Milling machine CNC conversion

Hi everybody
I'm new in this forum and I've been reading the posts for some weeks already. I would like to know if the following machines are suitable for a CNC conversion if not then why not? Reading other posts I managed to tick some specifications for the conversion however I'm still not 100% sure.
The first one is the Amadeal AMAT45FG ,1.5KW , is this suitable? I would like to convert the 3 axis, and if my budget allows then 4 axis. What I'm mainly not sure about is choosing the right servos for it, ( I think the servo for Z axis has to be much stronger?). I read in a post that would be better to replace the USB connection for Ethernet, if so would someone recommend me a good breakout board? Also I'm not sure how to choose the right ballscrews and if I need to fit gibs into the table.
My second option would be the Warco GH18.


Thanks for reading my post, and great forum you guys have here.

I can't comment on your choice of machine - my experience was only converting a Sieg. My one comment on that experience is to research the spindle controller electronics to work out how easy that will be to adapt.

If you're buying a machine to convert to CNC - plenty of reasons why to do this but the question needs to be asked why you don't buy a CNC milling machine from the outset? No criticism, but just that this is the perfect time for you to consider that.

Breakout?, you won't go far wrong with the AXBB if you're happy using UCCNC.

Servos?, cheaper to use Steppers, but with less performance. Just curious?

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Originally Posted by Doddy

I can't comment on your choice of machine - my experience was only converting a Sieg. My one comment on that experience is to research the spindle controller electronics to work out how easy that will be to adapt.

If you're buying a machine to convert to CNC - plenty of reasons why to do this but the question needs to be asked why you don't buy a CNC milling machine from the outset? No criticism, but just that this is the perfect time for you to consider that.

Breakout?, you won't go far wrong with the AXBB if you're happy using UCCNC.

Servos?, cheaper to use Steppers, but with less performance. Just curious?

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Yes, you are right on servos, I found some steppers that will handle the work, I'm planning to use Mach3, the reason is that someone I know can help me with it. I'm still not sure how to select the right ballscrews. I found someone on social media ( from East Europe I think ) who converted the AMAT45FG but the site doesn't provide much detail and they used belts to connect the steppers with the ballscrews, not sure if that would cause backlash.
https://gramho.com/profile/cncpaw/7666184830

Belts are designed exactly for this purpose - I run a 2:1 reduction for increased turning force (I was going to say torque), on the screws. It can help to reduce the working footprint (allowing the motor to be mounted inside the existing footprint). Don't worry about belts.

Personally - standard 1605 ballscrews for me - but I'm a cheapskate (and space was a bit tight under the bed).

Sorry - should have said that AXBB is also good for Mach3/4.

Thanks again Doddy for your reply, now I have a better idea , I'm feeling confident to carry on with the upgrade.

From my point of view, if you are using steppers, they should be direct drive. If you are using servos, you may or may not include a reduction ratio. When I look at typical torque / speed curve for steppers, doubling the motor speed by introducing a 2:1 reduction ratio reduces the motor torque at a given speed by the best part of 50%, so you don't end up much better off. In the meantime, you've lost half your speed.

With a servo drive, you typically have 3000rpm or so max speed with full torque available. With a direct drive and 5mm pitch, that would be an unusable rapid speed, even for bragging purposes down the pub (15000mm/min). So for a servo, a reduction (somewhere between 2 and 3) seems to make sense. A stepper couldn't pull the skin off a rice pudding at anything near those speeds.

As for stall force, unless you plan to use your machine as a press, that doesn't seem to be an issue. How much radial force can a tool take before it breaks?

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Originally Posted by adanlicea

Thanks again Doddy for your reply, now I have a better idea , I'm feeling confident to carry on with the upgrade.

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Plenty of options and ideas out there - start a build log and the critique will follow.

I realise my explanation about about positioning steppers may be a bit half-hearted (it's been one of those days). Image below hopefully explains - a major drive for me is space so rolling the stepper back into the machine footprint was a big boon. Shown are X and Y axis motors.

Attachment 28819

(Ignore the mess... thing to reorganise the shed and things are a bit...)

It's all your choice of course. Build Log!