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Offline Tweakie.CNC

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« Reply #10 on: May 03, 2018, 02:29:49 AM »
Hi Vogavt,

Within Mach3, running a macro or calling an M3/M5 takes some 100mS of time to complete and thus causes unwanted laser burn at the start or end of an engraved line. Because Mach3 blends axis moves then the TTL level of the A (or B or C) axis direction pin can be changed at the exact instant (or al least within 2mS) the X,Y or Z axis start to move. This principle is demonstrated in the linked video (although this one was made in the early days of Mach4 when there was still some confusion between Imperial and Metric units for the A axis).


I have attached my Gcode for a similar part (another Mach4 test). Here the A axis direction pin toggles when the A axis moves between 0 and 0.01. Although the code was produced for Mach4 it will operate perfectly with Mach3.

My laser switches ON when its trigger input is TTL(low) and OFF when the trigger input is TTL(high) so within Mach3 the Active Low state of my A ( or B) axis direction pin would be set to switch my laser accordingly.

(There are some safety concerns when using an axis direction pin (because a Direction pin TTL level is modal and the laser could be left ON when in EStop) so certain precautions have to be taken).

Hope this makes sense.

« Last Edit: May 03, 2018, 04:29:21 AM by Tweakie.CNC »