Surface finish issues are especially critical in aerospace and medical applications. Chips recontacting the work and high or unstable Built Up Edge (BUE) are the usual suspects of poor surface finish on machined parts, regardless of material. There can be other factors, such as a poorly maintained machine or exhausted metalworking fluids, but these are seldom the case when “the last job on this machine ran just fine.”
Here are our 5 tips that you can address on the machine to make poor surface finish go away:
1) Increase the speed SFM (especially on Carbide!). This will help reduce BUE.
2) Reduce the feed per revolution (IPR- inch per revolution). This will help reduce the flank wear.
3) Increase the top rake angle.
4) Add a chip breaker / chip curler.
5) Increase tool nose radius.
We have seen increasing speed to be especially helpful on aerospace and medical machining jobs on stainless steel. Increasing speed is also important when using carbide- carbide likes speed.
If you can see that the chip is recontacting the workpiece, then address your chip control issues first. Chip control is the first place to start. Adding chip control geometry on the tool is probably the easiest change on non CNC machines. Modifying the cam to break the chip should also be considered. On CNC’s, adding chip breaks into the program is also an easy adjustment. These are especially effective if the workpiece is a gummy material.
Built Up Edge (BUE) is impacted by three primary factors: material chemistry (which you can’t change- you already have the material); surface footage (slower speed means hot chip is in contact with tool longer, creating higher BUE); and tool geometry (the point is to slice or cut, not rub off the material).
Of course, you should make sure that your setup is rigid, your tooling properly seated, your coolant lines are delivering plenty of coolant to the tool/work interface, etc., etc.. But these 5 tips are ‘Tools You Can Use’ to improve the surface finish on your problem jobs, including stainless and other aerospace and medical materials.
Tag: Medical Machining
Precision machinists make the things that make today’s quality of life technologies go. And stop. Anti lock brakes – we make them. Airbag parts. Bonescrews and medical implants too.
Here are 5 reasons to choose a career in precision machining:
Ready employment. Even at the bottom of this last recession, there were openings for precision machinists advertised in the major newspapers around the country. Our parts are indispensable. So are our skilled machinists.
Great work. Our work is challenging, satisfying, and technical. At the end of the day, you can see the results of your skill and effort. Lives that will be saved. Cars that will run. Our industry (NAICS 332721) is just under $9 billion in value produced according to the US Census.
Great Wages and Benefits. We don’t know what the Obama administration has in mind for the benefits side of the equation, but set up machinist and toolmakers wages are on par with the wages that a business major might earn after a 4 or 5 year bachelors degree program. But no tutition bills to repay for the precision machinist.
Great life. How many fields do you know of where the people don’t have some worry about the future, and their place in it? Low cost competition from China and India has not killed our industry. We continue to make the high precision, high value added parts that make a difference in people’s lives, everyday.
Great values. Today shops are managed by international environmental management systems like ISO 14001 and international quality standards like ISO/TS 16949. We are sustainable, lean, just in time, and environmentally sustainable companies that make a difference. Making high value high precision parts. You can too. Come join us!
Go to the PMPA Industry Careers Page to get started with your career choice.
