rest on v blocks with leather straps as cushions. The drive pulley that the drive dog is connected to wobbles, a lot, 28 thou out of round, the journals only wobble 2 thou. I was told the machine was inspected and the table ways are worn along with the spindle bearing for the grinder wheel. The v blocks are just open, there is no stabilizing equipment or anything other than a tail stock adjustment. I have no idea what make or model this thing is, it's just old and green. I am expected to hold a 0.0001 tolerance perfectly across the whole roll, the thing is, these guys I work worth that are training me usually only check the ends and middle of their work, now that they're training me they measure every 2-4 inches, which is fine with me, but once we run the roll again just for a clean up or finish and stop it again and it stops in a different spot we get different measurements in certain spots, high and low spots in a wave, in the same spots every time, they keep assuming that I am adjusting the tail stock when they walk away or messing with the wheel while the table is traversing, I'm not of course, the problem is that the roll never becomes completely round with all of the machines issues and the speed they make me traverse at. They then try to show me how it's done and still have problems and then act confused and assume I did something again when they walk away for a moment. There are parts of the roll that are strainght, but, mic the whole od and you discover high and low spots, but they only find those spots by chance when the roll stops perfectly at those spots. Anyways, do the problems I describe such as the worn ways, spindle bearings and wobble in the work head sound like the culprits to my issues? Also, I can hear the wheel missing in the same exact spots every time and it is always right in sync with the wobble of the work head, I put an indicator on it and watched the needle move right along with the miss of the wheel, in the same exact spots every single time. Any input?

 

[JimDawson]

Well, until they realize that machine is just flat worn out, there is not much you can do. If possible get one of them to run the machine while you watch, you don't touch anything. Then do the same measurements . Once they figure out they can't hold tolerance, maybe something will happen. It is always possible that they are doing something different than you are and it actually works for them.

On the other hand, they may just be screwing with the new guy!

 

[rdh88]

Well, until they realize that machine is just flat worn out, there is not much you can do. If possible get one of them to run the machine while you watch, you don't touch anything. Then do the same measurements . Once they figure out they can't hold tolerance, maybe something will happen. It is always possible that they are doing something different than you are and it actually works for them.

On the other hand, they may just be screwing with the new guy!

I feel like they are screwing with me! Why would you need such crazy tolerances to crush wheat? But I've watched them do it a few times and say it's good then check again and get confused about what happened, they don't understand that you have to check multiple spots around the od, also, when the wheel misses, the guy says o it's just the coolant making it sound like that, umm no bud, I took a video on my phone with the coolant off and it does the same thing. Also, when you barely touch the wheel to the roll only one side of the wheel hits, and it hits harder traversing one way than it does the other. I'm talking to the manager on monday, this is crazy. I have no problem making certain sides of the roll straight , but rotate it a little and measure carefully, boom, low spot.

 

[JimDawson]

I'm guessing a few thou would not make much difference in this application. Now if you were grinding paper machine or printing rolls, they need to be accurate.

They may move you to a different machine on Monday, one that actually works. They've had their fun with you.

 

[rdh88]

I'm guessing a few thou would not make much difference in this application. Now if you were grinding paper machine or printing rolls, they need to be accurate.

They may move you to a different machine on Monday, one that actually works. They've had their fun with you.

There is only one other grinder that works and the other guy is on it. They really want me to make perfect rolls with this. O well, if they want to pay me to just grind away one roll all day then so be it.

 

[Billh50]

I have to agree with Jim. Sounds like the machine is worn out or they are screwing with you. I would tell them to show you what you are doing wrong and tell them not to walk away so you can't be accused of making any adjustments.

 

[brino]

I'm talking to the manager on monday, this is crazy.

Assuming this is not just hazing the new guy then this is where it gets tricky......

If other trusted employees are claiming to the boss that there is nothing wrong with that machine it could leave you looking like an incompetent whiner. It needs to be handled carefully.

To me it sounds like the extra inspection (caused by trying to review the new guys work) is showing issues they try to ignore during normal run times.
I agree with Jim above, get another operator to do a few in a row with you just observing (and them not walking away!), then stop the machine and go over those parts with that operator in detail. Mark one of your parts vs. theirs and compare them directly to one of your parts.

Also, if you can show a reasonable person (other operator, team leader, supervisor) that a dial indicator shows more slop in the machine than they try to hold the work to you may win some support.

It may be that everyone deep-down realizes that machine is very worn, but they still need it to produce parts and income, so they are willing to turn a blind eye to some parts that are slightly "out of spec". If so, the you'll have to accept those "compromises" to fit in there.....and possibly look for another opportunity in the background.

Good Luck, I feel for you!
-brino

 

[projectnut]

Another thing you might try is to "Blue" a section of a roller before setting it up in the machine. Have an "Experienced" operator assist you with the setup and see what happens. As mentioned before don't let the experienced operator walk away until the job is finished. If the machine is as worn as you say the results should be evident. I've used a worn Brown & Sharp many times over the years. Once you know exactly where the wear is you can some times compensate for it. However if the entire machine is worn I wouldn't expect even the most experienced operator to make high tolerance parts in a timely manner.

 

[4GSR]

First thing I get out of this is the grinding wheel is out of round. When was the last time the grinding wheel was dressed or trued up with a diamond?

 

[rdh88]

First thing I get out of this is the grinding wheel is out of round. When was the last time the grinding wheel was dressed or trued up with a diamond?

I dress the wheel every few passes, these are cast iron rolls and the wheel dulls quickly, still, it does not hit evenly one side always hits first even though it seems quite even when dressed. Also, it hits harder traversing one way than it does the other, I didn't even notice that myself, the other worker pointed it out, they really expect me to learn this machine in this condition and put out good rolls that black out under a light when stacked in a pair and they expect this much faster than this machine allows. I just have to bring all this to the attention of the manager and see if he cares or not. I have a feeling he's going to say make it work or you're fired.