An Article on Plunge Milling

To All:
    Here's an article on the advantages of plunge milling in the Sept. issue of American Machinist: An excerpt from the article below.
=================================================================http://americanmachinist.com/304/Issue/Article/False/84782/Issue
    Plunge milling works much like drilling: plunge straight in, withdraw, step over plunge again, and so on. Since all the cutting force vectors are right up the tool’s strong centerline, you can safely feed faster by plunging along the Z axis than by end-milling along the X and Y axes. Plunging leaves a scalloped wall that may require finish milling, depending on tolerances and size of the stepover. Plunge cutters also have built-in chip evacuation capacity, so blast air or liquid coolant is helpful but not required on vertical setups. ================================================================
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BottleBob wrote:

Bob, sadly I think your swimming against the tide with an ON topic post.
Hope all is well.
Best, Steve
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Regards,
Steve Saling
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Garlicdude wrote:

GarlicDude:
    Yeah, I sort of figured that out when I calculated that the Off-Topic posts were 87.7$ of the total posts in the last 30 days. LOL
    But it's kinda like seeing a cherished pet you've had for 12 years that is dying of cancer. You just want to help, even though you don't have the time to make a concerted effort.

    Things are fine. Thanks for asking.
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=========================================>
Yes, I was learned many moon ago, on a an ol Bridgeport, that plunge milling is the FASTEST way to remove stock(besides the band saw). Plungeing & slight back-off away from direction of travel for deeper pockets work great. All moldmakers know that? In a CNC vert. mill, you better have large *strong* thrust bearings in the spindle & high pressure coolent- preferably thru spindle. Its a great concept, but IMO most common machines are not designed for it. Maybe a 50taper 8-10"dia spindle with gear drive head? Hmmm maybe me Anayak will do that? It is a 30hp "turtle" that will push your part out of the vise without a significant load on the meter. Hmmm.
http://users.cin.net/~milgil/TheBeast.jpg
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cncmillgil wrote:

Gil:
    Plunge milling has been covered in posts in here years ago, but I think it's advantages bear repeating from time to time. I believe drilling is considered the fastest way to remove metal in cubic inches per minute.     I think we've all drilled out slots and then end milled the webs and scallops away in Bridgeports.

    I don't know about that, it's not like you HAVE to plunge mill with a 6" face mill. If your machine has the power to drill 1" holes in steel, then I would think it probably shouldn't have any problem plunge milling with a 1" dia. end mill.

    I'll certainly agree that stronger is better for large dia. plunge milling.
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BottleBob wrote:
    Let me make an addendum here before I get crucified.

    Please add "Per Horsepower" to the above sentence. <g>
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Sorry, should have made myself a bit more clearer, drilling is fastest. As far as milling Plunge cutting is the winner.

I've used 1-2" max range plunge cutters from Valinite. High positive inserts. They take raw HP. especially the first total solid cut. A G73 (chip break) works well on that initial cut, just to get the chips out. After that its "pound time" moving 1/4-1/2" stepovers, thus the need for good spindle/thrust bearings & *rigid* machine tool. I'm thinking box way machines would be a good choice for plunge cutting.- Properly adjusted gibs help tremendously. Been on a few old battle axes that bounce like a SOB, until the service tech. "tightens'em up". No more busted carbides!- go figure. Seems like the linear ball way machines are common place nowdays. IMO they are not as strong as the good ol adjustable (slow traveling) well oiled box way machines. In moldmaking the name of the game is rapid stock removal, without killing your machine. Thats were plungeing looses it. You have to be "set-up" for it & have the right machine tool for it. I'm thinking $Horizontal$ machines are much better suited for plunge milling, at least the Mori's & Mazaks I've used kick ass! Big spindles, lots of HP, & gravity on your side. But Horz. machines are not common place in mold shops. Owners see the price tag & say forget it! You can buy 2 verticles for the price of 1 horizontal! Wonder why? duh...........
So if yer considering plunge milling in the 1-2" dia.range on a *regular* basis, I'd look at your machine tool design. Otherwise you'll tear it up in no time. Old Fadels or Haas's (aluminum machines) will most likey need new spindles often. Hell keep one in stock<g> there only around 10k new.;-) The Tree spindles are as much as 40k! so I've heard.
Anyone doing "High Feed" milling?

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BottleBob wrote:

Plunge every chance I get! Even been experimenting with plunging along splines. Ex: plunge down a twisted cavity with the the tool axis tracking the surface, retract just off the surface then back out the same way. A lot of geometry but should be worth it for some deep shrouded impeller cavities.
-- Bill
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Bill wrote:

Bill:
    Plunge down spline curves? Sounds like a job for a lollipop cutter, eh. <g>
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BottleBob wrote:

Actually just about any cutter. It's the trick of plunging down then coming back up without gouging the sides (hence the tool axis control).
One of the other important things with plunging is to properly retract off the surface first so as not to drag the cutter on the way out. For most plunging, NX does this quite well as it calculates the retracts on each pass away from uncut stock. Other systems like to do some kind of modified drill cycle that drags the tool straight up.
-- Bill
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BottleBob wrote:

>
Actually just about any cutter. It's the trick of plunging down then coming back up without gouging the sides (hence the tool axis control).
One of the other important things with plunging is to properly retract off the surface first so as not to drag the cutter on the way out. For most plunging, NX does this quite well as it calculates the retracts on each pass away from uncut stock. Other systems like to do some kind of modified drill cycle that drags the tool straight up.
--
Bill


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