Grinding problem û canÆt meet Roughness 0.2 micro mm

[allenchu]

Grinding problem – can’t meet Roughness 0.2 micro mm

I had a problem in grinding operation. Is anybody can help me to provide your comment?

Material: AMS 5659 (H1025) Corrosion Resistant Steel
Dimension: (in mm)
Before grinding: 11.40 Dia X 8.20 Dia
Specification requirement:
11.20 Dia (2.10 in length) X 8.00 Dia (9.06 in length) the adjacent radius is 1.0
Roughness: 0.2 micro

Machine: CNC Universal Grinder.
Grinding wheel: GC100L8V3G (Silicon Carbide)
Max : 1793 rpm, 33 M/S
Only use one machine, one operation to complete the part.

Problem: the NG rate of roughness is 20~30 %

Question:
Is the Grinder wheel abrasive changed to Aluminum Oxide (WA)?

Is the Silicon Carbide abrasive will have the bad consideration to the part material compare to using Aluminum Oxide abrasive? This is an aerospace part.

Does is ok to use wheel 93A60J8V7N or 58A 80J8V&N instead? Or any comment, grinding parameters recommendation are welcome.

Do I have to make this part in 2 operations, rough and finish, instead of one operation? the cost may increase?

your valuable to minimize the NG rage will be appreciated.

Thank you in advance..

 

[saberblue]

Normally SiC wheels are used for non ferrous grinding while Al2O3 wheels are used for ferrous grinding

the first thing I would look at is where your 30% rejects are in the dressing cycle e.g. do they occur just after the wheel is freshly dressed or just before it is dressed or are they spread randomly during the run? very frequently this type of problem is associated with the dressing cycle.

 

[unclesyd]

Are you trying to rough in and finish grind in the same operational cycle?

What coolant are you using?

How close are you required to hold dimensions?

What is the current abrasive size?
Like the above post I would look at a Al2O3 wheel. I would also use the wheel manufacturer's expertise in selecting the proper wheel.

Could you post sketch of the part?

 

[allenchu]

The wheel dressing has been tried to every 8 pieces. I guessed the wrong wheel was selected, not relate to wheel dressing.
I used the 93A60J8V7N grind wheel today, the result is not good, and the roughness is 0.6.
Yes, I would like to rough in and finish grind in the same operation cycle. Does it possible?
I used the 93A60J8V7N grind wheel today, the result is not good, and the roughness is 0.6. I guess the grain size may change from 60 to 120.
The coolant data is list below.
Water-soluble cutting oil SC-33
Components: Organic ammonia 20~40%
Carbojylic acid 1~10%
Inorganic salts 10~30%

PH : 9.4
Dilution:
oil : Water = 1 : 10