Bad Surface Finish Suddenly. Same Part Same Program. Help?

Kawgomoo · Apr 13, 2017

Hello all. I am stumped on this one.

I am turning 6061 aluminum bar stock 1.5" Ive been running the same part for a week or so now with no issues.

I ran out of aluminum, and had a slug of Gr5 titanium laying about so i gave that a shot. Turned down the feeds and speeds, but not enough. The insert drill lost an insert halfway through the hole and pushed the bar back in the chuck about 1/2".

I pulled the Ti out the machine, reloaded the program i was cutting with before {confirmed its the same program} I replaced the inserts in all the tools, except the OD tool in which i just turned the insert to a new edge. Another bar of T6 had come in by this time so i loaded it up and got back to running my part.

Now I'm haunted by surface finish that looks a bit like a golf ball. Kind of faceted if you will. This finish is on both the ID and OD of the part, cut using different tools entirely. Ive changed the inserts, and even changed the entire ID tool.

The parts are coming out on size, but the finish is jacked up.

What is going on here?

Is the machine out of alignment? Did i just get a bar of weird material? I am totally lost right now. Chasing my tail in circles.

XD341 · Apr 13, 2017

Check the chuck. Sounds like maybe the Ti sliding on it left a burr or lode someplace. Skim the jaws to be sure?

Ox · Apr 13, 2017

A) Face the part past C/L.
Got tit? How much?
If so - turret (tool) out of center half that amount.

B) Moron likely you got some cheap material. This IS a new heat - right?
If so - please post the name of the mill on the cert and country of pour for us to be warned.

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Think Snow Eh!
Ox

Kawgomoo · Apr 13, 2017

I swept across the cut off tool holder and its about .0015 high.

The part is so much smaller than the bar stock it seems like even if a jaw was out it would still end up with a good part. I have steel jaws with sharp teeth so no skimming those.

The before part is on the left and the problem child is on the right.

Screen Shot 2017-04-13 at 3.54.01 PM.jpg

Kawgomoo · Apr 13, 2017

The bar is SAPA 6061-T6511H 22771810

JLarsson · Apr 13, 2017

Is your lathe noisier than is was before the crash? Bearing issue? Does the pattern geometry change if you change either feed or speed or both?

Kawgomoo · Apr 13, 2017

Nope no new noise, but something sure aint right.

Im just failing to understand what could cause a finish like this, which in turn leads me nowhere to look for a problem.

Ox · Apr 13, 2017

It looks like a loose part, or chattery toolholders.

Are your toolholders sticking out further than before?

Doo you have a 12' bar whipping around behind the machine?

It doesn't look like material to me.

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Think Snow Eh!
Ox

Kawgomoo · Apr 13, 2017

Could the chuck have internal damage? maybe not clamping tightly? I wouldn't know how to begin to check that. Ive grabbed the bar and gave it a wiggle, no noticeable play. Feels tight.

The bar is 6' long {i cut the 12 footers in half}. about 4' of which is in the spindle of the machine. There is a delrin liner/spacer opposite the chuck end so the bar doesn't flop around.

The OD cutter hasn't moved, its choked up as close to the turret as it'll go. The ID cutter is a 3/8" boring bar. I actually choked that one up an extra inch pulling it in closer to the holder. Even the surface finish where its parted off is horrible. Like its tearing the metal instead of cutting it.

Kawgomoo · Apr 13, 2017

oh and i pulled the bar out the machine, so i could clean and inspect the jaw surfaces. Nothing looks weird there. Blew them off, but no chips or chunks were stuck in there.

Ox · Apr 13, 2017

Doo you have ANY other alum in the joint?
Even a diff size?

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Think Snow Eh!
Ox

Kawgomoo · Apr 13, 2017

negative, i even cut up the drop from the other bar and used it for some other stupid crap the other day

Ox · Apr 13, 2017

How about you cut this one in half again?
Is it tight in a spindle liner?
If not - cut it to 8" long or ??? just to rule out bar whip.

1.500 sticking 2' out the back door is enough to cause whip if you are speeding.
I usually don't run much over 1500 with a bar hanging out very far.
If you have it up or over 2500 - that could be an issue.
(Depending on how tight your "bushing" is)

i even cut up the drop from the other bar and used it for some other stupid crap the other day

10/1 odds - "It seemed like a good idea at the time."

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Think Snow Eh!
Ox

Kawgomoo · Apr 13, 2017

Ive been turning like 600, I'm down to some ungodly 300ish right now. that helped, a little.

I took the other half the bar, put it in another lathe using a different holder and insert, got the similar ugly finish.

Cut an 8" piece or so off the 6' bar. Faced and profiled it in the manual lathe. Again ugly finish. A bit less ugly on this short bar. But still uglier than the 3" long piece of old bar i got left and did the same test too back to back.

Now i have that 8" bar in the CNC and its running under the program. Will see what we get.

Cross your fingers! {its gonna take a while to cut running this slow lol }

Ox · Apr 13, 2017

Sounds like material....

I keep hearin' about it, but I've never got any of that stuff before.
What service center did you get it from?

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Think Snow Eh!
Ox

Houndogforever · Apr 13, 2017

Kawgomoo said:
The bar is SAPA 6061-T6511H 22771810

I've heard Sapa extrusion is ass.

TDegenhart · Apr 13, 2017

Can you get a decent finish at all? That's the finish I get when the tool is dull, above center line or part is flopping in the chuck. I take out the cutter and look at it under a microscope and see a burnishing on the flank under the cutting edge. Clear sign that the tool is being forced into the work. Could also be the cutting fluid.

Tom

JP Machining · Apr 13, 2017

Find some Kaiser bar and if it still does it then its def tool/ turret related. If not then crap material. I vote for crap material, though when i had it, it didnt look like that, just more not nice and shiny, and spotty.

Ox · Apr 13, 2017

Houndogforever said:
I've heard Sapa extrusion is ass.

SAPA is to some degree = Alcoa.
SAPA took over Alcoa's "6000" series mills (if you want the short version) in a joint venture.

To date - I have never had bad SAPA and I buy from Copper and Brass generally.

Again - I would like to know "Country of melt" and service center.
SAPA does have mills elsewhere too.

Iceland is prolly the biggest melter of inget.
Not sure if that is relivent or not?

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Think Snow Eh!
Ox

Kawgomoo · Apr 13, 2017

I threw the paper work away on the bar. The one time i would need it. lol of course.

The first day on my new job as a welder i got a bottle of bad gas. Never happened to me before or since. Made me feel like a complete tool. Now here i am, 2nd bar I've ever bought from a new distributor and I'm back in the same new guy don't know jack boat. pfft. my luck.

So i cut 8" ish off the new bar. And ran it. Same POS finish.

I ran the other end of that same cut off in a different machine, different tool, different shape insert with different everything. same feed/speed 600/.005 per rev cut like shit

scraped and scrounged. Found a 5 inch ish drop off the old bar i had that was cutting good. Right off the dick i noticed the two bars are different in color. Old bar is matte grey like you'd expect. New bar is awfully shiny lots of black extrusion marks.

moved the work offset in the lathe, ran the first 3 ops {ID} on the OLD BAR with feeds/speeds set at 100% {600/.005} finish is 100% perfect. no golf balling at all. i was having to run the new material at 70% to get anything even close to decent, but you could still see and feel the golf ball texture.

So my mind is made up. This bar is jacked. Now to test the customer service at Industrial Metal Supply. Bah.

Bad Surface Finish Suddenly. Same Part Same Program. Help?

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