clean and not so clean cuts... why is that?

[drew]

figured this a good place to share.

video is uploading..... this will make more sense with it already seen...

So your vetrics (aspire/vcarve) makes lines vectors and then maps them... gives them dimensions and space to occupy.. it tells your machine where to start and where to stop, how deep, ect- numerical control, right?  well... some CAD/CAM software is superior to others as some are made for the professional designer.  these are usually hard to learn (eff a learning 'curve', they're just HARD to learn) though many of us trudge through them and learn it anyway.  Others, like vetrics, are superior in they are intuitive to learn and use... but with that simplicity comes some issues you may or may not know about.

In the video I designed a simple sign.  Using king color core as a medium (and MAN I love that stuff) which is two color/layered HDPE, it presents 'witness' marks as it cuts... there is no way around it.  much of those will relieve as time goes by... what it allows, though, is inspection of toolpaths after the cut.  the path the tool ran is unmistakable.  in this case i wanted the lettering proud of the surface which means i had to pocket the negative space out- wallow time- and with a clearing bit..

the clearing bit was a 1/4" Down Cut, and the fine tool was a 1/8" down cut. 

this isn't about the feeds and speeds- and yes I have better feeds and speeds for this material and better selection of bits to use- but i was in a hurry.  I'm almost happy I was else I wouldn't have this to demo and maybe help y'all out.

The sign on the left in the video was where i designed - the sign on the right is simply copy and pasted and rebuilt toolpaths to include it. 

at first i had a little graphic that was to be nested between the lines of text, but i decided it was too busy and removed it.  and... i just kept designing with just text and the box tool- that's it- we're talking 10 minutes of design tops.  When I was satisfied with the design and the strategy for cutting all i did was copy the design and paste it above the original design... then rebuilt the toolpaths to include those 'new' vectors.  When I went to hit 'calculate' I received a message saying "11 open vectors in the design are being ignored- 70 remaining"... do wha???

this was an exceedingly simple design- the text was still text and not converted to curves, which ruled them out, which means---- which means WHAT?

I'd left some remnants of the image?  nope... select all and right click enter node edit mode there were NO straggling nodes present... so what was going on?

what I'm going to suggest is vetrics didn't eliminate all the vectors... they 'hid' them instead and in the case of 'clipboard'.... they DIDN'T transcribe during the copy and paste of the design, but they DID remain in the RAM of the machine when recalculating toolpaths (one with a graphic, one without the graphic)... In other words, vetrics built the original toolpath WITH the graphic and then re-calculated WITHOUT the graphic- yet left space and frame for where the graphic was....

good damn information to know.

[drew]

Do you get as much tracking/witness marks with an up cut?

Oh yeah... and the upcut leaves nasty fuzzy surface cuts.  An oflute has its own issues that excludes their use here too.  The best tool to use is a downcut HSS bit with four flutes and the flutes flat across the diameter of bit- so flat that a bit of 1/8 diameter can be stood straight up on a flat surface and stay there.  It limits the inevitable witness marks or at least keeps them consistent making it look more on purpose... setting the depth of z is crucial when swapping tools, too, as the slightest out of sync will be seen. 

The problem with this cut was the graphic, which was a wave looking thing, was still visible- where the outline of it would have been- AFTER I removed it... its as if vetrics decided to simply alter the toolpath instead of writing a new one. 

I\'ve since started designing and then when satisfied, deleting all the toolpaths used during the design phase and drafting brand new ones as the final toolpath and one I carry to the machine.  Since then I\'ve not seen this weirdness. 

[Gattis Specialty Services]

Drew,
I've had the same issue when using copy and paste of designs, sometimes it will do it on the mirror function as well...I always preview it and turn off the wire frame toolpath and go with solid.
As far as a bit to use on the HDPE, and this tip came from Izzy...LMT/Onsrud 52-700 (1/4") and 52-703 (1/8") will leave almost flawless bottoms, tool marks are almost invisible (at least on the white). I was able to run at around 200 ipm at .1875" doc.
I recently upgraded to Aspire 11.5 and hopefully they have a patch coming soon, it's been buggy, can't add filets where I know they will fit, can't close open vectors, can't always snip away things that aren't grouped...etc.

[drew]

Just looking, that onsrud looks promising with its flat geometry entry.  I'll order some up and give it a shot. 

Like with acrylic, I don't use the cad to zero but do it by eye, and verify touching off in various places on the material.  I've found cutting at least .0825 deep is needed as the laminate isn't extremely consistent in depth at least with the 1/2" and thicker.  The flex of spoilboard under vacuum can impact this too- and it can certainly impact the witness marks too.

The four flute hss bits are fantastic, and I roll into it at 450ipm and 16krpm at .125 and get little swirls for chips.  The problem is that bit won't fit into finer locations. 

[drew]

I just cut this today.  Two sided. .125 deep.. 20" round. Used a 1/8" downcut spiral and a 1/16" downcut spiral, as well as a 90v to chamfer the edges.

Note to self: use a sharp vbit.  That stuff can fuzz otherwise and it takes 320grit and elbow grease to hand burnish it off!