"Nib" removal on MDF cutouts edges

[JAZZCNC]

Could do with some simple pointers and info on Zero points for work and axis etc.. I've forgotten more of what I learned 35 years ago than I thought

It's simple really.!! . . . .You have 2 coordinate systems to work with.?. . . . Machine coordinates and work Coordinates.

Machine coordinates are the area of your work envolope. Machine Zero is defined by referencing the Machine to switches. This is known has the HOME position.
From this Home reference point you can acurately find any point or work coordinate on the table.

Work coordinates are Defined by selecting a point on your work material and setting ZERO point. This Zero point will be the Zero point you set in Cad and you'll use this as a refernce to where on the Work material you'll place it.

Now the work material can be anywhere within the Machine coordinate enverlope and the WORK ZERO is always known by it's distance from the MACHINE ZERO.
So if you cock up or snap a tool etc and lose position then you can always accurately get back to WORK ZERO or any position in the WORK coordinates by sending the machine to the HOME position so it references to the switches again and resets the MACHINE HOME position. From this reference point it can find any other point on the table.

Taking it a step further You can have WORK OFFSETS. Essentially OFFSETS are the same as breaking the table into smaller individual WORK areas each with it's own ZERO point.
Most people don't often realise it but they are working in an OFFSET, it's G54 which is default WORK OFFSET. They define this every time they ZERO for the part.
But you can have Many OFFSETS each with there own unique ZERO point within the MACHINE coordiante system. These are given OFFSET numbers starting at G54 then G55, 56, 57 etc and depending on the control system there can be upto 255.
You set these WORK OFFSETS up in the control system by specifying MACHINE coordinates for each OFFSET Number. Then when the control software comes across this OFFSET number in the G-code it knows where to go in relation to MACHINE coordinates to find WORK ZERO for that OFFSET.

OFFSETS can be very poweful when used correctly and are great if you use fixture jigs. Each Jig could have it's own differant part with differant material and still be cut in the same G-code file in one go.

This getting little deep now but to recap.

Set Machine Zero by sending machine to HOME position. Then throw material anywhere on table and Define ZERO WORK position by Zeroing the DRO's on the screen or selecting WORK Zero some where on the material.

That's it really the part will be cut in G54 OFFSET (Check your G-code file and near the top you'll see G54, if not specified control system will default to G54) and ZERO point for the WORK will be where selected on the material.

The control system keeps track of the rest and after HOMING will accurately get you back to any lost WORK position if needed.