Bought a cnc machine, need a lot of help

[Paul53]

25473


Well, I have jumped in at the deep end, I picked up a home built machine this morning, the spindle is a Water cooled 1.5KW er11 and matching inverta vfd, I need to get a stepper motor kit, the guy used stepper 23, I will also need to rig up a pc, I have a few questions, does the port have to be parallel or can use usb? which is best? I am assuming I can mount the drivers etc inside an old pc and use the pc's power to run everything? I have no experience at all when it comes to building a cnc, so I am going to need all the help I can get, I know it is going to take a bit of time, but I am willing to learn. So any advice would be very much appreciated. Thank you. Paul

[Doddy]

Ah, I saw that on eBay when yo first posted, there's a couple of warning signs that you might want to address, see bottom.

Some very quick replies to the more basic questions:

"Stepper 23", I think you mean NEMA23 Stepper motors. I'm curious as to why the seller removed these from the machine.

Port can be parallel, can be USB. You'll need a Break-Out Board (BOB) that matches this. You ask which is best, there's many views, mine is that the UC300ETH is a good interface to the PC, using ethernet which would improve the comms robustness (vs. USB) and the PC processor loading (vs parallel), but adds £100 to the budget. You'd still need a parallel BOB (£5-10) as well.

The use of an old PC and the PC PSU?, a standard PC PSU offers +5/+12 supplies (maybe a dollop of low-power -ve supplies as well) - these would be of limited use - perhaps for the BOB logic supplies, but you're looking at somewhere between 24V-100V for the stepper drivers (depending on model used) - you could get a separate switched-mode PSU and mount this inside the PSU case, or make your own linear supply but this is moving further away from a standard "as-is" mechanical fit to a PC case. It's a cheap option, especially if you have a case lying around but go into this with eyes open.

About that machine - it looks like an awful lot of this is 3d-printed, including the spindle mount. This will likely compromise the rigidity of the machine - you should be mindful of this and understand if this is impacting your work - you can start to replace piecemeal.

I'd also start thinking about replacing the cabling with shielded CY cable to avoid problems with electrical noise from either steppers or spindle.

Hmmm, what is the drive system on the axis?, from that image it looks like this could be simple threaded bar - if so you might encounter problems with backlash and general accuracy, you could start to look to replace with trapezoidal screws (cheap) or ball-screws (not so cheap). But I'd get the basic machine up and running first.

[Paul53]

Ah, I saw that on eBay when yo first posted, there's a couple of warning signs that you might want to address, see bottom.

Some very quick replies to the more basic questions:

"Stepper 23", I think you mean NEMA23 Stepper motors. I'm curious as to why the seller removed these from the machine.

Port can be parallel, can be USB. You'll need a Break-Out Board (BOB) that matches this. You ask which is best, there's many views, mine is that the UC300ETH is a good interface to the PC, using ethernet which would improve the comms robustness (vs. USB) and the PC processor loading (vs parallel), but adds £100 to the budget. You'd still need a parallel BOB (£5-10) as well.

The use of an old PC and the PC PSU?, a standard PC PSU offers +5/+12 supplies (maybe a dollop of low-power -ve supplies as well) - these would be of limited use - perhaps for the BOB logic supplies, but you're looking at somewhere between 24V-100V for the stepper drivers (depending on model used) - you could get a separate switched-mode PSU and mount this inside the PSU case, or make your own linear supply but this is moving further away from a standard "as-is" mechanical fit to a PC case. It's a cheap option, especially if you have a case lying around but go into this with eyes open.

About that machine - it looks like an awful lot of this is 3d-printed, including the spindle mount. This will likely compromise the rigidity of the machine - you should be mindful of this and understand if this is impacting your work - you can start to replace piecemeal.

I'd also start thinking about replacing the cabling with shielded CY cable to avoid problems with electrical noise from either steppers or spindle.

Hmmm, what is the drive system on the axis?, from that image it looks like this could be simple threaded bar - if so you might encounter problems with backlash and general accuracy, you could start to look to replace with trapezoidal screws (cheap) or ball-screws (not so cheap). But I'd get the basic machine up and running first.

Thank you for your reply, yes I mean NEMA23 Stepper motors, he is building a smaller machine and needs them for that one, he has just moved into a flat and doesn't have the room for this one.

I do have a couple of old pc's, one will be used to run the software, I think it might be better to buy/build a dedicated control box

The spindle mount is made of wood, as are the side supports etc, yes it is threaded bar on the axis.

Thank you for the advice on things to look at and change, I am going to try to get this up and running (changing the cabling as you advised) and then start upgrading to make the machine more robust

[paulus.v]

Hi Paul!



does the port have to be parallel or can use usb? which is best?

Given the CNC you are starting with and having old PCs laying around, I think you will be better and cheaper to start with a decent breakout board using the parallel port. The cheap USB controllers are not that reliable and a good USB or Ethernet controller will probably cost more than the CNC you bought.



I am assuming I can mount the drivers etc inside an old pc and use the pc's power to run everything?

If you do not want to spend money for a proper control box you could fit them in a PC tower case, I have done it myself.
As Doddy already said, depending on the drivers specs, you will need at least 40-50 V power supply for the NEMA23 steppers. To power the BoB, sensors, relays, etc. the PC PSU is fine.

Paul.

[Paul53]

The next question is all about the steeper motors, do I buy a kit, or buy it all seperateIy, I know the previous owner had Nema 23 steppers, there are alot of Chinese kits on eBay, which is the best way forward with this? Thanks

[Clive S]

The next question is all about the steeper motors, do I buy a kit, or buy it all seperateIy, I know the previous owner had Nema 23 steppers, there are alot of Chinese kits on eBay, which is the best way forward with this? Thanks

Kits are never matched. motors you need low inductance 8 wire https://www.cnc4you.co.uk/Stepper-Motor/Nema23-3.1Nm/Stepper-Motor-3.1Nm-60BYGH301B-Nema23

if you want to future proof the machine or build another then use 80V drives and 68V toroidal power supply

[Paul53]

Thank you so far for the help and advice, my head is still spinning with all the info that is out there, I have been on the cnc4you website, as suggested Clive s to look at the NEMA23 stepper motors, they also do a kit https://www.cnc4you.co.uk/CNC-Kits/Stepper-Motor-Kits/Stepper-Motor-Kit-3.1Nm-x-3-Axis-Nema23, is it ok to get get the kit here, or just stay away from a kit as mentioned in a previous comment, and buy all separately? I am afraid there are going to be a load of questions and advice in the coming days and weeks, so I will apologise in advance:tennis:. Thank you

[driftspin]

Thank you so far for the help and advice, my head is still spinning with all the info that is out there, I have been on the cnc4you website, as suggested Clive s to look at the NEMA23 stepper motors, they also do a kit https://www.cnc4you.co.uk/CNC-Kits/Stepper-Motor-Kits/Stepper-Motor-Kit-3.1Nm-x-3-Axis-Nema23, is it ok to get get the kit here, or just stay away from a kit as mentioned in a previous comment, and buy all separately? I am afraid there are going to be a load of questions and advice in the coming days and weeks, so I will apologise in advance:tennis:. Thank youHi Paul53,


Do you feel you could build a toroidal transformer based power supply your self?

People here like the ~68volt DIY PSU icw 80v digital drives.

I build one too and do not regret it.

A simple DIY PSU consists of a transformer, rectifier and capacitors.

I bought my nema23's from cnc4you also.


Grtz Bert.







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[routercnc]

You could buy that kit and it would technically run your machine.

It does have low inductance motors (3.2mH) when wired in parallel, which is what they are recommending in the wiring diagram so assume their PSU can supply the higher amps required.

However, it is only running at 36V which is quite limiting for useable speed range until you run out of torque and start missing steps.

A 50V system would be better, or as most guys end up go for the 70V system. It’s one of those buy a quick system now and loose money in the long run when you find the limits or go with the final solution to start with.

[Paul53]

You could buy that kit and it would technically run your machine.

It does have low inductance motors (3.2mH) when wired in parallel, which is what they are recommending in the wiring diagram so assume their PSU can supply the higher amps required.

However, it is only running at 36V which is quite limiting for useable speed range until you run out of torque and start missing steps.

A 50V system would be better, or as most guys end up go for the 70V system. It’s one of those buy a quick system now and loose money in the long run when you find the limits or go with the final solution to start with.

So, decided to go with 8 wire NEMA23 stepper motors and go for a 70v system, need pointers on where to get the kit, steppers, drivers, BOB etc, well everything really, quite a few items on aliexpress. could you point me in the right direction please. Thanks