Cutting Tools for CAM: Why Backing Off Is Not Always Best


Shops are really afraid of running tools according to many of the tool vendors’ latest astoundingly high Surface Feet per Minute (SFM) and feed rate recommendations. This is very understandable in light of all the interdependent manufacturing process variables that must be kept in control. These include:

  • Traceability of manufacturing operations and results from and back to the model.
  • Good workholding solutions to optimize part rigidity and tool reach.
  • Appropriate equipment and tool approaches to minimize setups.
  • Optimal tool selections.
  • Optimal toolpaths for efficient material removal and finishing.
  • Appropriate coolant selection and application to optimize material removal while extending tool life.
  • Accurate and comprehensive simulation to assure part and equipment safety.
  • Fine-tuned post-processor behavior to translate CAM output into consistent machine behavior and allow multiple machines to be used for any given part.
  • Sufficient programmer/machinist know-how and training to assure that all of these variables are taken into account.

With all that is going on, is it any wonder that shop owners are afraid to run their equipment at the “ideal” feeds and speeds most frequently recommended by tool vendors? If mistakes are made regarding any of the variables listed above, a crash can occur, destroying a tool and holder, scrapping a part and damaging an expensive CNC machine while diminishing productive capacity for days or weeks until repairs can be made.

The time honored and most broadly practiced solution to this fear is to back off on the vendors’ recommendations (sometimes way back) just to be on the safe side. Besides, these recommendations are highly suspect anyway, going against much of what machinists have been taught throughout their careers.

Here’s the opportunity: We have known for decades that it is theoretically possible to machine at dramatically higher cutting parameters if we only had the right CNC equipment, tools, coatings, coolant strategies, workholding solutions and CAM software. Now all of these technologies have advanced to a point where we can actually turn the theoretical into the practical. So backing off on the tool vendors’ recommendations is not an option for those who wish to compete effectively against those who are taking them to heart.

That does not mean that we can jump in blindly. Tool vendors achieve many of their optimal machining triumphs in the laboratory under highly controlled conditions. You have to figure out how to do it in your shop where many different types of jobs are being processed simultaneously while customers are anxiously waiting for their deliveries.

So once optimal machining efficiency has been established as a goal, you must also decide to make haste methodically and patiently. A good place to start is where there is much to gain and very little risk, such as drilling.

Stay tuned for the next article in our series that will run in December and January!

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