CNC

This was not as much of a success as I was hoping.  Turns out making things fit nicely is hard.

The concept was simple – a custom pot rack for my apartment reminescent of something like this, but in wood.

So I sketched out a simple formIMG_4186

My initial plan was to only CNC the side panels.  I was going to cut the top from a stock piece of plywood and connect the side to the top with miter joints.  I’ve never done a miter joint, but I went ahead with my design assuming I’d be able to figure it out after the fact. Screen Shot 2016-02-16 at 8.58.36 PM

The vectorworks drawing was straightforward, but the question I was left with was how do I define the pockets that share an edge with the outer edge of the panel?  I dropped a rectangle right on top, hoping that the overlapping lines wouldn’t be a problem.

I took the file into Mastercam and after struggling for about 20 minutes trying to properly select the lines I wanted, I managed to coerce a gcode file out.  Mastercam wasn’t too bad though, after I got the hang of it.  Time to head to the CNC.

Setting up was straightforward, and I was up and running quickly and smoothly.  But about a minute into the cut I realized that I had sized the hole cutout incorrectly.  I set it at 1″ radius when what I wanted was 1″ diameter.  These things happen.

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After fixing that up, I started again, and it all went super smoothly.

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I cut the aluminium rod to the length I wanted and ground down the end to take off any sharp edge.IMG_4176

I used the panels with the bar in place to figure out the size I needed for the top panel.

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After cutting, I used the table router to create the joints I wanted.  I abandoned the miter joint because it seemed a little too complicated to get right without knowing how to properly make it.  So I took the hand router, hooked up to the router table, and took out some material from both the top and side panels.

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Eventually I ended up with something like this:

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Not perfect.  I took out too much from the top panel so there was a small gap left over.  I could have tried to tighten it up, but without a way to make really accurate cuts it would be have been a bit of a blind man’s game.  So I decided to push forward.

After some sanding, I fit everything together.

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Lastly, I epoxied it all into place, and voila, a highly mediocre pot rack for my kitchen.

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Lessons Learned:

1: Know not only what joints you want to use, but how to actually make those joints.

2: I could have easily designed the joints I used to be cut on the CNC.  This would have ensured they fit perfectly

3: Do a lot more measuring and planning before cutting.  I could have saved myself some trouble if I took the time to figure out exactly how long things needed to be.

4: Don’t use the hand router for joints that require precise depths…

5: Think about what parts are round and what parts are flat.  On the front face, where the side panels meet the flat face, there’s a mismatch between the roundness of the panels and the flatness of the face.  It doesn’t look great.  Doing this again, I would have had a flat face on he side panels that may curve once it’s away from the front face.

 

 

 

2 thoughts on “CNC

  1. Ben Light

    A few things. Making parts fit together is tough and very tough if it is your first CNC project.

    Your initial drawing should have your pocket rectangles extend past the contour shape, by at least the radius of your bit. This will ensure there are no rounded corners on one side of your pocket.

    I would have also added a pocket rectangle to the top of each shelf piece instead of doing the work on the table router. Again, the rectangle should extend past the contour shape.

    Did you cut the other two pieces of the shelf on the CNC?

    It is possible to get accurate results using the hand router and table, but since you are using the CNC, you might as well do all of the work on the CNC.

    1. jcharry Post author

      Thanks for all the input Ben. I realized a lot of this after going through the whole process. I definitely should have made all my parts on the CNC, but I didn’t plan my design well enough and ended up sort of winging it on the other two parts of the shelf that were not made on the CNC. I think I’ll do another iteration of this to iron out all the kinks and make my parts fit nicely.

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