Newbie controller questions

I have been bitten with an interest to mess with a CNC mill. In the course of doing some reading I am looking at controllers and trying to determine what I might need that would serve me into the future. I have come up with some questions that I have not been able to find a definitive answer for and wondered if someone could point me in the right direction.

1) What constitutes an axis on a controller? Obviously X, Y and Z are axes but would any of the following?

• Speed Control
• Coolant Control
• Auto Zero
• Limit stops

2) Are most/all controllers using a parallel port? Is USB just not used? Is there a reason?

Any help would be greatly appreciated!

1) No. Spindle control is different from an axis, and the others are digital (on/off) signals.
2) Parallel is the standard that has been around for a LONG time, and the most widely used Hobby-level implementation. USB is starting to ramp up more and more. There are USB solutions (and Ethernet as well) that convert to a parallel cable breakout. Look up SmoothStepper from Warp9. There are some others as well. USB is the current/future tech, but Parallel is LONG established and more than up to the job for most users.

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Originally Posted by mcphill

1) No. Spindle control is different from an axis, and the others are digital (on/off) signals.

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So all I would really need would be a 3 axis controller. What are the other axes used for in a, say, 5 axis?

Also, as I am planning to go the breakout board route, am I limited in how many on/off switches that can be run?

I think you need to clarify what you mean by "controller".

When you talk about the parallel port, you'd be using control software that sends signals through the parallel port. These signals tend to go to a breakout board, and then to the stepper drives.

Some people call a combination breakout board/stepper drive a controller. I think this is what you are referring to?

It is my understanding that a breakout board handles the input and separates the signaling to the stepper drives. The stepper drives act as an (for lack of a better term) amplifier to run the steppers.

I was referring to the breakout board as the controller.

Hi Eremius, what kind of machine are you planning?

Mach3 (if that's what you intend to use) can send movement signals to the stepper drivers directly through the parallel port. However given the nature of this setup the computer operating system will interrupt the 'fluidity' of the signals. This isn't of great concern to most hobbyists, but it does affect performance and accuracy. In this scenario the computer is acting as the 'Controller'.

The better option is to have a dedicated 'Motion Controller' which receives commands from Mach3 on the computer via Ethernet cable. This way the computer ends up doing what it does best and delegates what it's bad at. The reason this is better is because Mach3 simply tells the Motion Controller to move X clockwise 100,000 pulses, and the Motion Controller then generates 100,000 pulses seamlessly. Whereas if mach3 was to generate 100,000 pulses it may only get to 10,000 then need to do some windows system processes and this causes a delay in the stream of pulses hampering performance.A Motion Controller is designed to do one thing, and one thing only, control motion.

If you're making an aluminium gantry router that mostly cuts MDF, then parallel port Mach3 Controller would probably suffice, but if you're making a mill and cutting metals I would go Motion Controller route like the Ethernet Smooth Stepper. If you're wanting AC Servos then things get a whole lot more complicated.

Hope this helps.

Fenza

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Originally Posted by Fenza CNC

Hi Eremius, what kind of machine are you planning?

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That probably would have been good information to provide...

I am planning on a metal cutting mill.

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Mach3 (if that's what you intend to use) can send movement signals to the stepper drivers directly through the parallel port. However given the nature of this setup the computer operating system will interrupt the 'fluidity' of the signals. This isn't of great concern to most hobbyists, but it does affect performance and accuracy. In this scenario the computer is acting as the 'Controller'.

The better option is to have a dedicated 'Motion Controller' which receives commands from Mach3 on the computer via Ethernet cable. This way the computer ends up doing what it does best and delegates what it's bad at. The reason this is better is because Mach3 simply tells the Motion Controller to move X clockwise 100,000 pulses, and the Motion Controller then generates 100,000 pulses seamlessly. Whereas if mach3 was to generate 100,000 pulses it may only get to 10,000 then need to do some windows system processes and this causes a delay in the stream of pulses hampering performance.A Motion Controller is designed to do one thing, and one thing only, control motion.

If you're making an aluminium gantry router that mostly cuts MDF, then parallel port Mach3 Controller would probably suffice, but if you're making a mill and cutting metals I would go Motion Controller route like the Ethernet Smooth Stepper. If you're wanting AC Servos then things get a whole lot more complicated.

Hope this helps.

Fenza

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Yes, this helps very much. I am not settled on whether to use linuxcnc or Mach3 but I am leaning toward the latter currently. It appears that most of the motion controllers I have found while looking use USB.

My knowledge of USB isn't great but I've heard USB suffers from interference problems, whereas Ethernet doesn't hence why Ethernet has been the world standard for so long, it just works.

USB may be more convenient but I hear Ethernet is just better.

Are you doing a retrofit on manual mill or making the whole thing? And what kind of metals?

I will likely being doing a retrofit on a manual mill, currently my target is an X2 but that could change if something irresistible comes across Craigslist.

Ethernet would be an even better choice as then I wouldn't need the PC to be in the vicinity of the mill itself.

Sounds good :) what kind of stuff are you going to be making? And for hobby or profit if you don't mind me asking?

You may want to keep the computer near the mill though for setting up stuff

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Originally Posted by Fenza CNC

Sounds good :) what kind of stuff are you going to be making? And for hobby or profit if you don't mind me asking?

You may want to keep the computer near the mill though for setting up stuff

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Strictly for hobby. I really don't have specific plans to build anything; I do like to challenge myself with learning new stuff once in a while and this seemed like a good skill set to learn.