Re: CNC grinding & wheel dressing

> Date: Wed, 14 Mar 2001 20:57:03 -0500
> From: ron ginger <ronginger@...>
>Subject: CNC grinding & wheel dressing


>Are there such things?
>
>Anyone ever try to build one? Could Vector figure the angular axis to
>keep the dresser pointed in the correct direction?

There is at least one company in Upstate New York that sells a commercial NC dressing attachment with their grinding machines.

The hard part of a wheel dresser is the accuracy requirement. In grinding, form as well as surface or cylindrical or ID, the usual tolerance is .001 or less on the DIAMETER. That means .0005 in. or less per side. Typically the adjustment is .0001 on a diameter, and even that may be split into 1/4's or 1/8's with a vernier scale. This is doable, but one has to realize that 1/64 accuracy is just not going to make an acceptable dress tolerance. Also the grinding wheel is very susceptable to chatter if the dresser is not extremely rigid. The dressing process is akin to cutting one extremely hard stone with a harder stone. Zero backlash is a must.

There was a commercial product available from a company in Florida, I believe the Orlando area a few years back that was based on a pair of slides with about 5 inches of travel in each direction. The cost was about $6000 and accuracy/repeatability was in the neighborhood of .000010 , 10 millionths of an inch.

To program the dresser, the grinding wheel is treated as if it were the part in a lathe. The diamond is treated as if it were a radius tool in a lathe. The profile of a VNMG insert is a 35 degree diamond shape. That is about the geometry of the diamond dresser and steel shank. I have heard of some trying the PCD(polycrystalline diamond) inserts for this, but not tried it myself. Use either the Lathe roughing or multiple passes with the lathe finishing function to rough and finish the wheel. Vector automatically comps for the tool nose radius (the diamond tip radius in this case).

Depending on your wheel mounting and extension of the spindle, you may need to make the roughing passes as vertical plunges, rather than the traditional lathe side to side roughing. Either will work and the cycle will comp for conditions in which the angle of the tip of the dresser would gouge the side of the wheel as it roughs it's way into the wheel.

With or without a fixed scale, it would be very useful to have a shadowgraph style optical gaging system installed. This would help for instance with setting the diamond offsets in the first place, and would also make it possible to come back mid-stream in a run of parts and true up the wheel after it had worn from grinding part of the lot.



Best Regards, Fred Smith- IMService
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