Improving Surface Finish During High Speed Machining

Many factors can affect surface finish. This answer to a reader’s question focuses on imbalance and frequency sensitivity.

Article From: 3/14/2011 Modern Machine Shop

Click Image to Enlarge

Tom Delio

Tom Delio is one of the nation's leading authorities on high speed machining and machine tool dynamics. He answers questions from readers on challenges related to high speed machining. To ask your question, visit our High Speed Machining Zone and click on “Ask an Expert.”

A reader recently used the “Ask an Expert” feature of our High Speed Machining Zone to ask a series of questions aimed at better understanding high speed machining.

Question:

What is the best surface finish I can acheive while contouring an outside radius with a ball endmill during high speed machining? We use a large-radius cutter now (5/16 inch).

Response from Tom Delio, co-founder of BlueSwarf:

Surface finish can be affected by many things, including chip load, stepover, tool geometry and inclination of the tool. The benefit of high speed machining is that higher machining rates can be achieved with lower cutting forces and lower chip loads—both of which will improve surface finish.

However, one risk is the vibration resulting from imbalance and also the frequency sensitivity of the cutter at higher speeds. To best combat this, you must make sure your tools are well balanced. For high speeds, a level of G2.5 is the generally accepted standard. Also, it would be best to identify the frequency sensitivities with a tap test and then compute the sensitive speeds that need to be avoided.  Alternately, this can be done with testing by choosing your desired speed and simply trying speeds about 5 to 10 percent higher and lower and observing which ones result in a better surface finish.

Comments are reviewed by moderators before they appear to ensure they meet Modern Machine Shop’s submission guidelines.
blog comments powered by Disqus
Loading the player ...
MMS ONLINE
Channel Partners
  • Techspex