Jeffrey Sipprell

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November 6, 2005

Fabricating a Manifold

This is week two in our fabrication progress on the plastic manifold project, though for myself, it was the first time I got to get a little more hands on with the milling and vacuum forming of the week's model. It really really is a time consuming progress. First of all, we're limited by the fact that we have a 3 axis milling machine, which means you can't have any cuts that go beyond 180 degrees (a 5 axis can handle this as the head will rotate to get under there). So you have to be really rigorous in terms of the geometry you are forming as to eliminate all undercuts - which either means altering the geometry, spreading the piece further open, or splitting it into mulitple pieces (all of which were employed to some extent this week).

The process is somewhat straightforward - you prepare your model in rhino and then export it to surfcam. In surfcam you have to create your rough and finish cuts (the latter of which requires some thought on the tool paths since those lines will show up on your model unless you do something really fine) and then make sure all of the directions are what you want (an arduous task to be frank). Then you output your g-codes and open them on the mill, running each cut separately. Then you have a nice milled piece of foam.

Now you've got to duct tape all of the sides so the vacuum will only suck through the top face - which also requires you to poke holes through the foam (also requiring a certain strategy as these will also manifest themselves on the final form). Then you duct tape the whole thing down on the machine, put your plastic over it in the frame and turn the heater on. After 5-10 minutes it starts to droop and then you drop it on top and flip the vacuum on to suck it into the holes. This then becomes your permanent form (as if you kept using the foam it would degrade extremely fast). Now you've just got to repeat the vacuum forming steps with your clear PETG plastic which gets cast on the ABS plastic rigid form (don't forget to poke holes in that too!). Now you see why we don't sleep much.

As far as the model goes, our primary focus was the connection and how to be able to join multiple layers of plastic that will create a certain degree of pressure on itself without having to resort of any sort of pin or cap connection. I'd say we were half successful in developing a slit and skin condition that allowed for one shell to receive end tabs from various layers. However we were a bit overzealous in the number of layers that the shell could handle and thus are going to have to explore secondary and tertiary connections that will attach subsquent layers.

We've also gone away from having the piece be globe like and established the main form as a half globe with flared ends that will sit on a base. Since there were only two of us in Los Angeles this week (half the class elected to go to Hawaii whereas I did not (more on that later)), we kept the study pretty simple. So issues of light and color are still sitting on the perpetual back burner.

But this stuff is a lot of fun though and nothing beats the thrill of dropping hot melted plastic on to your form and watching it get sucked into all the forms and edges - especially when it's 2 am and you're taking a break from minimal surfaces (also more on that soon). Anyway, below is a plethora of pictures from the week's work in fabrication. And yes I'm well aware of what one of the forms resembles.

CNC Milling
Process Milling 01
Process Milling 02
Process Milling 03
Completed Milling 01
Completed Milling 02

Vacuum Forming
Process Vacuum 01
Process Vacuum 02
Process Vacuum 03
Completed Vacuum 01

Finished Product
Clear Plastic 01
Clear Plastic 02
Clear Plastic 03

Other Student Projects
Project A
Project B

Posted by jsipprell at November 6, 2005 6:29 PM

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