Hard-part-turning

I’m having a problem getting my hands around hard turning on our new Captain L370M lathe. The shop is starting to get more and more hard turning jobs coming in. The shop use to give this work to the manual machinist. Well since we laid him off last week, we don’t have that option anymore.

The finial dimensions of the product need to be: They are RC 62 hard.
Dia: 1.760 +0.000
-0.001
Length: 7.875 ±0.030


N0001 G00 X20 Z20
N0002 G50 S3500
NAT02
N0100 G97 S713 M41 M04
N0101 G00 Z0.100 T030303 (cNMG 432 TP2500 MF5)
N0102 X2.098 (msc# 88443650)
N0103 G96 S361
N0104 X1.774
N0105 G01 Z0.100 F0.008
N0106 Z-7.95 X1.774+0.0000 (TAPER)
N0107 X2.098
N0108 G00 X20 Z20 T0300
N0109 M00
NAT03 (CHANGE "X" OFFSSET OF TOOL #2 TO GET TO 1.760)
N0200 G97 S1013 M41 M04
N0201 G00 Z0.100 T020202 (DNMG 432 KY4400 T0420)
N0202 X2.098 (MSC# 03752516)
N0203 G96 S461
N0204 X1.774
N0205 G01 Z0.100 F0.008
N0206 Z-7.95 X1.774+0.0000 (TAPER)
N0207 X2.098
N0208 G00 X20 Z20 T0200
N0209 M02

If your manual machinist could hit those tolerence's on the manual lathe why lay him off?

Ron,

He couldn't make parts fast enough, and he cost almost as much as a button pusher. Of course, NOW they can't make ANY parts!

Ain't that a kick in the ass?

George

LOL looks like you need to hire a Machinist. BWahhhhhhhhhaaaaa

I've never seen a coated carbide insert capable of cutting Rc62 steel at any speed, much less at 360 sfm. I've used cermets to do finish cuts on steels with hardness in the mid 50's, running at speeds typical of HSS on mild steel, but to make any real progress you need to use either ceramic or CBN tipped inserts.

You better figure it out fast or you'll be next out the door.
Maybe try running the job on the lathe it was done on before, if you can.

Tom

cbrannam said:

I’m having a problem getting my hands around hard turning on our new Captain L370M lathe. The shop is starting to get more and more hard turning jobs coming in. The shop use to give this work to the manual machinist. Well since we laid him off last week, we don’t have that option anymore.

The finial dimensions of the product need to be: They are RC 62 hard.
Dia: 1.760 +0.000
-0.001
Length: 7.875 ±0.030

Click to expand...

I'm not trying to be a jerk here but please go back, re-read your post, and then ask yourself "what am I looking to get out of this?"

You haven't mentioned what it is about this operation that is giving you trouble. It could be surface finish problems, difficulty hitting dimensional requirements, or even process efficiency/cycle time, but nobody here will be of any value unless you tell us what you are looking for help with.

Casually perusing your Gcode, I notice that T02 is taking a pass at the same diameter as T03. If you find that your parts are coming out 0.014" too big then this might be to blame. You might have a reason for this that I don't understand, but it doesn't seem like good practice to write code without aligning it to the target dimension - you will find yourself working to shift offsets to compensate for the way the code is written. I would write my code to target halfway between the tolerance limits at 1.7595". How are you setting your tool offsets?

I'm also a bit mystified at your tool set-up. The first insert you use (T03) looks like a general-use steel insert and I can't imagine it's doing much good in your RC62 material. The second tool is a true hard turning ceramic insert and makes sense in this application. How are you choosing your speeds and feeds?

Regards,
Henry Wettersten

Bwaaaaaaaaaa! i want to hauwel with laughter. this stuff rocks..

You literally gave two dimensions and explained nothing about the set up in question. Your insert choices and speeds are interesting to say the least. More detail will go a long way.

gmatov said:

Ron,

He couldn't make parts fast enough, and he cost almost as much as a button pusher. Of course, NOW they can't make ANY parts!

Ain't that a kick in the ass?

George

Click to expand...

Shocking that you had a machinist who could hold +-.0005 for 8" in 62hrc mat'l on a manual machine no less but had to pay him as much as a button pusher. No value there.
You don't say what the problem is with your program. I don't know Okuma code. Does this program actually run? Do you think you can finish turn at 460sfm w/ .008 feed? What does your control think about that extra +0000 on N106&206?

Faster speeds, like adding a zero and a lot finer feeds might get you in the ball park if the inserts hold up. its not conventional turning. Use the heat generated by the speed to soften the steel, cutting it off with the equally hot but still hard insert. It's that simple. Above all read the manufacturers literature for speeds and feeds. But remember, in hard turning increasing speed can actually improve insert life.