Cutting pre-shaped material

[bcombs510]

Hello,

I have a ukulele neck modeled up in Aspire. I cut a test neck using a polystyrene block to make sure the toolpath works. That came out fine.

Now the question - the test in polystyrene was a full block measuring 3x3x24 and the model and toolpath in Aspire is made based on this. For an actual wood test I wanted to use Walnut and so I used the bandsaw to prep the blank just as if I was going to carve the neck by hand. This gives me two blanks from one block.

If I run the toolpath it’s going to be cutting air for a lot of it. That’s OK because I’m not worried about time to cut, but this can’t be how production shops do it. So is it a side effect of using Aspire where the toolpaths are made with an assumption of starting from a block of wood? Is there a way for the software / toolpaths to take into account a pre-cut blank?

Brad

[adze_cnc]

to make sure the toolpath works. That came out fine.

The toolpath or multiple toolpaths?

[TReischl]

...... but this can’t be how production shops do it. . . . .
Brad

That is correct. It is not a "side effect" of how Aspire does it. It is a matter of cost. Simple rule:

More features, more benefits, greater the cost.

I am not sure, maybe one of the "other software" users can chime in here. It seems to me that I saw something about defining the material and then applying the cuts to that defined material shape. Getting older, in order to remember what is important I do a memory dump of things that are not so important, LOL.

[litzluth]

I've corresponded with Vectric about this. The short answer is, there is no way to avoid cutting air.

Picture a wood blank that is stairstepped (progressively smaller x/y dimensions as Z increases--how most guitar necks are assembled) Using the existing rough/fine 3D toolpaths, the model has to encompass the entire x/y planform. So when the model tapers into the smaller stairstepped pieces, you spend a heck of a lot of time cutting air.

It would be a big improvement if Aspire could somehow recognize areas of the model where there isn’t any wood. If, for instance, you could load a toolpath in first that fictionally cuts away the wood that isn’t really there (because of the stairstepping), and the “rough/finish” 3D model toolpath then recognized that wood was “gone” because of the previous "ghost" toolpath and didn’t need to be cut, that would be a big improvement. But so far, that hasn't been built into Aspire.

[PRO4824]

Couldn't you scroll through the gcode in mach3 until you get down to the actual wood height and do a "Run From Here"?

[Charlie_l]

Assuming this is a 3D carve, just do the finishing cut, skipping the rough cut where all the air is trimmed?

[TReischl]

Not an easy thing to do. At first blush it would seem all one had to do was pay attention to the Z height. But with a rough bandsaw blank there will be areas where there is lots of wood on the sides.

[Dale Vanderlaan]

I have been hoping to come up with a way to do this too. To create a shape, perhaps an .stl file, and then use it as the beginning material shape and size. I make cellos using Aspire for the carving of the curved tops and backs. The material is usually a wedge-shaped 'tent' shape and a lot of air cutting goes on in the areas on both sides for the roughing pass.

I had even wondered if I could create a toolpath to create that original shape and then use 'rest-machining' to cut down from there but had no luck with that approach either. Here's hoping someone comes up with a work around or a software addition for Aspire in the future.

Dale

[ohiolyons]

I have been hoping to come up with a way to do this too. To create a shape, perhaps an .stl file, and then use it as the beginning material shape and size. I make cellos using Aspire for the carving of the curved tops and backs. The material is usually a wedge-shaped 'tent' shape and a lot of air cutting goes on in the areas on both sides for the roughing pass.

I had even wondered if I could create a toolpath to create that original shape and then use 'rest-machining' to cut down from there but had no luck with that approach either. Here's hoping someone comes up with a work around or a software addition for Aspire in the future.

Dale

If I understand what you are asking for look at the tutorials for the marlin and chess piece.

1) Substitute your precut piece for the tabs in those videos.
2) The additional work to performed on that precut piece is on another level.
3) When you do your Roughing and Finishing cuts on the new level.

[ich-fräs-das]

Hi,
I had the same problem with banjo necks and created the roughing pass in 3 parts with overlaps. First the outer parts head plate and bolton are milled and then the middle part with modified g-code. I deleted parts of the g-code with Mach 3 except the last 30mm.

BR
Eckart

[adze_cnc]

I've been wanting to post to this thread since I first saw it. Avoiding "air cutting" is actually reasonably easy. It just takes planning, some 3D modelling, and creating vectors to isolate things.

For example, were I to do this I'd isolate the heel and that would probably be the only thing I use a 3D Roughing toolpath on. I might also create relief profile cuts (to within 1/8" of the bottom of the material) to allow the finishing tool to plunge to full depth if necessary.

I am not sure, maybe one of the "other software" users can chime in here.

Before using VCarve we used a, now 10-year old, version of "other software". One of the useful things that "other software" had was the ability to control the start depth, total depth, and other parameters for their Z-level Roughing toolpath.

For example I needed to cut, just over a year ago, a press mould that had a very deep section (3 and 3/8" deep). I couldn't effect that in VCarve so I needed to plugin the security dongle and resurrect "other software".

For the first 2.5" of roughing I used a short bit that could take a large depth of cut. For the remainder (2.5 to 3.375 deep) I needed to use a 5" long cutter that would scream like a banshee and vibrate like an earthquake on all but the most shallow cuts. See image for simulation after 1st roughing pass and the red path of the second.

For the future I hope that Vectric can add such control to their roughing toolpaths.

Dual-roughing toolpaths

As for the cello plates: with a robust machine and 3/8" or even 1/2" ball end bit I could see a raster "roughing finish" toolpath cutting across the grain. Perhaps a narrow 3D Roughing toolpath to give the 3D Finishing path space to allow it to start shearing thin strips.

Pre-roughing a thin strip

Gives the finishing path "room to breathe"

[BillK]

I often remove large chunks with the band saw or by drilling out material. You can modify the roughing toolpath to not cut those parts. Then the finished 3D toolpath runs normally. If you are not doing 3D toolpaths, then just break it up in sections. If I’m making one, I’ll cut air, if many see above.

[adze_cnc]

Talking about production shops. Here's 8 necks cut at one time: https://youtu.be/zdMgYsR7ISk

[4DThinker]

When I've done a successful test cut, there is an option to save the toolpath preview as a 3D model.
When doing the final piece in good wood, and removing most of the waste areas ahead of time, I start a new job. Import the 3D model, then create a 3D finish toolpath of it. If the shape is not too complicated to do as a 3D model then running the 3D finish toolpath is all you need to do.

[gio14]

n similar situations, I do an offset of a certain amount to enlarge the model, then a 3D finishing process, then I bring the model back to its real size and perform a second 3D finish.