An exercise in delayed gratification

Waiting for parts sucks.

The only consolation I have about getting older and supposedly wiser, is being able to see ahead of time the things I need to do to prepare.  As well as knowing that I need to get them done if I actually want to feel successful when my parts DO arrive.  In this case, I needed to build a place for the CNC to live, because a 1000mm x 1000mm CNC machine wasn’t going to live on any surface I currently had.  This meant I needed to create a table.  I had just created a printer hutch over Labour Day weekend, so I had materials and experience from that to guide me in building the table.  However there was one other thing that I discovered from that build that I would need first.  With all the sanding involved I was using a shop vac to keep the dust under control.  A good amount of fine dust like you get from sanding can clog a vac quickly.  I needed a dust separator.  I saw one on Rockler for $79, but I thought I could build one cheaper and quicker.  Remember what I said about being “supposedly wiser”?  Yeah, this isn’t one of those instances.  While it did cost less in terms of cash, it didn’t cost less in terms of time and design changes needed in order to make it work.

IMG_20140914_185538085_HDRI chose to build it from two 5 gallon buckets, with the dust cone separator in the top, and the dust collection in the bottom bucket.  A dust separator works by using a cone to spin the dust laden air around enough that the momentum of the dust carries it into the collection at the bottom while the air is sucked up at a 90 degree angle.  There usually is a small amount of fine dust left in the air, but it should be significantly less.

I had to find a cone.  I racked my brain to find a cone I could hack into this purpose, and only after 8 months did I see that someone is using a traffic cone as the cone.  That’s pretty clever, but since I couldn’t think of that, I decided to create one out of sheet metal.  I need a template for a flat-topped cone, and a Google search later I had a calculator that helped me figure out the size of sheet metal to buy.  I found it here.  I needed to create a compass large enough to trace out the radius of circle I needed to cut.  I used a segment of a long strip of plastic, screwed into a board.  I notched the sheet metal where the halfway mark was, so it could sit up against the screw.  Then I drilled holes in the strip at the points I needed to draw.



I figured out later that I could use a binder clip and stick the pen/pencil through the clip, but at this point the problem was solved.   It’ll come in handy in the future.


Cutting sheet metal leaves murderously sharp edges, which is why I highly recommend gloves when handling.

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The top bucket needs to be fastened to the lid of the bottom bucket, but also needs to be sealed.  As anyone who has messed with HDPE will tell you, it sucks if you have to glue it.  Mechanical fasteners or heat welding it are the only two options.  In the case of the cone, it could only be fastened mechanically, which is something I planned on.  To attach the lid of the bottom bucket to the top bucket, I used screws and spacers.  IMG_20140920_131114397IMG_20140920_131139182

The seal was the tricky bit.  You can see here that I started with weather stripping.  Unfortunately, this didn’t last.  While nice and flexible to fit in the crack, it also was too flexible and so it pulled into the space too easily, leaving a gap.  I solved this by using silicone.  I gooped enough onto the joint that it forms a permanent placed gasket.  While it isn’t perfect, it will suck down into the gap whenever the vacuum is used.


One final design problem remained: how to keep the bottom bucket from buckling in when the vacuum is on.  I looked online and found a few people with the same problem and a solution: cut a small disk that fits about half way down.

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The finished product.

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Finally, there’s the problem of keeping the shop vac and the separator together.  This was solved by a bit of spare lumber I had sitting around, worked into a small cart that I could bungee the separator and the vac to.


Next post, I’ll detail the build of the table.


Research, research, research.

August, 2014.

The failed cut I tried by hand helped me understand just what I was attempting to do, and why a CNC could do it many times better than I ever could.  Not only would I get accuracy, I would also get repeatability as I go to cut multiple copies of something. I would also get cleaner cuts, as it would cut layers rather than the whole thickness all in one go.  So now the question was, how do I go about getting one?  I had a bonus from my company in August, of which I could use $900 for a machine.  I needed to do research.  Luckily, I have five friends that could help me, as they all have CNC experience.  Four of them I met at Solid State Depot, where I’m a member.

I started looking at designs: ones I could build out of MDF/Plywood, ones I could buy the parts for, and ones that were kits.  My friend Kevin helped me decide to go with a kit when he mentioned that my goal was to cut projects with the CNC rather than the CNC being the project itself.  My objectives were:

  • Needed to cut at least a 20″ x 30″ area, larger would be nicer.  This meant a minimum of 1000mm x 1000mm if I were to go the shapeoko route.
  • Needed to be somewhat quiet, i.e. not using a dremel tool.  My son’s room is right above where I’ll be cutting, and I don’t need it waking him up.  This meant a quiet cut spindle.
  • I wanted to use LinuxCNC instead of the GRBL setup that the stock shapeoko came with.  I was influenced in this decision by my friends at the hackerspace (one of which is a maintainer of LinuxCNC).  This meant a different controller board than the Arduino and motor shield that the stock shapeoko comes with.
  • I wanted it to be quick to assemble, as I wanted to get cutting with it right away.

I decided to do some research to find out if I could build the kit myself.  I made myself sick with research.  I finally came to the conclusion that the Shapeoko 2 kit was the best combo of convenience and cost, that I should go that route.  However, before I spent the money on the full “the works” kit, I asked my friends what they thought.  Most of them have gone the route of buying the mechanical kit instead of the full, and filling in with the parts they wanted rather than what comes stock.  An example would be the motors:  the stock shapeoko 2 comes with NEMA 17 motors, and they instead used NEMA 23 motors.  Another example is the controller: stock uses GRBL on an Arduino, and they use a parallel port optoisolator card with Pololu 8825 drivers, hooked to a PC running LinuxCNC.

I was ambivalent; on one side, I would have more work sourcing parts, but would get what I wanted ultimately, and cheaper than buying the kit which I would then have to upgrade.  On the other side, if I bought the Shapeoko 2 kit, it would be much quicker to get up and running, but I would have to upgrade it at significant cost.  My decision was made easier by Sparkfun throwing a moving sale where I was able to purchase the NEMA 23 motors at about half the regular cost.  At this point I remembered thinking to myself that with a deal like that on motors, I might as well try the blended approach rather than the kit, because then I would get what I really wanted.  I had friends that had done this approach, so I wasn’t wading into alligator infested waters.  Well OK – I was – but I wasn’t alone.

The sale at Sparkfun was on August 25th, 2014, and kicked off a buying spree to get all of the other components.  The research I had done was extremely helpful, and allowed me to buy a good many of the parts at great prices.  As for timelines,  I had to be realistic.  I wouldn’t get all of the parts until somewhere mid-September.  But I wanted so much to have it done, at least by mid-November.