Sometimes the parts come out of the machine hot and if you are attempting to grind to micron tolerances, this is a problem. The bore size of a hot part might measure in spec immediately after grinding; however, once it cools, it might shrink enough to be out of spec later on. The opposite might also occur, you could reject a hot part right off the grinder, but once it cools it could be on the money. To avoid these sorts of problems you want to have parts that are as close as possible to room temperature as soon as they come off the machine.
So why are the parts hot? The first thing to do is check your coolant. If your coolant is not taking the heat out of the grinding process, you are going to be chasing your tail. So check your coolant lines, your nozzles, the filter, etc.
If that does not work, you will have to get more analytical by identifying whether or not the parts are getting cooler or warmer during a production run. Let’s say you just dressed the wheel and you pick up part number 10 and it feels hot. You grind some more parts and check part number 20. It’s getting a little cooler. Check part 30. It’s better. Check part 100. Everything feels great. Then you dress the wheel and parts # 1,2,3,4 and 10 are all hot again.
This would indicate something going on with the dress. Maybe you are dulling the wheel during dress and it’s really struggling on those first ten parts and building up a lot of heat. It could also be the opposite. Maybe the parts feel fine at 10 and then they are getting hotter and hotter. That could mean that the way your process is set up, the wheel is dulling over time and you need to dress it more often to keep it sharp.
Finally, as in so many bore grinding problem-solving scenarios, remember:
- The more data you collect the better position you will be in to get to the bottom of any grinding problem.
- Sharpening the wheel with more aggressive dress parameters or a sharper acting dressing tool will often reduce the severity of most grinding problems or make them go entirely away.