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  #11  
Old 11-19-2015, 08:13 PM
boatbuilder2020 boatbuilder2020 is offline
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Mike,

Regarding that specific arm:

Just a thought/suggestion . . . think beyond design to how you might machine it, whether or not you could (or would want to) cnc machine it completely (to include mortises) and what would your expectations be specific to post cnc work (rasps, spokeshaves, etc.).
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  #12  
Old 11-19-2015, 08:26 PM
mike.davison mike.davison is offline
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Paul,

Ah, yes, it's good to back up and consider the goal. This is my very loose thinking:

It would be best if the part coming off the CNC machine is in need of minimal sanding and not much else. It would be good to avoid hand shaping. I would even say that's the goal of this effort. Do the shaping on the computer screen rather than by hand.

The joinery might be easier to do with floating tenons. using appropriate, custom jigs, rather than trying to do that on the CNC machine. Mill the surfaces ready for mortises to be cut and use floating tenons.

Where my thinking is right now. Likely to change as I learn what I'm doing.
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  #13  
Old 11-19-2015, 11:39 PM
boatbuilder2020 boatbuilder2020 is offline
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Thx. Mike.

Including the mortises would have been a fun challenge for sure!

I believe you picked a good example of a part that presents some interesting workholding challenges but also might be pushing the limits if you're looking for minimal post-cnc work. Ideally, I'd want to machine it 2-sides . . . top and bottom. Doing it that way would give your tooling a good angle of attack (and good finish off the machine) but I'm guessing this part may be too tall (z travel). If so, you'd have machine going the other direction. When doing that, the nice subtle fairly flatish curves of the top and bottom become nearly vertical making a smooth finish tough if not impossible. Not crazy bad but would require some extra work. And depending upon the wood type, maybe something a little stronger than sandpaper. Good news though is if you can live with some clean-up, it's doable in Aspire . . . just need to create models for each half. A couple centerline extrusions would probably do it . . . create complete cross sections, split em and use ea. for it's respective half.
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  #14  
Old 11-20-2015, 12:42 AM
mike.davison mike.davison is offline
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Well, Paul, this has been an educational journey. Interesting for a randomly chosen chair. :-)

I understand your description of how the arm is too tall to mill the top and bottom and that milling from the sides would make it harder to to get near-finished surfaces from the cnc milling process. Perhaps still ok, just more than light sanding.

I wonder if this is a case where the cnc machine would be best used to create accurate jigs to be used on a shaper to actually cut the arm. Maybe. Another approach to consider.

Huh. Well, thanks for the insight. Lots to consider.
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  #15  
Old 11-20-2015, 09:31 AM
boatbuilder2020 boatbuilder2020 is offline
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Didn't mean to talk you away from your Stinger. Here's a tool path preview of what I was talking about. Not bad and the model is fairly easy to make although might take some trial and error getting it the way you want it. Cool thing about working with software . . . no wasted wood!

Have a great weekend.
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File Type: jpg lrez quick arm example.jpg (24.6 KB, 39 views)
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  #16  
Old 11-20-2015, 02:03 PM
mike.davison mike.davison is offline
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The shift in design strategy, especially the higher reliance on software, is both an interesting journey and a frustrating one. It's pretty clear that one needs a short list of software that is useful (to oneself and the specific processes desired) and then to, as you say, put the blinders on, and learn how to use that software. The trick, I think, is coming up with a good 'short list' as the cost in dollars and time could be overwhelming without some focus. All obvious to the experienced folk, I know.

Aspire and Sketchup on that list. Thankfully, I already know my way around Sketchup pretty well. Beyond those tools I think a 3D modeling and/or CAD program is needed. Silo looks useful. Rhino or Solidworks are obviously useful (and expensive).

Thanks for the quick Aspire example for that chair arm. I'm curious how you did it. Is this a 2 rail sweep, viewed from the arm edge? If so, can you vary the arm width? Some other method?

Thanks. Enjoy the weekend.
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  #17  
Old 11-20-2015, 03:02 PM
CosmosK CosmosK is offline
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I’ll just throw my 2 cents and experience in. My history: been a design engineer for over a decade. I’ve used Pro-E, Solidworks, and Catia in my jobs. The first two are great. I’m now starting my own business and just got ADSK Inventor. I need a parametric CAD program for the type of things I design (assemblies, moving mechanisms). I bought Inventor mostly because it’s one of the major programs, but specifically because they still sell perpetual licenses (until Jan 16). All the others are either subscription based or mandatory maintenance. So, I dropped 5k, but hopefully can go in my cave and not have to worry about design software for many years to come. It’s not quite as user friendly as SW, but has some redeeming qualities of its own. I also looked at Geomagic and some others, but in the end did not want to be frustrated after being used to working in the more established packages and I have no interest in the cloud based programs. For CAM, I use Vcarve (I do basically zero design in VCP). I typically export 2D dfx and go from there. I haven’t gotten into 3D yet. With Inventor, you can get free HSM express for CAM, which seems to do basic CAM like Cut 2D, but I haven’t used it yet.

Aspire I’ll probably get someday. Seems to be great, but is a different ball of wax. It’s geared for carving and sign making. It can do some things easily that would take you forever in the traditional CAD programs (and you’d need expert skills).

Learning curve on the parametric CAD isn’t that bad. If you sit down for a solid couple days, you’ll be up and running. And, once you learn one, the same ideas are used by all of them (create solid based on 2D sketch, cut from solids with 2D sketch, fillet, chamfer, fancy things like sweeps and lofts). It really depends on what type projects you’re going to do. I don’t do a lot of complex curvature stuff so can’t give more specific advice on that.
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  #18  
Old 11-20-2015, 05:13 PM
boatbuilder2020 boatbuilder2020 is offline
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Mike,

It's a single "rail" with 3 profiles/cross sections. It was intended to be a rough estimation of 1/2 of the arm (the outside half). I think the complete approach I'd try would be:

Create 1 rail (which would run a long the centerline of the arm). Initially create complete profiles/cross sections . . . not 2 halves. Make a copy so you have two sets then trim and rotate as needed to make one set for the model for the outside half of the arm and one set for the model of the inside half of the arm. I'd do it all in one file. On a related note . . . if you were to do this in one file, you'd need to make sure that you never have both models turned on at the same time when creating tool paths and/or recalculating toolpaths.
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  #19  
Old 11-20-2015, 06:35 PM
johnb johnb is offline
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A short list would be nice now that I'm on my own. Ive modeled and progammed cnc for 20 years as a day job in auto motive tooling , even in that industry with a huge budget we ended up with several software prog rams to model in and program in. Due to limiting factors of each.

As part of a big company I sampled all the cnc packages a while back and as a small business I've searched again. Tough when your paying the bill yourself. What I've learned is all purpose is tough. Aspire is the best low end general solution for the money to do 3d 2d modeling and programming. I'm not sure what the best solution is one step up from there.

Things seem to get specific based on what you do.

Could never program in aspire like we did in the tooling industry. It would never work
Automotive software very difficult or impossible to do 3d sculpting like that's in aspire
Wouldn't want to do kitchens in either of the above software's.
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  #20  
Old 11-24-2015, 09:15 AM
Ger21 Ger21 is offline
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You might want to look at Autodesk's Fusion 360. It's currently free to hobbyists and most small businesses, and even the paid version is fairly inexpensive ($25/month). It's a very powerful 3D CAD/CAM package. It also has a very good renderer, and the latest update added V Carving capabilities.
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