Author Topic: Heart Transplant for a 3 in 1 machine  (Read 1807 times)

Offline dvbydt

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Heart Transplant for a 3 in 1 machine
« on: May 12, 2017, 03:25:14 PM »
It has been a while since I posted but I have been looking in. I have retired to near Ironbridge in Shropshire in the UK, which lays claim to being the birthplace of the Industrial Revolution! There are 10 museums dedicated to support this idea and they are all worth a look.

Downsizeing has meant that I sold  my previous workshop and now have a 10ft x 8 ft shed so a 3 in 1 machine is what I have chosen. It is a Chester Centurion, the large capacity will enable me to turn bigger wooden bowls as well as metal bits. It is not just a shed but has insulation and a small air conditioning unit for heating/cooling and dehumidifing. In the photo the walls have not yet had the plasterboard attached.

3 in 1 machines take a lot of stick because they are such a compromise , but I did own one years ago, so I knew what to expect.

The heart transplant is fitting a 3 phase motor and a VFD. The Centurion assisted in his own operation by making up brackets etc.
To be continued.
Ian

Offline mechman48

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Re: Heart Transplant for a 3 in 1 machine
« Reply #1 on: May 13, 2017, 06:46:13 AM »
Nice piece of kit. I had a similar version from Machine Mart ... usual disclaimer... as my first machine some years, ago very solid & capable but wasn't over enthused with the milling capability, too top heavy & not rigid enough, never the less enjoy  :thumbup:

George.
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Offline dvbydt

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Re: Heart Transplant for a 3 in 1 machine
« Reply #2 on: May 15, 2017, 04:18:59 AM »
George,

There seems to be two main types. The one I had years ago had only one motor to drive either the lathe or the milling head. It also had a means of moving the head up and down. This was not a very rigid setup, but the machine was inexpensive.
The Centurion has a separate motor for the head and  two solid clamps to hold it in position. Still not going to win any prizes for rigidity but good enough for my model making. The lack of vertical adjustment (there is a small amount) necessitates some really creative setups!

Ian

Offline dvbydt

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Re: Heart Transplant for a 3 in 1 machine
« Reply #3 on: May 16, 2017, 06:41:12 AM »
The first photo shows the original belt drive system and you can see that the motor has a very small diameter pulley. Even with the belts tight, slippage occurred. With the motor running at 1440rpm and no spindle brake, screw-cutting at 160rpm was a bit of a pain.

VFD to the rescue! There was a 940rpm 3 phase motor hiding in my shed that I had been hoarding  'cause “It might come in handy one day.”
Jim and Nick from a local company in Telford - electroaid.co.uk – were very helpful and I bought a Control Techniques Commander SE from them at a very good price.(Highly recommended – no connection.)

Locating the motor where the middle pulley used to be allowed me to use a direct drive from the motor to the spindle. VFD's can give useful torque from 10% to 200% of the motor's rated speed. So, with 75mm on the motor and 100mm on the spindle, that gives me about 60 to 1300rpm.

Double groove rather than single, SPZ pulleys were not that much extra from – bearingshopuk.co.uk -.( Another very helpful Company.) Using the Taperlock system made fitting the pulley to the spindle easy and if needed it is only 5 minute job to change the motor pulley and belts for different speed ranges.

Ian

Offline sparky961

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Re: Heart Transplant for a 3 in 1 machine
« Reply #4 on: May 16, 2017, 06:23:58 PM »
I've been watching with interest, as I have almost the identical machine marketed here in Canada by Busy Bee Tools under the Craftex brand name.

I've owned mine since the early 2000's and since then have made many, many changes to it.  I've had lots of frustration with the machine design, and made some pretty impressive things considering its limitations.  I'm interested to see what else you do, as it would seem you're off to a great start.

Offline dvbydt

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Re: Heart Transplant for a 3 in 1 machine
« Reply #5 on: May 17, 2017, 02:56:01 PM »
Sparky,

Thanks for looking in. If you have had yours that long, you are probably ahead of me with your modifications. Did you do any write - ups?

Ian

Offline dvbydt

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Re: Heart Transplant for a 3 in 1 machine
« Reply #6 on: May 19, 2017, 05:08:19 PM »
Next on the list was to fit the motor. The old pulley mounting plate also served as the feed gearbox cover and had to be removed and modified to fit the motor pivot blocks and the arc for the for the motor adjustment. As I mentioned earlier I needed to be creative with the set up to achieve this! First I chained drilled inside the curve then finished it of with a milling cutter to the line. Hylomar Blue was used as a sealant for the blocks and the plate reassembled. New oil replenished the gearbox. 

Off of the machine I programmed the VFD, not to difficult, I just followed the manual instructions.

Electrics next.

Ian

Online John Rudd

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Re: Heart Transplant for a 3 in 1 machine
« Reply #7 on: May 19, 2017, 05:22:30 PM »
Is that the final resting place for the vfd or is it just a temporary location?
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Offline David Jupp

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Re: Heart Transplant for a 3 in 1 machine
« Reply #8 on: May 20, 2017, 11:07:07 AM »
That guard added on the fan end of the motor looks as though it might be rather restrictive to air flow - I'd suggest you keep a careful eye on motor temperature.  If the motor has a temperature sensor in the windings, the VFD will almost certainly be capable of making use of it.

Offline dvbydt

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Re: Heart Transplant for a 3 in 1 machine
« Reply #9 on: May 20, 2017, 05:01:53 PM »
John - yes it is mounted on 4 short lengths of studding, mainly to clear the hinge on the door. There is no fan in this VFD so there has to be space around the heat sink.  It is in the end cabinet because it is isolated when the door is opened by a  micro switch. The contactor is mounted in the black plastic box on the top left, I had to reduce box  height to give clearance for the belts.

David - I don't disagree but swarf might  get in and rattle around with the fan without the guard! It will  need to be modified  if the motor shows signs of overheating - no problems so far.

Thanks for taking an interest.

Ian


Online John Rudd

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Re: Heart Transplant for a 3 in 1 machine
« Reply #10 on: May 21, 2017, 03:04:24 AM »
Not really sure if mounting your vfd inside there is a good idea? :zap:

My own preference would be to mount it out of the way of swarf/oil/grease and such....
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Offline mechman48

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Re: Heart Transplant for a 3 in 1 machine
« Reply #11 on: May 22, 2017, 07:12:14 AM »
Not over keen on having the VFD inside, how are you going to alter the frequency for raising or lowering the speed whilst in motion, surely you would need access to the frequency up/down push buttons, that would mean opening the guard for access then that would stop your machine so how would you vary the speed? ... unless I'm missing something...  :scratch: surely it has to be externally mounted for access & operation?

George.
George.


Always look on the bright side of life, & remember.. KISS..' Keep It Simple Stupid'

Online philf

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Re: Heart Transplant for a 3 in 1 machine
« Reply #12 on: May 22, 2017, 07:24:08 AM »
... unless I'm missing something...  :scratch: surely it has to be externally mounted for access & operation?

George,

I've not seen a vfd that has to be operated only by the front panel. As far as I'm aware they all have the possibility of being operated by remote switches and speed pots.

Phil.
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Offline DMIOM

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Re: Heart Transplant for a 3 in 1 machine
« Reply #13 on: May 22, 2017, 07:31:07 AM »
Not really sure if mounting your vfd inside there is a good idea? :zap:

My own preference would be to mount it out of the way of swarf/oil/grease and such....

Ian,

I too would worry about lubrication being thrown off the change gears onto the VFD...

Dave

Offline mechman48

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Re: Heart Transplant for a 3 in 1 machine
« Reply #14 on: May 22, 2017, 11:24:38 AM »
... unless I'm missing something...  :scratch: surely it has to be externally mounted for access & operation?

George,

I've not seen a vfd that has to be operated only by the front panel. As far as I'm aware they all have the possibility of being operated by remote switches and speed pots.

Phil.

Not having a vfd I'm not aux faix with them technically, just having seen all previous references to them shown as being mounted externally hence I raised the question, thanks for the heads up on other control methods.
George.


Always look on the bright side of life, & remember.. KISS..' Keep It Simple Stupid'

Online John Rudd

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Re: Heart Transplant for a 3 in 1 machine
« Reply #15 on: May 22, 2017, 12:08:59 PM »
George, just for your enlightenment....
A remotely mounted vfd can be controlled via the keypad, if you move away from the machine to alter settings or it can be controlled via what folk typically call a pendant, built in stop/start and frequency or speed....then theres a comms protocol via RS485 usually from some sort of 'computer'.....

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Offline dvbydt

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Re: Heart Transplant for a 3 in 1 machine
« Reply #16 on: May 22, 2017, 03:50:06 PM »
Mounting the VFD inside back box seemed the easiest solution. Wiring to the motor and the control circuit could be kept short and it could be included  the machine's safety system.
Using the feed gears is unusual for most of what I make except for screw cutting. Lubrication of the gears is usually only a spot of Molybdenum loaded grease occasionally. Keeping swarf from entering via the spindle bore is cured by using a plastic plug with an "O" ring.

I was more worried that the VFD would overheat from being enclosed,but it has inbuilt overheat protection and will cut out  showing  an error code, if it happens, I can always fit a computer extraction fan.

As John said, a VFD can be controlled in many ways and  interfaced to computer. My next post will show how I did it for the Centurion.

Ian

Offline dvbydt

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Re: Heart Transplant for a 3 in 1 machine
« Reply #17 on: May 22, 2017, 06:21:03 PM »
(I just had to watch the Crossrail London Underground program - utterly mind blowing!)

Right, firstly safety. The next phase of this conversion involves dealing with 250Volts AC - it can KILL. If you have not been trained in electrical installation and you want to do something like this, give the job to someone who has! This topic is about how I altered the electrical controls on the Centurion, it is not meant as a step by step instruction of how to do it. As such I have omitted some details that would be obvious to an electrician. At all times, never work on an electrical system unless you have double checked that it is UNPLUGGED!

Sorry about that, it sounds a bit elitist on rereading it, but it really can't be overemphasised.

I totally removed the lathe motor and the FWD/REV switch connections. The VFD draws it's power from the machine main contactor and is earthed directly to the replacement 3 phase motor and the input mains earth. The control terminal connections are shown in the first picture. A 10K ohm variable resistor  is connected to terminals 1,2,3 for the speed control. It looks fairly simple to control the direction, you need 24 Volts on pin 9 and 10 for forward and 24 Volts on pin 9 and 11 for reverse. This can easily be done with a centre off  single pole switch. However I liked the
multipole rotary switch that was fitted.

Making and fitting a new cam to the first switch bank was fairly straightforward. The photos are a better explanation than my words. They show the original white plastic cam and my new one. A hex key was sacrificed to broach the hole. This rotary switch was easy to work on, blue ones defeat me. I do not have the manual dexterity they require to reassemble, springs and contacts end up in the great blue yonder.

More next time.

Ian

Offline dvbydt

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Re: Heart Transplant for a 3 in 1 machine
« Reply #18 on: May 26, 2017, 10:51:49 AM »
So, if you look at the control inputs to the VFD, it needs a 24 volt drive enable signal and this is what my new cam provides in either FWD or REV.
24 Volts also has to be applied to the correct pins for FWD and REV. The switch was wired up and remounted.

The "Live" light was repositioned next to the start push button and the speed pot took it's place. I attached a piece of card to the control knob and used a rev counter to mark the spindle speeds. Then I drew it up properly and laminated the print. That is what is shown in the front panel photo. Eventually, I will get a proper scale engraved.

The carriage gib screws needed retightening far too often, so I made up some new ones that could be finely adjusted and locked in position. This has worked out much better.

All in all I am happy with the Centurion. It's "Horses for Courses." It fits in my shed and so far has managed to do all I need for now.
Does the lathe have torque like a geared head? No! But I can get more low speed torque with a smaller drive pulley on the motor. Is the mill as rigid as 626? No! But I am not trying to remove lots of metal quickly.

The mill will probably get a 3 phase motor eventually, maybe even using this VFD if I can work out a safe way of switching it off, then using a changeover switch to the mill motor.(You are not supposed to have any switchgear between the VFD and the motor.)

I'll finish this post next time with a "User Report" and some photos of what it has produced so far.

Ian

Offline dvbydt

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Re: Heart Transplant for a 3 in 1 machine
« Reply #19 on: June 02, 2017, 10:51:21 AM »
How has this all worked out? The first photo shows that at 350 rpm, 30 mm grotty steel can be cut at 5 mm DOC and 0.06 mm/rev - good enough.
I have also turned some small wooden bowls, the rotary table allows me to cheat and get thin walls easily. Finish is three coats of Danish Oil then waxed.

Screw cutting is very much easier because the spindle stops within in one second. The thread in the picture is 20 mm x 2 mm pitch, and the finished Arbor is part of  my next project. (Have I bored you all or would you like a write up?)

Criticisms :- Not that many because I had had a 3in1 before so I knew what to expect. The mill is not going to win any prizes at fast metal removal, I lock up the carriage and use the cross slide. The quill needs a depth stop, the return spring on the quill is TOO strong ( I have now  adjusted it) and the quill fine feed knob needs replacing with a proper hand wheel.
Apart from that, the scales are very clear, the alignments are good enough and it will do what I need but I would like to fit a two axis DRO eventually.

Ian


Offline dvbydt

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Re: Heart Transplant for a 3 in 1 machine
« Reply #20 on: July 17, 2017, 05:47:21 PM »
Now a 4 in 1, see my latest post.

Ian