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Hi all, I recently designed an open-source CNC router. My goal was to make a rigid, medium-format CNC router that can self-manufacture new machines and not require any specialized equipment for squaring the build.

All the design files, LinuxCNC configuration files, and build info are on my blog:  blog.nathantsoi.com/article/rigid-router-cnc


 

The design is based on 4590 aluminum extrusion and CNC machined parts that self-index on the frame, so no extra alignment tools are necessary:

 

I used closed-loop servo motors, but steppers should also work fine.

 

Here is the back of the X-Axis:

 

I also decided to use an old computer with an onboard parallel port, to save on cost. I built all the electronics into an old mac pro case, which looks pretty rad.

 

I also added a cheap PCIe parallel port and used it as an input-mode device for an MPG jog pendant that I also designed:

 

Finally, I added a button panel with physical buttons matching the GMocappy soft buttons and some potentiometers to control feed rates, which is really handy when I need to quickly change the feed rate or stop the running program.

 

I hope this is useful for folks who are interested in building their own machine from scratch.

Note that  7I97T and 7I97 hal files are interchangeable
with the exception that the 7I97T analog out resolution
is best with the PWM frequency set to 75 KHz and dither
enabled.

The zipped example files comprise a complete configuration
but of course there are many machine specific setup things
that need to be added/changed to match your specific machine.

 

I can download the file now, great.

I am completely new to LCNC and have never done a conversion so everything is a mystery to me. I haven't found an example of a retrofit with a 7i97t as it is a relatively new card.

I'm quite certain that I've omitted some crucial steps in setting my mesacards and the pc up. Perhaps I was a little too optimistic about the kind of configuration work i need to do.

Could you roughly break down everything I need to do from opening the box of mesa cards to having a completed hal file?

The zip file contains a basic 7I97 configuration file set (hal and ini files)

 

The 7I97T PWMgens need to be set in offset mode
(as shown in the example hal file)

It seems like you guys need to build a folder watcher,
The operating system has methods to do something if the contents of a folder changes. 
Python has an interface to this. There are a number of examples on the web. Here is one to get you going
thepythoncorner.com/posts/2019-01-13-how...-filesystem-changes/

The script just adds the Ethercat repositories/
Just folllw the steps in post 1 to install Ethercat.

Thanks for the reply, unfortunately it raises more questions than it answers. I won't get back to the machine before the morning but i will first try the command you suggested and post the result.

I can't seem to download your file, and even if I could I don't know what to do with it.

On which of hte cards do I need to set the pwmgen to offset mode and how would I do that?

 

You would need the stepspace defined as well
(I think the default times are quite long which may
prevent getting all the way to 25 KHz)

The direction timings don't matter

You can use maxaccel if you wish to change the spindle
accel and deccel times. Setting the stepgen Maxvel to 25000
will prevent it from ever generating more than a 25 KHz
frequency even if given a bogus spindle speed command.
 

try

mesaflash --addr 10.10.10.10 --device=ETHER --sserial

Note that you need to set the pwmgen to offset mode,
and for the 7I97T, use a 75 KHz PWM frequency with
dither enabled.

Here is an example config file that has the PWM setup

freeby.mesanet.com/basic7i97.zip
 

Yes, the servos have relative encoders. The previous owner of this unit had always planned to upgrade the control so that the encoders would be useful. It makes sense to me as well.

Since the 7I76e variants are not in stock right now, and my other machine that I will eventually build is a stepper motor machine, would it make more sense for me to buy one of the analog boards that are in stock right now? I suspect that some more snooping around the Mesa store might be in order...

Pardon my ignorance... Based on your comment I presume that the servo tuning is stored in the servo drives?

I have had the understanding that I DO want the LinuxCNC feedback loop in order to make a [more] closed loop system which is more better than having the control completely blind to the position (or loss of position) of the motors.

Hello,

my Mesa cards for the LCNC retrofit just arrived. I'm using 7i97t as the main card which is connected to the pc with ethernet. After some trouble updating Mesaflash i got that connected to the PC fine and the pins already work (in Hal show with an MPG encoder).

For the hal file I wanted to get a starting point by follwoing the Pncconf wizard and then editing the file as needed. The pncconf however has no infos on the 7i97t and I need to use the discovery function. THis also works and the card is detected. All seems well and I can even configure the Pins on my 7i84d which is connected through sserial to the 7i97t with a chopped ethernet cable connected as per 7i97t's instructions. When I start LinuxCNC with this config however, I get an error that a pin on the 7i84 is missing. If I don't configure the pins on 7i84d in Pncconf LCNC will launch but halshow won't let me see the I/Os on the 7i84d, only 7i97t.

when I type "
mesaflash --addr 10.10.10.10 --device=ETHER --readhmid
into the terminal i also cant see the pins on 7i84d. both cards have power and the status LEDs are indicating ok. 

Do I need a different firmware on the 7i97t?
Any help is greatly appreciated.

net remote-rapid-to-home halui.mdi-command-00 <= pyvcp.rapid-to-home

in the main hal file, I have 

[HALUI]
# add halui MDI commands here (max 64) 
MDI_COMMAND = G0 X0 Y0 Z0
MDI_COMMAND = G0 X20 Y0 Z0


if I change halui.mdi-command-00 to halui.mdi-command-01
my custom button will execute the saecond line.

What if I have more g code lines and I want to execute all of them?

Good day

Philip

Do the servo drives have encoder outputs? Al Yaskawa i have worked with do have them, so since you have 7i76E just add a 7i85 or 7i85S for encoder feedback and you get the best of both worlds, easy tuning and position control even when drives are disabled.

Thanks Aciera, that looks like it works. I'm unable to commit to a full run right now, but I added your comment, raised z=0 so I was cutting on air, and the program ran and started cutting (then I stopped it).