Physics behind milling and turning

[Russh67]

Hello everyone:

 

I am wondering if any one has any math formulas that will allow me to calculate a feed and speed taking into account material.

 

I am trying to find a more efficiet way of controling heat during machining, especially in plastics like ABS, Acrylic, polycarbonate and Noryl.

 

I am wondering if any one has any formulas they would be willing to share, or a web site??

 

Thank you

[YoDoug®]

This is probably the best solution to what you are looking for. I think it is not cheap though.

 

http://www.thirdwavesys.com/products/advantedge_fem.htm

[chip]

Spindle-rEdLiNe

Feedrate-100.00ipm + or - 50.00

[Russh67]

Thanks Guys...

 

Doug, Do you have AdvantEdge FEM?

 

If you do, how much? ........before I go into a whole thing here with upper managers.......

[Russh67]

Chip

 

I like you quote.....

 

I didn't know how to a pic in my reply so I attached this pic of a pic we have on our frig in the machine shop....

 

I think you might get a kick out of it.....

[within a thou]

Google the "SFM" for the material you are using then put that information into the formulas.

 

http://www.davehylands.com/Machinist/Charts/Formulas-Chart.pdf

[Russh67]

Thanks guys:

 

Looking to do something like take ABS Extruded bar. I want to keep the machining temp below say 190 degrees F, no coolant. I would love to be able to enter the themal coefients of the cutting tools and material into an exel spread sheet and be able to better predict cutting temperature.

 

I know this is mathematically complicated. Its been alot of years sinse I did this level of math in school......cant do it any more sorry to say.

 

We are wasting time and material getting feeds and speeds correct cutting plastics. Acrylic is a pain to machine. ABS is tricky too.

 

We are mostly turning plastics like ABS and Acrylic. CNC lathe is generally new to our shop. We are an OEM not a job shop.

 

ABS we use un coated carbide inserts and Acrylic, HSS is the way to go. Parts tend to be around 1" on average dia.

 

The FEM software "thirdwave" Doug recommended would be a great toy but its expensive.

[chip]

So much of this stuff is trial and error. you sort of have to cut a few pieces of graphite to figure out how to not chip the corners! cool magnet

[CJep]

Rush,

When I was on the bench I machined a lot of ABS, Delrin, Acrylic, Polycarb,...

 

When I was turning plastics they liked to have constant surface pressure, zero or sometimes neg rake tools (for softer materials the neg rake will keep it from climbing up on the tool), uncoated carbide or HSS with an almost razor sharp cutting edge, no coolant I would use air, 5psi usually was good, for tapping I used lanolin soap cut with water.

 

Milling I typically would calculate my feeds and speeds from chip load & SF/min, from what I remember I would run ABS & Delrin at 008 - 010 chip load & 900 SF/min, removing chips with air (no coolant)

 

The majority of my time was spent doing product development, if you're doing production,... (might need to slow it down to go faster)

[Russh67]

Thanks again guys...

 

Trial and error...been doing that.....Trying to keep cost down...I did find some math formulas for cutting force and all ..I looked at it and started to get a head ache. I have forgotten so much over the years..20 years plus since I did hard core math.

 

I am machining black acrylic about 1 1/2 dia x 2" long..Went through 2 1/2 feet of stock...I broke down and turned on the coolant.

 

CJep, I do have air in the machine we added it m20 on m21 off. it does work on od, id, I couldn't get the chip off. It snakes off nice but when the bar gets to far in the part it over. I am new to cnc turning. By hand its nice you can just pull of the chips as you go.

 

For Acrylic I have HSS insert I got from AR Warner and CO. They specialize in HSS inserts and tools. It's good stuff. Running constant surface speed mode to .002in per rev. s1100 max rpm.

 

I am finding the chips are wrapping around my 1/2 boring bar. There is no rake or chip break. There is a flat on the bar so it's in the machine straight. Just have to watch and pull off the rats nest I guess. Time consuming but still faster than manual.

[Paul Felger]

for the lathe work turn off the coolant and try a shop-vac if you dont have any air hooked up... works well

[Russh67]

Thanks Paul, and everyone else:

 

I've been trying every thing..Still learning, like I said before new to machining on a lathe..I do have air in the machine, still experimenting. I'm fortunate in the we a an OEM not a job shop so I do have some time it experiment...I will try....

 

As a fall back the coolant is ok for no...I don't like to use coolant.

 

 

Thanks again guys..