Re: Drilling toolpath optimization Re: New router video..

>
> Videos are often misleading and can show the special effects that
> the filmographer wants. Hopefully in the day of photo realistic
> computer animation and cheap desktop pc-video production, that will
> not be overlooked by a CNC newbie.
>
> Drilling toolpaths ( indeed any one of a multiple process CNC job)
> are often taken out of context of the rest of a CNC job and
> the "goal" becomes minimization of the cutting time with no regard
> to the most optimal solution for the job at hand.
>
> For a group of folks in the home-built world, achieving programmed
> motion is a major accomplishment and their "goal". Beyond that,
> other factors of CNC programming and part making don't really
> matter, unless they get in the way of making parts for CNC machine
> number 2, or 3, or 4, etc. Some even seem to go so far as to
> measure their manliness by bragging about theirs being
> the "biggest", fastest, longest, etc. There is a lot of shouting
> and pushing as the testosterone splashes around. In this group,
> CCED, it comes out as passive-aggressive as most of the rest of the
> off-topic caterwauling is suppressed.
>
> There is also a very large percentage of people in this group that
> see making their own CNC as only a small step toward their goal.
> They are more interested in how to leverage their available funds
> and components, to make not a working CNC, but rather a useful AND
> efficient machine tool.
>
> What is not evident from a video clip of a few simple drilled holes
> is how to approach hole drilling, and how to use a Cad-Cam program
> to improve things.
>
> Generally speaking the shortest travel distance yields the fastest
> G81 to G80 time. The zig-zag mentioned by Ballendo would most
> definitly be an improvement over the sub-optimal, down and back that
> was shown in the video. The zig-zag may not yield the most optimal
> approach if there is a relatively long distance between the start
> and end points. What's next after the holes are drilled? Move to
> tool change position to change the tool, move to workpiece changing
> position to change out the chunk of material? The moves before and
> after the drilling cycle may be more significant to the job
> efficiency than the drilled holes.
>
> The shortest distance solution may not take into consideration hole
> location accuracy. A drilling toolpath that eliminates the effects
> of backlash would for instance be preferable if the part required
> more precise hole locations. Even in a commercial setting this may
> permit accurate processing of a part on a machine with lesser specs.
>
> A G81 "center of grid" start to G80 "center of grid" end
> optimization would be better if multiple tools were to be used and
> if the tools can be changed over the workpiece.
>

Small snip

> Well that sounds like a good start for an article in Digital
> Machinist....
>
> Fred Smith - IMService

Good reply Fred.
I have left most of the post in as a reference.

Another point is also whether your CAM system can take full advantage of defining to toolpaths to take the shortest route.

Take a disk with five pie shaped pockets, to top one being central at 12 o'clock.
Now when you pocket this top segment you usually have the choice of a few paths go rounds, and then moves that take either a vertical or horizontal lines.
Perfect for this segment but when you move to the next segment round it lies at 72 degrees to the first.
So any horizontal moves or vertical moves waste loads of time as the centre line is at 72 degrees.

Some programs can allow you to choose a machining angle so it takes each pie as being central and so cuts machining time down.

John S.