Machining surfaces: Loft vs. Coons

[rob@fain]

Dear Forum,

Is there any difference between finish machining of surfaces. I am machining a loft surface thats coming out a little rough, I was wondering if it might be because of the surface type. Any suggestion will be greatly appreciated.

 

Thanks

Rob

[Steel Surgeon]

I would think the tool path would be suspect.

 

What tool paths are you using?

[rob@fain]

I'm using scalop, 1/2 ball with .008 stepover in 6061 alum.. I'm thinking it's a machine problem, I just didn't know if surface type had anything to do with it. The part is a light sconce for an aircraft, a very odd shape and the loft surface seems to look the best.

 

thanks for the quick reply

 

rob

[Gary]

I cut some alum surfs recently with same size cutters as you and i never did get the thing to finish like i wanted. I get better finishes out of steel. I think my problem was i was running it way to fast i guess. I only did a couple parts and was not impressed(polised me arse off). I would love some imput also from some of you guys that surface this stuff on a regular basis.

[Chris Rizzo]

6061 surface machines kinda crummy..likes to "smear" or tear, rather than chip. One rather important factor I've found is coolant. I've used different coolants, and had drastically different results. Best has been non-synthetics (Blaser 4000s, or 2000), worst are the synthetics (Cimcool 425?)

 

m2c

[rob@fain]

I cut a lot of surfaces on Komo Routers, 1/2 ball, 3/4 ball, 13,000 rpm 250ipm, .010 to .012 step. my surfaces are normally swept, coons or from solids, and usually good results, but this loft surface came out really ugly. Next time I'm using a different Machine, I really believe that is where my problem is, but I thought I would ask the gurus just to make sure.

 

Thanks again for all the help.

 

Rob

[Müřlıń®]

rob.....Scallop changes direction alot and if there is any slop in your machine there will be steps all over where it changes direction.

 

My old wore out mill use to leave about a .004 step.

 

Tighten up the gibbs, put an indicator on the machinetool and set the reversal comp for backlash and try it then.

 

Loft is one of the better surfaces....as far as smoothness...

[TheePres]

+1 Murlin

 

Thats why i avoid Constant scallops surface toolpath, because of machine reversals...sloppy!!

[Thad]

That's funny. We have recently "discovered" the scallop toolpath and really like it. Although, anything we cut gets stoned "on the bench."

 

Thad teh "We're not building parts for the space shuttle, ya know!"

[cadist]

I alaways prefer surface-- finish-- project/blend over scallop. since it creates unidirectional cuts and matching up with edge. Faseter generation great result.

[Müřlıń®]

+1 to Thad......

 

Scallop is a real timesaver.

 

If you don't have good acel_decel on your control, use the highfeed and make sure you set the the field where it goes faster comming up in the z and slower going down in the z.

 

I set mine to:

 

z+= default

z-=.3

 

That ought to keep youur tools in one piece while ramping downward in steel.

 

quote:

---

Thad teh "We're not building parts for the space shuttle, ya know

---

 

Project blend is also a very good toolpath...

 

Murlin teh more than one way to do anything....

[Thad]

Project-blend is another one of my favorites!

 

Thad

[rob@fain]

Thanks for the input, The parts I've finished I used scallop on the top and contour on the lower part, it seems as if fewer z moves I make the better. I think I will try the finish blend as Murlin and Cadlist suggested.

 

Thanks again for all the input

 

Rob