Which board to buy?

Hi all,

This is my first post, so nice to meet you!

I'm converting an old Drummond Round Bed lathe (100 years old) to CNC. I'm adding a vertical slide for milling, and possibly a rotary 4th axis in the future.

I'm trying to research the right bits to buy, for the lowest budget possible.

I'm looking for possibly 4 axis plus spindle speed control. My spindle motor is 24Vdc. I can easily set up spindle speed feedback for PID control.

Not sure on which stepper motors to go for, or drive board. I'm planning on 2:1 or 3:1 toothed belt driving the axes, so as to put less torque load on the stepper motors, and possibly get away with smaller / cheaper motors and drives.

Intended use is metal turning and milling, aluminium and mild steel.

Any guidance is very much appreciated,
Thanks, Scott

If you do not want to use to much money you can use the parallel port, that is the less expensive but also more limited situation (for 4 axis I think that you are forced to use 2 parallel ports for some IO).
If you want a better solution, more expandable, there are several members (including me) that are using hardware from mesa. In this forum there are good support for both situations.

Hi emcPT,

Thanks for your reply...

As I'm still learning, I've just googled Mesa boards and found PCI cards. Do you use these to give you an extra parallel port?

What drive circuitry do you use between the parallel port and motors?

Is there sone information somewhere on different ways to build the system?

Cheers, Scott

Thanks, Scott

ScottBouch wrote:

Hi emcPT,

Thanks for your reply...

As I'm still learning

Me too. I am doing a retrofit in a lathe also, and I am in the start.

If you choose the mesa, then you will not have the need use the parallel port. The mesa hardware have a lot of solutions (you can plug several mesa cards on the base card) as I am also finding out. I bought the hardware from mesa, and until know I think it is good for what I am doing. I bought a 5i20 (base card) a 7i33TA and a 7i37TA and I think I made a correct choose, but please note that I am using servo drives.
I bought the 5i20 as it is probably the board that is more used = more information and more help if I need, around here (or was because I bought it 1 year ago).

If you have not already you might want to take a look at Chapter 2 of the user manual for some general information.

www.linuxcnc.org/docs/EMC2_User_Manual.pdf

Rick G

Hi Chaps,

Thanks for the feedback so far! My Drummond RB has a 4" swing and 12" between centres.

I'm only planning on using the original leadscrew, I have another cross slide from a bigger lathe, and vertical slide from some sort of instrument.

Budget is my biggest constraint, i was considering the cheap Chinese boards on ebay. Do they work with LinuxCNC via my PC's parallel port?

I may have to stick to just 3 axis to save cost.

I'd really like to dp spindle speed control too, but I could bodge this externaly.

Cheers, scott

This is the sort of cheap Chinese board I've been looking at on Ebay...

www.ebay.co.uk/itm/261169442869?ssPageNa...id=p3984.m1438.l2649

It is a kit including 3 motors, but these are only NEMA17's. I do plan to use a toothed belt on each motor with a 2:1 or 3:1 ratio, to help with tourque, as speed isn't of great concern. They may be too weak though..

Has anyone got experience of these boards with Linux emc2?

The board in the link also does PWM spindle speed control, and takes a PWM input back from the spindle, I assume it uses a PID loop, but not sure how you'd configure the PID settings.

The boards suggested here do seem like a really good way to do it, but the cost (as reasonable as it is) may be prohibitive to the project.

I know you get what you pay for, and I also hate to spend good money after bad, but I'm really limited on this...

Cheers, Scott