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View Full Version : new to screw machines where to start?



Runner4404spd
04-30-2009, 03:55 PM
i own a machine shop that primarily does turning work. we are getting more and more order in the 2000 pcs range. parts are about 1 5/8 and smaller for the most part. i would really like to learn about screw machines, why they are faster, what are the benefits, what are the draw backs.

also i found a hardinge made screw machine and they don't seem to be very popular compared to citizens or tsugamis, any particular reason?

UK-Engineer
05-01-2009, 01:46 PM
Hi there

Swiss machines offer the following benefits over conventional

- Usually quicker due to smaller cutting tool envelopes and the fact that they are optimised as a production machine as opposed to a general purpose machines. Generally a modern swiss machine will always be significantly quicker than a conventional lathe on a like for like basis
- Due to guide bush principle (bar is supported at cutting point irrespective of length) you can take greater depth of cut and for longer distances too. The old rules about length to diameter ratio on conventional machines don't really apply to swiss machines.

Limitations are

- cost penalty over comparative conventional machines
- Generally better quality raw material requirement (Newer machines without guide bushes get round this partly at penalty of maximum machining length)
- Loss of about 6-8" of bar due to barfeed remnant
- The main machine manufacturers are limited to 1.25" diameter stock

Don't know about Hardinge and believe they stopped making them some years ago so you'd need to decide if that was an issue for you

Generally any of the Japanese machines will be of good quality and like everything else "you get what you pay for" is a particularly apt truism

Good luck anyway!

Runner4404spd
05-04-2009, 04:31 PM
i guess i'm still wondering if i really should be investing in a screw machine. if i was making 30,000 parts it would be a no brainer but i've got about 1500-2500 pc runs. i should mention that we turn primarily stainless steel of all varieties and some titanium. my lathes are doing the work just fine, but i would like to speed them. one thing i'm worried about is the need for better quality material as well as the inserts lasting. this newer stainless is very inconsistent.

opinions welcome here.

beege
05-04-2009, 04:44 PM
If I could I would. Screw machines are great for those lot sizes. 30,000 parts is more like a multispindle machine. Screw machines also have options for live tools and backworking, so the parts come off without the need for secondary milling/drilling/facing/chamfering. Screw machines also do longer parts because of the guide bushing principal. Material won't be much of a concern because of the much faster throughput. The most important aspect of the new machine decision will be service and application engineering. They should be able to help troubleshoot problem parts based on their pool of experience. I came to a shop where a 16 finish was needed in a deep hole. The wrong tool was used. Switched to gundrilling (in the machine with high pressure oil coolant) based on the sellers recommendation, and all was beautiful. Bottom Line: Do it!!

UK-Engineer
05-05-2009, 05:04 AM
Historically peoples perception of screw machines was that you had to have very large batches to make them economical but this is no longer the case and certainly here in the UK the majority of users batch sizes is around 1000-2000 and very often lower. The ability to store multiple tools in the machines enables quick setups between jobs.

Again stainless steel is very common as again many companies here in the UK machine parts for aerospace and medical industries where stainless steel use is almost universal. We tend not to have major problems with inserts as most of the tooling manufacturers are geared up for this and high pressure coolant on newer machines makes a marked difference and is worth it if you can afford it. Titanium is slightly different as although its not too difficult to machine, the raw material tends to fluctuate in size and can give problems with the guide bush. Most users group the raw stock and adjust the tension between different lots thus avoiding the necessity for self adjusting guidebushes which are not totally reliable in my experience.

Anyway good luck and i hope it works out for you - very few shops that i see only have one swiss machine and that's the best indication of their capabilities

PixMan
05-09-2009, 08:40 AM
i guess i'm still wondering if i really should be investing in a screw machine. if i was making 30,000 parts it would be a no brainer but i've got about 1500-2500 pc runs. i should mention that we turn primarily stainless steel of all varieties and some titanium. my lathes are doing the work just fine, but i would like to speed them. one thing i'm worried about is the need for better quality material as well as the inserts lasting. this newer stainless is very inconsistent.

opinions welcome here.

In what way is the stainless steel inconsistent? What is the type of stainless you're referring to? 303, 304, 316, 17-4ph or ??

In Swiss machines, I had the very best machining results and most consistent cold-rolled size from Ugine Stainless products. Their Ugima 303XL is just incredible. By contrast, you could spend more money on Carpenter Project 70 and get absolute CRAP. ;)

Runner4404spd
05-09-2009, 01:34 PM
we use standard 304 hex and round stock. sometime we use tubing. the material varies a little in diameter and cross section and also the stuff we've been getting recently varies in material composition. by that i mean, one bar will run fine and the inserts will last a really long time, other times the inserts wears so fast we get 4-5 parts out of it.

does the increase in production justify the increase in material costs for use in a screw machine? ultimately the guys i know that run screw machines, run , brass, 303ss, steel parts etc. none of them that i know of run 304,316,321, or titanium. and if they do it gives them fits.

PixMan
05-09-2009, 05:33 PM
...one bar will run fine and the inserts will last a really long time, other times the inserts wears so fast we get 4-5 parts out of it.



This is EXACTLY why I am suggesting Ugine (now known as Ugitech) as the best source for your raw materials! Lot-to-lot consistency of composition and size from them is the standard to which others should try to achieve. It's worth every penny for productivity improvement.

BauerDef
05-12-2009, 06:45 AM
Although i have no experience in hex or tubing stock, my shop has 4 Deco's, and they're the bread and butter no exception. We have medium to larger work capacity, 26mm, 20mm, and two 13mm machines. One 13 is cutting maraging now, the other 13 is cutting 8620, the 20mm is cutting brass, and the 26 416SS. I work in a job shop so our lot quantities are usually around 1000-5000 pcs. The machines are expensive yes, but like someone else said early, you get what you pay for. The machines are top notch, and Tornos service is awsome (at least on the east coast where i am). Titanium will be difficult. But most other materials are pretty easily managable. Especially if you can take the hit and get centerless ground stock, your tech's will love you. But get a decent worker on the buttons and a swiss type can make or brake a shop