Newbie General Questions

[Chems]

Hi all, I'm sure these questions have been asked before but the terms are so generic I can't get answers from the search, so sorry in advance for this.

I've been using a commerical CNC for the past few months and it has made me want to build my own. I've built a Z axis router lift which was controlled by arduino so I'm a little familure with the hardware.

My questions are these, what sort of CNC controller should I be looking at that can take command directly from USB that is suited to a DIY cnc?

How does the CNC machine get its depth right with the bit, the commmercial machine I've been using gets its bits automatically then slowly lowers them onto a touch plate and then works out how long the bit is, what does a smaller CNC machine do to work this out?

Thanks in advance!

[cutter100]

Hey Chems, welcome, I would say that most people use Mach3 for the controler. I have my desk top pc in the house , put the g-code on a flash drive and go out to my shop. Plug it in and open mach3 and load code. I'm kinda new but so far this is working fine.
the depth is coming from when you zero your z axis. After that it's whatever your g-code tells the z what to do. So far I haven't figured out how to hook up a z zero plate on my "hobby cnc board" so I get the bit close to the top of my material then turn off my motors , lower the z by hand to just touching the top, turn motors back on, and zero the dro. It's a pain since not all bits are the same.
Most say it's good to keep your table pc pretty empty of software other then to control your board, things like "updates and scanning" can mess up a running code.
Sorry, looking at your question again, go with the P/p cable not usb to hook pc to control board.

Hope that helps, each time I turn the thing on I learn something new...good luck

[awerby]

My questions are these, what sort of CNC controller should I be looking at that can take command directly from USB that is suited to a DIY cnc?

[The least expensive one I know of is the SmoothStepper, from Warp9. It plugs into Mach3, which otherwise requires a parallel port. ]

How does the CNC machine get its depth right with the bit, the commmercial machine I've been using gets its bits automatically then slowly lowers them onto a touch plate and then works out how long the bit is, what does a smaller CNC machine do to work this out?

Thanks in advance![/QUOTE]

[The most basic, old-fashioned way is to touch off the tool onto the top of the material. You get it close, then switch to step-mode jogging, and come down incrementally until you can pinch a piece of cigarette paper between the tool and the workpiece. You can call that .001" (if you're Imperial), or zero if it's not too critical. You can also add a touch-off plate to your system, which usually works by conduction, and has some spring-loading so you don't break your tool. Here's a link to one: ]

Campbell Designs - CNC with Bob Campbell

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[ger21]

My questions are these, what sort of CNC controller should I be looking at that can take command directly from USB that is suited to a DIY cnc?

Mach3 is the hands down favorite control software. But it normally only works with the parallel port. You can use a hardware USB motion controller with it, though, like a SmoothStepper or KFLOP

Two other options are USBCNC and Planet CNC

How does the CNC machine get its depth right with the bit, the commmercial machine I've been using gets its bits automatically then slowly lowers them onto a touch plate and then works out how long the bit is, what does a smaller CNC machine do to work this out?

Pretty much the same way, but without the $5000 automatic tool changer.

[Chems]

Thanks for all the replies, smooth stepper looks really good. Are there any tutorials out there showing it being physically connected to the drivers?