3/13/2015 11:11:21 AM

The black part on the left is molded incorrectly and does not fit on the double flatted gearbox shaft. The pocket is too deep also not allowing the attaching screw to tighten properly to hold the part in place.

The assembly is used to clamp a piece of card stock in place while it moves back and forth for embossing.

The bottom row center image shows the mismatched depth and the screw which never tightens properly.

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This is the computer model of the part and the actual injection molded part.

Inside the pocket you can see a sink mark. This problem is worse on some parts than others. The mfg says then cannot modify the mold so we will eventually need to make a new one.

3/13/2015 11:14:38 AM

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This was my concept to make a spacer to take up both the space at the bottom of the pocket as well as the space between the periphery of the motor shaft and the pocket.

I attempted to machine an aluminum spacer that would fit but I stopped when the wall thickness was about 0.005". So I decided that I would machine the pocket to accept a 3d printed spacer. This allowed me to size the spacer such that the SLS machine could print a good part then I created a pocket to accept the spacer.

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I needed to make a fixture to hold the parts to machine the pocket. I decided to use the counter bore in the part along with the other through hole to position the part for machining. I also added a hole centered between these 2 features to allow a 1/8 dowel pin to be used to remove the parts from the fixture after machining.

The top 2 photos are the computer model and the bottom 2 are the actual machined parts.

3/18/2015 4:19:45 PM

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The only important parts of the fixture are the pins extruding from the plate so I didn’t waste any time with finish passes on the bulk of the material removal hence the poor finish on the floor of the fixture. I chamfered all of the edges of the pins.

3/13/2015 11:19:22 AM

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This is the design for the 3d printed spacer part. My best guess was that I would need to build the inside of the part oversized by about 0.0040 “ due to inaccuracies in the build process. I labeled the parts with the #4 for identification incase I had to build more in a different size.

I reused the parts cage idea from some previous projects as it makes post processing these small parts super easy. I keep tweaking the design of the cage slightly each time I use it and just about have it completely dialed in now.

I sectioned the view so you can see how the parts are stacked inside the cube. After printing in the SLS machine, there is un sintered powder between all of the parts and the cage which has to be shaken / blasted out of the cube. This only takes a few minutes inside the glass bead cabinet and you don’t have to worry about losing the parts because they are contained within the cube.

You can see a short video clip of the cleaning process from an earlier build in a cage here!

You can see the earlier cage build log here!

3/13/2015 11:22:43 AM

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Here is the finished cage full of spacers and the initial test fit of the parts into the freshly machined pockets.

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3/16/2015 4:56:05 PM

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I mentioned earlier that I attempted to machine the spacers from aluminum in an attempt to not machine the sensor flag pocket.  The thinnest portion is about 0.005" (less than the thickness of 2 sheets of paper or 2 hairs)

I was able to force the parts together, but this would not have been practical in production.

3/13/2015 11:13:49 AM

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Here you can see a part still pressed on to the fixture in the #1 position a loose modified part with the larger pocket and a part with the spacer ready to be pressed in. I can press the spacer in with my thumb but it takes a significant amount of force to fully seat it in the pocket.

You can see a part installed onto the gearbox as well.

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3/16/2015 4:50:45 PM

Here is a cut away view of the spacer installed inside of the sensor flag installed on the motor shaft. You can clearly see that the screw can now bottom out and tighten properly. All of the rotational slop is also taken up with the spacer so that is no longer an issue either.

The following pictures are mostly redundant but included for archival purpopses.

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33070274 w spacer installed asm-1

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33070274 w spacer installed asm-2

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33070274 spacer sls 180 pcs in cube for sls build asm-1

3/13/2015 11:21:10 AM

33070274 spacer sls 180 pcs in cube for sls build asm-2

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33070274 spacer sls 180 pcs in cube for sls build asm-3

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33070274 w spacer installed asm-3

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