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manofgresley
10-09-2013, 04:30 PM
Hi

As anyone any experience of converting a small hobby mill. Namely a Hobbymat BFE65, similar to a Seig X2 etc; to variable DC speed control.

While cleaning and de-greasing the gearbox on my Hobbymat, i have found wear on the gears and in the bushes, and what looks like a crack in one of the spigots in the casting, it suddenly dawned on me, what if i can remove all the gears and the quill and replace with a VFD, or a 3 phase controller, so that i can vary the speed easily, currently i have only 4 gears, the fastest being 1600 RPM, maybe the machine could ru faster, it seems sturdy enough. I have ordered some Crack Detecter, so this new knowledge may determine the way forward.

Regards

Ray

m_c
10-09-2013, 06:09 PM
The desktop machine board over on cnczone has numerous threads on various conversions.

It has been done, as I did look at getting a X2 to convert a while back, and I'm pretty sure there are companies who'll supply the required bits, albeit over on the opposite side of the pond.

birchy
10-09-2013, 06:17 PM
...to variable DC speed control...I assume you meant AC control? If so, the mechanics are probably the hardest thing to do...in particular getting a motor small enough to fit the machine without giving up too many horses.

Regarding motors, the basics are that a 4-pole will run at approx 1425RPM at 50hz and a 2-pole will run at around 2850RPM at the same frequency. The big decision is whether to choose the slower 4-pole (for more torque at low speeds) or the higher top speed of the 2-pole but with reduced torque at low speeds. You can use stepped pulleys or gears to overcome this but I just didn't have the room for such niceties on my machine.

EddyCurrent
10-09-2013, 07:13 PM
Maybe you could fit a DC motor with associated speed controller, think of a variable speed mains electric drill for example or even a lower voltage system.

manofgresley
11-09-2013, 12:33 PM
Hi

Yes, that's what i was thinking of, DC motor control, do you know of any info i could look at ?

Regards

Ray

EddyCurrent
11-09-2013, 03:05 PM
Sorry, I don't know why I didn't see that in your original post, I think the term VFD in the thread title immediately made me think of AC (which it is) :nightmare:

Fracmo | Brushless DC Motors, Fractional DC Motors, Gearbox Design & Electric DC Geared Motors (http://www.fracmo.com/)

These look to be the part but no prices, I'm assuming it's something like 250Watts you need ?
They seem to be used in electric wheelchairs etc. so maybe a company who repairs them may have second hand units ?

also http://www.drivesystemsuk.co.uk/dc-motors-gearmotors.html

There are loads of DC controllers on ebay or Amazon at very low prices but obviously would need to be compatible with the motor and supply voltage.

m_c
11-09-2013, 05:23 PM
DC is different.
For cheap motors, old treadmills seem to be the way to go, combined with a KBIC speed controller.

Unless you really are trying to do the conversion as cheap as possible, I wouldn't use anything other than a KBIC, as they're quite popular, reliable, and not that expensive to buy new. I run a KBIC in my little lathe, as it came with a DC set-up and a dead Cheetah drive, and a KBIC was the cheapest main stream option I could find at the time.

EddyCurrent
11-09-2013, 06:16 PM
DC Motor for RDG-30VSM Milling Machine | eBay (http://www.ebay.co.uk/itm/DC-Motor-for-RDG-30VSM-Milling-Machine-/261284094097?pt=UK_BOI_Metalworking_Milling_Weldin g_Metalworking_Supplies_ET&hash=item3cd5bee091)

DC motor controller control board KBIC suitable for mini lathe | eBay (http://www.ebay.co.uk/itm/DC-motor-controller-control-board-KBIC-suitable-for-mini-lathe-/281165478667?pt=LH_DefaultDomain_3&hash=item4176c4bb0b)


24 VOLT MOTOR GEARBOX,BRAKE, 9 INCH WHEEL | eBay (http://www.ebay.co.uk/itm/24-VOLT-MOTOR-GEARBOX-BRAKE-9-INCH-WHEEL-/350871536508?pt=UK_BOI_Electrical_Components_Suppl ies_ET&hash=item51b192c37c)

birchy
11-09-2013, 07:41 PM
I've still got the 600W DC motor and associated electrics from my Warco WM 16 if you're interested?

manofgresley
12-09-2013, 11:31 AM
Thanks Birchy.

Yes, i am interested

Ray

Clive S
12-09-2013, 11:35 AM
Just a note perhaps better to remove the email because of spammers and do it via PM instead ..Clive

manofgresley
12-09-2013, 11:54 AM
Hi again

Thanks for tip on spamming. How do i send a PM ?

Ray

Clive S
12-09-2013, 02:05 PM
If you look at the top of the page you will see a link for (My Profile) if you click on that you will find the link to send private message. ..Clive

birchy
12-09-2013, 07:42 PM
manofgresley: I'll take some photos later and PM you.

birchy
13-09-2013, 01:21 AM
Here's a couple of pictures and a video of the motor running. Note that when increasing the speed, the motor "kicks" in about 2 or 3 spots through the speed range. It doesn't do it when reducing the speed. Not really sure why it does that but it's always been the same from brand new. I'm guessing it's a characteristic of the Chinese copies of the KB boards? It's never caused a problem as the motor runs smoothly if the pot is turned slightly past the "kick" point. Can anyone advise on this?


10091100921009310094


http://youtu.be/KJUev16HcRE

Clive S
13-09-2013, 09:00 AM
Note that when increasing the speed, the motor "kicks" in about 2 or 3 spots through the speed range. It doesn't do it when reducing the speed. Not really sure why it does that but it's always been the same from brand new. I'm guessing it's a characteristic of the Chinese copies of the KB boards? It's never caused a problem as the motor runs smoothly if the pot is turned slightly past the "kick" point. Can anyone advise on this?


Perhaps a faulty pot or dirt on the slider on the pot. ..Clive

birchy
13-09-2013, 06:07 PM
Perhaps a faulty pot or dirt on the slider on the pot. ..Clive
The machine has always done that since new...I just assumed it was a "feature" of the Chinese electrics rather than a fault?