CNC retro fit

Yes

-- Regards,

John Stevenson Nottingham, England.

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In article , John Stevenson writes

I love it when you play hard to get...

Cheers, I have been googling for a little, but thought I'd ask here as well.

For those of you that have done this, did you use servo motors or steppers, any reason why or was it what you had to hand?

Stephen.

Can you give us a bit more of an idea on size of lathe. It does have a bearing. Size and make would be nice as someone here may have direct experience of this make

-- Regards,

John Stevenson Nottingham, England.

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How you convert a lathe to CNC seems fairly straightforward.

(I am doing it myself so it must be)

Why seems to be a little more difficult and does affect the design.

Conventionally CNC lathes are only of use if you are doing productio runs of the same items or want to do complex curves and it is far mor difficult to do a 'simple' bit of freehand turning, unless you desig the system either to respond to the old manual controls as well, o build in manual encoders to control your motors.

On the other hand, converting a lathe to CNC 'because you can' seems t be a very valid reason in which case the added complexity of disengagin drives and gearboxes may be part of the attraction.

Robi

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This is changing rapidly just as CNC mills were only useful for a few/ many off they have now reached the stage where one off's are perfectly plausible hence the increasing number of CNC mills in the home workshop.

In the last 6 months the biggest stumbling block of getting a decent controller to understand small batch jobs or one offs has been addressed. Mach3, which in it's earlier guises as Mach1 and Mach2 was a mill controller has now evolved into a lathe program. At the moment it's fully functional but there are moves in the background to get this even better.

I also am doing a lathe conversion but I'm also working in the background on the controller side of it with some very clever people to bring full conversational programming to Mach3. Sorry that sounds a bit too grand, I'm helping Whether I make my conversion a commercial venture or a part of it remains to be seen but information will be freely shared.

At the moment low cost lathe is limited to a bit of jogging on the keyboard and running CAD CAM generated G code. Turbo CNC is good at this but is a dated DOS program. DeskCNC is also able to do this but the information is that tightly held that it must be under the official secrets act.

Mach3 has made fantastic strides already. Take a look at this on screen video here.

Eventually all aspects of Mach3, mill and turn will have these videos free of charge.

At the moment Mach3 has a set of what they call wizards but in reality is conversation programming. Current wizards do taper turning, facing, screwcutting, ball ends and radii to name a few. These are being worked on and made better. New wizards will be able to be stacked to do a complete job from start to finish. Most lathe work is made up of a very few simple routines so this is entirely possible. Later they are hoping that where the complex shapes are concerned like a candlestick for example, you will be able to bring in a dxf of one side, give it relevant measurements and placing and get the program to write the code from that. The whole idea is that everything is done inside the controller.

With the addition of an electronic handwheel and a changeover switch or two handwheels [ both possible at the moment ] you have manual control of the machine for jogging and simple turning tasks. I have tried MPG's as they are called [ Manual Pulse Generator ] with clickable detents and free running.

To be honest and against what I would have thought, after about 5 minutes use of a free one you even get a feedback, not by feel but by visual and sound. I was quite happy to 'manually' turn a stepped shaft dead on size on a strange machine to me.

Later on it's hoped that a teach wizard similar to the Mill Teach wizard will be brought into lathe. This means that that one stepped shaft I did could be replicated again and again, The program stored or discarded as necessary.

Mach3 will support front or rear tool posts or both and it's possible at the moment to run auto tool changers up to as may tools as the changer is capable of holding but this is also being improved.

Invertor or VFD motors are also addressed and it can even do constant surface speed turning.

As our Chinese friends say "We live in interesting times"

-- Regards,

John Stevenson Nottingham, England.

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Hi, this is all just intial research at the moment, but I have a Colchester Triumph 2000 I want to tinker with.

Stephen

Why? I need to cut complex curves (internal and external) and this seemed a good idea/bit of fun :-)

Stephen.

Mach3 is an amazing piece of software, the functionality to price ratio is staggering. I can't imagine why anyone would choose a different system for a diy cnc project. I've just changed my cnc lathe over from turbocnc to mach3 and have been very impressed so far, and as John says it is improving all the time. It does need at least a 1ghz PC, but that isn't exactly state of the art any more (I got a new PC in the house and put the old one in the workshop -which was when I was able to change to mach3). I still program on a CAM package and send the files into mach3, but as the wizzards improve I think it will be quicker and easier to do everything in mach3 -especially as my tool changes are manual anyway.

Regards

Kevin

Absolutely...and also just the job for knocking out chess sets as xmas pressies when you can't think of anything else ;-)

Regards, Tony

Give the size of the lathe, I could make quite a nice garden chess set.... Don't give me more ideas, please!

Stephen.

Continuing this thread, a question for those that have converted a lathe, how did you deal with the backlash in the lead screws? did you convert to ball screws or deal with it in software, either compensating (not sure how) or adding a DRO for positional information?

Stephen.

Compensating is a bad move, all you are doing is chasing errors. Far better to get rid of the errors in the first place. Ballscrew's are not that expensive if bought surplus, Ebay or other means. There is a guy on Ebay selling ex Denford screws, new, old stock for less than £100 per axis. A couple of thrusts or angular contacts on one end to control the float and a steady bearing the other end and you are away.

No need for DRO's except the machine controller ones. I have seen conversions where they have fitted DRO's to keep a check of the main controller. I often wonder if they get the wife to follow them in a spare car every time they go out.

Some do fit DRO's to keep tally as if they have MPG's the main controllers loose position as they can't accept the feedback from the controller. All the MPG does is act as a power feed and bypasses the controller. Might as well not bother IMHO if that's the only way the controller can work.

Mach3 BTW keeps check at all times and reads the MPG's then sends the signals out to the drivers. This allows you to use the machine in full manual mode and know where you are.

-- Regards,

John Stevenson Nottingham, England.

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When you gonna start taking orders? ;)

Chris

Candlesticks?

(Ducking quickly ... ;-) ) Regards, Tony