Which C N C Lathe...?

[richardandtracy]

I have been making pens for a little while on my metal lathe. The accuracy I can obtain is adequate (0.001"), however this comes at a price in time. I have averaged 13 hours per pen, and that is not adequate.

 

Having analysed where the time goes, there are three areas that bug me.

1) Changing the setup between one tool & the next,

2) Tapers.

3) Ensuring repeatability between one pen and the next.

 

Taper turning seems to take out a huge chunk of time, particularly on the section. Also, with the section taking 3-4 hours and being very liable to failure, this is the bit where I think I need help.

 

So, I thought to myself, 'Where can a relatively unskilled worker speed things up?'

 

There is only one answer. CNC.

 

Does anyone know a relatively small CNC lathe with a radial mill/drill capability to enable gilloche style milling on the barrel?

 

I have looked around and found one that would need my requirements - a Daewoo Puma 1500Y with 4 axis control, but at 5 tonnes it's a little big for my workshop, and with two 3 phase motors (one 5kW and the other 15kW), it's not practical for a home power supply.

 

Does anyone know a smaller lathe that may do the job?

 

Regards,

 

Richard

[Jopen]

Have a look at Optimum... just to inspire yourself... ... and hide your wallet!!!

[Top Parker]

Denford cnc, Boxford cnc, Emco cnc lathes plus a bench top cnc Mill with 4th axis and a dividing head or chuck, all can be found on UK flea bay. You can convert some of the Chinese mini-lathes or a better quality Myford to cnc yourself.

 

If you want to try Guilloche I'd go for the rigidity of something like a Plant straight engine lathe.

 

Prepare yourself for a big learning curve.

 

On the other hand you could make your pens in batches, obtain a taper turning attachement for your lathe, or look around for an old hydraulic copy lathe.This would get the time down.

 

If you need any help pm me.

Bryan

[richardandtracy]

Thanks. They have given me a few names to research & think about.

 

I have thought about converting my lathe a couple of times. I am sufficiently wary of electronics to regard it as a last resort rather than a first...

 

Regards,

 

Richard

[manojd]

How are Proxxon PD400 cnc lathes? Has anyone used them?

[richardandtracy]

In my research I have looked at them - a place just a mile up the road from me has a catalogue that sells them, though the shop staff knew nothing about them!

 

The lathe is small (MT3 headstock & MT2 Tailstock) and is very lightweight (45kg, 100lb), However it appears to have a remarkable degree of precision in everything. The non-cnc version retails at about £2050, and is correctly priced based on the quality of the lathe. The CNC version (which I haven't seen in the metal) is about £4300 with the thread cutting add-on. From what I have read of it, it would be a great little machine BUT it doesn't fulfil all my reqirements. The problem is that it's a simple 2 axis machine with no control over the chuck rotation, so it's impossible to wriggle the chuck back and forth while the saddle moves, so you can't create gilloche style engraving.

 

Regards,

 

Richard.

[BigShed]

Have you considered going for a 4 axis CNC mill or router instead of a CNC lathe?

 

For example this one with the optional 4th axis

 

http://www.carving-cnc.com/cnc6040-series/cnc-6040z-s80-new-router-engraver-drilling-and-milling-machine.html

 

 

or a smaller version with the 4th axis

 

http://www.carving-cnc.com/cnc3040-series/cnc-3040z-4d-new-version-router-engraver-drilling-and-milling-machine.html

Edited May 22, 2013 by BigShed

[richardandtracy]

Yeess. Sort of. I have, after a fashion.

 

The reason why I'm sounding a bit hesitant is really down to a lack of knowledge of the capabilities of CNC rotary tables. I am not sure if you can do traditional turning with them using single point tools and get the speed up to 2500 rpm or so. If you can, and not wear them out, then that sounds ideal. However, if that is not the case, then I'd rather pursue a cnc lathe first to see if I can get what I want from that. If I cannot find the lathe option, then a mill may be the next thing to check out. It will need a different way of thinking how to do a pen, but it will be a much more flexible machine.

In fact a 3 axis mill (X,Z & rotary) will be the minimum required to accomplish what I want.

 

As you may have gathered, I am learning how much I don't know at the moment, so that I can start to find out exactly what I do need to know.

 

Regards

 

Richard

[Inspector]

http://cornlathe.billooms.com/index.html

 

I assume you know of Bill Oooms and his work with CNC ornamental lathes made from wood lathes. Contacting him might put you on to a machine suited to what you want.

 

The 4th axis for a CNC mill is usually a stepper motor driven rotary table and are not spun anywhere near lathe speeds. They rotate the work under the mills cutters and can be used for carving in the round. With very fine cutters it could do gillochee like work but I doubt it would be as fine as traditional tools. It would be able to do nontraditional patterns since it will cut in any direction. A traditional fixed graver could probably be made to work on a 4 axis CNC mill but I can't recall ever seeing anything written on it.

 

Pete

[richardandtracy]

I was not aware of Bill's work - absolutely amazing work, thanks for showing it.

 

However...

Having read his description of making his lathe and all the fun he has had getting it up and running, I am now more firmly convinced than ever that converting my lathe is a last resort. And may even be one step beyond the last resort.

 

Regards,

 

Richard.

[BigShed]

I guess it comes down to what you want to do. A CNC lathe is ideal for repetition work, but I doubt whether that is what you are looking at.

 

If you already have a metal lathe then nearly all the things you need to do to make a pen are already covered.

 

If you want to embellish pen barrels then a CNC lathe doesn't strike me as the best option, but the CNC router/engravers I linked to can do that with their eyes closed.

 

Think about it, on the lathe you are holding your pen between the headstock/chuck and the tailstock, you will need an additonal powered tool/axis to embellish the pen barrel.

[Rich L]

...

 

Think about it, on the lathe you are holding your pen between the headstock/chuck and the tailstock, you will need an additonal powered tool/axis to embellish the pen barrel.

 

Not necessarily true. With a C-axis control like what is on the Puma and smaller machines like what I have (still heavy, though), an engraving cutter or point can be dragged along the surface of the cylinder. C-axis control is slow, deliberate, programmed and interpolated movement of the main spindle axis. Drag engraving effects can be accomplished as well as bright cut engraving. Runout management is critical. Programming a guilloche-like pattern will be non-trivial.

 

Rich

[richardandtracy]

I agree it's non-trivial. However, I am a moderately capable programmer, and writing a program to generate the g-code (or whatever the system used) would be far easier for me than doing the engraving by hand. One of my 'hobby' programs has been a 3D Finite Element Modeller to create stress analysis models from scratch. It's permanently under development, and it now tops 90000 lines of code. The models I generate within it can interface with NISA, Cosmos, NASTRAN and Radioss Finite Element systems and also CAD systems via DXF & 3D graphics packages via the .obj format. Compared to that, designing a program to write a tool path would be comparatively relaxing.

 

Amongst other things, I am trying to de-skill the operation, because I fully appreciate of my lack of skill when it comes to using a metal lathe - I regret to say, I can operate computers much more easily and quickly. Furthermore, programs can be tested before use and as a result you can 'see' the object before wasting any money on material. And can do it during lunch breaks at work etc.

 

Regards,

 

Richard

[richardandtracy]

...

Think about it, on the lathe you are holding your pen between the headstock/chuck and the tailstock, you will need an additonal powered tool/axis to embellish the pen barrel.

You are quite correct about the additional powered spindle. At the speeds I expect the engraver to operate, a 50W motor driving a simple spindle & collet via a belt would be sufficent. I have enough power tools to rig one up, or even use my 43mm collar woodworking router as the tool (the runout is 'marginal' on this, I've had deflections of 0.02mm under light loads, which is why I was thinking of a spindle).

 

Regards,

 

Richard.