My Cubify Cube 2 with SketchUp:  First Cartridge Lessons Learned

by Jay Bowden December, 2013

Got this Cubify Cube 2 for Xmas (daughter Karina wanted one after Maker Fair). 

It kept slamming the glass into the print head when I tried to adjust the Z height, but it printed the Rook example file apparently OK, and kind of impressed me I have to admit! (top edge stones broke off the rook, though, when dropped on our ceramic  tile floor).  A firmware update solved the slamming problem. 

Here is a short history of my first cartridge of filament (looks like weed whacker line, this is what it extrudes to make things).

I was appalled that the $1299 Cubify Cube did not include a Designer program.   After the $1299, they want you to buy Cubify Invent for $49 more.  Not big money, but enough to drive me to SketchUp Make which I believed had a broader following and a longer history (though not all historically with 3d printing).

SketchUp Make (the “free” non-commercial version) was fraught with hazards and frustration, but eventually yielded something I could print on the Cube.

BowdenBox

I started designing the box that I wanted for the circuit boards I ran into in my work life (these already existed but often had no provisions for mounting at all).  In short, my vision was of a “symmetrical closed box with snap-fit latches to hold it together”.   Shape? Whatever you want (I chose an oval like a dental floss box I admired). 

I searched for someone else who had designed this box, but struck out (I did not actually contact Colgate though).  I would have to design it myself…so I began to learn SketchUp.

To be able to talk about it, I decided it would need a short, catchy name.  How about BowdenBox?  (By the way, the name tends to be a terrible problem with the Cubify Cube printer when searching for related information: “cube” and “printer” are really common and all kinds of unrelated junk shows up in searches so I wish they had given it a more searchable name!)

My biggest complaint with SketchUp is tutorials in which something is magically happening on the screen, the author is describing it, but I cannot figure out what keys/mouse buttons he is pressing to get that to happen!  Invariable he says something vague like, “just move it to here” but in SketchUp things (to me) are never that simple!

Eventually I got something to print.  I also experimented with spray painting from a can, and was happy with the result.

The box was too big, though, and I learned how to use the ruler in SketchUp.  SketchUp has this way of trying to figure out what you want.  This can be very helpful at times, and very frustrating at other times.

Additionally, SketchUp is very unfriendly when it comes to SOLIDS.  It took me much iteration to get the SketchUp/Cube combination to print a solid bottom on my box.  I learned that in SketchUp, if you have ANY “extra geometry” in an item, meaning a line that does not strictly need to be there, then SketchUp decides the item cannot be a solid.

An example is if you draw a line from the edge of one face of a cube into the middle of the face.  Even though the line is on the plane of the face, SketchUp decides the cube is not solid!  And, as far as I can tell, the only way to know if SketchUp thinks something is solid is to GROUP it (or COMPONENT) and see if it reports a volume:

Add that (irrelevant) line on the face, and the same cube is NOT a SOLID GROUP!  What a learning experience that was!

Because of the way I gradually drew my design, the bottom had multiple faces in the area I wanted to be solid.  I had to get rid of these.   

Also I had some faces that protruded harmlessly into areas that I wanted to be solid, and I had to get rid of those.

I believe that the Cube Client software built some supports for one of the faces of the bottom, but SketchUp thought that that face had zero thickness, so the results you can see are supports, but no bottom. 

With the bottom filled in, my next problem was with the “raft” which is what they call that crosshatch grid that the printer puts down to build your item on.  These rafts were, for me, merged into my box and not easily removed! 

I tried printing upside-down to see if that helped my raft situation, but no.  And the inside floor was a mess of separate fibers in that print.

But I discovered the setting in the Cube Client software to turn them off, and that was how I proceeded.

And later, I set the Print Mode to SOLID and turned Supports off (since my box, when printed right-side up,  had no need for supports at all).

Now my BowdenBox was fitting together…..kind of. 

Next I had a bit of a problem with the CubeStick™ glue (operator error here).  A lip forms every time I put the cap back on the bottle, and sticks the cap to the top of the bottle.  It is water soluble, so I ran water over the solidified lip to get the cap off.  In the process, though, I got water on the sponge within the glue bottle top, and the next two times I printed, the base dislodged from the glass due to the dilution of the glue I had caused.  I am glad I was there to cancel the print before it extruded a basket of hay. 

One more error in the Solid vs. Hollow category: I added posts, and SketchUp told Cube Client software they were hollow.  Sometimes, they built OK, other times they would be knocked off as the printer tried to make them with walls too thin and then the result was some lumps (rather than the triangles) wherever the debris fell after they were knocked off.

Back to solving the fit problem.  There was only one part to this, printed twice.  That was the point of the BowdenBox.  But they had to be close to identical to fit.  The fit was not perfect, and I tried to figure out why.  Was this just the limitations of the Cubify Cube?

The snap-fit bumps were not lining up with the corresponding holes (dimples really).  What was going on?

I searched and searched for an error I was making in SketchUp.  I found nothing.

The Cubify Client software lets you orient the item you are printing.  I printed my box 180 degrees rotated to compare to the 0 degree rotated print.

I cut one in half, then used hot glue to temporarily glue the sides together with the side bumps lined up,  so I could see the mismatch.  I outlined the snap-fit bumps in marker pen.  Clearly, when the side bumps were lined up (on both sides, though only one is visible), the end bumps were significantly off.

Finally it came to me: this could be skew!  Was my Cubify Cube out of square?

I added a simple test a rectangle to my box model and printed that (partly, I halted the print when I had seen enough). 

Indeed, the rectangle printed (and LOOKED) out-of-square.

Still the problem could be in SketchUp, or the SketchUp STL export plug-in.  I needed something square from the Cubify site, and I found the NestedCube.STL and printed this, stopping the print when I had enough of the base to see the skew clearly.

Proof and everything!  (A Firesign Theatre reference)  My Cubify Cube was not square.  After some borderline-silly interactions with Cubify Support (I could not just tell them about the NestedCube.STL file I printed from their site, I had to actually send them back their own file so they could evaluate it…also I was asked to explain what “skew” meant, I should have said out-of-square in the first place I guess), they agreed…

I hoped there was a secret menu they would give me access to that would fix this, but apparently it is not subject to a cal factor adjustment.  They said they would send me a whole new Cube printer!

I had asked if it was found to be a factory defect, could they please replace my cartridge of filament.  But if I get the whole new package it will come with a full cartridge and another bottle of CubeStick glue too!  This cartridge has printed everything in the picture at the top, plus 2 bracelets for Karina, plus 2 iPhone stands, and is still not empty.

So I look forward to getting this and printing perfect BowdenBoxes any day now!  It was bad luck that my choice of the oval shape kind of hid the skew problem.

I am toying with the idea of making my OWN YouTube tutorial on SketchUp, with every key I hit meticulously enumerated from start to printout. Whenever that becomes the highest priority I guess!

Thanks for listening!

BowdenBox (iteration 10) as of 1/8/2014:

The replacement Cube printer arrived.

I had to iterate the design a few times to get things to fit (learning the limitations of accuracy and the behavior of the PLA plastic).

The 17th time was the charm!  "Production" Run completed:

 Now I have a box I can add things to, like a belt clip, or a screw eyelet or ....