Peck - Centre Punch Feature

Closed

Feature Request

Scott PridhamAug 182 comments

Feature Request – Plasma Peck/Divot Marking

I would like to request a Peck Mark / Divot Marking feature for plasma operation.

The purpose is to use the plasma torch to create a very small divot at the centre of a hole location, effectively acting as a CNC centre punch. The mark can then be used to accurately locate a drill without plasma-cutting the complete hole.

The important requirement is that this should not use the normal pierce sequence or wait for Arc OK, because by the time Arc OK is received the plasma may already have pierced or significantly damaged the material.

The required sequence would ideally be:

Move to the programmed XY point.
Perform the normal material touch-off/IHS if required.
Raise to a configurable Peck Mark Height.
Disable THC and normal pierce-delay logic.
Turn the plasma Torch Start output ON.
Keep Torch Start ON for a very short, accurately controlled period.
Turn Torch Start OFF immediately when the peck timer expires, regardless of Arc OK status.
Retract Z and move to the next point.

The main configurable parameter should be:

Peck Pulse Time: preferably adjustable in milliseconds, for example from approximately 5 ms to 100 ms, with 1 ms or finer resolution.

It would also be useful to have configurable:

Peck/mark height
Retract height
Touch-off enabled/disabled
Peck pulse duration
Optional delay between successive marks
THC disabled automatically during the operation

For example:

Move to XY
Touch off
Move to 2.0 mm mark height
Torch Start ON
Wait 10 ms
Torch Start OFF
Retract
Move to next mark

The timing ideally needs to occur at the motion-controller/firmware level rather than through a normal G-code dwell, so that a 10 ms or 20 ms pulse is repeatable and is not affected by PC, USB, network or G-code processing latency.

This is similar to the PlasmaCAM/DesignEdge “Mark Point” or peck marking function, where the torch is fired for only a fraction of a second to leave a small centre divot without completing a pierce.

The end goal is a small, repeatable plasma crater that can be used as a drilling centre mark, particularly for holes that are better drilled than plasma-cut.

2 Comments

Scott PridhamStaffAug 18Edited

and yes i got CHATGPT to make my feature request

forgot to add should be a similar feature to mark centre of holes
also the timing of the pierce has to be repeatable and programmable

Travis GillinStaffAug 18

Built and it'll be in the next release (v2.5.0). It works almost exactly like your sequence, and marking hole centers is precisely what it does.

How to use it:

Right-click any hole → Operation Type → Peck Mark. Works on one hole or a whole set picked with Contour Select (C). It replaces the cut for that hole with a single mark at its exact center — same place your drill wants to start.
Or make it automatic: add a Peck Mark action to a cutting rule keyed on hole diameter, and every matching hole on the sheet marks itself instead of cutting.
Pulse time and peck height live in Cut Parameters → Peck. Pulse is in milliseconds, 1 to 1000, 1 ms steps — defaults are 10 ms at 2 mm. Rules use those values by default or can carry their own.

The sequence per mark is what you asked for: normal touch-off/IHS (floating head or ohmic, whatever your machine already has configured — nothing new to set up), raise to peck height, torch ON, hold for exactly the pulse time, torch OFF on the timer, retract, next mark. THC is never engaged during a mark, and the pierce-delay logic is completely out of the loop. Critically, it never waits for arc-OK — the OFF fires when the timer expires whether the arc reported or not.

On your timing concern — this was the first thing I dug into, and the good news is FluidNC already does dwell timing exactly where you wanted it: in the firmware. When the controller hits the pulse command it first waits for all buffered motion to physically finish, then counts the dwell on the firmware's own 1 kHz clock — 1 ms resolution, on the controller, with the PC completely out of the picture. And because JetCad3 streams ahead into the controller's buffer, the torch-OFF command is already sitting inside the controller before the pulse starts counting. So a USB or network hiccup can't stretch the pulse — worst case it delays the next rapid, never the torch-off. Repeatability is roughly ±1 ms, every mark, every time.

The torch itself fires through the same firmware-side output the normal pierce cycle uses, so your existing torch wiring and touch-off config carry straight over. Posted code labels every mark with the hole size and pulse — ( PECK MARK - 12.70mm DIA 10ms ) — and the sheet view draws a crosshair on every pecked hole so you can see at a glance what cuts and what gets a divot.