Taig lathe DC motor

[Peter Cook 6Participant @petercook6]

I enjoy seeing the projects other members have completed, and am in awe of the standard of engineering on show. As a contribution, and in thanks to those who have helped me up the learning curve I offer phase 1 of my first real project.

I have converted my Taig lathe from a basic synchronous motor to an Arduino controlled DC setup. Speeds now available range from <100rpm to 10,000 rpm ( spindle limits).

The new motor is a 200V DC 200W 4000rpm ex vibration plate spare from E-bay which came with a a driver unit (the black box) which accepted a PWM input.

Implementation has involved learning turning, milling, Arduino programming, 3D design, 3D printing, and resurrection of my 50 year old electronics expertise.

Phase 2 is to build a new baseboard to bury the wiring, Phase 3 is a leadscrew and thread follower system for screw cutting.

More images are in the Album.

 

Edited By Peter Cook 6 on 02/02/2021 23:36:30

[Peter Cook 6Participant @petercook6]

[Paul LousickParticipant @paullousick59116]

Looking good Peter,

I would be interest in seeing an article on the hardware and software, etc that you used.

PauL

[Michael GilliganParticipant @michaelgilligan61133]

 

Well-said, Paul

+1 from me

… but it does prompt an interesting question regarding the publication of articles in the magazines :

Do we have similar ‘Code of Conduct ‘ constraints to those of the forum ?

If so … publishing a detailed “bill of materials” may prove unacceptable.

MichaelG.

Edited By Michael Gilligan on 03/02/2021 08:28:02

[John HaineParticipant @johnhaine32865]

Nice! But to be pedantic the original motor was almost certainly a single phase induction motor, not synchronous.

[HollowpointParticipant @hollowpoint]

How are you finding the motor? Does it perform well? Good torque? I ask because I have just bought a similar one for a cowells lathe.

[IanTParticipant @iant]

I believe I have the same motor on my Cowells drill now – giving variable speed on it's three pulley settings. It's a 200W, 200v DC brushed motor. It seems to have enough power but I only use it for small work – having a larger 12-speed Warco for any heavier drilling.

The motor is held in a 3D printed 'saddle' designed using Open SCAD and 3D printed on my Sovol S01. I thought about replacing the existing control board with one of my Micromite speed controllers – very easy to do as it's just PWM (a few lines in MMB) but decided to retain the existing controller – at least for now.

I 3D printed a box for the controller but used Solid Edge 2020 to design it – partly to practice my emerging skills in 3D CAD but also because this was very much a one-off, custom design. I was quite pleased with the result and the new set-up works well with the existing IR remote. I've still got a few things to do before it's finished but getting there – albeit slowly.

Regards,

IanT

Edited By IanT on 03/02/2021 12:03:15

[IanTParticipant @iant]

Here is another view of the Drill/DC motor set-up. I'm afraid I cannot see how to rotate this image – it was the right way up when imported…

Regards,

IanT

[IanTParticipant @iant]

BTW – if anyone has the same DC controller board (as can be seen above) that originally came with this DC motor – I'd be quite happy to share the STL file for the printed box to mount it in (or the Solid Edge .par file if preferred).

I'm sure it's not perfect (e.g. could be improved) and takes about 11 hours to print but I was quite pleased with it.

Regards,

IanT

[Peter Cook 6Participant @petercook6]

Thanks for the kind comments.

John H – Quite correct it was a 1/4HP induction motor not a synchronous one. My excuse is that it was late when I typed the posting.

Hollowpoint – I have not really used it in anger yet so can't really comment. However tests show good torque down to 400rpm on the motor (more than the induction motor) and adequate down to 200. That gives me 135rpm (400) and <68 (200). I can control the motor down to about 70rpm (26 rpm on the spindle), but there is no useable torque down there. Top speed is limited by the spindle bearings which are rated for 10,000 rpm.

Ian T – that looks exactly like the kit I got (down to the same remote control), however I decided against using the DC control board, display and remote as you did. Investigation of the motor power control (the black box) showed that the input from the control panel to the board was a simple 5v PWM signal and the 5v supply and input stage on the board within the power controller was fully isolated from the power side.

I decided to build an Arduino based controller (another learning curve) which would also measure and display the spindle speed. The display is a standard 4 * 20 character LCD display. Like you I designed (in my case using MOI) and printed a box for the Arduino, the interface circuitry and the display (two more steep learning curves – the box was my first attempt at 3D printing).

The speed measurement is by a Hall sensor (again standard Arduino kit) activated by a couple of small magnets let into the back of the spindle pulley. Another bit of 3D printing holds the sensor in place between the pulley and the back of the headstock. The control knob is a rotary encoder (I decided a simple pot was too coarse for the 0-4000 rpm of the motor). The run/stop switch and control knob are in a separate box so that I can move them about and find the best (most convenient) location before building them into the new baseboard.

In the longer run I plan to add feedback control to the spindle speed using the PID libraries available for the Arduino – but so far attempts to do so have ended in failure – I am going to have to get out my old control theory books to get the parameters right.

If anyone wants any more info, please let me know.

[Grindstone CowboyParticipant @grindstonecowboy]

Nice work, I'd be interested in doing something similar at some point.

Rob.

[IanTParticipant @iant]

Hello Peter,

Yes, I realised that the board could be replaced with any PWM signal source but decided that I'd try the existing set-up first and avoid adding any further to my TUIT list. The existing board let's me set speed incrementally or just use the three pre-sets (slow, mid and fast) which is what I tend to do – but in theory I have a 9-speed drill now.

Regards,

IanT

[HollowpointParticipant @hollowpoint]

Posted by Peter Cook 6 on 03/02/2021 13:18:01:

Hollowpoint – I have not really used it in anger yet so can't really comment. However tests show good torque down to 400rpm on the motor (more than the induction motor) and adequate down to 200. That gives me 135rpm (400) and <68 (200). I can control the motor down to about 70rpm (26 rpm on the spindle), but there is no useable torque down there. Top speed is limited by the spindle bearings which are rated for 10,000 rpm

.

Good to hear about the motor.

Since you mentioned making a new base board you might be interested in this I made using aluminium extrusion:

**LINK**

[Colin ReedParticipant @colinreed51485]

It looks like I bought the same motor package to upgrade the standard single phase AC motor on my Taig/Peatol lathe. Checking the paperwork though I bought it late 2018, so It’s about time I got on with fitting it!

@petercook6 – how has the motor performed since you fitted yours? Also, how did you mount it – mine doesn’t have any screw holes in the motor tube. I tried to find the photo album you mentioned in your original post but couldn’t locate it.

Colin

[IanTParticipant @iant]

Hi Colin,

My motor also has the two tapped holes in the body but I guess you could use some form of strap to hold it in the saddle. Here is a view of the Open SCAD script I wrote.

And this is the saddle script itself (which can be modified for other motor sizes by just changing the varibles):

//
//
// Sadddle for DC Motor
//
// IanT
//
BL = 107 ; // Base Length
BW = 60 ; // Base Width
BD = 20 ; // Base Depth
ML = 107 ; // Motor Length
MR = 39 ; // Motor Radius
HD = 25 ; // Hole Depth
HR = 3.1 ; // Hole Radius (Clearance)
D1 = 20 ; // First Hole Distance
D2 = 70 ; // Second hole Distance
//
difference () {
translate ([0, -(BW/2), 0])
cube ([BL, BW, BD]) ;
translate ([0, 0, (MR + 6)])
rotate ([0, 90, 0])
cylinder ( ML, MR, MR) ;
translate ([D1, 0 ,0 ])
cylinder ( HD, HR, HR) ;
translate ([D2, 0, 0])
cylinder ( HD, HR, HR) ;
}

 

Regards,

 

IanT

[Michael GilliganParticipant @michaelgilligan61133]

Since you mentioned making a new base board you might be interested in this I made using aluminium extrusion:

**LINK**

 

^^^ That’s very tidy

[ apologies, I messed-up the quoting ]

MichaelG.

[IanT]

On IanT Said:

Hi Colin,

My motor also has the two tapped holes in the body but I guess you could use some form of strap to hold it in the saddle. Here is a view of the Open SCAD script I wrote.

 

Thanks Ian. I think I may still have a version of Open SCAD on my laptop from when I was first looking into CAD, before eventual moving to Fusion 360.

Colin

Edit: looking at the SCAD code it will probably be quicker to create the model from scratch using the parameters in your script.

[Peter Cook 6Participant @petercook6]

Colin,

Mine did not have holes in the motor tube either. It did however have three holes in the shaft end plate ( and the other end).

Having checked, it weighs about the same as the Sherline motor which people happily mount to the headstock so I decided to do the same. I used a length of 25mm square aluminium bolted to the T slot on the back of the headstock, and fabricated a motor mount plate that pivoted on a length of 10mm silver steel rod, and uses an M5(?) locking handle to secure it.

The motor performed extremely well. Power was more than adequate, and using the standard pulleys I could get from about 100rpm to 10,000 rpm with reasonable torque. However there were a couple of downsides, which are fairly obvious in the top view above. The motor projects quite a long way past the headstock, as as I mainly use collets it interfered with getting the carriage with my DRO(!) close to the collet. Using a chuck instead of collets it was far less of a problem. The other issue was the proximity of the ventilation holes in the end of the motor to flying swarf. I made a solid aluminium cap to cover the end of the motor to cut the risk. Heat was not a problem.

With 20/20 hindsight I would/should have mounted the motor the other way round. For other reasons I wanted to swap the motor for a BLDC one as part of a revamp of the controller, and I did mount that motor the other way round using a similar mount to the back of the headstock which is far better. I think the same sort of mount would be OK for your motor.

[Colin ReedParticipant @colinreed51485]

Hi Peter,

Apologies for the late reply – I’ve just seen your post.

Thanks for the detailed reply. That’s a neat solution – I’d better get my callipers out and fire up Fusion 360!

I also like your BLDC motor setup. What voltage does that run at?

Colin

[Peter Cook 6Participant @petercook6]

The BLDC motor runs at 48V. Under the covers at the back are the driver, a 12v stepdown board to drive a leadscrew motor and the Arduino. Couple more pictures. The first is a better view of the BLDC mount – I also have a belt guard  (swung up out of the way in the picture). The second shows a better view of the lathe with its base and control panel while the third shows the wiring spaghetti under the covers at the back.

good luck. It’s worth the effort.

[Colin ReedParticipant @colinreed51485]

That’s a really neat setup Peter!

I actually like the sound of the BLDC motor better than the DC one I originally enquired about.

The ELS sounds great – how are you finding it? I have watched the Clough42 videos on Youtube when he was developing his ELS. I didn’t realise there was an Arduino based version, or have you developed it yourself? I’ve never used an Arduino before, but have had a play around with a Rapberyy Pi Pico in the past.

Colin

[Peter Cook 6Participant @petercook6]

The BLDC solution is great, the main issue is probably cost. I got my motor for about half what they are currently asking. It only has one quirk. Over a small range of motor rpm (600-750) it has a tendency to suddenly stop of its own accord. I THINK the issue is that at low RPM the back EMF in the windings is low and over current trips the limiter in the control box. One day I will change something, but at present I simply ignore that motor speed range (use a different pulley setting).

I don’t really have an ELS (yet!). There is a small geared brushless (JGB37-3650) motor in the lathe foot ( 60mm square aluminium box section) which with my Arduino code gives me variable speed power feed in both directions which I find handy.

The motor outputs 6 pulses per rev, which with the gear ratio gives me about 400 pulses per mm of carriage motion. So in THEORY I can track the position of the carriage to about .0025mm. So far I have implemented an electronic autostop which will stop the feed at a predetermined point. However the motor has inertia, so depending on load (cut depth) the carriage stops plus or minus .05-.1 mm out, and I loose track of those final 20-40 pulses.

I don’t know if its a “feature” of the motor, a problem with my Arduino code or a quirk of the Arduino pulse counting hardware. Until I find out the problem, my ambition to have a fully functioning  ELS is on the to do list. As all the screwcutting I need can be met with taps and dies, the demand has not risen enough to drag it up the list.

Even further down the list is an idea to replace the brushless motor with a stepper motor and do it properly, but that means re-engineering the leadscrew fitment – so that is even less likely.

Good luck with whatever you choose to do.

[bernard towersParticipant @bernardtowers37738]

Thats an awful lot of electronic circuitry  to make a few clock bits and surely threading at the sizes a Peatol can handle a tailstock die holder suffices. And yes I do use two of them.

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