New to CNC milling (using mastercam), question regarding Cutting parameters vs Feeds

Philipraposo1982 · May 15, 2020

Good day everyone,

I have a question and I am hoping for some clarification.

Lets assume I am machining a face on a 304 SS plate and my cutter is a 3/8 diameter and my SFM = 150 and my FPT = .0015

I make my facing operation in mastercam and I am in my cut parameters, are the default values good enough? How does changing the stepover / overlap values affect the cut? how can I determine the optimal settings?

GENERALDISARRAY · May 15, 2020

in facing, the params mostly effect time/efficiency. By changing the parameters you can get it to maybe two passes instead of 4.

But they are altering your engagement values, probably not a big concern with a 3/8 endmill. But may affect finish and tool life.

I use dynamic facing with an endmill.

dodgin · May 15, 2020

Philipraposo1982 said:
how can I determine the optimal settings?

A LOT of the following: Google, Practical Machinist forum browsing and trial and error.

Those defaults are decent for 304SS, in my opinion...but it depends on the details.. What brand end mill? Is it coated? What kind of coating? What's your setup look like? How's your coolant situation?

New to machining or new to CNC machining? If the former, an apprenticeship is traditionally like 10k hours...so figure on that amount of time for figuring out the basics and even then you're just scratching the surface.

Nibleswick · May 16, 2020

1/2 to 3/4 the diameter of your tool is a decent rule of thumb for facing stepover. Go smaller if you have tight flatness or parallelism tolerances on a thin plate, but it wouldn't matter too much with and end mill that small generally.

(Edit) I should mention that I'm assuming this is a finishing pass. On deeper cuts it depends on just how deep and what the end mill is designed to handle well.

zero_divide · May 16, 2020

(Shameless plug)
Try Advanced CNC Speed And Feed Machinist Calculator - HSMAdvisor
Or FSWizard Machinist Calculator

There you can see how changing engagement values, coating type, etc changes the recommended cutting parameters.

That, or write a simple excel spreadsheet based on numbers from MH that accounts for dozens of those variables at the same time

mhajicek · May 16, 2020

I use HSMAdvisor and the Helical Machining Advisor. Both give good numbers and have slightly different strengths and weaknesses.

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New to CNC milling (using mastercam), question regarding Cutting parameters vs Feeds

Philipraposo1982

Plastic

GENERALDISARRAY

Hot Rolled

dodgin

Hot Rolled

Nibleswick

Aluminum

zero_divide

Stainless

mhajicek

Diamond

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