how to set up a 5 Axis cutting machine---stepconfig setup and G-code generation

hello, I'm working on a cutting machine with 5 axis: X Y Z A and a Y₂ axes coupled with Y axis.
Y axes is parallel to Y₂ axes, and their speed needs to be the same.
Y axes has axis scale 100 steps/mm and Y₂ axes has axis scale 224 steps/mm,
how do I set up the stepper configuration for this machine?

From the stepconfig wizard I can only set up a 4 axis machine;
if I modify the .hal and . ini files to make a five axis set-up,
how do I make sure Y and Y₂ axes move in harmony.

My g-code is generated using inkscape, which is a set of 4 axis G-code (X Y Z A);
the version of Linuxcnc I'm using is 2.7.6;
the controller-bard is a Al-zard 6 axis LPT-CNC-H parallel board.

The attachment is the 4 axis step-config file I used previously, before adding the Ysub]2[/sub] axes.

If this is a new project I think you will find your life easier if you upgrade to master as it supports joint Axes and separates joints from the axes so you should be able to hand code all 6 axes.

thanks for your reply rodw, I'm not sure what "master" you are referring to, I know the newest linuxcnc version is 2.7.8, my current version is 2.7.6. could you explain a bit more? - btw, it's not entirely a new project

Master is version 2.8, the current development version so it could be buggy but I've found it solid while I've been using it.
See buildbot.linuxcnc.org/

I see, 2.8; i will try, but I still don't know how it works after I set up the 5 independent axis; the G-code is 4 axis G-code,
how do I control 5 axis by the 4 axis G-code?

Because both of your y axis are commanded by the same code. It is better to think of both of them as one axis, for normal operations. The only time they need to be controlled (semi)-independently, is during the homing/gantry squaring routine. That part is handled by the control in Master (2.8-pre) once you've configured it correctly.

say, I set pin 16 the pulse output for Y axes, and pin 18 for Y2 axes (for Y2 homing). For normal operations,I think the controller board will only produce pulses at pin 16. if I connect both Y2 and Y to pin 16, when G-code command Y axes to move forward 100mm, Y2 will move 100/224 mm due to different axes scale, and that is the problem.

I would highly encourage you to switch to the development branch of Linuxcnc "Master" for this setup. Not that it isn't possible to set up something that would work in the current release of 2.7, but because it would be a little more complicated and be a bit of a kludge.

Even in Master, setting up a gantry config is complicated, and full of many options and paths to sort out what you need and want.
I am not sure what example configurations are currently included with the Master distro, but i'd be very surprised if there isn't at least one for a gantry. You should be able to more or less follow the example with the exception of where you need to scale your two Y axis differently.

In a parallel port only pins 1-17 are usable for io (pins 18-25 are just grounds). If you need more io you can use up to 3 parallel ports (by adding a parallel port card) or you will need to look at other interface hardware, such as something from Mesa or Pico Systems.

giantstone wrote:

. if I connect both Y2 and Y to pin 16, when G-code command Y axes to move forward 100mm, Y2 will move 100/224 mm due to different axes scale, and that is the problem.

In master we talk of joints, and joints can be combined together to make one axis.

So in master you would say set joint 0 = X and Joints 1 & 2 to be Y1 and Y2 (which are commanded as one Y axis). Each joint has separate scaling settings in the ini file so having different scales each side of the gantry will be trivial. When your gantry homes in master, after 1 homing sensor is hit, the other side continues until it hits its home sensor. You set the home offsets so that the gantry is perfectly square and the homing sequence sorts it all out perfectly.

I see, this joint concept solves my problem, it's cool.
I'm switching to Master, thanks very much for your instructions.