Re: [CAD_CAM_EDM_DRO] Modified G78 pecking ?

turbulatordude wrote:

> Hi,
>
> G78 calls for a drill pecking that uses a full retract on each peck.
> The holes I am drilling only need to have the drill retract to let
> the chips ride up the drill. The small up then down lets the chips
> out of the hole quite successfully.
>
> Is there a multi-stage peck ? one that would start, approach the
> part, drill, withdraw a little, then continue drilling for the
> pecking cycle, then withdraw fully ?

I have a C program that will drill a circular array of holes by this kind
of peck cycle. If you tell it one hole at radius zero, it will just do one
hole. You can tweak parameters to get the desired amount of pecking
action. You can take a look at this program, and download a DOS executable
or the C source code at http://pico-systems.com/gcode.html

The program, as it stands, does a full retract and then rapid feeds to
almost the same depth as it had last drilled to, and then slows to the
specified drilling feedrate. I can tell you how to change it if you don't
want to try that yourself.

> Something like drill 0.02", withdraw 0.01" the take another 0.02" so
> that the top of the retract was only slightly above the last drilled
> hole and not fully to the start ?
>
> or is my best bet to move the Z to just above the part and peck from
> there ?
>
> My problem is drilling long holes in aluminum with tiny bits. 3/64
> drill into a 1/4 inch plate. it's 6063 aluminum so it's kinda
> sticky, but produces long chips.

Flooding with coolant is a BIG help. You might be able to drill such a
hole in a single pass with the right drill bit. If you will be doing a lot
of this, get some cobalt-HSS drills, such as M42. They seem to do a
lot better than plain HSS drills.

Jon