Machining Sheet Metal

[rchacich]

I am not a machinist, but I am designing a cnc mill to machine sheetmetal. It will be used on 16 ga crs and sst. Using a 1/4" end mill (mist cooling), I need to choose a spindle rpm, hp, and feed rate. I am hoping someone will have some input based on thier experience.

I am looking at 2 options for a spindle motor. 2 hp and 5hp at 18,000 rpm. I can use a VFD to slow down the spindle, but the HP will be proportional to the rpm.

The 2 spindle motors will require different machine designs since the forces will be greater with the larger HP motor.

Any input will be greatly appreciated.

Best Regards,
Ron Chacich

[Delw]

I havent cut alot of sheet metal but the stuff I have cut (galvanized a/c and electrical work type) I had to go under 5krpm's( I wanna say best ran about 3500rpm) I used 1/4" 6flute coated carbide.
Like I said I havent cut much and if I went over 5k it would burn the endmills, I also sandwhiched the sheet metal between 2 alum plates with .010 clearance on profile.
Personally I would rather cut 304 stainless however its more than likely due to inexperiance on sheet metal and I have cut lots of nickle alloys and stainless but gal. sheet metal has kicked my butt every time.

the machines I used were fadals and also a hand mill for stupid stuff from buddies with projects my handmill I believe has a 5hp motor on it in never bogs down.
wish I could help better.
Delw

[rchacich]

Dlew,
Thanks for the input. I thought that 18K was more like a router speed rather than a milling speed. I got the 18K rpm from a specification sheet of a German made machine.
Ron

[senna6666]

woowwwwww

18k rpm ????? for this rpm you must have "diamant" (caled in my country) tools
1/4" - 6,35mm i propose
if you use HHS mill max rpm without burnning the tools its 1000rp maybe 1200rpm with allot "emulsion" (cooling liquide)
max. deep for this tool its 1/2d or R 6,35/2=3,175 - i going max 2mm - "in secure area"
feed rate YOU must decide - or use data for this tool
if you have "high sound" (how to explain????----piiiiiiiiiiiiiiiii) feed rate its too small for this cutting speed (rpm) - rmp must go down (slower) or feed rate faster
but if you have too much material (Z-axis too deep in material)for this tool and increase feed rate i propose you will brake the tool !!!

For "WIDIA" tools or how you call - i propose Carbide you can go with 1500 - 2500 and allot coolin liq.
deep - you can go on 5 mm without problem
and feed rate ..........???????
Try this method - for example - take this tool and chose some rpm-hss lower-carbide middle and diamant high and very high
deep : R for HSS 0,7-1*d - carbide (widia)
and feed rate go from lower to higher - just try to hear (listening)
(if you dont have data for your tools)
when you find apropriate rpm vs feed rate - believe me you will know !!!
after "famous" high sound - when this sound stop you can go up with feed rate for 5-10% and this is it !!!
Again : if you dont have any data for tools you use

These are the data from my experiences on conventional machines !
and this is max. value for this type of tool ?

I hope this will help you.

P.S. Sorry on my bad English