CNC mill speeds

David G

Well-known Member
I want to set the maximum speeds on the axis so they are useful, but safe for a beginner.

What would be appropriate?
 
Well, a Servo feed on a manual Bridgeport gives about 35 IPM at full speed/rapid.

I wouldn't want to crash it at that speed, but it's slow enough to react in time to stop it, maybe...
 
For first run programs I set my rapid override control to 25% which is 500IPM. On the parts I make in quantity then the override goes to 100% which is almost 2000IPM.

My experience with stepper driven machines is they will start losing position at high speeds. I think that just below that point is where you will end up setting your maximum assuming your control system has a rapid override capability that can be used while setting up and test running a program.
 
Our HAAS VF2 HSS on G00 moves is nasty fast. In class we run it at 25% rapid which is ~60 IPM . all crashes happen after it goes beyond intention. which going slow doesn't actually help fix. Some speed restriction may be needed to prevent over running the steppers. Check the specks. Especially starting and stopping events at speed. Jim
 
Of course there are many ways to "skin a cat" here but here is another possibility.

Go ahead and set up your maximums to the suggested rates for a pro. Then in your programs don't use a G00 (rapid traverse) command. You could command a faster feed rate at those times when a pro would use rapid, then slow feed rate back down when you're not cutting air.

Let's face it, you're gonna crash ! We all do, though it does lessen with experience. Some crashes are totally impossible to avoid even if you are watching very closely. I know you are wanting to ease into this, as anyone would to save that shiny table and that new drill chuck. But it is only a matter of time.

I have never ran a set-up like you are building, always use a commercial controller like Fanuc or Mitsubishi . I have no idea if you can wire up a rapid feed rate override like others have mentioned. If you can, i would. It will make you feel like you have another chance to save a crash anyway.......then definitely a huge E-stop to stop things that are still rotating after the crash.

I have really enjoyed watching your build on this machine, but have no concept of how you electronics guys make this stuff work.
 
You guys are scaring me, those are fast speeds.

After you have been running a while you'll get comfortable with faster moves.

One thing to keep in mind is that you will get best tool life with a decent chip thickness. When you feed too slow the tool rubs a bit before enough pressure develops to "bite" in and cut the material. Different materials behave differently in this regard, but all do it to some extent. At one extreme is brass where rubbing is negligible. At the other extreme are most stainless steesl, some tool steels, Titanium, and other exotic metals that once a cutting tool has rubbed them to any degree, the resulting work hardened surface in some cases is no longer machinable.
 

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