[Kiwi 007]

I have a Luxcut BF 54V (which is a rebadged Optimum BF46) which I am accumulating the necessary hardware to CNC this machine.

I am going to use DMM servos, a set of ballscrews by RSK which will bolt in place of the original screws.

Two of the things I am looking at are,

1/ Machining the ways and fitting linear rails, the CNC version of my mill has linear rails for the column.

2/ Changing out the existing spindle motor and fitting a AC Servo, as I wish to be able to tap and thread mill, and in the future possibly fit a auto tool changer.

The existing motor is a 2.2kw BLDC, the same as this one.
2200W REPM Brushless DC Motor (MBL-123IM-300HA) - China Bldc Motor, Brushless Motor

The machining I do ranges from Alloy to steel to stainless, and some of it is up around 40 RC.

I would like to be able to tap up to 1/2" UNC in steel so some low down torque is required, plus I'd like to be able to machine alloy at a reasonable speed. Does anyone have any suggestions as to what size and speed of Servo would be best to power the spindle??.......Kiwi

[Flexo!]

This page has some good values: EMUGE - Products | Tap Holders | Torque Reference Values for Tapping

32nm required, so about 10kw @ 3000rpm

I have a 1500w BLDC motor putting out 4.8nm (@6krpm) and it can tap 10mm Aluminium. It could probably tap M6 in steel which would match up to the above table.

Without some kind of reduction you'd need quite a large servo.

What can the machine do with the gear ratio on low? If you can trust your motor specs, in low gear your machine should do 73nm @ 600rpm, enough for 3/4" UNC...

[Kiwi 007]

Flexo thanks for the reply, a 10kw motor sitting on the head might be a bit of a push.
I was hoping to get away from the noisy gear drive (gets a bit annoying after a while) so perhaps a 1:2. 2:1 belt drive system.

Have seen a few AC Servos around 3kw or so on Ebay, no sizes listed so as to fitment??.......Kiwi

[MrBean_pm]

Heya Kiwi,
Have you made any further progress here? I have just started my project finally, so check out my thread too.

Cheers,
Beano

[digits]

I put a 1.8kW servo on my smaller BF30 clone with a belt drive (1:1 ratio IIRC) and it is great for mid size cutters, but really, I miss the back-gear for drilling steel etc. The way the big industrial machines get away with a single speed drive is to have a massive servo - 10kW sounds about right

As you've said, IMHO a multi-ratio belt drive is probably the right way to go. I would question though whether you really need to replace the stock motor. Most of the smaller machines and clones have brushed DC motors with IMO fairly iffy controller boards. Can't you use the stock drive motor and brushless driver board with a belt-drive system?

[embraced]

Not only do they have big servos, but their servos are the 'spindle servo' variety. Totally different torque curve - constant power after 1000RPM or so (more torque!).
They're something I would love to strap to a hobby machine if I were a neurotic billionaire.

Have a look at the PDF I've acquired to understand what I mean..Attachment 246124

[SCzEngrgGroup]

Not only do they have big servos, but their servos are the 'spindle servo' variety. Totally different torque curve - constant power after 1000RPM or so (more torque!).
They're something I would love to strap to a hobby machine if I were a neurotic billionaire.

Have a look at the PDF I've acquired to understand what I mean..Attachment 246124

Buy yourself a Novakon Pulsar - it has a 2kW servo spindle.

Regards,
Ray L.

[Kiwi 007]

Well I've been too busy to actually do anything apart from accumulate the parts required for the conversion, ball screws, Mitsubishi 750w servo's plus many of the other parts including the cabinet from a cnc version of this.


The machinery dealer I bought this from has just had a trip to the manufacturer and they have developed the cnc version of this, it now has linear ways for x, y & z, plus a tool changer, but still running steppers, I'm trying to find out the price of the basic machine minus the steppers, cabinet etc.

While looking around I came across these spindle cartridges, wonder how long before the price drops, 3.7kw would be ample I think using a BT40 taper. Spindle cartridge

[embraced]

Interesting, when you find out some information about the machine you describe, could you post it here?

[Kiwi 007]

The Mitsubishi servo motors I have (6 in total) are a mixture 3 x HF-MP73k and 3 x HF-KP73, the only difference I can see are the MP's are ultra low inertia and the KP's are just low inertia which of these would be best suited for the X,Y & Z axis?

[MrBean_pm]

Hey Kiwi,
Glad you're still active....I have also now started getting the parts for my BF46, see thread in this section.....

I have 3x DMM Tech 750 w servos and drives! cables! and also just got my Mesanet control card and 7I77 breakout board, as well as a neat little wallmount cabinet, 10A electronics psu, and a few other things....will post a few pics tonight.


What I need to know is if you can give me the details of the guys you got your ballscrews from, I remember you got them in NZ but dunno where....are they all 25mm? Would luv some specs.....otherwise if I can ask you for some basic measurements of them, I can order from HiWin.

I was also seriously considering converting mine to linear ways.......


Edit: All else being equal, the motors with the lowest inertia will almost always suit a CNC application better....

Cheers,
Beano

[Kiwi 007]

I got the ballscrews through Scott Machinery in Christchurch, all the ballnuts bolt to the existing mounts which will make mounting really easy.

If I manage to get the price of the bare cnc machine with linear ways and it's affordable I'll sell my ballscrews as the new machine will come with them, but then I've been chasing this machine for a couple of months now.

Cheers
Kiwi

[digits]

Very interesting to hear about the CNC version, but I'd guess the price will be truely eye watering if it's anything like their smaller machines that they've CNC'ed!

Are you going to do anything to offset the weight of the head in your CNC conversion - e.g. a counter-weight or gas-spring?