Grinding Journal - Summer 2007 - (Page 17)

Summer 2007 material characteristics of the part’s surface. These results should take you back to the process discussed earlier for analysis. Do you need to adjust the feeds or speeds of your process? Have you chosen the correct grinding wheel, and are you dressing it correctly? Is your coolant clean, or is your machine set up correctly for the part? To answer some of these questions, look at your part. The surface texture of a ground part should have a Illustration Visible Grinding Error Surface shows irregular, short “comma” scratches regular surface with a silky gloss. Marks, commas or scratches should not be visible. Physical and/or chemical grinding errors Look at the chart below to help diagnose the most common grinding errors. In many cases there could be more than one cause and you may have to check multiple scenarios to fix the problem. Possible Cause Abrasive grains in the coolant Remedy 1) Check coolant filtration, change if needed 2) Clean wheel guard 3) Clean the machine Chatter marks: Surface shows marks that are distributed over the entire circumference and lie parallel to the workpiece axis 1) Wheel not properly balanced 2) Vibrations from outside source 3) Qs too low (wheel: workpiece speed ratio) 1) Never let coolant run onto a standing wheel (rebalance the wheel) 2) Use a Steady-rest 3) Ensure machine is not next to a vibration source 4) Check the Qs ratio (wheel: workpiece speed ratio) Burning marks: Helical marks or local yellowish/ brownish discoloration of the surface. 1) Overheating in the grinding process. 2) Insufficient coolant supply 3) Wheel too finely dressed 4) Wheel too hard 1) Increase dressing feed speeds 2) Check the Qs ratio (wheel: workpiece speed ratio) 3) Increase coolant supply; use coolant with higher mineral oil % 4) Use softer grinding wheel 5) Reduce material removal rate Grinding with angular marks A grinding wheel which has been dressed too fast and transfers the error onto the part 1) Reduce wheel dressing speed 2) Always dress the wheel from one direction Grinding Journal 1

Table of Contents Feed for the Digital Edition of Grinding Journal - Summer 2007

Contents My Thoughts Exactly When Lives Are at Stake Walter Consolidating Production The Art of Grinding: Knowing the Source of Grinding Errors and How to Fix Them The How and Why of Conventional Vitrified Grinding Wheel Selection Grinding Glass Flat Problem Solver

Grinding Journal - Summer 2007

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