Ml4/5 hybrid build

[Carl DorlingParticipant @carldorling51660]

Progress

[Carl DorlingParticipant @carldorling51660]

Hi all just thought I would share my myford ml hybrid with you. I have managed to fit VFD and three phase motor it works well but lacks torque at low rpm I need to fit some form of back gear ( suggestions ideas welcome) it’s been lots of fun and I’ve learnt a lot so far , still some way to go though but it works reasonably well . I also had a lucky find as someone chucked a good bench drill in a skip ten minutes work all working ! One mans rubbish and all that please let me know what you think.

[Neil WyattModerator @neilwyatt]

Lovely blue!

Hmm, easy way=countershaft and pulleys.

Hard way – epicyclic gearbox

Neil

[Paul LousickParticipant @paullousick59116]

Countershaft and pulley arrangement on a Southbend lathe.

[HopperParticipant @hopper]

Can't tell from the pics but it looks like you might be able to halve the diameter of the pulley on the motor and double its speed, which should give better torque characteristics? If that's a poly V belt it should work ok with a very small pulley.

[Joseph Noci 1Participant @josephnoci1]

Hi Carl,

Before going to that effort, perhaps investigate the VFD settings related to the low speed/frequency range.

Unless your VFD is a Vector mode controller ( most low cost units are not) is will have a user adjustable output voltage versus output frequency curve. At low speeds the output voltage is reduced since the output frequency is also lower, and the motor impedance at that frequency is to low for 'higher' voltages.

However, the standard V/F curve as programmed in by the VFD mnfr generally errs on the very safe side.

Find in the VFD manual ( or post the VFD part number and I will try dig up a manual and try help you) where the programming parameters are and then we can slowly adjust them up at the lower speeds. Do this with the drive belt disconnected and when the motor begins to grumble a little at the low speed desired, back off slightly. The worst you may have to do if the exercise is successful, is to add a muffin fan to the motor to cool it at the low speeds, as the motor fan is useless there.

I have 1kw motor on my EMCO V10, and in top gear on the headstock, the motor to spindle ratio is 1:1. The motor is a two pole motor, and I can drill a 20mm hole in aluminium with a feed rate of approx 0.4mm per rev. at 30 rpm. The motor is happy – I am not, because there are headstock fibre gears in the path of all that torque and so I don't do it…But the motor can be coaxed to do it!

Regards

Joe

[Carl DorlingParticipant @carldorling51660]

Hi thanks for the input the pulley could be smaller so will acquire a new one, and the VFD is a power flex 40 a present from work 🙂 I don’t have a manual for it my motor is a 50 hz 3/4 hp three phase but no extra fan.

[Joseph Noci 1Participant @josephnoci1]

Carl, do I understand then that you are going the route of changing pulleys rather? – No problem if you wish to – a pulley change is easy enough. If you do want to try reprogramming the VFD we would need to know the actual part number of the VFD you have – Powerflex 40 appears to be the series, with the actual type embedded in the part number of the series. I have a Powerflex 40 manual, but certain parameters are relevant to certain part numbers…

Joe

[Carl DorlingParticipant @carldorling51660]

Hi just the motor pulley , I’m going into hospital tomorrow so won’t be able to look for a part number for a week or so. The lathe works well but the low speed torque limits the thread cutting.

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