Centerless Grinding - Part Slip on Regulating Wheel

[jpw1]

We are centerless grinding a steel shaft using water soluble coolant at 4%.

We are seeing part slip on the regulating wheel. It appears to be the worst immediately after dressing.

The jobsetter thinks that the regulating wheel is loading and causing the problem.

Any suggestions or comments?

 

[saberblue]

Check the angle on the reg wheel and the dress rate they can both cause this type of problem--

I am a fluids guy so look at the coolant:
1-is the concentration right?
2- tramp oil can cause wheel loading and wheel slippage?
3- if it is a soluble oil and the emulsion is splitting - increasing particle size this can cause wheel slip?
4- over use of anti foam can cause wheel loading as well?

A.R. "Andy" Nelson
Engineering Consultant
anelson@arnengineering.com

 

[unclesyd]

One other thing you might want to look at is the particular coolant additive being used.

Is it still the same as it was before the problem started?
It might be one just as good as but not suitable for grinding.

Has the manufacturer changed the formulation of the bulk coolant as very minor changes can and will cause problems under the right conditions?

Make sure the shop hasn't combined two into one, like 49a with 49b because they look and smell alike.

If your are able check the bacteria level in the sump.

Is the steel the same one used to setup the process?

 

[DMAJ254]

I would look at the blade hegith and feed angle. Would seriously doubt its the reg wheel loading up. If angle isnt correct there isnt correct point of contact and that may allow slipping.

 

[steveh]

If the slippage is accompanied by rattling of the part it probably is low coolant concentration. 8-12% is usually a good level for soluble coolant. Too low a concentration will actually let the blade pick up part material and swarf and cause the part to lose contact.
Another possiblity is that the parts aren't straight when they go into the grinder.
Tramp oil (as mentioned by saberblue) is another likely culprit.
If the reg wheel speed is too high or the part is too high above center the part will slip. This always causes part rattle.
Last (and probably least)is the chance that the reg wheel is dressed at too fast a rate. The dress should normally be no > than 3 inches/minute when running long bar stock.

 

[saberblue]

You need to be very careful "playing" with the fluid concentration as it may (very often depending on specific fluid parameters) change how hard or soft the wheel acts. As a rule of thumb as the lubricity increases (largely hydrodynamic but to a lesser extent boundary and EP as well) the wheel will act softer and as we reduce lubricity the wheel will act harder).

By changing the concentration of a soluble oil by 5% you can change wheel hardness by a grade to a grade and 1/2.

A.R. "Andy" Nelson
Engineering Consultant
anelson@arnengineering.com

 

[tricky1975]

yr using the wrong coolant. end of. forget all the bollocks you have red. the roller on a centreless grinder gets eaten away by normal coolant. i'll let you know what i use. email me. cncgrind@microprecision.co.uk