CoolHand
Hot Rolled
- Joined
- Sep 6, 2005
- Location
- Missouri . . . Near the Middle.
Title says it all, I am side milling aluminum in a small VMC and I am getting a less than satisfactory surface finish.
The machine is a box way C-frame 3 axis VMC made by Moog/MHP in the early '90's. 5000 RPM spindle, BT40 taper, 5/7.5 HP belt driven two speed gear reduction head (IE belt drive from motor to spindle, with a two speed shifting head. Low speed has a single counter shaft for reduction, high speed is straight through).
This is the part in question, machined from a 6063 T-6 extrusion:
I am currently just worried about the sidemilling finish on the final contouring pass around the outside of the piece. Surface finish here is the main concern.
I removed most of the outer material with a two insert carbide cutter 1" in dia, running at 5000 rpm, 0.35" DOC, 90 IPM feed, no coolant. That runs fine, quiet and fast, all is well. The first pass leaves 0.015" for a finish pass, which I take with a 3/4" dia 5 flt gold coated (no idea what the coating is, though I suspect it is TiN) solid carbide EM with a 50 deg helix and 1" LOC (IE super stiff) in a Kennemetal 3/4" ID milling chuck. The radial DOC is 0.015", the axial DOC is 0.655", spindle speed is 5000 rpm, feed is 90 IPM, and this time I have the coolant on. It cuts fine, quiet and fast, but I am left with this surface finish:
I can just barely feel the marks with my fingernail. Other than that, I have no idea how deep they are. They take a while to sand out, which is what brings me to you all. I'm tired of running the sand paper. lol
So, here's the question:
What can I do to improve this finish? Is it my spindle? Everything I cut (sidemill) ends up with this finish on it, but I tend to cut everything with the same data, so that doesn't really prove anything. Also, end milling surface finish is excellent, so I would tend to think this is not spindle or tool retention related, but WTH do I know? Is my cutting data off? Am I using the wrong cutting tool? The problem is not chatter, the thing didn't make a sound while it was cutting.
I'm not opposed to spending money on new tooling if needs be, but I'd just as soon use what I have if I can. I also have quite a lot of stuff on hand here as well, so if the cutter is at fault do feel free to suggest a better tool, I might have one in the drawer already.
Even with the less than stellar sidemilling finish I'm pretty happy with the way this part turned out. As a test I ran the feeds and DOC's at nearly double what I had ran them at in the past, and everything cut beautifully, so I'm gonna call it a win. Cycle time was down by over half. Right now it's running at about 3.5 mins with five (5) tool changes.
Bear in mind that this is a second op on a cut to length extrusion with a few holes drilled in it, so not every single operation in that piece was done in this set-up. This go 'round first takes the outside contours, then it opens up the big pockets on the inside. The outiside contour is cut while the piece is full cross section, the thin walls are created afterwards when the pockets are cut.
Any assistance you all can offer would be greatly appreciated. I'm getting awful tired of sanding.
[ 05-21-2007, 01:46 PM: Message edited by: CoolHand ]
The machine is a box way C-frame 3 axis VMC made by Moog/MHP in the early '90's. 5000 RPM spindle, BT40 taper, 5/7.5 HP belt driven two speed gear reduction head (IE belt drive from motor to spindle, with a two speed shifting head. Low speed has a single counter shaft for reduction, high speed is straight through).
This is the part in question, machined from a 6063 T-6 extrusion:
I am currently just worried about the sidemilling finish on the final contouring pass around the outside of the piece. Surface finish here is the main concern.
I removed most of the outer material with a two insert carbide cutter 1" in dia, running at 5000 rpm, 0.35" DOC, 90 IPM feed, no coolant. That runs fine, quiet and fast, all is well. The first pass leaves 0.015" for a finish pass, which I take with a 3/4" dia 5 flt gold coated (no idea what the coating is, though I suspect it is TiN) solid carbide EM with a 50 deg helix and 1" LOC (IE super stiff) in a Kennemetal 3/4" ID milling chuck. The radial DOC is 0.015", the axial DOC is 0.655", spindle speed is 5000 rpm, feed is 90 IPM, and this time I have the coolant on. It cuts fine, quiet and fast, but I am left with this surface finish:
I can just barely feel the marks with my fingernail. Other than that, I have no idea how deep they are. They take a while to sand out, which is what brings me to you all. I'm tired of running the sand paper. lol
So, here's the question:
What can I do to improve this finish? Is it my spindle? Everything I cut (sidemill) ends up with this finish on it, but I tend to cut everything with the same data, so that doesn't really prove anything. Also, end milling surface finish is excellent, so I would tend to think this is not spindle or tool retention related, but WTH do I know? Is my cutting data off? Am I using the wrong cutting tool? The problem is not chatter, the thing didn't make a sound while it was cutting.
I'm not opposed to spending money on new tooling if needs be, but I'd just as soon use what I have if I can. I also have quite a lot of stuff on hand here as well, so if the cutter is at fault do feel free to suggest a better tool, I might have one in the drawer already.
Even with the less than stellar sidemilling finish I'm pretty happy with the way this part turned out. As a test I ran the feeds and DOC's at nearly double what I had ran them at in the past, and everything cut beautifully, so I'm gonna call it a win. Cycle time was down by over half. Right now it's running at about 3.5 mins with five (5) tool changes.
Bear in mind that this is a second op on a cut to length extrusion with a few holes drilled in it, so not every single operation in that piece was done in this set-up. This go 'round first takes the outside contours, then it opens up the big pockets on the inside. The outiside contour is cut while the piece is full cross section, the thin walls are created afterwards when the pockets are cut.
Any assistance you all can offer would be greatly appreciated. I'm getting awful tired of sanding.
[ 05-21-2007, 01:46 PM: Message edited by: CoolHand ]