As one of CADPRO’s Manufacturing and CAM technical specialists, I was particularly excited about this year’s EMEX, as it was the first year that I’d have simultaneous access to additive and subtractive manufacturing on our stand. For those of you that don’t know, CADPRO are now selling the awesome Markforged 3D printers in New Zealand, which allow you to print incredibly strong parts, at your desk. We also had the great little CNC router from Vertigo Technologies. Designed and Manufactured in Westport New Zealand, with full local technical support, and delivered fully assembled.
While preparing for the show, I thought it would be fun to find something to make on the stand, that would show the capabilities of both technologies. I stumbled across AtFAB and their “Ninety-Minute Lounge Chair” which is made of CNC cut plywood parts, and is locked together with 3D printed keys. It is completely open source, with plans that are free to download. You can read more about it here. The only catch was that the chair, as designed, required sheets of 18mm ply that were 2400mm x 1200mm, and the router’s bed size was 1200 x 600. I figured that I could adjust the dimensions to suit the smaller sheets, and it should still be wide enough for me to sit on. I happen to be of slightly narrower build than most of my colleagues, which meant that I should have a place to sit, that wouldn’t get taken. Win win, or so I thought…. We all ended up spending the entire 3 days on our feet, talking non-stop to over 1600 attendees!
The workflow to prepare the chair for manufacture was fairly straightforward. I opened the AtFAB DXF files in AutoCAD and adjusted the widths of the parts to suit the narrower sheets. I then tweaked the various notches and cutouts to suit. To adjust the notch widths to tighten up the joints (the original design was based on ¾” ply) I scaled the parts by about -3%. I then manually nested the components onto my new sheets and saved out a new DXF cut file. Incidentally, if there were more parts, I would have used the new nesting utility that is part of the Autodesk Product Design and Manufacturing Collection. From there, I imported the DXF into a Fusion 360 sketch, and extruded the parts to a thickness of 18mm to suit the plywood that we had. The parts could then be connected with joints to virtually assemble the chair and check the fit.
With the assembly modelled and checked, it was then simply a case of switching to the CAM workspace in Fusion 360 to toolpath the parts using a combination of 2D Contour and Adaptive clearing. I used multiple stepdowns, with a 45 degree ramp between the Z heights and a feed rate as high as the router would go. I have found that for thicker material, it seems to cut more efficiently using shallower Z steps at a higher feedrate, than deeper and slower.
It was a difficult task to try and run the machine while having conversations at the same time, but by the end of the show, the 8 or so components were complete, and I finally got the chair together and sat on it for a couple of minutes before we had to pack up the stand and head home.
I must have made a mistake in the process, because it turned out that the final assembly of the chair had one part misaligned. Oh well, it was a first attempt. I look forward to having another go at it soon.
If you’d like to know more about any of the technologies used in this article, please get in touch.