How to recycle HDPE (bottles, caps, etc.) into sheets / blocks to CNC 2015-12-04

Serge E. submitted a new resource:

How to recycle HDPE (bottles, caps, etc.) into sheets / blocks to CNC - A very good Instructables showing how to easily recycle HDPE and work with the material

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Never tried ... still collecting bottle caps. I suspect you would have to make certain not to have air bubbles and such. But you would also need to square the piece afterwards which could prove tricky at best, no ?

JustinTime's approach would seem ... better since the block is squared first, then a guide hole drilled to be finished with actual acme rod to make a "perfectly" matched thread :

 

Wouldn't the machinist wax make the resulting material soft or weak ? In any case, in the home brewed form it is a very thick material which can be shaped under pressure to then be cut or machined to whatever shape needed.

Those panini grills sure are expensive ... If I get one, the wife will want to use it to make lunch which I wouldn't mind. Will wax paper be good enough to make my HDPE melting/forming safe between sandwiches ? The kitchen oven is off limit, some fumes and lingering vapour could be a health issue. I'll just have to find a second hand panini grill ... Kijiji might have some ?

 

I should of read a bit about the machinist wax, instead of thinking of candle wax

There is a bunch of sites with info and recipes for home made machinist wax. This one even includes a recent recipe with the LDPE (instead of usual HDPE) : Make Your Own Machinable Wax | MachinistBlog.com It is otherwise dated ....

MachinableWax.com gives an idea of pricing and such for the real stuff. It isn't cheap... They even have 1.75mm filament spools for 3D printers They offer 10m samples for free (?? just shipping for USA and International destinations) : MachinableWax.com - Product Details | 3D Printing Filament | 3D Filament Wax | 3D Printing Wax | MachinableWax.com, Inc.

It apparently can be remelted and molded to use over and over ... Cost is not that bad then. Just have to keep the chips clean (separate shop-vac, clean machine, etc.)

 

Here's an interesting article about recycling HDPE ... as a business :

New recycling process crafts unbelievable art out of plastic garbage

It's actually a KickStarter campaign, which, until I swallow the Zano ... situation, might not be something (KickStarter or even crowdfunding in general) I would promote right now. But, the problem is the rotten apple (the folks at Zano) and how KS is - or more exactly is not - handling the situation. There is absolutely no backing of backers. They are left out to dry. KickStarter enjoys its 5+% commission, a substantial amount, while the folks from Zano burned through an amazing 3.5M+$US with no deliverables !

But I diverge ...

In passing, crowdfunding is not all bad since, for example, the V-slot was given a boost as a KickStarter campaign. But nature teaches us once burned, one needs to stay away or at least be very careful. So caveat emptor everyone ... To date, BTW, I have backed nearly 40 KickStarter campaigns over 18 months with only two leaving scares. Oddly enough, they are the early ones (Zano and LIX). I should of known better ...

Where was I ? Oh ya, HDPE ...

Check Carter Zufelt, the artist, web site : Work for a small sampling of what can be done with recycled HDPE. His KickStarter (ok, here it is) is basically asking for grocery bags (apparently they are made of HDPE - I have to check this out !), he will send you the shipping address for 2.95$us (?!), and selling blocks and smallish items, like a 1" cube of HDPE for 15$us. For 5$us he will send you a PDF ... in January 2016 ... explaining how he does it.

Rather than pay and wait, just do a Google to find several articles, YouTubes, etc. with enough information to do it for FREE... In fact, check out the few included in this ressource to get a fairly good start. You might have to experiment a bit to get it right.

As makers and DIYers you already have a lathe, CNC mill/router and/or some other machine to work the resulting HDPE into some works of art. The CAD/CAM software on the ready as well. Might even do some last minute Christmas gifts ...

Speaking of which, cleaning out a very dark corner of the house - the entry way closet, I found this cute little griddle :

a Hamilton Beach Breakfast Sandwich Maker, model 25476C., currently selling for 30$cnd.

I think someone won the thing, figured I might be able to use it and the thing slowly migrated to a far corner of the closet.

Do you think it gets hot enough to melt the HDPE ? I figure the plates might come in handy to also help form the HDPE into relatively thick disks. It's suppose to be 600 W. This might be on the low end of what is needed ... But worth a try.

I will also borrow this almost lost CD/DVD/credit card chewer :
A Royal 12 pages confetti CD/credit card shredder. The image is the newer model (cross-cut).

I fed the thing old diskettes a while back, the ones with the metal hub and sliding protector. Noisy as heck, had to do some forward/reverse, but it took it all. CDs, DVDs and credit cards were made into confetti in no time flat. The HDPE shouldn't cause problems ... unless the blades went dull on that diet of armoured diskettes.

Once I wash the collected HDPE, cut it into flat strips which would fit in this shredder (max 9" wide, so it will be a quick job), the resulting HDPE confetti shuld melt in the sandwich maker. It says a sandwich is ready in 5 minutes ... Sweet, eh ?

The trick will be applying enough pressure to finish with a dense HDPE ... pock. I might need to cut a wooden disk to clamp to sandwich maker's "ring assembly" (hold he egg in while it cooks). Do you think there will be an issue with the 5 year warranty?

 

Well, I just could not wait to try the Sandwich Maker.

I unboxed the thing, checked it out and plug the sucker in. It got hot in no time. Less than the 5 to 7 minutes told in the doc.

In the excitement, I threw in some water bottle caps. Just a handful, not much, really. The stuff melted from a whitish to clear colour in less than 5 minutes. 600 Watts looks like plenty good. There was a sligh odour ... I think it's the factory smell of the Maker more than the plastic melting.

Sh.... ! I forgot the wax paper !! Oh well, I'll see how easy it will be to scrap the HDPE off the teflon looking surface ...

It's going to take a lot of bottle caps. So threw in a second handful once the first few became clear as glass. Then a third, and a fourth ... The confetti cut will be much better then these bottle caps ...

So what do you think will happen next ?

 

Ain't she cute ? Warming up as I have a cup full of water bottle caps waiting to jump in ...

Well, there goes the first few water bottle caps. Turned from a cloudy whitish colour to clear as glass very quickly.

I completely forgot to use wax paper to avoid a sticky mess on the Maker's surfaces. It's way too late now. In went several other bottle caps. Each handful melting just as quickly. We can see the general shape of the caps.

I figure I will let things cool down as the stuff is mega gooey and HOT. In theory, the HDPE will sort of shrink and twist cooling down with no pressure. If the machines surface, being brand spanking new, are slick enough, I suspect the HDPE will just slide off. Then again, if it is teflon like, that's plastic and I might end up with a ... big mess. Crossing my fingers ...

 

Call me lucky !

Maybe it's just because the surfaces of the Maker are brand new, but the HDPE seems to come off on it's on :


What was gooey and stuck to the top surface just hangs over the layer lower down.

The stuff is still too hot to be handled as unprepared as I am right now of this apparent success.

The stuff looked as thick as molasses when crystal clear. Maybe it was viscous enough to self level ?

It's turning back to white, as seen in this picture.

I can't wait to get my hands on the old CD/DVD shredder and go through the coloured HDPE I have stock piled in the garage !

 

Ok, do this in the garage or have the fan going as there is a bit of a plastic odour. You will see in some of the following photos that the HDPE touching the heated surface started to discolour to a yellowish ... almost light brown as it cooled down. That's probably the source of the odour ... direct heat to the plastic.

600W is plenty of heat, maybe even too much ...

Otherwise, pretty nice if I do say so myself for a very first time :



The material returns to its whitish (original) colour during cooling.

Pressure is definitely needed during the 'cooking' to remove air bubbles and during the cool down phase to avoid the material warping out of shape. Can you see the warping in the last photo above ? Maybe just during the cooling down will be enough. During cooking will make a big gooey mess !

The Sandwich Maker has a heated surface at very bottom and top. In between, there is a three part contraption. The bottom 'ring' is to hold bottom half of the bread/bagel/... over the hot plate. It's about 1.25" thick. Toppings can be added. The 'egg' seats on the center 'skillet' portion. The top third is an other 'ring', only about 3/4" high. It holds less toppings and top half bread/bagel/... When ready, the skillet pivots out of the way, the entire assembly lifts off and the sandwich is ready to eat in less than 5 minutes. The whole thing is about 3.825" in diameter (inside).

It will do a nice thick pock (say 1/2" or even 1"), perfect for coasters and small objects. One of the videos way up explain how to fuse several layers together, making for even thicker pocks.

I used the skillet to hold the bottle caps so they are not directly on the lower heated surface ... But they touched the top heated pad. A piece of wax paper might be enough to avoid the yellowing there. I'll have to figure something out for the bottom ... or just flip to whole contraption over, doh !

The fun part of this is I can always shred the HDPE over and over to remelt. Colour mixing will get weird, but I can play with any ideas without having to run out to the store for more raw material. That will be perfect to play with ... shhhhh ... a Cbeam machine (I had my arm twisted and went for one recently).

 

Looking at the resulting 'disk', it does seem to self level ... but I had my little Maker apparently on a slant. .. The disk is about 3/16" thick on one side and only 1/8" on the opposite end. Man, yet an other thing to level.

It didn't take that many caps for this 'prototype blank coaster'. Wish I had counted them

It is quite smooth. short of a few air bubbles at the bottom - a few bottle caps were upside down and some air stayed trapped, and visible pattern of caps' edging on the top side of disk. Pressure during cooling should fix both. I can't see any air bubbles deep within the disk. That's good! I did add the caps in small batches, so it probably help this aspect. It probably allowed for an even melt as well. The disk is nice and solid - no flexing at all. This stuff seems quite strong when thick enough. Maybe I'll be able to do some test plates when prototyping. It will certainly be a cheap way of getting plates.

I better drink a lot of water, make sure there is plenty of laundry being done, lots of washing hair, ... I'll knock on neighbours' doors for anything with a /2\. There's the folks at work. The area schools, restaurants, ...

I haven't started and I already need my next /2\ fix !

 

Serge E. updated How to recycle HDPE (bottles, caps, etc.) into sheets / blocks to CNC with a new update entry:

UPcycle HDPE with an office confetti shredder, a sandwich maker and your favorite CNC machine

Read the rest of this update entry...

 

Here's a bit of information I found of particular interest in this HDPE :

Bottle caps are normally injection molded at a factory which means they have to be made of an HDPE grade that flows well into a mold. Melted bottle caps will flow without any pressure unlike milk jugs and detergent containers ...

Containers, bags, etc. do not use the same grade or quality of HDPE. Some, obviously, have pigments or other substances to be coloured. Others might have 'fillers' to modify the property - like the biodegradable starches or the UV absorber to degrade the item when exposed to sunlight. You might even be able to add your own fillers - change the colour of the bottle cap white, even maybe add fibers of some sort, well mixed, to make a stronger HDPE ??

Do experiment safely and outside or in a well ventilated space, like your garage / shed with fans to the outside or opened doors at the very least.

As a bonus : maybe one of those electric pans or griddle would work to melt your HDPE? Do not forget, even with a thermostat they have an electrical element which is turned on to raise the temperature and off to let it cool down once it goes over set temp. You will need to keep the HDPE somewhat off the heated surface to avoid yellowing or, worse, burning (fumes!) In other words the surface temperature will rarely be at the ideal level and mostly above or below it. An oven may offer a more stable working temperature since it is the air (volume) being heated ...

 

A few (or maybe many) more pictures to follow.

The shredder made fast work of cutting up the material. Actually, it was more like ripping it apart. I just needed to squeeze and snap the scissors at the larger chunks. However, if there is not enough material to shred, it isn't really worth the trouble especially if you want to keep the colours separate. If the shredder is already available, use it. Just don't buy one for this ...

The sandwich hdpe melter turns out to be a good way to experiment on a small scale. But it won't be that great for making a good sized block to create anything more than maybe almost finished coasters.

That's ok though. It's all about learning ...

The device fluctuates from about 165°c to 215°c - temperature of the heated surfaces. Not quite the 190°c needed for HDPE. Cool end is ok, but hot end of that range causes some yellowing of the bottle cap if it touches the heat source.

The bottle caps melt perfectly. In fact, they melt quite fast. I just add a dozen or so at a time not to touch the heated surface directly (avoid yellowing). In fact, remelting the puck resulting from initial melt works just fine ... and almost as quick. Did the remelt a few times with no apparent issues on the material.

However, the coloured hdpe of, say, a liquid soap container takes much longer. I am not certain why. The pieces I used were somewhat thicker - the part the cap screws on. In fact, it took for ever (just about).

The larger panini grills would be best as one can flip the mass of HDPE being melted as often as needed, square it and drop in mold to cool down under pressure of clamps. With these grills, you will need the ... teflon like sheets to easily work the melted (really just softened) hdpe.

Maybe boxing day will have low prices on those grills.. It's only in ... a few weeks. I'll check Kijiji to see if anyone is looking to get rid of one ... The wife will hate me if I buy a brand new one just to melt plastic.

 

Some Google'ing and here's the apparent reason the bottle caps melt easier than the liquid soap containers :

milk jugs don't flow as well as buckets and bottle caps do when they are melted because milk jugs are blow molded and buckets and bottle caps are injection molded hence the higher flow rate of the bottle caps and buckets

It's not melting easier, it just flows a whole lot better.

Given the higher flow rate, the melted bottle caps and such should not be clamped under (too much) pressure - it will be flowing through whatever crack it manages to find. The other hdpe stays, apparently, much thicker so it can take all the pressure you can give it. In fact, it needs it to be formed into a shape.

 

Some interesting info about recycling HDPE /2\ and LDPE /4\ :

Eco Corner: Plastic Bag and Film Recycling - More than Shopping Bags | City of Evanston

 

And a word (or two) from "funny1048" over at Instructables on the difference I noticed with melting HDPE :

From: funny1048
Date: Dec 6, 2015. 12:12 AM
Subject: Plastic Smithing: How To Make your own HDPE Plastic Anything (DIY plastic lumber)

Yeah, the bottle caps will flow more like honey and the containers have more of a consistency like dough its all due to the molecular chain length of the hdpe. If you make something that requires structural strength such as plastic lumber the best type would be milk jugs or detergent bottle... If you want a better flowing plastic for injection molding use the bottle caps.

One other thing I recently found out was that the melted plastic should be kneaded with oven proof gloves because flakes of hdpe cut from the bottles may have invisible areas of stress even if it looks like it melted together uniformly. Kneading it will blend the plastic evenly and remove the areas of stress between the melted flakes.

Eventually I will be able to eliminate this step by building a filament extruder which extrudes flakes into a long filament and then I'll be able to chop the filament into pellets because the pellets wont create areas of stress unlike the flakes. Its probably not required to do all of this for what your doing but its just some useful information i decided to share.

Interesting, eh ? So my shredder cut HDPE must be stressed as heck ... it will need a good massage when melting it.

 

A small world indeed.

My melted bottle caps started yellowing after several run through the sandwich maker. Some of the caps added to see how thick I could go with this machine were also touching the hot surface until they soften. Those yellowed in no time. An oven would be better, I just didn't have one within reach. But Christmas is just around the corner ...