You haven't said which lathe you have but below £3k adding an extra £1k to your budget will get you into the realms of a very good lathe for amateur use. This device, being specialised electronics will become virtually worthless the moment it is bought, and uness from a major supplier has no garuantee of long term support.
The link you have given seems to be a £500 CNC type controller.??? I haven't tried translating it.

Well to all intents and purposes it is full CNC with a wide range of internal wizards. It isn't clear if you can run g code from external CAD/CAM which would be a serious limitation IMHO given the price. So ~£500 for the control box, then you need motors and drivers and PSU. John Stevenson looked at some of this type of packaged controllers – have a look at this thread – and was very impressed.

One thing this unit doesn't seem to support is probing to support tool setting which is a serious shortcoming in my view.

I would have thought leaving the gearbox in "A" which is a direct 1:1 drive would not be a problem apart from any possible backlash .

You do have the added complication of a feed shaft and lead screw so would need to decide if just the leadscrew was going to be used all the time or still have a way to use the feedshaft for manual machining (assume the handwheels can still be used? )

Few videos of it in action on their channel

I made a ELS to the design by Joe Noci, I wouldn't be without it now. All up cost probably well under £200, but I didn't keep track

The other option would be to drive the leadscrew from the tailstock end, should be enough sticking out the end of the bracket to fit an adaptor to. Then you can just use the gearbox to drive the feed shaft and never move the selector to screwcutting position.

That will get rid of any backlash in the leadscrew, you just need to sort out the cross slide screw backlash if you want to do say ball cutting as cross slide will need to move in both directions.

I am considering building a CNC cam grinder. This would involve either a stepper driven leadscrew for positioning the saddle longitudinally along the bedway and a ball screw driven by a stepper for the cross slide. The cam would then be formed by controlling the relative position of the cross slide to the rotation of the headstock spindle (by use of an encoder). The encoder would need absolute positioning capability so would likely have to be something like a 4k 'greyscale' type.

My concern is would the reaction time of the cross slide be sufficient to accurately grind the cam form given that the peak acceleration/deceleration rate of a cam can be in the region of 0.006" per degree. The ideal speed of the cam for grinding would be around 300 rpm to allow a small enough grinding wheel (running at close to 4,500 rpm) to fit into the space needed. this gives a time per degree of 0.00055 secs which equates to a cross slide speed of nearly 11" per second or 54.5 ft per minute.Can the control systems, both software and hardware, handle these type of positional reaction speeds?

I realise that 'professional' systems are capable of these sort of speeds but are the 'hobby' systems capable likewise? Any comments and suggestions would be most welcome.

As an additional note the reason for building the cam grinder is that I have a 'spare' bed and headstock and saddle that can be modified – It's too good to scrap and it seems a worthwhile project to make some use of it rather than leave it to 'rust in peace'

Martin

John,

Thank you for your valuable comments.

I needed to run the component at around 300rpm to give the correct surface speed for a small(ish) grinding wheel. As shown in the YT videos of the professional cam grinders the wheels tend to be quite large diameter. The 'rocking bed' system was originally pioneered by Brown & Sharpe in their cam grinders but the basis of my machine needed to be based on a fixed bed to utilise the old lathe bed, although admittedly I could build a rocking system to superimpose on the bed itself. The requirement for the master cam and follower (which must mirror the wheel diameter and requires a host of followers to allow for wheel wear) is something I'm trying to avoid. Ideally I therefore want to go from a CAD design straight to the cam form.

I have built one before, about 30 years ago, from a lathe bed and it was very successful in what it did. However it used a hydraulically driven cross slide which was able to achieve very high rates of movement, it did require a separate hydraulic power pack to drive it with 200 bar pressure and used Moog valves to control the motion. We adapted an engine ECU (64 bit) with a dual encoder using hall effect pickups and a 60+1 tooth master spindle trigger wheel and a secondary 29 tooth trigger wheel (to give differentiation) to allow a resolution of 0.06 degree.

I agree with you about the 'nose' speed problem. That can be solved by a programmed variable speed applied to the main spindle, I think!

The infeed would be performed by continual offset steps down to a pre-determined 'stop'. The offset steps only being allowed when motor current indicates the current 'step cut' has diminished to a near 'spark out' level. Or it could attempt to maintain a set motor current level and apply off setting steps accordingly???

Thanks again for your valued contribution.

My apologies to the OP for hi-jacking his thread, I suppose this did deserve a 'New Thread' but sometimes it is easier to jump in when the thread has either got 'tired' or reached a conclusion.

Martin

I'm currently installing on an old Super 7. It is a cheap way of getting the equivalent of power cross feed and gearbox (gearbox alone now goes for the cost of the complete kit).

I could easily pull it all off if I switched machines.

The challenge with the install is how to physically connect the components : spindle encoder, x and Z motors.

Some observations:

I have the 'hidden under the cross slide' DRO from machine DRO and this would complicate putting the Z motor on the back of the cross slide (where it would probably look nicest. So I'm putting mind on the front, using a bracket bolted to cross slide T-slot.

The toothed belts/wheels for printers (and 3D printers) are cheap and good for light loads. '2GT' 2mm pitch 6mm wide. Lots of options next day delivery on Amazon. Excellent for spindle encoder… but I didn't find them until I had already used 5mm pitch 10mm wide. I will see if it is enough for cross slide…. an 80 tooth wheel replaces the dial gauge while retaining the handle which is really neat. 60 tooth might work and be even neater.

Certainly happy to stick with bigger belts for leadscrew. I put it on the handwheel end.

Document from rocketronics suggests not to gear down steppers too much (steppers lose torque at higher revs so gear down for torque doesn't always help) and stick to whole ratios.

Now I just have to wire it all up…