What are the requirements for grinding? Surfaces flat and parallel to what tolerances? Dimensional tolerances? To what surface finish? The economics will depend quantity, which may justify expenses of developing a optimized process.

Maybe EDM to a rough shape first?

Tom

What are the requirements for grinding? Surfaces flat and parallel to what tolerances? Dimensional tolerances? To what surface finish? The economics will depend quantity, which may justify expenses of developing a optimized process.

Abrasive,
I imagine a ceramic rectangle of 8 x 5 mm coming out of a disc of 8 mm. This disc is grinded on two sides only. In this way I have a ceramic with 2 rounded sides and 2 straight sides
Surface finish of grinded sides Ra about 5 to 10 µ is OK, not very critical. Parallellism about 0.2 mm for the entire length of 6.2 mm. Quantities a few million pieces per year.
I'm thinking of something as centerless grinding, feeded in continu.
Tomwalz, what is EDM?
Regards,
Jos

It seems you will be better served buying tooling, pressing and firing these ceramics to finished size.  If grinding is necessary for reasons not stated, costs will be driven more by handling than actual grind time.  It seems these parts could be autoloaded into simple fixtures for grinding the two faces and avoid bonding adhesives or waxes.  Feel free to contact me with your email if you would like to discuss it further.

I don't need the grinding, it's just to adapt the shape to different dimensions. But we already have the complete line for discs and now need rectangles of different dimensions. It's a question of economics. I want to check if the grinding can compensate the costs for all specific tooling we need for rectangles (much more than just the pressing tool).
Sawing is also a possibility. But also here I don't want to use adhesives.
I'm interested in autoloading fixtures for grinding and also the appropiate grinding machine.

M. Ceramicguy, I would like to mail you. Where can I find your e-mail-address?
Regards

EDM is electro discharge machining.

See the March 2002 IDR (Industrial Diamond Review) for an article on grinding ceramics.
tom  

Tomwalz,
I'm not in the possibility to get the article in an easy way. Is it worth the effort? What I'm looking for is a DOUBLE HEAD SURFACE GRINDER WITH AUTOMATIC THRU-FEED WITHOUT USING WAXES OR ADHESIVES.
Parts are discs, put on their round side and grind down to become near-rectangles, by grinding upper and lower part.
If this magazine writes about this subject I'll do much effort to get it.
To my knowledge EDM is a slow process which has benefit for some typical situations (very hard materials) which cannot be resolved by other means. Isn't it?
Thanks anyway.

email me at tomwalz@email.msn.com and i will send you some web addresses.

Industrial Diamond Review is:
http://www.idrmag.com/

You want March 2002 and I think it is called EDC grinding

The following have some really good new technology for grinding ceramics.  

Agathon Switzerland    New grinder technology
AGIE Charmilles Group    EDM technology
Al Bouchard    Multi pass technology
Blaser Swisslube, Inc.    Coolants
Diametal    Wheels
GE Superabrasives    Wheel design

Keep me in mind if you want to braze ceramics.

tom

josBCC, You may want to talk with a vendor of doubledisc grinders or makers of wheels for those machines, since this is such a niche technology/industry that public information is hard to come by. Companies like Landis/Gardner are specialist in the wheels used in this case. You might also try contact the folks at JL Lucas (www.jllucas.com). Getting into doubledisc grinding could be expensive if you need to invest in equipment. So the economics may be a relative term. What about outsourcing the job? Shops that specialize in doubledisc grinding may be willing to develop special fixturing as part of the job.

JOSbcc,
   You appear to be talking about a Double Disk Grinding machine with some type of Ferris Wheel or Elevator type of loading fixture to securely hold groups of parts as they pass between the Wheels.  This would require rather large diameter wheels and would be great for automating the operation.   

The Thrufeed System as applied to double disk grinding,  which you mentioned earlier as a take-off of O.D. Thrufeed Centerless Grinding, would be difficult to implement due to the tendency of the parts to rotate as well as tip unless you kept heavy continuous pressure on the in-going parts as well as the out-going ground pieces.  IMHO, This would be a high scrap process.

Another option, for smaller production quantities, would be to clamp a stack of the pieces in a ratchet type fixture which allows the two opposing sides to be simultaneously ground on a Straddle Grinder.    The Stack of parts would then need to be indexed 90 degrees with the Ratchet mechanism to grind the other 2 opposing sides.   The Tolerences required would dictate the design of the fixture.   Having extra Fixtures would allow the parts to be pre-loaded into the fixtures so that down-time would be minimized.   Advantage would be smaller diameter wheels and lower cost machines and fixturing.   

If you decide to perform either of these operations and are wanting to do large quantities, Structured Porosity Vitrified Bond Diamond Wheels would be very effective for this type of operation and cut your wheel maintanance, trueing, dressing costs.

Hope this helps.

RamingtonStall