Reducing CNC lathe setup time

We make our own parts using a four axis lathe. Part runs typically max out at 500pcs per setup, machining time is typically 2-3.5min/part
using 6-10 tools and 4-8 stations. Machine has 12 position VDI turret with 6 live positions and a subspindle instead of tailstock, headstock is C-axis. Control (Fanucklehead 18T) has 16 offsets and G54-G59 work offsets.
I determine the operations, write the program, order the tools, setup the machine, run tryout/productionizing, and then do all subsequent production setups.
We want to reduce setup time for production runs. Prototype/tryout is a time consumer, but only comes around every so often. Here's how I do a production setup:
-Change spindle liner (5min) -Change chuck jaws (15min) -Change out all tools in the turret (30min-1hr) -Center any tools that require recentering (30min-1hr?) -Touch off all tools (30min) -Run first off (10min)
Naturally these times can vary.
Once the next batch of new parts have stable production programs, we're going to start working towards reducing setup time as it can be murderous.
Because the turret is VDI, the holders are *not* repeatable. If a tool holder is removed, the tool must be recentered/touched-off when it is reinstalled which is really a major pain in the arse. There are screws that press on a dowel in the turret which allow you to set the holder's location, but I haven't had the time to sufficiently prove these are repeatable, AND not all VDI holder have these screws!
If the holders were repeatable, I'd simply download/upload the offset table which would remove the necessity for recentering and touching off. I'll test our holders' ability to locate repeatably, but at this point I'm not exactly impressed with VDI (can you tell?)
ANYWAY, I'm interested in suggestions or other points of view on how to perform a setup in a more timely fashion. Unfortunately a Y-axis lathe is not in the budget, so leaving the machine setup for all our parts is not an option!
Thanks for any thoughts.
Regards,
Robin
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Unfortunately the reason VDI was created was to do exactly as you propose. However the design is a complete failure. Not the tooling. Some of the German manufacturers make some real precise stuff. The problem is in the machine builders turret design. If the tooling does not match the turret exactly the tools twist off centerline axis causing all kinds of problems. Repetability being the main thing you lose. Your ridgitity is compromised as well. All machine builders add band aids to their turrets to combat this twisting, but that is all it is. A band aid. To cure your problem you should contact on of the VDI holder manufacturers and have them custom build your turret for their tools. Problem solved.
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wrote in message

As a matter of fact you can use the VDI holder as a gage to measure how far off your turret is. Un clamped and un pinned the VDI holder will twist to the exact position every time. You can accurately measure it. The problems occur in trying to inhibit this twist.
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All good ideas Dan. I see your religion is "Continuous Improvement" too. Another aspect in set up reduction is creative planning. Smoothly transitioning from similar parts to similar parts is more efficient than dramatic transitioning from extreme to extreme. Although your goal is still to be less than 20 minutes for the most extreme transition. Having one job evolve into the next i.e. big to small, complex to simple, many features to few features etc. is much more efficient than hopping all over randomly.
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That's a good point. I worked at a place once where we could plan out a week+ worth of short run jobs (our own product) and that is a huge time saver. Most job shops don't have that ability though. I'm not sure where Robin is working nowadays and whether or not his company is making their own products or if it's just random job shop work.
--

Dan

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I should have mentioned that. We make our own parts exclusively on the lathe. Planning 1-2 weeks of parts will be within our grasp soon. We're launching a couple of new (though similar) products so scheduling is unstable right now. Once things settle a bit, I'd like to have that kind of planning in place at all times.
Regards,
Robin
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We hate changing collets /bushings on our citizen f12's so much that we now have three of them ome that runs 1/4 one that runs 3/8 and ont hat runs 1/2
the toolholders arent so much a problem as when it happens we cant leave a turret position as-is then we can at least setup the assembly offline and then either enter ther offset manually or execute via a handful of G10 via thew dnc--
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On Wed, 6 Jan 2010 19:33:44 -0800 (PST), "Robin S."

=======It has been correctly observed that no one has ever made a dime doing set-up.
A quick scan of your procedure does not suggest any big improvements, but scheduling may offer some savings, for example by eliminating the need for chuck jaw changes, could save you some time.
Given the short part runs, more general/universal tooling may also be helpful, even with a *small* increase in cycle times. In [too] many cases we become involved in selecting the perfect tool/insert rather than an adequate/acceptible tool/insert. A reduction in the tooling you use can also reduce your tool crib inventory/tooling costs in addition to reducing set-up times.
A conversation with your customers may also be in order. They should understand that "set-up" is just as much a part of the job cost as the material and machining (and they are charged for it), and that by increasing their orders they can reduce the allocated per part set-up cost.
Unka George
(George McDuffee)
The past is a foreign country; they do things differently there. L. P. Hartley (1895-1972), British author. The Go-Between, Prologue (1953).
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On Jan 8, 4:22pm, F. George McDuffee <gmcduf...@mcduffee- associates.us> wrote:> Given the short part runs, more general/universal tooling may

Certainly a sound concept, especially with our short part runs and currently long setup times.

The lathe only makes our own parts. It's nice being able to work directly with the product designer in order to streamline part manufacture. I can only imagine the increased headaches jobbers have to deal with.
Regards,
Robin
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As I said in reply to Dan's message, I'm wondering about the clamping ability of collets versus chucks. Any thoughts?

T01 and T02 are 80 and cutoff (with puller). I'd like to have more standard tools but our parts vary fairly dramatically so I'm going to have to be a bit more cunning that currently.

We've got some ER holders with flanges. I really like the flanged bushing idea too. With a height gauge the preset would save some minutes for sure. That's a pretty quick implimentation too.

We didn't get one with the machine. It may be time! If it works, it would be a big time saver.

Agree! I'm starting to get that rhythm (switch out turret, center tools, set offsets) and that routine saves time and reduces errors. I'm a one-neuron kinda guy.

You're right. And I always like taking the TIG machine for a jaunt.
Inserts, tools, VDI holders, hex keys/t-handles, misc fasteners, coolant jets/hoses, bushings, air gun, rags, part bins, calipers/mics/ ping gauges, pc, etc. Oh - and documentation!

I could store each job-specific box on the setup cart mentioned above. That's very appealing actually.

I am a habitual cleaner in the shop. During my apprenticeship the default task was to find a broom and go. It's cathardic and an absolute requirement!

Thanks very much Kirk. I really do appriciate the time you took to write down your thoughts. Your post will also be boiled down and systematically consumed.
Regards,
Robin
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In general collets are better at holding, just so long as you don't have some smooth bore POS collet.
Here's why: you can run higher chucking pressure with a collet over a chuck. Also centrifugal force acts on chuck jaws and reduces chucking pressure proportionally with increases in rotational speed (rpm's).
Often you'll find that the three jaw power chuck that comes with the CNC lathe from the factory usually has a maximum rotational speed that is less than the maximum rpm the machine is capable of running.
The taper in the collet also provides mechnical advantage. -
http://en.wikipedia.org/wiki/Wedge_ (mechanical_device)
Of course most three jaw power chucks rely on the same "wedge" principle for actuation.
I've used these - http://www.microcentric.com/html/collet_chuck.html and never had a problem with clamping.
The SK collet - http://www.microcentric.com/html/co_quck_change.html is double serrated and hardened so it has excellent grip.
The easiest way to understand workholding "gripping" power in turning is to understand that the workholding device applies a uniform pressure over the surface area it is in contact with on the work. So if you reduce the surface area the force applied where the work holding contacts the work increases. Serrations reduce the surface area.
Or think of it like this; lay your hand flat on a table, take a piece of wood roughly the size of your hand lay it on your hand, now put a 10 pound weight on it. You can feel the pressure, but it's not bad. Now hammer a nail through the wood, put the point on you hand and put the weight back on. The nail punctures your hand because you concentrated all the force (weight) on a very small area, the nail tip.
Another great way to improve grip is to have the collet coated with carbinite - http://www.carbinite.com/ This takes surface area reduction to the extreme by providing hundreds to thousands of minute points of contact. But the coating adds thickness, so order oversize collets, or bore your own and have them coated.
When it comes to bar work, chucks suck. Get a quick change collet chuck.
--

Dan


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