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CNC-2116 - Up and running, sort of (2015-03-21)
Yvan256:
The bottom plate of the Z axis assembly is done. There's a notch in the corner because I'm still not using milling tabs to hold the part when cutting and I was away when the MDX-3 was done cutting. :-[
You can see the top and bottom panel in the photos below. The bottom plate has half-depth holes for the 8 mm rods just so they won't fall down when the machine is working, although they would probably hold in place by friction alone. I didn't take the picture with the rods in place because I need to cut them to the proper length.
I'm still missing the three vertical panels that will go between them, I should be able to start cutting those tomorrow.
The MDX-3 is currently busy cutting a long panel with tabs for the X-axis assembly, I'm hoping it will be done before bedtime...
Yvan256:
One of the four long panels with tabs is now done, but I was getting tired of looking at this MDF-colored assembly... boring. :P
Since the little Hang-On Shop Vac is red and black and the Black & Decker RTX is also red and black, I started painting the panels. I've decided the panels with their face visible from the side would be red and the panels with their face visible from the front, top or bottom would be black.
I've also decided to paint the side of the parts the same color as the panel itself instead of the face of the joined panel to get an interesting effect, to show off the assembly method of the whole machine instead of trying to hide it (i.e. the tabs will show up in black through the panels).
And here are the results so far. It looks better in real life than in those photos, I guess the close-ups really magnify the defects and the texture of the MDF.
For reference, the paint used is Crafter's Acrylic from DecoArt, Bright Red DCA22 and Black DCA47. I'll be applying two or three coats of gloss varnish DS13 after two coats of paint. In those photos, the red panel has two coats of paint and the black panels only one.
Photo 1 shows the left side of the X-axis assembly so far, upside-down to be able to take the picture.
Photos 1, 2 and 3 shows the "interesting effect" I was talking about, showing off the assembly method (tabs are in black) instead of trying to hide it by having all the side red.
Photos 3 and 4 show the bolt+washers+nut assembly method discussed in a previous post, from both sides. Since the MDX-3 can only cut perpendicular to the panel itself, I need to carefully drill the holes for the bolts, manually.
Photo 5 shows, once again, a close-up of the home-made fuel line coupler that attaches the motor shaft to the threaded rod.
Yvan256:
Some parts require manual drilling on the edge of the panel. Messing up one of those hole would mean re-cutting a part and wasting another 4 to 12 hours of CNC time depending on the size of the panel. Some panels have zero holes to drill manually but others may have four or more, that increases the chance of messing up when doing things manually.
So right now the MDX-3 is currently busy cutting a drilling jig to make sure all my manual drilling is spot-on, every time. First image is the design in Sketchup, with the four panels to cut in the back, the complete drilling jig in the middle and the jig without the top panel on the right to see how it will lock in place for the panels with tabs. The big round hole in the middle of the two top panels is for a drill bushing insert (Lee Valley Tools Item 25K6220). The first photo is the MDX-3 cutting those four panels.
edit: the MDX-3 is done cutting all the holes in the four panels and is now starting to cut the outlines.
Progress on the Z-axis assembly. I still need to cut the back panel and the panel that will actually move the RTX up and down. The second photo shows what it looks like so far with the panels held in place by gravity, until my drilling jig is complete. I still need to apply varnish for the final touch.
Yvan256:
Just to recap things since I've joined BYOAC, I'm building a CNC machine to be able to cut parts for my arcade projects.
But I need to apologize to everyone who reads my threads.
My MVS-99-6 and ColeCade projects have been on hold practically forever.
My CNC256 project is taking forever to properly start and my perfectionism means I keep starting over. Since these are personal projects I can allow myself to aim for perfection. There is no set deadline, no launch date to meet and no budget to speak of except my own spare time.
Having the MDX-3 to cut parts, however, is helping me to concentrate on the designs in Sketchup and have perfectly cut parts on my desk a few many hours later. This was the missing tool in my process.
But... the MDX-3 is old and was probably never designed to cut MDF with a 1/8" end mill bit, so the panels are taking forever to cut. What should be a 15-20 minutes job is taking 6-8 hours.
So I decided to make "CNC64", a smaller machine with the same cutting envelope as the MDX-3 so that I don't have to trash the 100+ small MDF panels that I have.
And since CNC64 will only be built using panels as big as it can cut, I guess it could become the "reprap" of the CNC world. I guess I'll build a second CNC64 with the first one just to prove the concept and to see how long it takes for it to "replicate" itself.
The smaller CNC64 will require fewer panels (current count is only 37 CNC-cut panel) and a simple rectangular table saw/hand cut base with not much precision required and thus will be ready in a much shorter time than CNC256. Without counting the base and without optimization of cutting multiple smaller parts on a single 6x4" panel, the MDF cost is currently around 8$CAD for one CNC64 machine. That's without counting the machining or design time, however. ;D
It also means I can practice some design ideas on a smaller scale and in the end I will have two faster machines to cut more panels at the same time, if needed. At the very least it will give me a more portable machine for when I only need to cut smaller panels.
Back to the topic of my previous post, the two side panels of the drilling jig would have required a drilling jig to make precise holes. The first hole I drilled on the side wasn't exactly centered and the second hole just split open the MDF because I tried to drill too fast. :angry:
I also messed up the two side panels of the Z-axis assembly, once assembled the whole assembly wasn't even level. Not a good start for a CNC machine. :o
So, from all this came a new joint method. The method I showed earlier is based on the joint method used by the first version of diylilcnc but since 3/8" MDF is a much thicker material I decided to combine the tab and the bolt coupling in a single, compact part with no post-machining drilling to do. Take the panels, join them, bolt them. The only way I can mess that up is by doing a mistake in the Sketchup design.
In the five photos below you can see that each joint requires six parts:
* A tab with a channel for the bolt and a hole for the nut and washer
* A hole for the tab and a hole for the bolt
* A bolt
* A nut
* Two washers (to make sure that the MDF doesn't get twisted and ripped apart while tightening the bolt)
The channel for the bolt is not cut all the way through, so there is an "inside" and "outside" for the panel. I'm doing it this way for two reasons:
* It looks cleaner from outside
* It makes a stronger joint because there is more material for the washer and nut to sit on.
For reference, the small test assembly shown in the last photo is only 30 mm wide (left to right), 20 mm deep (front to back) and 30 mm tall (bottom to top, without the bolt head). The tab itself is 15 mm wide and 3 mm tall but I'm switching to 5 mm tall for the final parts for an even stronger joint. This means the tab inserts more or less 50% into the thickness of the other panel (I measured the thickness of the MDF a around 9.7 mm).
I'm calling this joint "100% CNC-Cut Compact Joint", or "100CNCCCJ" for short.
... okay, I need a better acronym, not to mention that it probably already exists and already has a name.
Hopefully, CNC64 won't take too long to build, then CNC256 and then I will finally be back to posting about arcade projects!
mcseforsale:
Cool...a place for your nuts!
Love the build so far.
AJ
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