I own a 7x12 metal lathe. recently i have been trying to tackle the project of converting it to cnc. Where i stand right now is having a stepperworld.com fet3/dynamic stepper kit, that basically came with everything. I do however would like the run threads on my machine and also constant surface speed. I did some research on what people use to control the spindle and i purchased a c3- index pulse board from cnc4pc.com Does anyone have this or have a clue to hooking this up? I am new to the whole mini cnc world so keep that in mind. I also would understand that this pulse card can probaly read the speed of the spindle but can it control to raise or lower the speed? Or even turn the spindle on or off? Any help would be great. Please keep in mind though i am new to all of this.
I would not call myself qualified in the field of CNC, but I hope I can be of some help. I must also add that I at the moment do not own a lathe. Maybe soon thouh... So take my advice with a pinch of salt.
I of course have no idea how advanced you are in electronics, but the C3 card is only used to give your control software an idea of where the spindle is at, as an index pulse, not to control the spindle. I would think that the C6 card (or similar) is used to "control" the spindle. http://www.cnc4pc.com/Store/osc/prod...products_id=58
If your spindle motor is AC 3 phase, and you already have a VFD(Variable Frequency Drive), you would then connect the computer to the C6 card, and the C6 card to the VFD. But as cnc4pc says: this it not something you should do if you are not comfortabe with electrical power and so on... You would probably have to change a lot on your lathe. But since you are CNC'ing it anyway, I guess it would be ok. If you own a VFD you probably know that it usually needs a 0-10V control voltage to run. This is what the C6 card provides, by changing the step/dir signal provided by the paralell port from the control software (at least that seems what the C6 card needs to work, but I could be wrong?!). If the VFD needs PWM to run you should probably look at the Digispeed XL2 card.
Also, if your lathe uses a DC motor, then you would have to solve it another way. I know that you can control some of the DC motors with a VFD, but I have never seen any with my own eyes so to say. I know that there are people here that knows all about it though. If you have read around the CNCZone, I'm sure you know. You could just change the DC motor to a AC 3 phase, as many others already have done here though. Or if you want to be really cool (in my eyes in any case) you could use a servo as a spindle. I'm actually thinking about doing that if I ever get a lathe. But this is in all probability a bit to expensive for most.
How to connect the C3 card it is probably best found on: http://www.cnc4pc.com/Store/osc/prod...roducts_id=129
look on the side for "wiring guide", there are two. I hope you have a multimeter, and know how to use it. If you don't, then do not try it. It seems like the C3 board needs a separate 5V supply though. I'm not sure if the FET3 board could supply it (It probably can, but without any ciruit diagram who would dare to say that it does). Another question for the StepperWorld maybe?! Or even better, if you already have a 5V supply in your controlbox.
I looked at Stepperworlds homepage, and there seems to be little information regarding your kit. It seems to be able to use limit switches if you would like, but it doesn't say how many and so on. You could probably use the C3 card with one of the inputs on your board, if you are not planning on using the ports as limits. But if I were you, I would contact StepperWorld, and ask them if it would work to do so. You would also need an output to be able to control the spindle with a C6 or similar board. If you will only use 2 steppers to control the lathe, you could use the other stepper outputs to control your spindle with the C6 card.
I'm not really recomending anything though. You should not do anything that you are not confortable with. Think it through, and be sure that it will work, before you do it. At least that's how I always try to do it.
When it comes to "constant surface speed", I have no qlue how to do that. Should be doable with the right control software settings, (if you already have a variable speed motor control and a spindle index pulse setup) but since there are lot's of other much more qualified people here, maybe someone else would like to chime in!? =)
You probably have to give a bit more info about your motor and what software you are planning or using, and so on though.
I hope I haven't missed anything, but since it's very late here, assume that I did. Maybe it would be of some help at least
In any case, good luck with your convertion.