Thursday, December 09, 2021
Machining Fundamentals: Intro to Speeds and Feeds
Fusion 360 Blog: We created the Machining Fundamentals series to help you brush up on your CAM knowledge, whether you work in a machine shop or are just getting started. In-house machinists at our Birmingham Technology Center host each episode and provide a detailed overview of a tool/process. In the last edition, we covered Work Coordinate System (WCS). Here we introduce speeds and feeds — what they are and how to set your own values in Fusion 360.
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2 comments:
Feeds and speeds are something that it seems comes with practice. I've now gotten to mill two different things as well as use the lathe on one and a lot was learned from actually getting hands on with the tool. Figuring on the feeds and speeds by hand is definitely not as difficult as having to assign values to each of them. I have broken my fair share of pilot bits while using a drill but I had the experience of setting the speed to hagh and snapping a small mill bit because the computer program was just going too. I adjusted and was able to complete the task with no further issues. A similar set of values that is set up in a standard way that I appreciate is on Laser cutters. Someone has done the leg work of figuring out the scan and cut values for the various materials and thicknesses of material and there’s a spreadsheet that sits there so no experimentation has to be done.
I have to agree with Owen on this, feeds and speeds are incredibly vague and often come from personal experience. Even though there are calculators galore out there, none seem to quite get it right with the different machines we use, so we still go off our intuition or give ourselves a wide margin of safety. Fortunately, we aren't doing much machining outside of plywood, MDF, Aluminum, and occasionally mild steel, all of which are forgiving. I like how this article really went into why we should care about them, and more importantly why they matter in different operations. For example, lead in and lead outs put far more strain on the tool. I discovered that our mill doesn't scale its feedrate when milling slots recently, so the first pass puts a full load on the tool, while later passes only put about 25% on it. Nevertheless, the feedrates for these operations are constant, without a way to change them. Another example of where this is important is the technical design of CNC parts. Inside corners are already painful, but without proper care the feedrate and speed of the spindle can immediately jerk when it gets there. That is because the tool is usually only engaging half the circumference, but if it hits a corner that can jump up rapidly for a brief moment, causing quicker ware. It is better to add fillets with a larger radius than the tool to ease it around the bend. Hopefully fusion helps folks along in that world though!
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