You’re probably used to receiving feedback from machine shops on things like surface finishes, tolerances, and proportions of features.
But do you ever wonder why your shop can’t deliver on your exact specifications without increasing the cost and lead time of your part?
If you’re happy to remain in the dark, read no further. But if you want a little insight into what goes on behind machine shop doors, we’re pulling back the curtain today on how we calculate feeds and speeds.
In CNC machining, feeds and speeds have a huge impact on part quality and price. For any given tool and material combination there is a large starting range for feed rate and surface footage. Surface footage is used to calculate tool and part RPM based on diameter. The high end of the combined feed and speed range can be up to 500% faster than the more conservative end, depending on cutting conditions. For every job, part, and toolpath, there are many variables that have to be considered to find the right range.
Feeds refer to how fast the tool is moving per revolution of the tool or the part. Each tool has a range for feed rate that can be adjusted depending on the specific application.
When turning, for example, a higher feed rate can improve chip management and reduce cycle time. If the feed is too fast, however, the surface finish gets rougher and there can be inconsistent or reduced tool life. The goal is to find the sweet spot with a combination of good finish, good tool life, good chip control, and the fastest run time.
Speeds refer to the RPM that a tool or part is rotating at, which is determined by surface footage and diameter. Similar to feed rate, manufacturers provide a starting range that can be adjusted to fit the application.
At the correct RPM the tool will remove the most material in the shortest time while wearing as little as possible.
Feeds and speeds directly impact each other, the finish, and the cost of a part. For example, if you have an issue with chatter, the first step is usually to increase the feed or decrease the RPM. Sometimes the solution is a combination of both. While there are multiple ways to address finish or cycle time issues, the correct way will vary depending on the requirements of the specific job.
Since there are a lot of variables to consider, calculating speeds and feeds has one of the biggest learning curves in CNC machining. At Wagner Machine, our experienced machinists have the skills and expertise to determine the ideal feeds and speeds for complex machined parts.
When someone runs into a situation that has them stumped, we ask each other questions, collaborate, and learn from our own experiences. As we like to say, “No one knows everything, but as a group, we’ve got it pretty well covered!”
Our goal is to be as creative as possible within even the narrowest range of options—but it helps when our customers afford us a little flexibility. Sometimes the difference between a 32 and a 16 surface finish can save an entire day of programming and setup time. Part design can limit our options, but if we anticipate feed and speed limitations, we’ll always make a suggestion for how we can get your part done faster and more cost-effectively.
Next time you need complex machined parts, rely on the experts at Wagner Machine. Request a quote today for your next project!