Myford S7, VFD's & Coolant Pump

[Bluechip]

My S7 is run off a Transwave  Static Converter. It has a 3-Ph. GEC motor on it, Star / Delta, currently on Delta, 240V Ph. to Ph. as you might have guessed. So, I can shove a VFD on it and away I go ??

Well ..
[1] It's 1/2 HP and many folk seem to run 3/4 HP on a S7.  Any reason ?
[2] It's got a suds pump, 3 phase. This is wired to run if required when the headstock motor is running. Not unreasonable. But how will this react to a VFD on it?
Has anyone else come across this ??? 

Two things spring to  mind:

[1] Bugger it. If the headstock motor's running slow then so will the pump .. it gets what it's given.
[2] I don't use suds anyway .... amputate & dump ...

I now stink of Soluble Oil .... 

Dave

[Jo]

Should be no problem running the 1/2HP 3 ph off a VFD. (Programming the VFD can be a pain). You will need a second VFD for the pump.

You will not be able to use the existing switch gear wiring, so it will be new wiring all round  .

It could be worse it could be honing oil 

Jo

[Bluechip]

Just wondered if there was some inherent inefficiency with a VFD that made a 3/4 HP a better bet. IIRC some S7's had a 3/4 HP s/phase as standard ??

I have not spoken to Drives Direct ( about a 15 min. drive from here ), but I imagine the VFD is self contained and all the stuff on the S7 is redundant.

I wouldn't bother with the expense of a separate VFD for the pump. Just chop it off, sling it and pretend it never happened. 
Only ever used it once, damn thing chucks out 200 GPH, suds everywhere until I shut the valve down .. never again ..

Dave

[Ian S C]

If you decide to keep the suds pump, it could be run on a separate circuit, using the mains supply and capacitors on the other phases.
Ian S C

[mikemill]

I fitted a VFD and new motor to my S7 around six months ago and has transformed the use of the lathe, instant speed control; forward and reverse makes cutting threads a joy.
Regarding coolant I fitted a windscreen washer pump to my CNC mill with speed control, all well and good but still too much suds running everywhere. I now use a plastic toothpaste tube type bottle with a long nozzle puts just enough suds where its required, now have one on every machine works a treat.
 
Mike

[Jo]

I have not spoken to Drives Direct ( about a 15 min. drive from here ), but I imagine the VFD is self contained and all the stuff on the S7 is redundant.

If the switches on the front of the Myford are just push contacts you could use them to form your VFD pendant. You will need to add probably a 10K pot for the speed control but my advice would be to still use changing the belts for control as that way you keep the torque and should be able to continue to use that smaller motor.

1/2HP motor is not that underpowered. Mr Silky's 2 speed motor is only 1/2HP on the low speed setting and he happily take off 2mm deep (4mm on diameter) cuts in steel. Why he needs 1.5HP at 3000 RPM  I am not sure. 

Jo

[Bluechip]

Jo;

It's got the Industrial Stand, like this:

http://www.lathes.co.uk/advertphoto/151103super7bpxf/img0.jpg

Behind the panel are some clackity contactors, not just buttons.
Might just go for a package from Transwave with a 3/4 HP TEFC motor. Could not contact Drives Direct for some reason but they do a similar set-up for much the same price. circa £300. Comes with all the bits.
I'll just kick the coolant pump caper into touch for the time being, no big deal.
The tank seems to be infested with some 'orrible Quatermass-style gunge lurking under the soluble oil ... 

Dave

 

[Jo]

  If you accepted that this was a one way trip you could replace the two push buttons with some momentary switch buttons. Replace one of the pointy switches with the speed pot and the other with a three way switch for the forward/neutral/reverse. And there you have your remote pendant.

As long what is under there doesn't look like the smell jelly stuff that Mr Silky came with in his tank

Remind me why are you doing this if you already have a static converter: If you add a small pilot motor to the static it would behave more like a rotary converter 

Jo

[Bluechip]

I have delusions of grandeur, viz. This variable speed thingy which mikemill and numerous others deem very desirable.

I suspect you have been using up-market Tool-room quality machines for too long. Have you forgotten the joys of having your pinkies gobbed up with black crap after a S7 belt/pulley swap ??

Don't see any reason why it shouldn't be a one-way trip. Why would anyone want to go back?



Dave

[Jo]

I have delusions of grandeur, viz. This variable speed thingy which mikemill and numerous others deem very desirable.

It won't make it like using a Hardinge 

I suspect you have been using up-market Tool-room quality machines for too long.

One can't use a Mr Silky for too long

Jo

[Niels Abildgaard]

Some power get lost from motor to spindle in Your present setup.
A better lathe drive scheme:

http://i.imgur.com/kjnlMT9.jpg

My Boxford use a Powertwist A belt that is 1/2 inch wide and it is tensioned so that it slips when I make something really stupid.
A 10mm wide powertwist can go round a 45 mm diameter motor disc and if the biggest myford disc on spindle is 90 mm? a 375watt 4 pole motor will be fine I think.
My friend is chairman in the Society for prevention of change or cruelty to Myfords
but has installed a VFD and does not move belts or use the clutch anymore

<a href="https://www.youtube.com/watch?v=VZvs_4cADZ8" target="_blank">http://www.youtube.com/watch?v=VZvs_4cADZ8</a>

[pgp001]

I converted my Myford S7 to run on an inverter, I did not want to make any permanent changes in case when I am gone someone wants to put it back to original.
So I put my engraver to use and made a complete new front panel from Aluminium faced Traffolyte sheet, the inverter is mounted behind a cutout so I can see the digital display.

The original single phase main motor was swapped for a new three phase one, the coolant pump was already single phase so I just wired that to its own switched supply.

This is one of the most useful mods I have done to the lathe.



Phil

[Don1966]

Did mine a while back and love it Dave. I don't have the pump on mine. This is my version of the installation.   http://www.modelenginemaker.com/index.php/topic,2278.0.html

Don