Setting up soft limits in UCCNC .. "Logic"

[JAZZCNC]

I'm a bit concerned that anyone thinks that "going past zero" is in any way relevant when you are using Mach3/UCCNC. Maybe in the days of archaic controllers that did not have any homing/work offset capability, this might have mattered but not today.

The Problem here Neale is that word HOME confuses people. They mix it up with WORK ZERO and think that HOME is where the JOB starts.
99% of new users fall foul of this so when I deliver machines to new users I always spend at least 30mins or more explaining and showing how the COORDINATE SYSTEM's and WORK OFFSETS relate to each other and how they relate to CAD etc.

Now John11668: and anyone else who doesn't quite understand. This is where SOFT LIMITS can come into play to save the day.? Let us say your HOME (machine zero)position is at the end of travels on each axis and you have 1000mm of travel.

You ZERO the WORK coordinate 100mm from the MACHINE ZERO. The job is drilling holes in a 1000mm long piece of stock with the last hole located 990mm from 0. What do think will happen .?.....Yep CRASH.!! . . Because your last hole would actually be located 1090mm from MACHINE ZERO. . . . But not if you have SOFTLIMTS turned on because the controller will pre-run through the G-code when you first load it and will warn you that you are going to exceed the SOFT LIMITS and the day is saved...

So hopefully this shows how MACHINE ZERO and WORK OFFSETS play together.

[John11668]

Hi Jazz and thanks for your response .
I dont think however you have quite clarified things for me.
So ignoring backoff for now .
I home to machine zero in all axes and the machine defines its position as 0,0,0
I have set soft limits X of 0 and 400.
Soft limits Y of 0 and 200,
and Soft limits Z of 0 and -50
So I have now defined a box 400x 200 x50 which is the envelope within which all work MUST be done .

We now come to the workpiece which I have to plant on the table completely within that envelope and clamp it. I have to bear in mind if I am doing an outside profile that I must consider the cutter and allow at least a cutter radius all round.

I am guessing that my workpiece origin or start point is defined somewhere within it , whether it is right hand end, middle, or wherever so I identify that origin, jog to it , and set all my work parameters to zero at that point.

So really it is only if I have placed my job wrongly and that the toolpath will stray outside the envelope that a soft limits alarm should arise .
Are you saying that it should arise prior to hitting the start button . or will it only arise when the work zero position is defined .

[JAZZCNC]

So really it is only if I have placed my job wrongly and that the toolpath will stray outside the envelope that a soft limits alarm should arise .
Are you saying that it should arise prior to hitting the start button . or will it only arise when the work zero position is defined .

Ok lets say you define your WORK ZERO in X half way up the work envelope (or put another way 200 in MACHINE coordinates.) And you defined the X ZERO point in CAD to be bottom left corner of the part and the part is 400mm long in X. When you load the code and it does it's Pre-check it should warn you, I don't think it does when you push cycle start the control should warn you before then. (In UCCNC this feature might need turning on in the settings, I think it's called Softlimits pre check)

It's easy to test just set WORK ZERO for X & Y up the top so the part falls outside the cutting area and set you Z axis at the top of travel so no damage can be done if it it doesn't work but you'll know straight away because it shouldn't work at all in which case hit the stop button.