Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?

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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

mondo

Hi, William,

On 14/08/2020 19:10, William F. Adams via Discuss wrote:
>Have you actually made a sketch of how a couple of the fingers, 
>say, actually mesh together, when prepared by what ever router bits you can use? 

Yes, see the links in my previous message.

Please give a link to where you have sketched the shape of the fingers, and how they mesh, being capable of being produced by standard router bits, perpendicular to the surface of the wood. i.e. in the sort of machine that i thought you were intending to use - a flat bed cnc router. I am not talking about your openscad drawing showing a few sides that seem to be able to interlock, but where you have actually looked at the final detailed shape of the individual fingers, and how you will machine them. Afaik, this is not possible on a flat bed router, unless you mess around standing them on edge, in which case it then becomes a trivial problem (other than the work holding), or you're happy to use gap filling glue.

You say you have designed a joinery system, well if it involves a four or five axis bed/spindle, you will be in with a chance, but if only three, then no chance, unless you go for two or more operations. I suppose a cnc version of the edge milling box joint jigs may do, but that is not a challenge. There is probably a reason why there is no cam programs that will do what you want, after all, finger joints are pretty popular, but already covered by various mechanical jigs. There are, however, laser cutting cnc systems for finger joints, if you want to see burn marks on the edges.

If you were to standardise on the minimum gap between the fingers, then a design for a small mortiser would be interesting, and you'd get square corners.

Best wishes,

Ray


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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

OpenSCAD mailing list-2
Ray West asked:

>Please give a link to where you have sketched the shape of the fingers, and how they mesh,
>
being capable of being produced by standard router bits, perpendicular to the surface of the wood.
>
i.e. in the sort of machine that i thought you were intending to use - a flat bed cnc router.

Please see: https://community.carbide3d.com/t/cnc-finger-joint-box/8880/113?u=willadams and the posts above/below that.

You can see the details of the radiusing tool definition at: https://community.carbide3d.com/t/design-into-3d-boxes-magazine-storage/16238/54?u=willadams

I've also done a diagonal relief using a V endmill which worked surprisingly well:

https://community.carbide3d.com/t/design-into-3d-boxes-magazine-storage/16238/16?u=willadams

>I am not talking about your openscad drawing showing a few sides that seem to be able to interlock,
>
but where you have actually looked at the final detailed shape of the individual fingers, and how you will machine them.
>
Afaik, this is not possible on a flat bed router, unless you mess around standing them on edge,
>
in which case it then becomes a trivial problem (other than the work holding), or you're happy to use gap filling glue.

I've done them standing on edge. It's a tedious pain.

>You say you have designed a joinery system, well if it involves a four or five axis bed/spindle,
>you will be in with a chance, but if only three, then no chance, unless you go for two or more operations.

Yes, to two or more operations if you consider a tool change an operation, but only one setup.

>I suppose a cnc version of the edge milling box joint jigs may do, but that is not a challenge.

Agreed, been there done that.

>There is probably a reason why there is no cam programs that will do what you want, after all,
>finger joints are pretty popular, but already covered by various mechanical jigs.
>There are, however, laser cutting cnc systems for finger joints, if you want to see burn marks on the edges.

I've used generators intended for lasers as a starting point for some projects, but no interest in a laser --- agree that the burn marks look ghastly.

>If you were to standardise on the minimum gap between the fingers, then a design for a small mortiser would be interesting,
>and you'd get square corners.

Not sure what you mean by that.

William

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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

nophead
I have a CNC router with a tool changer operated by compressed air but I have never got around to setting up the tool changer. It would be ideal for that sort of job but would require accurate tool Z height calibration but I have solved that problem before. https://hydraraptor.blogspot.com/2007/05/how-long-is-your-tool.html

I have also never used it with wood but someday I will get around to it.

On Fri, 14 Aug 2020 at 21:38, William F. Adams via Discuss <[hidden email]> wrote:
Ray West asked:

>Please give a link to where you have sketched the shape of the fingers, and how they mesh,
>
being capable of being produced by standard router bits, perpendicular to the surface of the wood.
>
i.e. in the sort of machine that i thought you were intending to use - a flat bed cnc router.


You can see the details of the radiusing tool definition at: https://community.carbide3d.com/t/design-into-3d-boxes-magazine-storage/16238/54?u=willadams

I've also done a diagonal relief using a V endmill which worked surprisingly well:


>I am not talking about your openscad drawing showing a few sides that seem to be able to interlock,
>
but where you have actually looked at the final detailed shape of the individual fingers, and how you will machine them.
>
Afaik, this is not possible on a flat bed router, unless you mess around standing them on edge,
>
in which case it then becomes a trivial problem (other than the work holding), or you're happy to use gap filling glue.

I've done them standing on edge. It's a tedious pain.

>You say you have designed a joinery system, well if it involves a four or five axis bed/spindle,
>you will be in with a chance, but if only three, then no chance, unless you go for two or more operations.

Yes, to two or more operations if you consider a tool change an operation, but only one setup.

>I suppose a cnc version of the edge milling box joint jigs may do, but that is not a challenge.

Agreed, been there done that.

>There is probably a reason why there is no cam programs that will do what you want, after all,
>finger joints are pretty popular, but already covered by various mechanical jigs.
>There are, however, laser cutting cnc systems for finger joints, if you want to see burn marks on the edges.

I've used generators intended for lasers as a starting point for some projects, but no interest in a laser --- agree that the burn marks look ghastly.

>If you were to standardise on the minimum gap between the fingers, then a design for a small mortiser would be interesting,
>and you'd get square corners.

Not sure what you mean by that.

William
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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

mondo
In reply to this post by OpenSCAD mailing list-2

Thanks, William. I now see we are both right. Your quadrant table is the fourth axis, in effect. Seems you've had a few arguments elsewhere, too.

A mortiser tool bit is basically a square tube, with sharp edge at the bottom, and a drill running through the centre. The drill clears the majority of the chips, leaving a thin ridge and corners for the tube to shave off. It basically drills square holes in wood. If you rigged up a similar unit, but with a cnc controlled x/y table to move the wood around, then it could profile nice square notches. It would most likely need more pressure than is capable to be exerted by the z axis drive of the usual cnc routers, however, but there are ways around that.

If you knew someone who could harden and temper tool steel (It is quite easy), then drill a  hole lengthwise through a steel bar, and countersink the end (It'll give a sharp edge), then use an ordinary auger bit in the centrer. You will need to cut away part of the side of the bar, to let the chips escape. Or you can buy them ready made, of course.

If you limit the size of material you want to process, then you can build a sturdy gantry type flat bed cnc router, with a beefier z drive stepper and ball screw. A sharp bit, say 0.25 inch square will not take much force to push it through most woods. It will not be particularly fast, especially if you are doing all the cutting with the mortise bit, but there should be little further processing required.

A bonus would be that you could use openscad to design the machine.

Best wishes,


Ray

On 14/08/2020 21:37, William F. Adams via Discuss wrote:
Ray West asked:

>Please give a link to where you have sketched the shape of the fingers, and how they mesh,
>
being capable of being produced by standard router bits, perpendicular to the surface of the wood.
>
i.e. in the sort of machine that i thought you were intending to use - a flat bed cnc router.


You can see the details of the radiusing tool definition at: https://community.carbide3d.com/t/design-into-3d-boxes-magazine-storage/16238/54?u=willadams

I've also done a diagonal relief using a V endmill which worked surprisingly well:


>I am not talking about your openscad drawing showing a few sides that seem to be able to interlock,
>
but where you have actually looked at the final detailed shape of the individual fingers, and how you will machine them.
>
Afaik, this is not possible on a flat bed router, unless you mess around standing them on edge,
>
in which case it then becomes a trivial problem (other than the work holding), or you're happy to use gap filling glue.

I've done them standing on edge. It's a tedious pain.

>You say you have designed a joinery system, well if it involves a four or five axis bed/spindle,
>you will be in with a chance, but if only three, then no chance, unless you go for two or more operations.

Yes, to two or more operations if you consider a tool change an operation, but only one setup.

>I suppose a cnc version of the edge milling box joint jigs may do, but that is not a challenge.

Agreed, been there done that.

>There is probably a reason why there is no cam programs that will do what you want, after all,
>finger joints are pretty popular, but already covered by various mechanical jigs.
>There are, however, laser cutting cnc systems for finger joints, if you want to see burn marks on the edges.

I've used generators intended for lasers as a starting point for some projects, but no interest in a laser --- agree that the burn marks look ghastly.

>If you were to standardise on the minimum gap between the fingers, then a design for a small mortiser would be interesting,
>and you'd get square corners.

Not sure what you mean by that.

William

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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

OpenSCAD mailing list-2
In reply to this post by OpenSCAD mailing list-2
Proof of concept for this: https://community.carbide3d.com/uploads/short-url/Av8DyvPseArwbfWZcxKOLhoFQBW.zip

Parsing design (AST generation)...
Saved backup file: C:/Users/willa/OneDrive/Documents/OpenSCAD/backups/Design into 3D_ Fingerjoint-backup-vaTVHyKD.scad

Compiling design (CSG Tree generation)...

ECHO: "G0 X,", 0, " Y", 0, " Z", 8
ECHO: "G1 Z", -3.175, " F", 150
ECHO: "G1 X", 0, " Y", 4.20625, " F", 600
ECHO: "G0 Z", 8
ECHO: "G0 X,", 9.5875, " Y", 0, " Z", 8
ECHO: "G1 Z", -3.175, " F", 150
ECHO: "G1 X", 9.5875, " Y", 4.20625, " F", 600

&c.

see the post at: https://community.carbide3d.com/t/cnc-finger-joint-box/8880/126

So if we just had a command which would write out only the echoed text less the clutter, we'd have a CAM solution for OpenSCAD files which are coded in a style where a declared piece of stock is subtracted from in a fashion which matches how one wants the CNC machine to cut things out.

William


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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

mondo

Hi William,

for the purpose of testing that the gcode generated is the gcode you can use, it is simple to open it in any text editor, e.g. notepad, and do search and replace a few times.

so search for 'echo' and replace with 'space', then same for double quotes and commas. Finally search for spaces repeatedly replacing two spaces with one,  this results in

 G0 X 0 Y 0 Z 8
 G1 Z -3.175 F 150
 G1 X 0 Y 4.20625 F 600
 G0 Z 8
 G0 X 9.5875 Y 0 Z 8
 G1 Z -3.175 F 150
 G1 X 9.5875 Y 4.20625 F 600

which is valid gcode, at least for my machines. That will allow you to break out of the theory, and you can attempt to machine the pieces, and see if they fit together as expected.

On 15/08/2020 05:16, William F. Adams via Discuss wrote:
ECHO: "G0 X,", 0, " Y", 0, " Z", 8
ECHO: "G1 Z", -3.175, " F", 150
ECHO: "G1 X", 0, " Y", 4.20625, " F", 600
ECHO: "G0 Z", 8
ECHO: "G0 X,", 9.5875, " Y", 0, " Z", 8
ECHO: "G1 Z", -3.175, " F", 150
ECHO: "G1 X", 9.5875, " Y", 4.20625, " F", 600

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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

OpenSCAD mailing list-2
Yes, as noted, that was just a proof of concept. I'll be doing some actual cutting/testing with this today.

I've since found that wrapping things up in str() so as to convert to a string as part of the echo() command cleans up the internal double quotes and commas, so the find-replace and filtering is now trivial (parse each line and only write out those which begin w/ ECHO, just without that text or the colon or the quotes).

So, could we please just get a command which would do that with a user configurable file extension?

William

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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

JordanBrown
In reply to this post by OpenSCAD mailing list-2
What does your input OpenSCAD look like, that emits proto-gcode?  I don't see that in any of the pages you've posted.

I'd like to figure out how to drive my CNC machine from an OpenSCAD model... so far, I'm not seeing how, other than some tool chains that seem fragile, unpleasant, or both.



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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

OpenSCAD mailing list-2
Jordan Brown wrote:

>What does your input OpenSCAD look like, that emits proto-gcode?  I don't see that in any of the pages you've posted.

I posted my source code at:

https://community.carbide3d.com/uploads/short-url/36SA8hMSvesRwUOKFocbbdxQmrl.zip

in the message: https://community.carbide3d.com/t/cnc-finger-joint-box/8880/126

and I've attached the current copy to this message.

Current settings are:

Capture.PNG

>I'd like to figure out how to drive my CNC machine from an OpenSCAD model...
>so far, I'm not seeing how, other than some tool chains that seem fragile, unpleasant, or both.

This is just a proof of concept so far, but I think it shows progress.

Just to review --- which CAM options have you looked at or considered? Thus far I've tried or worked with:

 - export STL --- process in a 3D CAM tool such as MeshCAM or pyCAM
 - export DXF or SVG --- process using a tool such as MakerCAM or Carbide Create

the other thing I've considered is:

 - opening the .scad file in FreeCAD and using its CAM workbench

Curious if there are any other options to try.

William



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Design into 3D_ Fingerjoint.scad (19K) Download Attachment
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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

JordanBrown
In reply to this post by OpenSCAD mailing list-2
On 8/15/2020 5:20 AM, William F. Adams via Discuss wrote:
So, could we please just get a command which would do that with a user configurable file extension?

Remember that the people doing the work are volunteers, working in their spare time on things that interest them.

It does seem pretty simple.  I'd offer to do it myself, but ... I got OpenSCAD to build successfully in December, and since then I've found the time to spend maybe two or three hours on the features that *I* want.


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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

OpenSCAD mailing list-2
On 8/15/2020 5:20 AM, William F. Adams via Discuss wrote:
>So, could we please just get a command which would do that with a user configurable file extension?


and Jordan Brown responded:

>Remember that the people doing the work are volunteers,
>working in their spare time on things that interest them.

>It does seem pretty simple.  I'd offer to do it myself,

I would appreciate that.

>but ... I got OpenSCAD to build successfully in December,
>and since then I've found the time to spend maybe two or three hours
>on the features that *I* want.

Understood, hence my mention of a machine.

I'm hoping to shake some funds loose for Bounty Source --- an estimate on what should be offered?

William

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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

JordanBrown
In reply to this post by OpenSCAD mailing list-2
On 8/15/2020 5:59 PM, William F. Adams wrote:
Jordan Brown wrote:

>What does your input OpenSCAD look like, that emits proto-gcode?  I don't see that in any of the pages you've posted.

I posted my source code at:



Interesting.  So pretty much you have two programs interlaced - once that models a 3D object, and one that emits a toolpath, and they don't really have much to do with each other except for sharing some dimensions.

The shape of your fingercuts is a cool workaround for the round shape of the tool.

>I'd like to figure out how to drive my CNC machine from an OpenSCAD model...
>so far, I'm not seeing how, other than some tool chains that seem fragile, unpleasant, or both.

This is just a proof of concept so far, but I think it shows progress.

Just to review --- which CAM options have you looked at or considered? Thus far I've tried or worked with:

 - export STL --- process in a 3D CAM tool such as MeshCAM or pyCAM

This is what I was looking for.

Last time I looked - don't remember exactly when, but a long time ago - pyCAM seemed to be abandonware.  Looks like it may have been revived.

I don't remember whether I tried MeshCAM.  The fact that it's $250 was a big stumbling block.  I'm spoiled by the mostly-free world of 3D printing.  I think the only paid slicer in common usage is Simplify3D, and it's only $149.

I looked at HeeksCAD and played with it a bit.  I seem to remember it crashing a lot.

I looked at Fusion 360.  I don't remember whether it would import STL, but it was very slow and I think I had a hard time understanding how to use it.

 - export DXF or SVG --- process using a tool such as MakerCAM or Carbide Create

Only marginally interested.  I want to model in 3D, not 2D with a fixed depth for each shape.  (Maybe that's an unrealistic thing to want.)

The toolchain should be able to do something useful with a half-sphere:
intersection() {
    sphere(20);
    translate([-100,-100,0]) cube([200,200,200]);
}

And maybe that demonstrates my naïvety; tool head geometry might preclude doing that because unless the bit is more than 20mm long the tool head might hit the sphere getting to the edges.


Tools like Carbide Create are commonly called 2.5D, but if I understand them correctly I think that I'd only give them 2.2D.  The device is fundamentally limited in that it can only cut down (and so there cannot be *any* overhangs of any kind), but it's perfectly capable of cutting slopes.  Carbide Create and the ilk basically have you draw out something in 2D and then specify a depth for each shape; they don't seem to have any notion of slope.


Maybe I should get over it, treat the CNC as a 2D device - basically, a cutter - with very limited 3D capabilities, rather than wanting it to be the subtractive equivalent of a 3D printer.



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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

RobWLakes
In reply to this post by JordanBrown
Wouldn't this require a post OpenSCAD package that operates on .STL files to drive a milling machine, somewhat of the complexity of a slicer eg Cura for 3D printers?

Otherwise if you are working from pure logical shape identities, why use OpenSCAD in the first place? It almost immediately makes extracting coordinates of shapes impossible or very convoluted.

It seems the answer to this is more than adding a filter to an output debugging stream into a new file format. Especially if a more generalised milling capability than the example given is required. If people designed their models in STL with the same caution as they do for 3D printing (eg resolution, overhangs, speeds, temperatures, etc etc) then it should possible to program a post STL processor that could prepare GCODE files for CAM that can work.

Personally I would find this a very attractive proposition, and useful to extend my (basic) OpenSCAD skills into this area. Cura began with just one line of code at sometime. But it certainly has grown full of useful features.
Cheers, RobW

On 16 August 2020 10:48:35 am AEST, Jordan Brown <[hidden email]> wrote:
What does your input OpenSCAD look like, that emits proto-gcode?  I don't see that in any of the pages you've posted.

I'd like to figure out how to drive my CNC machine from an OpenSCAD model... so far, I'm not seeing how, other than some tool chains that seem fragile, unpleasant, or both.



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Victoria, Australia
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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

JordanBrown
In reply to this post by OpenSCAD mailing list-2
$&#@*(.  I hate mailing lists that set Reply-To to the list.  I meant that to be a private message; that's why I hit "Reply" instead of "Reply All".

On 8/15/2020 6:36 PM, William F. Adams via Discuss wrote:
>but ... I got OpenSCAD to build successfully in December,
>and since then I've found the time to spend maybe two or three hours
>on the features that *I* want.

Understood, hence my mention of a machine.

I have a machine.  Just no time.  I should make some time for some of this stuff; quarantine has freed up a bunch.

SainSmart 3018-PRO
https://www.sainsmart.com/collections/genmitsu-cnc/products/sainsmart-genmitsu-cnc-router-3018-pro-diy-kit

It was $200 on Woot.  That was within my "try it for fun" budget.  I just wish it had limit switches.

I'm hoping to shake some funds loose for Bounty Source --- an estimate on what should be offered?

Not a clue.  For me, personally, unless it was a ridiculously large amount it wouldn't be a factor.  My day job pays enough to keep me in toys.  Spare-time projects are for fun.  Offering me $50 or $100 wouldn't get my attention at all, and I don't think you want to offer $1000.

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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

OpenSCAD mailing list-2
In reply to this post by RobWLakes
Jordan Brown wrote:

>Interesting.  So pretty much you have two programs interlaced -
>once that models a 3D object, and one that emits a toolpath,
>and they don't really have much to do with each other except for
>sharing some dimensions.

I'd describe it rather as a program which shows cutting out parts which has options to show said parts in various positions and to write out the G-Code (and some extra stuff which needs to be deleted).

>The shape of your fingercuts is a cool workaround for the round shape of the tool.

Thanks! I've been working on this for a while now.

<big snip>


>I want to model in 3D, not 2D with a fixed depth for each shape.  (Maybe that's an unrealistic thing to want.)

I think that's a fine thing to want --- there's no reason it couldn't be done using the technique I'm showing you'd just have to model the movement of the tool in 3 dimensions --- hopefully I'll learn enough math to make that happen presently.

>The toolchain should be able to do something useful with a half-sphere:
intersection() {
    sphere(20);
    translate([-100,-100,0]) cube([200,200,200]);
}
>And maybe that demonstrates my naïvety; tool head geometry might preclude doing that because unless the bit is more than 20mm >long the tool head might hit the sphere getting to the edges.

It should be possible to do a ball-nosed endmill traveling over the surface of the hemisphere to shape it, then have a square endmill do a waterline path around the lower perimeter of it to cut that out.

>Tools like Carbide Create are commonly called 2.5D,
>but if I understand them correctly I think that I'd only give them 2.2D. 
>The device is fundamentally limited in that it can only cut down
>(and so there cannot be *any* overhangs of any kind),
>but it's perfectly capable of cutting slopes. 

That's 2.5D described as a limitation over full 3D.

>Carbide Create and the ilk basically have you draw out something in 2D
>and then specify a depth for each shape; they don't seem to have any notion of slope.

Mostly. One can do V carving and textures --- I even did a joinery design abusing the Advanced V carving feature in Carbide Create.

>Maybe I should get over it, treat the CNC as a 2D device -
>basically, a cutter - with very limited 3D capabilities,
>rather than wanting it to be the subtractive equivalent of a 3D printer.

There's always directly programming in G-Code --- with tools such as G-Sharp it might be workable:

https://github.com/NRSoft/GSharp

and there are more listed at: https://wiki.shapeoko.com/index.php/Programming


And Rob Ward wrote:

>Wouldn't this require a post OpenSCAD package that operates
>on .STL files to drive a milling machine, somewhat of the complexity of a slicer eg Cura for 3D printers?

No, please see my code from my previous messages --- basically rather than modeling the shape, one models the stock and carves away from it using tool-shaped geometry and one captures the tool movement as G-Code.

>Otherwise if you are working from pure logical shape identities,
>why use OpenSCAD in the first place? It almost immediately
>makes extracting coordinates of shapes impossible or very convoluted.

I'm not, and I'm using OpenSCAD because it has a neat front-end in 

https://www.blockscad3d.com/

and I've pretty much managed to solve extracting the coordinates.

<snip description of something more complex than what I envision>

I will note that if one modeled a tool such as:

https://www.amazon.com/gp/product/B07XG6MTMH

or a ball cutter on a narrow shaft one could do undercuts.

>Personally I would find this a very attractive proposition,
>and useful to extend my (basic) OpenSCAD skills into this area.

Thanks! --- I'd be curious what you think of my code or my discussion of this at: https://community.carbide3d.com/t/cnc-finger-joint-box/8880/126

I'll take Jordan's hemisphere description and see if I can make that into a test cut file to cut tomorrow.

I also need to make some test cuts for kerf bending plywood --- since I don't want to go through the tedium of faking it out in Carbide Create directly coding this in OpenSCAD is attractive.

William


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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

JordanBrown
On 8/15/2020 7:30 PM, William F. Adams via Discuss wrote:

I want to model in 3D, not 2D with a fixed depth for each shape.  (Maybe that's an unrealistic thing to want.)
I think that's a fine thing to want --- there's no reason it couldn't be done using the technique I'm showing you'd just have to model the movement of the tool in 3 dimensions --- hopefully I'll learn enough math to make that happen presently.

Generating the gcode in the general case is roughly equivalent to the problem of generating gcode for a 3D printer - what a slicer does.  There's an awful lot of calculation there.

The toolchain should be able to do something useful with a half-sphere:
intersection() {
    sphere(20);
    translate([-100,-100,0]) cube([200,200,200]);
}
And maybe that demonstrates my naïvety; tool head geometry might preclude doing that because unless the bit is more than 20mm long the tool head might hit the sphere getting to the edges.

It should be possible to do a ball-nosed endmill traveling over the surface of the hemisphere to shape it, then have a square endmill do a waterline path around the lower perimeter of it to cut that out.

I was thinking of the fact that the tool head - the thing that holds the bit - is quite a bit larger than the bit itself, and on a near-vertical surface with a bit that's shorter than the object being carved there's a risk that the head will hit the piece.

And Rob Ward wrote:

>Wouldn't this require a post OpenSCAD package that operates
>on .STL files to drive a milling machine, somewhat of the complexity of a slicer eg Cura for 3D printers?

No, please see my code from my previous messages --- basically rather than modeling the shape, one models the stock and carves away from it using tool-shaped geometry and one captures the tool movement as G-Code.

Another way to look at it is that you're specifying the tool path, and building a parallel OpenSCAD model of the tool path.

That's an interesting way to look at it - totally upside-down from how I normally think about modeling.  Normally I think about the shape of the object and the toolpath is largely the slicer's problem.

I will note that if one modeled a tool such as:


or a ball cutter on a narrow shaft one could do undercuts.

The fact that tool head shape matters is part of what makes my head hurt when I think about general CNC.


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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

mondo
In reply to this post by JordanBrown

The free version is fine for wood, with the correct cutter. I use it for all the stuff I do with panel type stl files. There are ways of overcoming the apparent lack of roughing with the free version. It has quite a nice tool profile set up. But, like most things, It'll take a bit of effort before you are happy with the results, so if you are interested be prepared for breaking a few tools, damaging the machine bed, ruining material on the way.

a small oomph machine is fine, just take lighter cuts, and do work suited to the machine, like milling pcb's, model making and so on.

On 16/08/2020 05:39, Jordan Brown wrote:
Playing with DeskProto.

Pretty cool, though it seems like the Free edition is too limited for real use, because it doesn't have the multi-layer "Roughing" process.  If you ask it to cut an STL, it tries to do it in one shot, which only works if it's really thin or your machine has a lot of oomph.[*]
[*] "oomph" is a technical term.
But the "entry" edition might be OK, and a $250 the hobbyist version of the multi-axis edition is competitive with the other paid desktop CNC programs.  (It's still more than I really want to spend.)

How much I want to spend is largely driven by projects - it's not that $250 is a huge amount in an absolute sense, but so far my CNC has all been in the nature of "so what's CNC like?" rather than having any actual projects that I want to do.

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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

mondo

Oh, and if sign making may be a thing for you, then the guy at http://www.scorchworks.com/ has some very useful software, written in Python, so you can fiddle with it yourself. I've attached an image of a lump of wood, gcode generated by scorche's software, and cut with a 60 deg trend router bit (dragon.jpg) and the other .jpg  gcode was generated by the free desk proto, using the tapered cutter I referred to earlier, with 0.25mm radius ball end, using about 0.35mm stepover- it took a while. but unlike 3d printing, it rarely fails in the middle of a job. A lighter machine would use a smaller cutter, and may need two or more passes. You can fake that by offsetting the z axis, or run it with a larger diameter tool before doing the final cut. You need to try it and see. A useful source of free stl files for this sort of thing is sketchfab, a number of museum artefacts are being digitised. You may need to pass them through meshlab, to straighten them out, and find the errors.

For less 'arty' stuff, then I often write the raw g.code, over the years I've written code to programmatically generate flanges, hole patterns, whatever, or import dxf to deskcnc. Other than machine set up, there are only a few commands you need to know. You can try deskcnc for 30 days or so for free. I may be able to offer a licence key at a reduced price, (the price in 2014 was 135.00 gbp, with v2 controller and cables 230.00gbp) I could contact the author, if requested. (there is a free dos version, somewhere, but that is way beyond its sell by date), but it comes into its  own with its specific cnc controller.



On 16/08/2020 12:34, Ray West wrote:

The free version is fine for wood, with the correct cutter. I use it for all the stuff I do with panel type stl files. There are ways of overcoming the apparent lack of roughing with the free version. It has quite a nice tool profile set up. But, like most things, It'll take a bit of effort before you are happy with the results, so if you are interested be prepared for breaking a few tools, damaging the machine bed, ruining material on the way.

a small oomph machine is fine, just take lighter cuts, and do work suited to the machine, like milling pcb's, model making and so on.

On 16/08/2020 05:39, Jordan Brown wrote:
Playing with DeskProto.

Pretty cool, though it seems like the Free edition is too limited for real use, because it doesn't have the multi-layer "Roughing" process.  If you ask it to cut an STL, it tries to do it in one shot, which only works if it's really thin or your machine has a lot of oomph.[*]
[*] "oomph" is a technical term.
But the "entry" edition might be OK, and a $250 the hobbyist version of the multi-axis edition is competitive with the other paid desktop CNC programs.  (It's still more than I really want to spend.)

How much I want to spend is largely driven by projects - it's not that $250 is a huge amount in an absolute sense, but so far my CNC has all been in the nature of "so what's CNC like?" rather than having any actual projects that I want to do.

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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

OpenSCAD mailing list-2
Well, the longitudinal hemisphere cuts work:

Capture.PNG

Except performance begins to really bog down.

I'll try switching to my MacBook and OpenSCAD to finish this off --- is there any prospect of performance in OpenSCAD improving?

William



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Re: Is there an OpenSCAD dev who wants a CNC machine? (was Re: Managed to model a finger joint box with relieved fingers --- now how to actually cut it? Allow OpenSCAD to write out files?)

OpenSCAD mailing list-2
Performance was much better in BlockSCAD on the MacBook (though I got a warning about excessive RAM usage in Safari).


Unfortunately things bogged down again in OpenSCAD after I exported the code, and even when I manually reduced the number of passes to get a rendering things look rather rough.


Suggestions on improving the performance of:


(see attached)

would be welcome.

William


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