tools don't last and chips too stringy

[NCPROG1]

Greetings all,
We've got a Citizen A20 swiss machine, our first swiss. We are turning 3/4" dia. 303 stainless. We bought it turnkey so our programs and tools were written & selected for us. We turn with a Sandvik CCMT 09 T3 08-UM insert grade 1025. (3000-3600 RPM @ .002-.008 ipr @ .025-.125 d.o.c.)
Here's the problems: The original program took the .75 dia. to .5 dia. in one pass. Works fine untill you have to clean up chips. Long, thick, stringy, sharp and they hang on tools and catch in the conveyer. The formentioned insert is a chip breaker but we can't seem to get it to break the chip. If we adjust the parameters to get a good broken chip, tool life decreases dramaticlly. (Sandvik says 20-30 min. per insert is appropriete, we've gotten 120-180 min/insert on other machines) They aren't kidding when they say swiss is a different animal.
So, what advise, suggestions, tool grades, speeds and feeds, depths of cuts, and other tidbits of seamingly useless information can you pass on to help us eliminate the perpetual buildup of chips while increasing tool life to a point that we're not changing inserts every hour. All reasonable responses are appreciated and will be thoroughly examined for usefull information. I hope I'm not asking too much

[Palerider]

I haven't used that Sandvik grade before, but for an 80 Deg diamond on 303 your depth of cut seems too high for a smallish lathe. I would probably back off the Depth of Cut to .05 inch per side max (probably less) and increase the feed.
For Stainless lately I have been using a CCMT From Iscar Grade IC907. In 316 and 304 it performs really well. I am using a small CNC chucker lathe with a 5C collet and 5HP. In 303 You should be able to tear it up. In stainless my inserts recommend 660-980SFM with a .002-.010IPR feed. I would think you would be fine in the higher range of speed in 303, but I haven't had success with feeds of over .004-.005 for roughing due to my power and rigidity issues (1/2 shank tooling.)

Hope this helps.

[extanker59]

I disagree. When I went from a Okuma lathe to a swiss, the guy showing me the ropes was going WAY slower than I did on the Okuma. I talked him into trying my way (faster, getting the chip to break, etc...). It failed with broken inserts.
Go 300 SFM to start, low DOC (try .05 but be ready to go less), and do not exceed .002 feed rate. I'd try .001 to start when roughing. When finishing, .0005 is not too slow (amazing to somebody trained on regular lathes, like me). I've been told the oil (coolant) can't take the heat away at the higher SFM and feed rates but it does improve lubricity which is why the slower feed doesn't kill the inserts. I'm not sure if that's correct but it does work.
The chips are the biggest problem. Less DOC might work.

[cogsman1]

I cut 303 on the A20 all the time and the tools last forever. You MUST have another problem. 303ss cuts like brass I have to try to get the chips to NOT break. I think your speed is too slow for a swiss machine.
What oil are you using? Check your tool center height.
A comment to the other replys, on a swiss you can very rarely do a rough and the finish pass or multiple passes due to the stock support, guide bushing, you can only pull the stock back a small amount appx. .800" on that machine.
I love cutting 303ss, the insert edges last all week and I have used many different manufacturers inserts. You should call up your favorite insert rep and have him help you get this running better. I use Sandvik, Iscar, Mitsubishi, NTK, Kennametal, Utilities, .....

[extanker59]

I agree that you SHOULD do it in one pass. But sometimes the part won't allow it. I just came from a swiss shop where there were many people better than me and they would do it in multiple passes when needed. Again, the chips are the problem.
Furthermore, the speeds recommended in the book are not for swiss. The tools in my previous shop would last for whole shifts and more. Slower is the key.
And yes, everybody knows you can only turn in Z the length of the bushing land. So to make a long shaft by multiple passes, you would have to do the length in multiple Z passes as well. Standard training in a swiss shop.

[HuFlungDung]

Long, thick, stringy, sharp and they hang on tools and catch in the conveyer

Sure doesn't sound like 303. Seems more characteristic of 304 or 316.

Try stock from a different supplier.

[cam1]

Good Idea, ask for the mill ticket from your supplier.

[NCPROG1]

That's a lot of information to process. We'll try all of the ideas we've recieved.

cogsman, we're using blaser vascomill it's a premium oil for swiss I don't think that's an issue but I will check into the tools center height. Thanks for shareing. By the way I don't have a favorite tool salesperson. You have given me hope though saying you run it all the time. I'd love to see it cut like brass.

extanker: I also believe it should be done in one pass. The part is small enough to do multiple passes but that's not the way of the Swiss. That is the way it was originally programmed by the "experts"

Huflung and cam1: Good idea, it might be too late for the batch we have now but a paper trail that says 303 would be nice.

Thank you all for your time and valuable information. We'll jump into many of these thoughts and ideas next week. I'll try to keep you updated. Have a pleasant weekend

MGK

[lennie]

Sometimes it is difficult to get the speeds and feeds to a happy medium as far as tool life, surface finish, chip sontrol, etc....
Are you in a position where you can afford to invest in a high pressure coolant pump? (1500 psi ot more.)
It does add a bit to maintenance concerns, and you would want a reliable fire suppresion system, but I have had great success with just such a set up, and although I am not well versed in Citizen equipment, I believe they have a system made specifically for their equipment.

[NCPROG1]

Thanks lennie but I don't think that will be an option. We have other needs in other departments that are higher on the list of priorities.

[PixMan]

If you're machining 303 stainless on a sliding headstock machine and have these kind of issues, definitely look into material. I'd be using Ugima 303XL or their Ugima 303UX (depending upon application fo the finished part.) That material is a bit more money than standard stuff from say Castle, Yarde or others, but well worth it in machinability, tool life, and overall productivity.

That grade from Sandvik is OK, but you'd do much better with their GC1020. Expect that grade to last all day at 500sfm or more. With sliding headstock machines, you're always better-off to take single pass cuts so you don't back-up the stock and risk damaging the guide bushing on a burr, or worse, have the part come off the carbide and start whipping around. This make choice of insert top form geometry (chipbreaker design) difficult, but not impossible. If you switch to the Ugima material, chip control will be a problem of the past, I assure you.

You are using what I consider to be the very best all-around cutting fluid for a Swiss machine. Expensive, but worth it. Best of luck to you.

[yoopertool]

In my years as a swiss machinist I havent been able to find any insert which will break stainless adiquately. Taking a smaller DOC will make it even worse. Even if you do get some slight breakage one time, the next material lot may not break at all. The only thing that I found works well consistantly is having a thin insert with a sharp edge and a deep profile which will make the material curl more and not be so long and stringy. The insert I like the most right now is actually designed for aluminum but also works great on some of the more "free machining" stainlesses. It is the Seco VCGT3251 ALKX. Another thing which always helps is making sure that you have lots of coolant not only flowing on this inserts themselves, but also pushing the chips down and away so they wont block the oil from the insert. I typically run around 3000rpm @ .0015ipm in 303 at that diameter and my inserts last all day!