flute bowl questions

[bluridg]

want to make bowl using flutes from perimeter to center. from 0 at perimeter to 1.25 deep in center , using 1.5 dia ball end bit. set bit specs to .0625 pass depth, .2 stepover, 50 feed rate, 5 plunge depth. cutter moved back and forth, completing each flute before cutting the next one. that bit removes so much wood, it would bog down. it cut each flute 11 times. why did it not take 16 times? the drawing was 9.5 in diameter but finished cut was 10 in diameter. also how can I do a finish cut without running different program just slightly deeper? ted

[FixitMike]

For the rough cut, set the start depth at -.03". This will cut the surface .03" higher than the finish cut, the same as if you set Z0 .03" above the material.

For the finish cut, set the pass depth setting for the finish tool at 1.5". (And the toolpath start depth at 0.) It won't actually cut any deeper than the 1.25" flute depth, but it will make the finish cuts in one pass for each flute. The cuts will be .03" deeper than the rough cut.

Save both toolpaths to a single .tap file, but be sure the rough cut is above the finish cut on the list, so it is run first.

When making flutes, the cutter centerline follows the selected vector, so the actual cut will be to each side and beyond the ends of the selected vectors. That is why even though the vectors are 9" across, the cut is 10".

Try using an end mill for a smoother result.

The attached file shows what I mean. I only cut 1/4 of the bowl so the toolpath preview won't take forever.

[tmerrill]

set the start depth at -.03". This will cut the surface .03" higher than the finish cut, the same as if you set Z0 .03" above the material.

That will not work. The Start Depth box will not allow a negative number so all you are actually doing is setting it +0.03" deeper.

Tim

[PaulRowntree]

completing each flute before cutting the next one. that bit removes so much wood, it would bog down. it cut each flute 11 times. why did it not take 16 times? the drawing was 9.5 in diameter but finished cut was 10 in diameter. also how can I do a finish cut without running different program just slightly deeper? ted

The FlutePlus gadget avoids these problems : it does all of the paths to constant depth before moving to the next depth, just like a pocket. It also treats the 'Profile' vectors as boundaries (not tool-centre trajectories), so the final bowl diameter is fixed by the vectors, not the tool diameter.
One way to get a slightly deeper finishing pass is to set the cnc controller to be slightly above Z=0 for the roughing cut, then set it down to the correct height for the finish pass. If using FlutePlus, a better way is to calculate the roughing toolpath with the depth a smidge shallow using as many passes to get to that depth, then recalculate with a single pass to the exact depth.

[FixitMike]

The Start Depth box will not allow a negative number...

It will too allow a negative number. It just ignores the negative sign when calculating the toolpath start depth. Fix needed.

[tmerrill]

Semantics. The important point is the program only allows a positive start depth and therefore only uses the absolute value found in the input box.

It has been this way since the very first version and I personally don't see it as 'broken' - you just need to understand how the program works.

Tim

[bluridg]

thanks for all possibilities of help. paul, I have flute plus and still learning it's capabilities. this was written before I had superflute. forgot to change. this direct comparison shows the improvements you have done. re finishing cut. if I start a little above surface, leaving everything else unchanged, seems the run would be dependent on " pass depth" and would cut a lot of air until got down to bottom of bowl. would seem to make sense to write another program for the finish cut changing only the pass depth in edit tools. in this case make "cut depth" 1.3. then wouldn't the finish cut be made in one pass? I reccomend to everyone. get fluteplus. it makes a great program ( Vectric) even better. ted

[PaulRowntree]

if I start a little above surface, leaving everything else unchanged, seems the run would be dependent on " pass depth" and would cut a lot of air until got down to bottom of bowl. would seem to make sense to write another program for the finish cut changing only the pass depth in edit tools. in this case make "cut depth" 1.3. then wouldn't the finish cut be made in one pass? I reccomend to everyone. get fluteplus. it makes a great program ( Vectric) even better. ted

I think it is easier to do it in the Vectric software, and keep the Z=surface calibration of Mach3 exact. Saves wear and tear on my memory cells ...

With the Jan 20 version of FlutePlus, you can turn off the roughing cuts without having to mess with the tool's Pass Depth parameter. Uncheck the check box shown in the attached image, and it will be the same as setting the Pass Depth to a very large number, but just for this toolpath. Again, easier on my brain cells. This makes it simple to run the roughing passes down to 95% of the final depth, then a single finish pass at 100%. Two toolpaths, but the gadget remembers parameters between runs, and the Profile/Rail vectors stay selected between gadget runs ... You can do a tool change between the roughing and finish passes if necessary. For smooth bowl shapes, (not like yours) you can do roughing passes with a reduced number of the 'rail' vectors to save a lot of roughing time (with the Rail Skip Count number).
Cheers!

[bluridg]

paul, re fluteplus, how do I change "home position" at bottom of toolpath window? ted

[PaulRowntree]

The most recent version (2014-02-07 Aqualung) does a hack to avoid the corner start point and reduce Z motion. The previews should show less useless tool motion in all directions.

A couple of posts back I referred to a January version .. it works well, but in general, always grab to most recent version posted unless there is a solid reason otherwise.

[bluridg]

paul missed those posts. I need a way to pull up each post you submit. I learn even when not directly involved. thanks ted