Wednesday, March 13, 2019

Shredding HIPS, Reinforcing Table x2


First of all, I decided to start rocking on the giant box full of HIPS that's been sitting in the living room. High-Impact Polystyrene (aka PS-HI) is a firm plastic that's less brittle than standard PS. I've been finding it in printers, where it does a great job in many parts. However it also does a really good job of jamming my shredder! This was the worst jam yet, making me disassemble the shredder enough to pull several spacers out. You can see them sitting on the shredder.

I also looked at a recurring problem I've been having- that of ruining the elastomers in my Lovejoy coupler (red-orange thing at right). The coupler has been properly spaced but still has eaten that black elastomer spider, resulting in $30 of expense for a new spider as well as about a week of downtime before I could buy a new one.

I realized the thing HAS been going out of alignment, but not because of bad adjustment. The table has actually been flexing upward when the shredder encounters high resistance. To solve this problem and stop spending money, I threw some short 2x4 braces into the middle of the table.

  Here you can see the five screws I sent through the table. These line up with the coupler.

Below is a view from underneath the table. On left is the blue piece of aluminum that braces the motor. On right of course is the shredder, and at the bottom you can see that short bit of 2x4 recycled from a part of last year's 4P project. I could send a 2x4 all the way across underneath the table, but it would be more work. We'll see if this works, and if not I'll figure something else out.


I did a little more shredding after that and noticed that it did reduce flexing on the coupler. However the motor and gearbox tend to flex. I'm not sure how to fix that except for bracing near the bolt holes. If that became a problem I might look into steel tabletops. I don't anticipate having to do all that though. It seems like it'll work fine.

Tour of the Sheet Mold!

And now for a quick tour of my sheet mold designed and built by Artisan Metal Works of Flagstaff, AZ!


1. Filling the Mold. Install spacers of desired thickness. Pour in appropriate volume of flakes, about 3-4 scoops from an old chip-dip container in this case.


2. Topping it off. Put the upper portion on! This is a flat sheet topped with box section tubing. When the plastic is melted, I crank the jack under the oven, which smashes this mold together until the tubing hits the spacers. At that point I know the plastic sheet is of uniform thickness.

3. Melted & Cooled. The excess plastic squeezes around the edges, filling up the sheet entirely. At this point the plastic has usually contracted enough to let me pull the top right off, with sheet attached. If not I can unbolt the sides to really get everything free.


4. End Product. Here are five sheets I've made so far! These are all made from broken sleds collected from the forest. The top one is a thinner version with my short spacers. I'm hoping to experiment with a thicker one too. These are about the size of a clipboard, but maybe not long enough to actually use for that purpose.


Oven Comes Home for Good!


 Boy am I glad to have the oven finally! It came home on 19 February and I've been playing with it since. Thanks to Artisan Metal Works in Flagstaff for helping me out on this. They've done great work at a price that works for my project.

Above, of course, is the sheet mold inside the oven. This is a four-part system with removable spacers as well. All very modular and nice. Check out the next post for a tour of the mold.

Here is a photo of my oven and shredder tucked away in the garage. unfortunately I don't have much room so they have to be really crammed in there! You can also see bins full of broken HDPE sleds- all Paricon Model 648's.


Praxis Plastics Demo's Locally, Hits the Airwaves!

 I suppose it was one month ago now, but time has been flying. I hauled my shredder over to Snow Mountain River who I'm partnered with, and put on a little demonstration for them.



It went well despite being a cold and windy February day on the mountain. I didn't get much shredding done, but was able to chat with several interested individuals. One of those individuals turned out to be Melissa Sevigny of our local NPR station, KNAU. She posted the nice, three minute long interview at the following link:

https://www.knau.org/post/nau-student-turns-broken-sleds-climbing-gear

You may notice I added some needed structural elements to the lower part of the table. This helps keep it from twisting too much with the torque of that 1-1/2hp motor.

I'm also happy to report that though it's heavy, the shredder pulls pretty well on the bike trailer! It was only a two mile ride but included a few hills.


Tuesday, March 5, 2019

Snow Mountain River Recycling Demo (Praxis hits the airwaves!)

I did a demonstration at SMR on February 13th! The weather wasn't great so the turnout wasn't as good as I had hoped, but one person who came was Michelle Sevigny of local radio statio KNAU! Here is the resulting interview.



https://www.knau.org/post/nau-student-turns-broken-sleds-climbing-gear