forum.cncdrive.com

As per my post in "general discussions", I am posting this here for a feature request:

"Offline mode" should not change the machine coordinates (it does not actually move the machine).

Below are two use cases, but in short: It is quite useful to put the machine in offline mode while aligning the gcode file with the actual material on the machine bed. But since offline mode changes the internal coordinate system during the process (even thought the machine didn't move), the
* soft limits are broken
* your z-probe could malfunction (because the default macro for that observes soft limits)
* maintaining concurrent coordinate system (G54 to G59) is difficult and error prone (so much so that I am thinking to remove the button from the screen so I am not tempted to use it

It would be nice to have a setting that the machine coordinates are not touched in offline mode.
As a possible workaround: Could UCCNC capture the machine coordinates when entering offline mode, and restore them when exiting offline mode ?
Thanks.


Use case 1: You are cutting a part from a much larger base material, and you try fitting the part optimally in this (maybe expensive) material to reduce waste. The (0,0) in you gcode is in the part's center, but you want to fit the part neatly into a corner of the expensive material.
* move spindle to a recognizable spot on the base material, eg where you want the top-tight corner of the part to be
* go offline
* move the virtual spindle, using the toolpath preview as a guide, to the top-right corner in the preview (this ruined you machine coordinates)
* go online and cut

Use case 2: Your parts require many toolpaths and requires more time changing tools than cutting. Therefore you want to cut two parts "simultaneously" but from separate sheets. Or you are cutting from the same sheet but want to avoid, for example, knots in the wood. At any rate, you can't "simply" create a gcode file two instances of the design. You want to locate each of the designs on the machine bed and switch between G54 and G55 coordinate systems.
If you use offline mode while setting up the machine for coordinate system G54, you actually changed the position of G55 on the machine bed. That could be a costly mistake.

I don't know exactly what "Offline Mode" does, as I've never used it.
But in the 25 years I've been using CNC's, I've never seen anyone work the way you are describing.
Virtually everyone else jogs the machine to where the origin should be on the part, and zero's the X and Y axis at that position.
It sounds like you are trying to do the same thing, but without moving the machine?

I believe that if offline mode worked as you suggest, then it would no longer be "offline". And it would defeat the purpose of the Offline Mode, whatever it's intended purppose may be.

Also, once you go into "Offline Mode", all machine coordinates should be considered "lost". The only way that an "Offline Mode" can maintain machine coordinates, is if all the axis have absolute encoders on them.

What is normally done is you set the point of origin on the first part in G54. Set the xy to zero Then move to the point of origin on the second part that will give you the offset of the second part. Then appy that offset to the G55.

Now you can start the part run from the first part in G54 then switch to g55 via the Gcode and run the second part.

Just a thought, (;-) TP

The suggested methods work (and offline mode can be avoided), if you can easily pinpoint the zero point in the stock. But, say I want to cut a square with the gcode setup such that (0,0) is in the square's center. If I want to cut this square out of the top-right corner of the material, I would have to
* know the square's dimensions,
* manually measure half that dimension from the top and right of my stock, mark it
* move the spindle to that mark, and
* zero it.

My approach eliminated the manual measurement.

You are going to say "program the gcode (0,0) to the top right corner and all is good". Yes, somewhat. But assume that you are programming the gcode in the office, then you go to the machine for setup. Assume you have an ABS sheet with a textured side and a clean side, ie you can't just flip the material over at will. Also, the machine has limited dimensions so you can't just rotate the stock around as you wish. Once you mount the stock you realize that the most efficient material use would be for the square to be cut from the top LEFT corner. So I would have to go back to the office and re-generate gcodewith a different origin .... ?! And tomorrow I want to cut the same thing again. I keep constantly changing my gcode ?
I don't know. If you can locate the gcode's (0,0) easily in your stock, then yes, you don't need offline mode.

I don't know that your offline method is any more accurate than jogging the machine and setting zero. How are you accurately setting your offset? Just eyeballing it on the display?

Maybe consider adding a laser crosshair pointer for locating your zero point. It's a very popular method for many people. Other people will use a corner finding probe device for setting the origin.

Mmm. I didn't think my "problem" was that unique. Practical example. See this file and my material stock, and my desired location for the cutout (marked green). Without knowing more, I can align gcode and machine, without calipers: Move machine to desired cutout top right corner, go offline, move cursor (simulated machine) to top right corner, go online, cut (I would usually verify by moving machine to the bottom left, just to make sure there is material there).
Without offline mode (at least my own) approach would be: look up how large the square really is, measure the material from top right corner, mark the zero (with a pen mark that I can remove later), move there, zero the machine. Doable, but it does mean looking up the dimensions of that square and manually measuring.

Let me know if there's a better way. But until then, I'd say the feature request is not all that misplaced, is it.



BTW, just another quirk of the offline mode: If attempt to probe the z-axis with a touch plate, you must first home the machine, so UCCNC is sure where the machine really is. But using the offline mode you can destroy that position knowledge. There is no (new) request to home if you attempt to probe again.

Sorry, I just don't understand why you need to use Offline mode.
In Vectric, set zero to bottom left corner.
In UCCNC, jog to bottom left corner location. Zero X and Y axis. Regen toolpath.
At this point, I don't see what's different to you using offline mode, and what benefit offline mode gives you.

Well, the advantage being, you can position the cut within the material regardless of the zero position in the gcode. If tomorrow I want to cut the same piece out of the material top-left aligned, and the day after top-right, or centered for a change... I never need to rebuild the gcode file.

Well, the advantage being, you can position the cut within the material regardless of the zero position in the gcode.

You can do that with my method. You are just jogging to a different spot before zeroing. And if you always use the same zero spot in your CAM software, you are always doing it the same way.
99.99% of people do it this way.

In the example images posted above, I cannot see how one can position the machine without additional knowledge about the feature/cut dimensions, and without getting a tape measure or calipers out.

My approach may be unusual (is it?) but it has proven handy for me. It only really became an issue once I started using G54-G59 coordinate systems concurrently, because jogging in offline mode will affect all coordinate systems.