Speeds and Feeds Training: When We Went from 400 RPM to 800 RPM, the Cutters Squealed Like a Pig

An Example of Increasing Speeds and Feeds

Over the last few weeks, our blog entries have focused on the basics of calculating and the effects of surface feet per minute, SFPM. Today, we want to give you an example of how we use machining fundamentals to troubleshoot and solve problems for our customers.

Nolte - Fixture

A few weeks ago, we were called in by Superior Equipment to problem-solve for one of their customers. The customer was cutting a piece of hot rolled steel using gain cutters made of high-speed steel. These cutters didn’t give the customer speeds fast enough that would get them within their machine’s horsepower range.

So, we developed a short- and long-term solution. We immediately took the high-speed steel blades back to Dayton and put our Monroe Edge on the tools. When we went back down to customer’s shop, we increased the SFPM of the cutters to come within the horsepower curve of their vertical machining center.

Nolte - Before Cutters

We then developed a long-term solution for the customer within one week. We made a set of solid carbide saws that contained 60 teeth compared to the previous cutters they used, which only had about 16 teeth. Using more teeth in the saws allowed us to dramatically increase the feed rate.

Nolte Video - Before Photo

Click here to see and hear the cutters chattering.

Once we prepped the edge on the cutters, we started playing with the SFPM. Previously, the customer was running the cutters at 400 RPM and 8.3 inches per minute, taking one rough pass and one finish pass. Given that we added substantially more teeth on the saws and would have a lot more contact, we first tried using solid carbide cutters of the same form, but the cutters chattered.

We decided to cut the slots in a single pass and removed one cutter; starting at 600 RPM and 32 inches per minute, the operation cut as needed. Continuing to test scenarios, though, we tried mounting two cutters at a higher RPM (800 RPM and 15 inches per minute) to reduce the load, but that presented problems.

Nolte Video - After Photo

Click here to watch what happens after GTS comes in.

So, we ultimately decided on a single cutter process, at 600 RPM and 32.4 inches per minute. This was three times faster than the customer originally ran and was within horsepower range of the machine, so there was virtually no load at all.

The new process we developed for the customer consisted of staggering the cutters on the arbor and running one slot at a time. At the right SFPM, we ran two passes (which was the same number of passes they originally had), but the operation cycle time was reduced by about 60% since we used carbide cutters with many more teeth. That switch from a high-speed steel cutter to a coated carbide cutter allowed us to increase SFPM. And, just like we reviewed in last week’s video on increasing SFPM (skip ahead to 3:41 in that video), you have to be mindful of increasing SFPM with different materials. At the same time, the new material effectively helped solve our customer’s cutting issue.

Tom's Bird

Original photography by Tom Greene

Our solution, using those fundamental principles of adjusting SFPM, just shows how innovative thinking, technology, and speeds and feeds basics deliver results for our customers. When we started this process, the cutters squealed like a pig; by the time we were done, they were humming like a bird.

 

 

 

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