New to cnc, looking for CAD/CAM advice

[dixdance]

I'm just getting into cnc, want to use it for complicated pearl inlay work. I've been working with Fusion360 (the price is great - free) but I don't need all the 3D features and complexity, 2-1/2D is all I anticipate doing.

I'm wondering what people are using? Is there software that is particularly suited for cutting inlays and pockets, and not too expensive? I do my designs in Illustrator, took a while to get comfortable with, but now I enjoy drawing with vectors. My machine is an old Techno Davinci, may need to upgrade the controlller.

[amowry]

I use Rhino 3D and Rhinocam, and they're great. More user-friendly than Illustrator, IMHO. Expensive, unfortunately. There may be something less expensive that can convert Illustrator drawings to g code.

[Marty Jacobson]

Rhino3d and Rhinocam do work, they're about the bare minimum I would recommend. The nicest feature in that combo is the automatic tab generation, which allows you to make jigs and fixtures really easily without worrying about fixturing too much. I used that combo for the first year or so, but the lack of parametric functionality means that for every custom part, you have to build a new static model.

Fusion360 uses the HSM CAM engine, which is the same one I use. You can change the thickness of a carved top plate in a spreadsheeet, hit rebuild, and then output your g-code with a new thickness for every individual piece of wood.
$40/month to work with HSM is completely worth it, IMHO. Nothing else even comes close to the ease of use of HSMWorks/Fusion360 CAM.

And I know you may not think that you need complicated CAM software, but in my experience using CNC for making microfluidic devices, microscope parts, medical devices, and inlay for lutherie, the lutherie applications are the most complicated. So use the best CAM package you can get your hands on. HSMWorks was $10,000 a couple years ago when I started using it and teaching it. $40/month is a steal.

For example, to make an inlaid fretboard, you need to make the inlay pieces, the fretboard itself, and then you have to profile the fretboard. Then you have to cut fret slots. That requires either separate models (or separate layers) for each stage of the process, or in a a parametric model, you can just choose which state of the model to use for which CAM operation. Much less headache-inducing.

I can't think of a reason why you'd need to upgrade your CNC controller, unless it is malfunctioning or frustrating to use. With the right post, a modern CAM package effectively works as an upgrade for your controller. There's nothing new about how the motors get to the coordinates, all the new fancy optimizations are done by the CAM software to make motion smoother, etc. by choosing more intelligent routes and linking.

[CarlM]

Illustrator is not really suitable for creating geometry for CAM. You really need a CAD package. I have spent a fair amount of time cleaning up geometry from industrial design packages, some more sophisticated than Illustrator. Usually what happens is that it exports and translates as a lot of little pieced up geometry, splines and slivers that has to be fixed and connected before a CAM package will program it.

Of course for 2D stuff it is not all that difficult to learn the M and G codes and program the stuff manually. Did a fair amount of that in the days before computer aided design came along. The CAM packages are essentially though if you do things like plate carving or necks.

[dixdance]

Thanks for the replies, very informative. I'm a retired furniture maker, just making banjos now. All the woodworking cnc guys I know use Rhino, seems popular in that sphere. I have a banjo maker friend who uses it, but he grew up with it in his dad's shop. He also does his drawing in it.

I started with Fusion because it was free and I didn't want to invest anymore until I was sure cnc would work out for me. And I'm sure that if I get comfortable with it I'll find all sorts of applications, that's how I justify all the time & $$ spent so far.

Carl, I'm not sure I understand what you're saying about Illustrator. I use the pen tool to hand trace jpeg scans, and the curves are a closed path. I try to minimize control points, but there are quite a few. How else can a bunch of intricate curves be represented? I think I'm doing ok in the CAD part, but I'm struggling with the CAM. All the G code I've generated thus far is very jittery, makes the machine shake!

[Marty Jacobson]

Here's one I'm finishing up today. Lines were done in Illustrator, like you said minimizing control points. Circles don't come in nicely and have to be redrawn, but everything else is OK after some minor cleanup. The biggest thing is to make sure you don't have duplicated geometry (lines sitting on top of one another), which can happen with Illustrator sometimes if you use things like Live Trace or Live Paint. But intentionally hand-drawn art exported as DXF and then cleaned up in CAD does work. Drawing directly in CAD is better, but for complicated inlays gets a little time-consuming.
Here's the line work after cleanup:


And the inlay:


If your machine is jerking around, there are a number of things that could cause it. First I'd start with the controller configuration and make sure that the pulse rate and all that are set up properly and that you're not getting any lag from serial interface issues. I use a buffered SmoothStepper and Mach3 to avoid those kinds of things, but if your Techno is set up properly it should be fine.
Jerking can also be caused by excessive single-axis acceleration values. 20 inches per second per second is a safe value which should still allow fast feed rates around tight curves. This is also the acceleration value recommended by Ron Reed who engineers and sells the PreciseBits inlay cutters.
Other than that, setting a smoothing value of about .0005" and approximation values for your geometry of .0005"-.001" will give buttery smooth motion regardless of the complexity.

If none of those work, then your postprocessor is probably not matched to your controller.

[amowry]

The jitter could be caused by controller settings rather than the g-code. Maybe try dialing back the maximum acceleration? I mention it because my machine came with the acceleration and jerk set very high, so it seemed like it was trying to tear itself apart any time it moved

[amowry]

Marty beat me to it

[mirwa]

I have around 6 cnc machines, I think as part of modern luthiery you have to embrace technology and work smarter and more efficient.

I use vectric/aspire, its an all in one package. You can do your initial drawing, you can then turn that drawing into G-code and then it outputs that G-code to suit your machines software.

One of the best, here is a link to some examples of what I have done with it

http://www.mirwa.com.au/Inlay_examples.html

Steve

[Karl Hoyt]

I have a shopbot desktop that came with Vectric (makers of aspire) but the 2d version called V carve. i find it very easy to use and sooner or later I'll upgrade to Aspire to be able to cut Jazz Box and Mandolin tops/backs and other things. With just the 2 d I've cut out rosette channels and. Guitar profiles, inlays, electric guitars/basses, signs, and other wooden parts for cabinets jewelry boxes etc.....it sure beats taking half a day to make a jig to cut a part that takes 3 minutes to cut. I love that little machine . It's built like a tank and the customer support/service is outstanding.

[Marty Jacobson]

Just an update. After playing around with it for an hour or two, I think Fusion 360 is awesome, totally worth the price of admission (free if you make less than $100k/year).
I would recommend that any luthier or woodworker currently using Rhino/etc. switch over immediately. It is much more powerful than anything previously in reach to us lil folk.

Everything shown below was created using the same methodology I would normally use. And generally, the commands were more intuitive than in SolidWorks.

I teach about 400 students a year to use SolidWorks. I am considering switching to Fusion360 based on my experience with it so far.

[goddard]

Marty, would you mind if I asked what general methodology you use to define arched plates? I have a system that more or less works but it's pretty clunky. I've been generating contour lines with a python script and lofting between them. It sounds like you have something way easier figured out.

[Marty Jacobson]

Well, every instrument is different. But in general, you have two options.

First approach:
Break the plate into the center area, which is a simple domed shape. Figuring out the exact shape of the inner domed geometry takes some experimentation. Once you have the inner shape, you can make an elevated perimeter shape which is angled upwards a bit. Then, by lofting between the inner domed shape and the outer drafted edge, you get a recurve.

Or:

[Marty Jacobson]

Second approach:
Break the shape into four or more radial profiles. Loft them with a guide curve around the edge if necessary, though sometimes it's not needed. Offset the resulting surface downwards. Scale the lower surface in the Z axis to result in proper graduations, or repeat the process and create the lower surface from scratch.
Or you can do it all with solids like this, but the methodology is the same.

[amowry]

Thanks for the tip aboit Fusion 360, Marty. I'll have to check it out.

[goddard]

That's very helpful, thank you!

[HoGo]

Hey Marty, how about HW requirements of the Fusion360?
I can run Rhino decently (no fancy rendering) on my rather ordinary laptop with complete F-5 mandolin 3D model.
I can't see many differences from Rhino in your modelling. If you ar emodelling new thing from scratch it is easy to do like you show in RHino, but if your hands are tied and you want to replicate measurements and archings of original with as many crossections as possible, is there any noticeable advantage in HSM?
I never considered real need of parametric modelling of mandolins as there are tyically few options (neck width, arch heigth, grads) that can be adjusted in few minutes once your standard model is done. And RHino is capable (partially) adjusting the surfaces to new shape of curves (if correct procedure for modelling was used in the first place)

[Matt Harris]

If I'm not mistaken Fusion 360 is cloud based, so you are unlikely to have any performance issues.

[Marty Jacobson]

Hey Marty, how about HW requirements of the Fusion360?
I can run Rhino decently (no fancy rendering) on my rather ordinary laptop with complete F-5 mandolin 3D model.
I can't see many differences from Rhino in your modelling. If you ar emodelling new thing from scratch it is easy to do like you show in RHino, but if your hands are tied and you want to replicate measurements and archings of original with as many crossections as possible, is there any noticeable advantage in HSM?
I never considered real need of parametric modelling of mandolins as there are tyically few options (neck width, arch heigth, grads) that can be adjusted in few minutes once your standard model is done. And RHino is capable (partially) adjusting the surfaces to new shape of curves (if correct procedure for modelling was used in the first place)

If you already have a CAD model in Rhino and you don't want to make changes, then sure, your work is done. Focus on building instruments.

If you are trying to do high-detail, tight-tolerance models of surfaces (vintage car, F style mandolin, or whatever) then you definitely want to be using SolidWorks, Fusion, Creo, or similar parametric solid/surface-to-solid design system. You could do it in Rhino, manually moving the control vertices like we used to do in product design fifteen years ago. But modern parametric CAD allows you to apply nondestructive modifiers to surfaces and solids, allowing a very smooth workflow and the generation of multiple configurations. You could have 15 different Loars documented in the same assembly without having to re-create any geometry from scratch.

HSMworks is integrated CAM, so if you are building using CNC, it is essential. The version included in Fusion 360 for free is $10,000 separately. RhinoCAM doesn't hold a candle to its ease of use or toolpath optimization.

I personally vary every single instrument I build, so this is huge for me. I get a sense for a piece of wood, change some numbers in a spreadsheet, and the toolpaths are automatically updated to match my targets for that piece of wood. If I want to make the plate a little thinner after roughing, I can adjust again and post out a single refining operation to get it to my next target. It's basically exactly how most people approach working by hand, but with less arthritis.