Heavier Spindle on Fox Alien

[IanTParticipant @iant]

I have a Taig ER16 milling head that isn’t getting used very much these days. I used it mounted on the end of my small EW lathe with the ‘boring’ table fitted. I fitted an old shower pump motor to drive it. The existing combined set-up is quite heavy but as it mounts on a vertical slide, that doesn’t matter too much.

I purchased a Fox Alien 3020 CNC router a year or so ago and it is a robust little machine. In truth, I haven’t used it very much but there are several things that I feel need improving, including the 300W spindle motor. My wandering mind has turned several times to the Taig head but concerns about the weight have stopped me progressing the idea. Mention (elsewhere) here of BLDC motors has prompted me to wonder if I might get away with it, if a lighter motor was fitted.

The Taig head is a good small milling spindle and has far less “stick-out” than the 300W spindle currently fitted. When compared to a larger water cooled spindle, I suspect the weight would not be so different – and I already have the Taig head. I’d need to keep the ‘Z’ stepper on for longer to stop the ball screw moving but would the NEMA 17 manage it? I can’t find a part number on it to check the spec…

What do you think? Worth exploring?

Regards,

 

IanT

[Peter Cook 6Participant @petercook6]

Two thoughts.

If you use the Taig spindle you will be limited to 10,000 rpm, at least that is the spec on my ER16 lathe headstock. Will that be fast enough for the router? They seem to run 2-4 times that speed.

If you will be using the head, you are unlikely to be using low speeds. Directly coupling a high speed DC or BLDC motor to the spindle shaft, rather than using pulleys would let you mount the motor directly above the spindle and minimise any cantilever effects. The T slots in the headstock would provide a reasonable way of mounting such a motor. High RPM motors seem to be somewhat lighter than lower speed ones.

 

[BazyleParticipant @bazyle]

You could put the motor in a fixed position with a tension arm for the belt – look a the Alexander / Deckel 3A die-sinker drive.
I’m not convinced about the cantilever with that headstock and effect on rigidity. One of the previous threads on spindles had a design about 32mm dia and I was thinking it could be tucked in at the side of the existing Z slide to give minimal overhang while losing a little bit of X range. A dia < 25mm would be nice but that seems to put it down to a ER8 collet.

[IanTParticipant @iant]

Thank you both for the feedback.

Peter, yes the Taig head is rated at up to 10K RPM – but then so is the existing 300W spindle. Also the spindle speed required is related to the diameter of the cutter and number of cutting edges.

Bazyle, I did actually toy with an ‘engraving’ machine type drive but decided it was too complicated. I also thought about using a flexible drive to a lightweight countershaft, thereby removing the motor weight.

Other than the chinese high speed air/water cooled spindles, people also seem to use Makita routers. I wouldn’t think any of these are very light though.

So whilst I still like the idea of a powerful motor mounted ‘weight off axis’ so to speak, I haven’t managed to convince myself there is a practical way to do it yet. Hence my pondering if a BLDC might provide enough power and low weight.

Regards,

 

IanT

[Peter Cook 6Participant @petercook6]

Ian, when researching the BLDC motor I have on my Taig lathe I was fascinated by the claimed power output and price of the DC Outrunner motors used on scooters and drones. Things like these. That one claims 1750W output at 9000 RPM and only weighs 256g. 42mm diameter and 50mm high.

They do take a lot of amps, and I’m not sure how you would mount one – I was never clear what rotated and what stayed fixed – but as an idea I was tempted!!

 

[Russell EberhardtParticipant @russelleberhardt48058]

Interesting build of a spindle using an outrunner motor here:

https://www.mycncuk.com/threads/3793-Diy-Brushless-Spindle

Russell

[Peter Cook 6Participant @petercook6]

Thanks Russel that’s interesting. Didn’t realise the shafts came out that easily. Now all Ian needs is to find a suitable outrunner motor with a shaft that matches the Taig spindle OD and fit the motor directly to the back of the headstock.

[IanTParticipant @iant]

I’ve played with smaller 1400KV BLDC motors before Peter, using a 20A ESC coupled to a Micromite to generate the PWM signal. It’s not obvious from the photos but the star shaped frame attaches to the end furthest from the spindle.  Obviously, this end doesn’t rotate but the rest of the body does. So it may not be simple to mount but it’s not impossible either, although it may need some form of ‘finger-guard’.

The motor weight is certainly good for this use and I wasn’t looking for that much power – I think 800W would be ample. Heat may be an issue, as may be noise (which it certainly would be using the Makita). In terms of price, this motor and a 40A EXC would look to cost about £50, so that would be very affordable compared to the alternatives, given I already have the milling head. As mentioned, I can control this motor/ESC combination with a very simple Picomite controller (which I also already have) so again not a problem. I could probably link it to the CNC spindle speed control as well (?)….

It all sounds a bit too good, so there has to be a ‘Gotcha’ somewhere  🙂

Heat, Noise, Duty Cycle?

What motor did you end up using for the Taig btw?

Regards,

 

IanT

[Peter Cook 6Participant @petercook6]

I got a Nema 34 86BLS71 motor. 3000rpm 220W 48v DC. I got it for less than 2/3 the price they are currently asking. Last picture here shows it mounted to the headstock.

One thing that decided me against trying the outrunner route was the  belt tensioning. It wasn’t clear what radial force was acceptable, while the NEMA  motor seemed to have more than adequate capability.

[IanTParticipant @iant]

Thanks Peter, unfortunately those NEMA 34 motors do appear to be quite a bit more expensive.

However, I understand your concern about the radial force acting on the spindle of this particular BLDC design of motor. That could be overcome I think, although I’d still be concerned about potential heat generation & low duty cycle. Noise might be something that I could live with, if mitigated by an enclosure.

Another option might be to use the existing 300W motor to drive the Taig as a ‘suck it and see’ exercise without spending any money on it…

Anyway, thanks for your thoughts, much appreciated   🙂

Regards,

 

IanT

 

 

[IanTParticipant @iant]

PS Sorry Russell – missed your earlier post. Certainly another thing to think about, although having the pulleys/belt present does allow more options..

Thanks

 

IanT

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