Denford Software & Machines

Hello

For quite a while I have been working on a VSD conversion for my lathe. This consists of replacing the motor and pulley set with a 3phase motor driven by an electronic variable speed drive.

First I converted the motor. This required replacing the shaft driven cooling fan with a motor driven fan. The heat produced by a motor with VSD is the same regardless of speed. A shaft driven fan is too slow at slow speeds and soaks up a lot of power at high speeds.

I used a recycled centrifugal computer fan. This required covers to direct the air and a diffuser to prevent overloading the fan motor.

I made a hand rest to turn the wooden former and to spin the metal.

Dazz

Hello

The next major part was to make the new pulleys. I an replacing the Vee pulley with a poly-vee pulley that fits on my car. Automotive belts are substantially cheaper than industrial belts.

I made both the pulley and a new jack shaft.
Dazz

Nice work

I've always wondered about metal spinning and never seen the process in real life.

Hi

Metal spinning is not as easy as it looks on YouTube.

Aluminium for spinning must be one of the soft grades (100% Al is good). A random piece out of the scrap bin is unlikely to work.

Aim for a bell-shape during the spinning. The edge needs a curve to stop wrinkling. The photo above shows the edge curved back to the right. This is bad and difficult to recover from.

The spinning tool must be applied from right to left to draw the metal down over the form. Equally the tool needs to be applied from left to right to prevent the metal from thinning out to nothing.

Practice a lot.



Dazz

Nice work Daz.

I have to ask - how do you take such nice photos of shiny pulleys. Whenever I photograph shiny parts I can never find an angle that doesn't leave either shadows or bright areas.

Pete. wrote:Nice work Daz.

I have to ask - how do you take such nice photos of shiny pulleys. Whenever I photograph shiny parts I can never find an angle that doesn't leave either shadows or bright areas.

Hi

The top photos were just snapped with a flash. Nothing special.
The ones with the white background used a light source that is very diffuse. Note no hard shadows. The shot is overexposed by 1 stop.

Dazz

Hi

Another step closer to completing a VSD conversion.
These are photos of the motor pulley.

The motor is 1.1kW which means that it will be able to produce at least as much torque over the speed range as the standard motor.
VSDs provide constant torque regardless of speed.

This pulley is attached to the shaft with a taper lock bush.

The next step is to finish the new motor mounting arrangement. The standard one is too wobbly.
I will be replacing the cast base and motor mount with a fabricated welded base frame and motor mount.

Hi

The next stage is the replacement motor mounting arrangement. The factory mount is too floppy to use with poly-Vee belts. They need the pulleys to be accurately aligned. The new mount is a bolt in replacement for the factory items.

The mount was fabricated from rectangular steel tube. It is much stronger than it needs to be but I just made use of materials on hand.

The hinged motor mount is designed to allow the motor to be extracted while still bolted down to the mounting plate.

The yellow items are nylon bushings intended to provide a firm fitting hinge that won't rattle. The hinge pins are supported at one end so that the motor mount plate can be slid off. A bolt on the end of one hinge pin stops the motor mount plate sliding off by its self.

Two height adjusters are included for extra rigidity but only one is needed.

I need to paint it while I prepare the VSD and related items for installation. I plan to fit a digital tachometer and load meter.

Dazz

Hello

The next stage was to fit the motor and new mount. With this done, I made up a temporary control box to test what I can do with the VSD and how I would use it.
See the video Youtube demonstration of Viceroy TDS with VSD

I now have to design and build a proper control system. This will include a tachometer and a electrical load (current) meter.

Dazz

Great work as usual dazz!
What is the drive you've used ?

Hi

It's an ABB industrial VSD unit connected to an ABB 1.1kW motor.
I have machined a couple of items and I have already noticed an improvement in finish.
With the old V belt, the cabinet used to rumble and the lathe vibrated. It's dead smooth now.


Dazz

Hi

The photos show a sample of the finish achieved on my next project.
This is a manky old piece of hot rolled mild steel.
With HSS, the finish is like sandpaper on this metal.
With cermet tooling and smooth VSD, the finish is what you see.

Note the reflections of the tool on the workpiece. Not too far from a mirror finish.

Dazz

Really nice Dazz.
Can someone remind me why we don't make these machines any more

Hello

After starting over 4 years ago, I have finally completed the VSD conversion on my Denford Viceroy.
Youtube Video of Denford Viceroy fitted with VSD and new controls

Excellent work Dazz, hope it gives you years of problem free running. Whats your next project ?

Hello

I am converting my other lathe to VSD and have fitted a 3 phase/4kW/ 220VAC motor.
It's only taken a year so far.
There is no Nardini forum on the web so I won't be posting progress on this anywhere.

I made a poly-vee pulley on the Viceroy

Dazz,

Really nice control panel on your 3ph conversion - I assume that's a special you made.

Curious about one thing - you say you have full torque at low speed - are you using a particular VFD with vector control to do this, or just a 'normal' 3ph convertor? What model have you used?

Thanks,

Youra.

Hello

The control panel was something I designed and made specifically for the Viceroy.

I am using an ABB ACS50 drive. This is a small industrial unit, as opposed to the cheap economy (hobbyist) units.
The ABB motor is also an industrial grade. Unfortunately this grade of equipment is expensive.
I was lucky because I got the motor new and unused for free and the drive at a significant discount.


Attached a motor loadability curve for a Teco motor I am using but the curves are much the same for all brands.
Basically it shows that the motor can produce 100% constant torque from zero to 50/60Hz with a electric forced fan cooling.

With shaft driven fan cooling, torque falls away at low speed to account for decreased cooling. This may be responsible for the myth that AC motors are incapable of providing full torque at low rpm. The graph shows that the motor can deliver ~280% torque at zero frequency, but only for a short time to avoid melting the windings.

Above rated frequency, power is held constant which means torque falls away in an inverse relationship to frequency.
A good quality drive will take full advantage of the motor capabilities.

Hello

Here is a drawing of the driver and intermediate pulleys I made for the Viceroy VSD conversion.
Note that the threaded half holes for the taper lock bush are not shown.

Hello

Here is a close up of the upper control panel.

I made a cardboard mock-up to test appearance and ergonomics.

The panel was mounted on a stand over the hole for lamp.
All of the cabling goes down through the inside of the headstock.

All of the VSD controls a fully remoted so there is no need to access the VSD.
That is mounted above the motor inside the cabinet.

Apart from the upper control panel, there is no external indication that a VSD is fitted.
I have tried to make it look like it could have been factory fitted.