Beginners Controller Question

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12 Mar 2019 08:04 #128416 by MatthewMachinist
Hello,

This is my first post here, I am a Machinist currently working in Cad/Cam, my background is mostly manual machines but I did have a 3 year stint on cnc mills in a jobbing shop, we programmed the cnc's 100% of the time in G code on the pendant.

I am looking at my first CNC build, I currently have a RF45 mill which is an option for conversion but I am looking at other options. I am working on a Bill of Materials and most components have been selected.

However I am really confused about the controller, my planned setup will be...
Old computer with parallel port, Ubuntu and Linux CNC
Parallel Port cable
CNC Controller?
Anything else needed?
Nema 34 - 900 oz in 6.1 amp stepper motors

So I should mention that my weakness is electronics, so I am really not sure what is needed/ suitable to drive the stepper motors. I would like an all in one 4 axis unit, I have seen some cheap ones with a 3 amp limit which I am pretty sure are too small for the Nema 34 steppers. I have had a good look through the list provided in the link below, but I am just not sure what the best option is in 2019. Can someone point me in a good direction?

wiki.linuxcnc.org/cgi-bin/wiki.pl?LinuxCNC_Supported_Hardware

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12 Mar 2019 14:40 #128438 by bevins
LinuxCNC is the controller.

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12 Mar 2019 14:56 #128441 by andypugh
You could look at the Geckodrive G540, though that too is only 3.5A.

You might want to consider the closed-loop stepper drives available from Leadshine.
That would be an individual drive for each axis, but that might not be a bad thing, it allows axis-level repair rather than looking for a whole new G540. These have performance rather closer to a servo than a stepper.
www.amazon.com/Leadshine-Stepper-86HBM80...-D1008/dp/B06ZY1KWLY

The 4-axis cards tend to use TB6560 or TB6600 chips, and those won't drive 6A steppers. So you are likely to be looking at individual drives anyway.

The parallel port will work, but is limited on step rate and IO pins (you will need to share limit swith inputs, for example, and won't be able to use a high-count spindle encoder). There is no harm in starting with a p-port then upgrading to something more capable (Pico. Mesa, General Mechatronics etc) later.

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13 Mar 2019 05:50 #128487 by MatthewMachinist
Ok thanks for all the info Andypugh, I needed a nudge in the right direction and I think that did it.

I like the look of the closed loop steppers that you provided the link for. I think they are ideal, I have done some research and found that they run cooler and have more torque so that sounds really good to me.

I did have a bunch of follow up questions but I have done a bit of research and found some answers myself...
forum.linuxcnc.org/30-cnc-machines/33344...re-do-i-need-exactly


So as near as I can tell I need...
3 closed loop steppers each with individual drive
Breakout board such as this one... buildyourcnc.com/Item/electronicsAndMoto...allel-breakout-relay
Power supply
Enclosure
Parallel Port cable or better system to go from breakout board to computer
Computer with Ubuntu, Linux CNC and parallel port or better.

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13 Mar 2019 12:06 #128505 by andypugh

MatthewMachinist wrote: Computer with Ubuntu, Linux CNC and parallel port or better.


The LinuxCNC LiveCD will install a suitable version of Linux, you don't need to install the OS first.
(if the machine currently boots in to Windows then I think that the installer will allow for dual-boot configuration).

You have a choice of two installers:

This one is based on a reasonably up to date version of Debian Stretch and uses the preempt-rt kernel. This might not have good enough latency for parallel port step generation on some hardware (though I have one PC where is gives better latency than I have ever seen with RTAI). It is compatible with the Mesa ethernet-connecte cards and I would suggest trying it first.
www.linuxcnc.org/testing-stretch-rtpreempt/
Choose the latest (Oct 18) image that suits your hardware (32 bit or 64 bit is the choice, ignore the Intel / AMD part, it isn't a split based on chipset manufacturer)


This LiveCD image will install Debian Wheezy and an RTAI kernel. It will often have better software step generation potential than the preempt-rt version but is an older version of Linux that might not install succesfully on the most modern motherboards.
Debian Wheezy went out of long-term-support last year.
www.linuxcnc.org/linuxcnc-2.7-wheezy.iso

More details on how to create a bootable image from the .iso files here:
linuxcnc.org/docs/2.7/html/getting-start...etting-linuxcnc.html

If you prefer to run Ubuntu or Mint then that is possible (instructions on the page above, and on this forum) but it is a little more effort especially if you are new to Linux.

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