toolpath strategy for complex shape bookshelf

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toolpath strategy for complex shape bookshelf

Postby alex pavel » Wed Dec 05, 2018 7:13 pm

Hello! I am new to vcarve and the CNC world. I recently bought a CNC machine in order to produce furniture. I want to mill a bookshelf and i need your advice for the toolpath strategy i should use. I have uploaded some 3D images with the piece. The piece dimensions are around: 450x2100x2600. The machine limits are 2500x1300x300 mm. I will use Oak Wood with about 40mm thickness.

I was thinking about slicing the piece in 40mm parts and then for each slice, getting the vector boundary. And for each piece i would have 3 toolpaths: 2D Profile, 3D Roughing, 3D Finish. I would add tabs and in case i have concave areas, i would turn the part over and cut the other side too.

What are your thoughts? I appreciate any suggestion and feedback from you.

Thank you!
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Re: toolpath strategy for complex shape bookshelf

Postby Rcnewcomb » Wed Dec 05, 2018 10:03 pm

What are your thoughts? I appreciate any suggestion and feedback from you.


You are correct that a 2D profile will be a better strategy than trying to do it all as 3D. I assume you would use the same end mil for 2D and 3D roughing.
You may wish to add alignment holes for a few dowels to help with gluing the layers together.

Look at the work that Neathawk design did using slicing on a very large project: Arch of Titus Project and Video
Also look at Jim McGrew's Chess Pieces
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Re: toolpath strategy for complex shape bookshelf

Postby alex pavel » Wed Dec 05, 2018 11:51 pm

I was thinking about using a roughing mill for the 3D roughing tool path. Can i use the end mill for roughing? I was actually wondering why can't i just do the 3d roughing with an end mill. Any idea 's the difference between using an end mill or a roughing mill for 3D roughing?

I actually didn't think about using dowels to align the pieces. Good idea! Is this a practice when doing 3D work on a CNC? Is it helping on just aligning the pieces, or also keeping the parts together?

Nice projects! I really enjoyed watching how they did it and what came out of it.

Cheers!
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Re: toolpath strategy for complex shape bookshelf

Postby martin54 » Thu Dec 06, 2018 3:33 pm

An endmill will be fine for any sort of 3D roughing you want to do, Roughing endmills tend to be a lot more expensive & are really designed for production type work on industrial machines which are rigid, have powerful spindles & generally run faster. There are people on the forum that run industrial machines & I am sure some will use them but I would bet the majority of forum users wouldn't be able to run their machines fast enough or cut deep enough to see any real advantage :lol:

The use of dowels is generally just for alignment, there is no need to use them for any 3D work in general. They are used quite a bit with 2 sided machining or when tiling to ensure acurate alignment on the CNC.
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Re: toolpath strategy for complex shape bookshelf

Postby ger21 » Thu Dec 06, 2018 3:48 pm

but I would bet the majority of forum users wouldn't be able to run their machines fast enough or cut deep enough to see any real advantage


A roughing bit will actually allow you to cut deeper and faster, as they require less power to cut. They're also much quieter while cutting. But yes, they are expensive.
And don't confuse a chipbeaker with a roughing bit. A true roughing bit can cut much more aggressively than a chipbreaker.
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Re: toolpath strategy for complex shape bookshelf

Postby alex pavel » Thu Dec 06, 2018 8:14 pm

Good info. Thanks! I guess i'll use a roughing bit then, since i want to reduce my machining time as much as possible. The machine has 24000 rpm and weighs about 1.6 tonnes, so i guess i could harness the capability of a roghing mill :)
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Re: toolpath strategy for complex shape bookshelf

Postby martin54 » Thu Dec 06, 2018 9:32 pm

alex pavel wrote:Good info. Thanks! I guess i'll use a roughing bit then, since i want to reduce my machining time as much as possible. The machine has 24000 rpm and weighs about 1.6 tonnes, so i guess i could harness the capability of a roghing mill :)


No idea what sort of machine you are using but at that sort of weight sounds like an industrial type machine rather than a hobby machine, the 24,000rpm is spindle spped & isn't really relevant, a very low power spindle could easily have a high speed.
Unlikely to be the case with your machine though, if you want to reduce machining times then the extra expence of a roughing bit will certainly be worth it for you especially if this is a business where time equals money :lol: :lol: :lol:

Gerry is the expert not me but I still don't believe that there would be much gained on a lot of the hobby type machines that people on the forum seem to be using like Piranha's & x-carves, no personal experience with either type but neither seem to be rigid enough or capable of speeds that would make to much difference :lol: :lol:
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Re: toolpath strategy for complex shape bookshelf

Postby ger21 » Fri Dec 07, 2018 1:17 am

No, I wouldn't use or recommend a roughing bit on a Piranha or X Carve. They usually aren't available in small enough sizes to even fit in one. :lol:
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Re: toolpath strategy for complex shape bookshelf

Postby ger21 » Fri Dec 07, 2018 1:19 am

alex pavel wrote:Good info. Thanks! I guess i'll use a roughing bit then, since i want to reduce my machining time as much as possible. The machine has 24000 rpm and weighs about 1.6 tonnes, so i guess i could harness the capability of a roghing mill :)


You won't want to be running anywhere near 24,000 rpm, unless you'll be cutting over 1000ipm (25m/min).
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Re: toolpath strategy for complex shape bookshelf

Postby rscrawford » Fri Dec 07, 2018 2:47 am

Just an observation, but if you want the bookshelf to look anything like that picture, then you need to use veneers and not make it out of solid oak. That bookcase is most likely made from MDF and then has a veneer laminated to it.

Carving that out of solid oak in slices will give you a very different look (mostly end grain) and will require a lot of sanding and finishing because the slices will not align exactly when you glue the whole thing together (that solid wood will definitely move on you as its cut, which will make the slices not align properly).
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Re: toolpath strategy for complex shape bookshelf

Postby alex pavel » Fri Dec 07, 2018 3:17 am

rscrawford wrote:Just an observation, but if you want the bookshelf to look anything like that picture, then you need to use veneers and not make it out of solid oak. That bookcase is most likely made from MDF and then has a veneer laminated to it.

Carving that out of solid oak in slices will give you a very different look (mostly end grain) and will require a lot of sanding and finishing because the slices will not align exactly when you glue the whole thing together (that solid wood will definitely move on you as its cut, which will make the slices not align properly).


The images i attached are 3D renders done in other software. The wood texture in the render is not scaled correctly, i just wanted to have a rough idea about how would it look like.

Hmm...Do you think it will move that much? I've seen furniture made of solid wood with layers. Here: https://www.dezeen.com/2016/10/03/ultra ... re-design/
I am not sure though if it was milled as one block or as individual pieces and then glued.
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Re: toolpath strategy for complex shape bookshelf

Postby Wayne Locke » Fri Dec 07, 2018 5:41 am

What is the size of the bookcase you are trying to make? The picture of the completed piece seems small although there is nothing to show scale.

I am pretty sure that the pictured piece is not veneered. I have done a lot of veneering and veneering of curved panels over the decades and I don’t think that you could veneer it.
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Re: toolpath strategy for complex shape bookshelf

Postby Rcnewcomb » Fri Dec 07, 2018 5:51 am

Alex,
Here are links to some of Russell's work:
Chairs
Round Chair, copy of Hans Wegner's classic chair
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Re: toolpath strategy for complex shape bookshelf

Postby ger21 » Fri Dec 07, 2018 1:19 pm

alex pavel wrote: The piece dimensions are around: 450x2100x2600.


Are these numbers correct? They seem much too big.

18" deep??

7 ft x 8-1/2 ft??
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Re: toolpath strategy for complex shape bookshelf

Postby alex pavel » Fri Dec 07, 2018 1:24 pm

Rcnewcomb wrote:Alex,
Here are links to some of Russell's work:
Chairs
Round Chair, copy of Hans Wegner's classic chair

I know about Russell's work and I love it! I never questioned his expertise. In fact I appreciate his and everyone's feedback. I'm just trying to learn how possible it is to make this out of solid wood.
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