Gallery, Projects and General => The Design Shop => Topic started by: mc on June 21, 2019, 02:53:46 PM

Title: New CNC lathe idea
Post by: mc on June 21, 2019, 02:53:46 PM
Over the past year or so*, I've come to the realisation that most of the parts I make would be far better suited a gang tooled lathe, with live tooling and the abilty to use the spindle as A-axis.
At the moment I have a Denford Cyclone with a 6 position tool changer, which does the job, but doesn't allow me to do rigid tapping (could probably be solved by upgrading the VFD, or swapping the whole motor/VFD for a servo), which means I have to 2nd and 3rd ops on some parts.

So I've been mulling over various ideas. I don't have the space or power for a fullsize machine (both are solvable, but at a cost I'm not really willing to pay!), and the only thing that comes close from industrial suppliers is the Haas CL (Chucker) lathe, but they seem very vague in their live tooling option, and it still has a turret.
Modifying my existing Denford Cyclone isn't really an option, as I still need it running to make parts. Buying another to modify would be an option, but they're getting rare(r).

Now while tapping some parts on my much abused Clarke CL500, the flat dovetail bed got me thinking. Machine the surface and add suitable stop strips for mounting a couple linear rails against, make up a carriage assembly with another couple linear rails to carry a suitable cross slide with mounting for gang tooling. Then for live tooling, use VDI holders on the main cross slide, then have another floating carriage assembly behind carrying a motor that slides in and engages when needed.
Then upgrade spindle motor to a big servo via toothed belt, and I have a machine that ticks the boxes I need, without requiring a bigger workshop, or giving Scottish Power lots of money.

However, I can't help but wonder if there would be a more suitable base machine.
I do think the Clarke CL 430/500 bed is a bit narrow, but I can't find anything else that uses a flat top bed. Everything I've looked at seems to use single/double V ways, which could be machined flat, but I can't help think that would be a bit of a waste. I'd be happy to end up with a machine around the same size as a Cyclone (about 4 to 5 foot long), and I need something with a base I could fit on the big milling machine.

Of course, the other option would be to get some castings done, but I have no idea on cost.

This is currently in the idea queue for machines that would make things far more productive, and allow new products, but not with any immediate need.
So any thoughts/suggestions are welcome.

*the final realisation was a product idea I have, could be done with a roller box, but a roller box is far too big to fit in my current Denford Cyclone.
Title: Re: New CNC lathe idea
Post by: nrml on June 21, 2019, 05:14:30 PM
Can't you mount a piece of tooling plate of whatever width you choose onto the bed of your lathe and mount the rails on that? I don't know if the model of lathe you mention will allow you to increase the height of the headstock above the bed to preserve the swing or if it would even be necessary for the parts you intend to make with it. It certainly wouldn't cost much.
Title: Re: New CNC lathe idea
Post by: mc on July 25, 2019, 04:00:22 PM
So this is still bouncing around my head, and while doing some random youtube watching earlier, a video about building an epoxy base popped up (This vid for anybody interested ( - I'm sure there are plenty other vids about epoxy casting, but that's the on that happened to popup in my suggested list earlier).

Not sure why I hadn't considered that as an option before, but it would open up the ability to create a wider base. Off course, it opens up various other issues like what to do about a headstock (spindle itself is easy, but not sure I'd want an epoxy headstock casting..), what to use for rail mounting surfaces (alu, steel),  is it better to create a substructure to cast around, or just cast the rails in situ then level, and I'm sure there are plenty further questions that will come up..
Title: Re: New CNC lathe idea
Post by: efrench on July 25, 2019, 08:28:54 PM
As punishment, you must read the entire epoxy granite thread on cnczone  :ddb:
Title: Re: New CNC lathe idea
Post by: mc on July 26, 2019, 02:24:03 AM
As punishment, you must read the entire epoxy granite thread on cnczone  :ddb:

I should have guessed such a thing exists, but I can already sense I'm starting to circle a black hole..
Title: Re: New CNC lathe idea
Post by: PekkaNF on July 26, 2019, 07:46:47 AM
I have been reading this OP leasti three times.

For some reason I am thinkking "Swiss" type sliding head lathe concept.

That has too many axes, CAM might be interesting, but interesting slide arragement.

Those are optimized for pretty close tolerance bar, but I am thinkking that if you don't need a automatic bar feeding and extreme rigity for high production a collet chuck traditional or capstan type lathe spindle arrangement might suffice?

You don't say what dimenssion of parts you are planning and do you need a bar feeder or something excotic for HMS.....but here is the reason for my suggestion:
* You are thinkking of sh%t load of gang tools and live tooling for "cross slide" no problem there, but if you want to trash that around on two axis, it needs a whole lot of power.
* My reasoning is that put two "crossslides", roughly on same plane, businessends facing each others and facing spindle axis....I would first check both vertical. Downside is that can't work at the same time (antique designns had multiple slides radially out of spindle axis, but no gang tooling.
* To move spindle horizontal relative leisure speed and adequate accuracy does not need that much energy for acceleration. Short movement does not take that much space and structure probably would be more compact than traditional lathe derivates....OP says that real estate is in premium.

Do you need a second spindle? That would complicate this scenario considerably.

Am I completely off the mark?
Title: Re: New CNC lathe idea
Post by: mc on July 26, 2019, 12:20:01 PM
The big issue with swiss/sliding head lathes is you need accurate bar stock to begin with, as accuracy is highly dependant on stock/bushing tolerance.

To give you a rough idea of the most complex common part I make at the moment, it's around 40mm long and 16mm diameter, has a threaded centre hole, and two flats. At the moment, it takes 3 tools on the cyclone (OD turn, drill, and parting), it then goes in the manual lathe to get tapped, then in the mill to get two flats added, then deburred by hand.

I'd like to do that on a single machine. Load a length of bar, walk away for a period of time, then come back to collection of parts that just need minor finishing. To achieve that, I'd need an OD turn tool, static drill, rigid tap, mill, chamfer

That part gets paired with another part that takes 4 tools on the cyclone, and needs one of the drills swapped an offset reset between part runs.

I have plans for more items of a similar size, where one requirement is an offset centre hole, and also likely need the use of a rollerbox to get the accuracy (it is one part that would work well on a sliding head lathe, but a roller box is far simpler!), but a roller box won't fit the cyclone.
I also have a tentative idea for some parts around 50mm diameter, that could be machined more economically from bar stock on a lathe, than flat plate in a mill.

I could very likely go and buy a shiny new suitable lathe on finance, but I don't want that monthly headache, plus it would take up a fair amount of floorspace, and that's even if it would fit in the available height.
I'd think I could build something capable of what I need that would fit within a 4x6' footprint, and be no higher than 5'.

Another thing I do keep thinking about, is would I be better going for a slant bed (the cyclone is slanted), knowing it would be harder to make, or will a flat bed with suitable covers be good enough to handle swarf.
Title: Re: New CNC lathe idea
Post by: PekkaNF on July 26, 2019, 07:06:48 PM
Bar stock feeder changes things....I just though that if you get away without busking business then there are some DIY benefits. But you need the whole shebang.
Title: Re: New CNC lathe idea
Post by: MetalMagus on July 29, 2019, 07:22:21 AM
Depending on the size of the parts you are making. Would a Taig lathe work.