[adt2]

I half-expect to get crucified for asking this question, but such is life. I just completed the construction of my first CNC machine, a 4x8 unit of my own design (but based heavily on designs from FineLine and CNCRP). I have one or two minor, niggling issues to work out (like a mysterious rattling on the Z-axis when moving down - but not up) but otherwise the machine is ready to rock and roll. I think.

So I went out yesterday morning to fire it up and do a test cut, and....the computer was fried. After a bit of troubleshooting, turns out the power supply was cooked. Long story short, I now have a new machine and am ready to go. I think.

My question is this: Is there a step-by-step "how to configure and/or fine-tune Mach" guide out there somewhere? I have the basics in place, I think - the computer recognizes the machine and the jog controls move the various axes in one direction or another (although I'd love to know how to reassign the arrow keys; based on the orientation of my machine to my keyboard, the left/right keys make the machine go forward/back and the up/down keys make it go left/right, which is confusing as hell).

I have a couple of small test projects to cut; created them with Vectric and exported code based on Mach controller. It just seems like there's probably a fair bit of tuning that ought to be done, based solely on the number of Mach menus I've looked at but can't decipher.

[ger21]

Config > Hotkeys to change the jog keys. But be aware that you can't change the Mach3 screen orientation, so the keys will match the machine, but not the screen.

Probably 90% of the stuff in mach3, you'll never use.

Once it works, you need to setup the motor tuning (velocity and accel and steps/unit), then set up any switches you might be using, and that's about it to get started.

Best thing is probably to just ask a lot of questions if you need help.

[adt2]

Thanks, Gerry.

My first (specific) question is: How do I tell Mach what the size/shape/orientation of my table is? In other words, my X-axis is 96 long, Y-axis is 36 wide, and Z-axis has 6" of travel. I'd like "home" or "origin" or whatever to be at a specific corner of the machine. As I stand at one end of the machine, looking down the X-axis, I'd like the "origin" point to be on my right at the end closest to me, so travel away from me on X would be positive, and travel to my left on Y would also be positive. Negative X- and Y- values would not be possible, as the origin is also the machine's limit.

In CAD terms, I need to define the extents of the drawing area - lower left and top right corners. How do I do that?

[keebler303]

You will need to install limit switches at those positions. Then you can tell mach to "home" the machine and it will go until it hits those switches, thus knowing where it is on the table and setting that point to 0,0 or any other position you tell it to set to. These settings are under "homing". You should also have switches at the opposite ends of travel but you can get by with "soft limits" which will tell mach not to go past a certain coordinate position in either axis.

Without switches, you will have to just eyeball it every time. So you probably want switches.

Matt

[adt2]

I actually already have limit switches at those locations; I'm just not sure what to do in Mach to tell the software that they're there, and where "there" is.

[ger21]

Set them up as home switches in ports and pins, and when you click the ref all button, the machine will move towards them. In order for Mach3 to find them, you need to tell it what direction they're located in.

Go to Config > Homing/Limits. If the home switches are at your X and Y zero positions, you'll want to check "Home Negative" so that the axis travels in the negative direction towards the switches. The Z home switch is usually at the top of travel, and is homed in a positive direction.

Once you get it to home, then you can set up softlimits.

Now, to make parts, Mach3 doesn't need to know what size your machine is. You just need to zero the coordinates to match where the origin is in the g-code file.

[adt2]

You just need to zero the coordinates to match where the origin is in the g-code file.

So as long as my origin in the artwork is, say, at the bottom-left of the drawing, and my "home" position is the bottom left of the machine, I should be good to go, right?

[ger21]

This may create confusion, but I have to say it.

"Home" can actually be anywhere.
There are (at least) two sets of coordinates that you'll use on your machine.
Machine coordinates (Absolute) and Work Coordinates (offsets).

When you "home" the machine, you define where the machine coordinates origin (0,0) is, which in most cases, is the bottom left. On my machine, "home" is the bottom right, but machine 0,0 is the bottom left. Machine coordinates never change.

The Work coordinates origin can be anywhere on the machine, Typically, you mount your part anywhere on the machine, and set the Work origin to match the part origin.

I typically don't use different coordinate systems, so my work coordinates match my machine coordinates. I use fences to locate my part, so I never have to zero my X and Y axis. Just home the machine, load the part, and go.

[adt2]

I am envisioning the spindle starting at the same corner of the machine for each job, and returning there after each job. IOW, the origin of my parts will always be in roughly the same area so the spindle doesn't have far to travel before it starts cutting (assuming it returned to that corner of the machine after its last use).

I was thinking of routing a trough along the X and Y limits to insert a short fence into which would allow a positive registration point for the material before cutting.

[ger21]

One thing to consider is that the spindle starts at the origin, it will most likely be in the way when you're loading and unloading parts. That's why I home mine to the other end.
In addition, my screenset has a "Park" position that lets me easily send the machine anywhere I want on the table. I include an M code at the end of all my g-code, to send it to the park position. If I'm running a lot of smaller parts, I can change the park position so the machine doesn't need to move as far.