I bought a plastic welding iron from Harbor Freight and used it to repair HDPE based 5 gallon buckets. The tool is like a soldering iron, but uses air from a compressor to help regulate the heat. Need to have patience using the tool for the best results. I have also made a few molded items using glue sticks and a glue gun.

Hi Shawn,

Have you checked older issues of “The Home Shop Machinist” for an article on how to build your own plastic injection molding machine. I’m sure there is an article on this subject and if I remember correctly the article was spread out over several issues. You used to be able to buy back issues of the magazine from the publisher. Sounds like an ambitious project. Good luck.

Yes tom i have looked at them i believe online, The process is simple and the ones I saw use a lever with a heating chamber. I thought for a simple one I could use a screw type method and that way I could perhaps even lay it horizontal and if I need a certain shape I could use an extrusion type method. I believe harbor freight is working on having one built for sale but not available yet.

By the way Don, the heat gun I bought is digital and can control temperature to 1350 degrees, the lowest setting is 250, but I found that if you go around halfway you get the plastic to melt pretty well and works great.

Shawn,

Sounds like a good idea. I’m think a used jeweler’s vulcanizer would work great for your application. I sold one a couple of years ago and let it go pretty cheap. I would think with this economy you might be able to buy a used one at a good price. The vulcanizer consist of a heavy duty press with two opposing, thermally controlled, aluminum plates. By now newer ones probably have digital readouts for the temp. setting. What is the melting temp. of the milk carton plastic?

shawn
there is a company or more out there where you can buy liquids . i.e plastic resins and such they are usually to part mixtures it would give the same result as injection except you are pouring instead.
also i do body work{no longer} but anyway auto body filler works really well if you want to make a mold or even a finished product. try it with maybe a mold that you use to make candies with. mix it pour it in and in minutes its hard.
watch it, it does get hot.

Hi Shawn, what brand is your plastic welder? Thanks- Don

If you use acrylic (a form of plastic) you can heat it in your oven at home just enough to where it is not quite melted but “bendable” and form it to pretty much any shape. Alot of times you can even use a jig. You know in woodworking they often use jigs. But you can apply the same concept to bending plastic in your oven. For example, you can place a flat sheet of acrylic over a rounded object such as a bowl…. As it “melts”, it will bend and form around the bowl. It takes alot practice to find just the right temperature and time to get it to where it is not quite at the completely melting stage but ‘sagging" stage. You should also use some film release available from companies such as Castolite. Use plenty of fans and ventilation as the fumes are of course toxic. But I don’t think anymore toxic than spray paint. Ive done it many times.

Also, be careful because it is a fire hazard… watch it closely. Because I can not be there as you do it, i do not accept any responsibility for the outcome. I am only sharing my experience.

i like the disclaimer cody.lol

don, i dont have a plastic welder, i use a heat gun which is a wagner. I use resins a lot, but they are expensive and I wanted to experiment with being able to recycle some here rather than setting it to the curb for someone else to deal with. hdpe is excellent and has great properties, plus gives a great insight to what goes into the process.

shawn

my brother inlaw is an office person who works for a company who buys used and old plastic from Dupont and others. there is always a ton of this laying around. have you tried plastic pellets? or is that what you are talking about?
they had many colors.

not really robert, my main desire for doing this is being able to recycle from what I already have. I think we as inventors and engineers owe the world a little repayment and being ingenious as we often are, finding ways to reuse what we already have. Just as I have been playing with papercrete(concrete using portland cement, water, and shredded paper with or without sand) as my fiance delivers newspapers and we often have many extra, this eliminates some of the transport cost of taking it back for recycling and puts it to use here. Plus it gives a little more respect for the processes as using my drill press actually took quite a bit of elbow grease, even though plastic melts easily, it doesnt often flow that easily and takes a bit of pressure which explains why injection molding machines go into the hundreds of tons of pressure. Resins work well for some things but are messy, smelly, and generally not as eco friendly though that is a relative term.

Shawn,

You may want to pick the brain of Floyd Coates, owner of American Plastic Molding Corp.
He’s written a story for us for our June issue and is very inventor-friendly. http://www.apmc.com/

shawn

i understand on the recycle issue , i cant understand why so much goes to landfills . waste waste waste

on the idea of useing your drill press maybe this might work.. alot of injection molding is done with worm gears and screw drives.. maybe welding a big nut to the end of a piece of pipe with a cap welded to the end and drilling the desired size hole for it to come out. then on the nut end use a bolt with enough threads to bottom out in your pipe so that it pushes all of the plastic out. thus you would have your own screw drive injection molding tool.. the bolt would be easier to turn

that’s exactly what I had in mind as soon as I get some of my other projects finished I plan on doing something like this.

update, my one project i was working on a cabinet idea for some people and I used a one inch aluminum rod and turned out a cut off cone shape and fit it inside a pipe. I used a heat gun to melt hdpe from milk cartons into the pipe and when i had enough in there i put the aluminum in the pipe and used my drill press to apply pressure. the pieces turned out a bit rough(i didnt allow a hole for air to escape) but they worked out well, i smoothed them off on the lathe and drilled holes in and screwed them to the bottom of the cabinet. I am working on the idea with the screw thread and a pipe with a small section cut away to put plastic in, the heat gun works well for heat as it doesn’t scorch easily and you heat a small amount at a time while adding more plastic, while keeping heat on the whole mass, then compress it it works well. I just need to make some molds using metal or even epoxy.

shawn

they make a cast lite product that they use to make matchbox cars you can get it to maybe make your molds

also dura-glass would hold up to alot of heat and is easy to work with. you can get it at any auto body supply store. also they would have release agents that you can brush or spray into your molds

I am actually working with something called rockite, which is actually a concrete patch but is real smooth and machines easily, I am making both half of the molds now, hopefully it will work well as it is easy to work with and not too expensive.

shawn
if you are not using a 2 piece mold or if you are gonna made a mold of an object use wax to make the part then
put or pour your mold material around it then melt the wax out. then cut the mold in half. just in case you were
not aware of this process. bu tit seems you are on top of thing .
now you have me wanting to mold some of my own stuff lol

I made the first half, machined the design into it, then filled with wax and coated the surface with wax, then poured the rest over this. when set I pulled the two apart and melted the wax away, sanded the surfaces smooth on a flat surface with sandpaper on it, then drilled the hole for the plastic and made some air holes. The only problem is when I heated the plastic and turned the allthread with a flat piece on the end, the weld that held the nut to the end of the tube broke off, turns out I was welding the nut onto cast iron, didnt realize at the time so I have to redo it so it wont break as there is a lot of pressure.

yea welding to cast with out a nickle rod wont work lol.

I realized that after the fact, the piece i grabbed to use to weld the nut to was in my scrap bin i thought it was steel. never had a weld break yet til this thats why it had me puzzled. I had a nut used to fasten drain line on and put the metal on the end of the pipe and screwed it on then welded the nut on i guess I will turn down a piece of steel and use it instead.

I think Stephen posted some mold making videos on the Inventor’s Library site the other day….he has been developing a library of manufacturing videos over there.

http://theinventorsmentors.forumo.biz/index.htm

Mark

Ill check it out. I actually finally got things working well, melted plastic and turned the screw and it went into the mold, only thing is I underestimated how much plastic I would need this time and wound up with a tiny blob inside the mold. but got it working so just need more plastic. the previous times I used more than was necessary so I cut the amount back, but a bit too much. the rockite seems to work well though and it holds up well.

Ya, that happens…we fill the mold with water to get a good idea of the volume….it works pretty well most of the time.

Mark

shawn

when you cut up your plastic to reuse it do you keep it all about the same size? i know that the plastic that most companies gets and use is only about the size of less than a 1/4 " x1/4"
so i would say size has something to do with burn rate and temps needed and so on.
if you dont mind wasting a paper shredder and if you are only going to use milk cartons try running it threw a paper shredder

Hi Shawn,

There is a toy or craft kit with plastic dodads that you iron together and is non toxic. Perhapts you could melt them and use them for a pour.

phil

shawn is wanting to use ,used bottles and such from his trash ..recycle

Phil,
HDPE melts very well and would be recycling, heat gun on high melts it well. got most of the kinks out of the device just have to make a threaded end which works better than what I have already,actually got a pretty decent first sample though, just need to tweak things some but came out better than I expected.

shawn

what about color ? is it black ? our you using clear milk jugs?

This statement caught my eye.
Places that process styrofoam for recycling use a small oven which melts it down to a brick, so It seems it should be possible to do something like this with a mold as well(with good ventillation)

My wife and I once had an oven that had confusing knobs for it’s top burners. I would sometimes turn on the wrong one. Also, we keep burner covers over the burnes we weren’t using. The covers were covered with acitate I think it’s called. (a clear plastic like substance) Any way, I placed a styrofoam cooler on top of one of these covers and started what I thought was another burner to boil water. After noticing a smell I lifted the partially melted cooler from the cover and opened all the windows. What I found on the cover was about 1/8 inch thick melted and rehardened styrofoam and acitate. What was cool about it was it weighted almost nothing, it was like holding air, and strong. I used to lift weights and I’m a pretty big guy and I couldn’t break this 1/8 inch slab. But, the gases given off in melting it were pretty noxious so I never tried it again.

Good story eh?

Shawn, we recycle milk jugs where I live. The biggest problem with them is getting people to rinse them out. Sour milk attracts rats like crazy. Not to mention the smell, ugh!

phillip

Styrofoam
is used in structural panels on cars and trucks in the front end crumple zones.. it absorbs energy very well

right now I just cut the plastic into strips and estimate because the machine I made for injecting has some empty space(i can turn down an insert to fit just no time lately) so I have to use extra plastic. styrofoam is another one I have looked at but have to be careful as fumes can be very toxic though I plan to try in the future(also due to air in styrofoam would take quite a bit to fill a certain volume, likely about ten times by weight). the problem with plastic is the pressures I actually broke the metal collar I screw on to hold the nozzle on but so far my trials are proving good.

Sounds like you’re having fun! Good luck with your project!

http://www.edisonnation.com/users/toolman911965…
I have some pictures of what I have done so far, very crude but works pretty well. check my albums. I machined the mold using my drill press and a slide vise, when the pieces were molded I found out it wasnt as straight as it looked but works pretty well for my needs.

i found every thing on this site, all machines are on very reasonable price.
specially plastic molding machines
mega-machine.site11.com

I am aware of those sites, but being me have to do things myself just been very busy lately around here and havent been on here much.