Cnc 4th axis or duplicator lathe

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Brian
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Cnc 4th axis or duplicator lathe

Sun Dec 24, 2017 2:19 pm

I am weighing my options for the next acquisition. I maintain my limited space but will make room for a shaper and something for turning.

I have a product planned which will require turnings and complicated shapes. So I have in mind possibly acquiring a benchtop cnc, something like a shopbot.

I understand cnc to be a lousy ‘do-all’ but I think it may be a top notch dedicated tool to a few tasks. I wonder however if having a 4th axis is actually worthwhile or if it is considerably slower than a dedicated turning machine. Certainly my space requirements are coming into mind but I thought it best to discuss these options with you folks before I set my mind one way or the other.

When it comes to more simple things like tenons and so forth it would seem that cnc is a waste of time.

Appreciate any thoughts on the topic.
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Chris Hall
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Re: Cnc 4th axis or duplicator lathe

Tue Dec 26, 2017 11:48 pm

How many square feet are you working with there Brian?
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Brian
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Re: Cnc 4th axis or duplicator lathe

Wed Dec 27, 2017 12:48 am

Chris, my basement shop is about 300 sq ft and my garage is another 200sq ft.

I posted this up on SMC today as well, and a fellow replied with some detailed information on time to produce a given turning. Simple turnings which take 85 minutes on a CNC w/ fourth axis would take approx 7-8 minutes on a duplicator and something like four minutes on a dedicated CNC lathe. The last option is out of my price range, so it looks like a duplicator is the way to go for turnings. Even a short run of 10-20 chairs would consume a ridiculous amount of time on a CNC.
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Re: Cnc 4th axis or duplicator lathe

Wed Dec 27, 2017 8:45 pm

By coincidence, I watched an interesting presentation on the topic of digital fabrication today, something you might want to take a look at as well if you haven't already seen it:

https://www.youtube.com/watch?v=9JJydlt137g
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Brian
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Re: Cnc 4th axis or duplicator lathe

Thu Dec 28, 2017 11:55 am

Thanks for posting that Chris, that is quite interesting. They touch on a few things I've thought about as someone mainly interested in hand work. I've had to break from that as I'm continuously confronted with the fact that I also need to make a living. While I've enjoyed projects which I've made entirely by hand it seems that my clients are much more interested in seeing my design work come to life and for it to be tangibly priced more so than to have me sock away hours doing every last thing by hand. However, everyone of them I've spoken to about it prefers that handmade be a large part of it, and I also desire to keep it that way.

I won't likely ever go the complete opposite direction, but I'm coming around to the idea that as one man with a limited ability to output the only way to leverage that to its maximum is through adding machinery and CNC with hand tools used to finish the work or to accomplish things otherwise difficult and tedious through machinery. There are advantages both ways of course.

If you'll forgive my conjecture; CNC is in my opinion is provided as being more than it really is, with exception to some very expensive pieces of machinery that are capable of roughing rapidly, it is really a crappy 'do-all'. Unless it becomes very specialized it isn't the best and fastest. For instance, in my research there is not likely a better/faster way to make a mortise than a CNC swing chisel mortiser. They cut a perfect double mortise with haunch in 20 seconds or something like that, but by comparison a CNC router is not making a mortise very quickly and of course the corners need to be round which considerably slows down the other end of the process, making tenons which then also much be done with a router.

I assume this because I've requested pricing on parts and have gotten what I consider to be insane pricing back of which I can do considerably better by hand but have to commit my hours. When you have a machine which costs $300-500k you need to charge a considerable hourly rate to get a return on it and of course when it is not the fastest way to make something then it becomes uneconomical rapidly.

So anyways, I digress, but I think of them as basically a fine way to make something which is complicated by using complex curves but outside of that I'm not sure they're always the best approach. In fact I think the people who use them tend to make everything complex curves so that they can best utilize their machines. I'm not sure that it results in an object I want to live with, often times I'm happier still with simpler forms. At times I think the complex curve is a very good result.
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Chris Hall
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Re: Cnc 4th axis or duplicator lathe

Thu Dec 28, 2017 5:12 pm

"If you'll forgive my conjecture; CNC is in my opinion is provided as being more than it really is, with exception to some very expensive pieces of machinery that are capable of roughing rapidly, it is really a crappy 'do-all'. Unless it becomes very specialized it isn't the best and fastest. For instance, in my research there is not likely a better/faster way to make a mortise than a CNC swing chisel mortiser. They cut a perfect double mortise with haunch in 20 seconds or something like that, but by comparison a CNC router is not making a mortise very quickly and of course the corners need to be round which considerably slows down the other end of the process, making tenons which then also much be done with a router."

It's true that there are faster machines of more specialized types, however, with each additional machine ever more room is needed and of course the cost goes up. A CNC swing-chisel mortiser makes sense if you make lots of doors. But if you only make doors from time to time...

While a generic CNC might well be slow at a variety of tasks, there is the point that while the machine is operating, you can be doing other things with your time, so the time-sink aspect is, perhaps, not as critical as it is with a machine upon which you need to keep your full attention.

It's the same with non-CNC machines too though. If you buy that duplicator, once your product run is done, say you move onto other things that don't require the duplicator, and it just sits. It only does a narrow spectrum of work. That's the achilles heel of very specialized machines. If it is too specialized, it might become useless to you should the things you make change, or, possibly worse, because you have such and such specialized machine, you continually find ways to keep it in use and bend your product design around the machine, and indeed, move more and more to mass-producing products within the capabilities of your equipment. With a machine that is adaptable to handle a variety of tasks, this is less the case. One of the reasons I like my milling machine so much - though I would like to move a notch further into modern, with a machine that has some limited programming for the standard movements along axes.
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Brian
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Re: Cnc 4th axis or duplicator lathe

Fri Dec 29, 2017 2:39 am

I agree, totally even though I’m off on a bit of a tangent there it’s likely a poor decision to stake both space and investment into a dedicated machine unless one is setting up a factory.

The lathe I have in mind is a Minimax, basically a normal lathe with a duplicating attachment built into the design. Not a commercial type automatic.

Do you have a DRO on your machine? I find it invaluable on my mill. Might be a simple add on to make life a bit easier.
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Re: Cnc 4th axis or duplicator lathe

Fri Dec 29, 2017 8:41 am

Oh yeah, I have a DRO, though only on X and Y. There's provision on the readout of a third axis, and a spare glass scale on hand, but it is not mounted. It would be possible to fit it in several places. On other FZ-5V mills, I've seen glass scales on the knee's travel, on the quill, and even on the ram for the milling head. One could potentially have readout fitted for rotation as well, and if one could fit scales onto all directions of movement, there would be 6 possible.

The DRO is a godsend really. Same on the SCM planer now I have fitted an i-gaging unit.

With your lathe plan you're fast becoming Mr. Minimax!
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Brian
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Re: Cnc 4th axis or duplicator lathe

Fri Dec 29, 2017 10:00 am

Hah! If only they would start sending me the machines for free :)

I think the quill would be more useful, there are times where I would really like to read depth of plunge without raising the bed, such as when drilling holes at an angle.

How do you like the igaging? I have the standard scm but it reads to .00” which is probably good enough but I’d certainly like it to read three places like every other gauge I own.
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Re: Cnc 4th axis or duplicator lathe

Fri Dec 29, 2017 11:19 am

It's not the resolution of the SCM digital readout that's the problem for me. The device simply won't hold accuracy, with each raise and lower of the table creeping ever farther from the number you wanted. It might be an effect of running the machine, rated for 220v. service, on 208v. service, but that's just conjecture on my part. The i-gaging works perfectly so far. I've had it a year or two now.

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