Vevor Vacuum Pump And Chamber - and the challenges of Home-Made Machinable Recycled Plastic Stock

[@PaulRansonArt]

I'm no expert but when ever I see plastics being recycled they are usually turned into small pellets first. I wonder if the greater surface area would aid the melting process and allow off gassing of the plastic. BTW - take very great care with this process. Off gassing plastics can expose you to some pretty nasty toxic fumes. Prolonged exposure can be extremely hazardous. Do take care with your experiments. Best wishes - Paul

[@Jimfoxyboy]

I've been to a plastic mold injection shop. Yes, the plastics they use comes in pellet form, in vast quantities. Its put under high heat and pressure before its injected into a shaped mold.

[@murmenaattori6]

In industry it's a tradeoff between more surface area for gasifying fumes and less surface area for less oxidation and better layer cohesion. The grain size should noy be too small or too big.

[@thedeloachsdoyoutube8377]

Maybe he could use his charcoal chopper to shave it into little pieces and then chop it up. He needs a big wood grinder or something.

[@Kamikaze3557]

Work in a plastics blow molding and injection molding factory in the 60s and 70s, yes, pellets or small flakes and sometimes powder.

[@slade9382]

Have a look at what Brothers Make are doing on KZbin. They used recycled plastic and an extruder to make planks of plastic and other objects. The machines they use may well be out of your price range (they aren't overly cheap, but not crazy expensive), but you may gather some good ideas from the way they do things. Thanks for the entertainment Tim, and good luck.

[@dustbunny2886]

when we made blanks for custom stubs we used at least 5 tons of constant pressure on the molds till cooled for something the size u are making and don't overheat the material u are using , always dry the material before melting in an oven 13 years of plastic welding and fabricating experience

[@EastBayFlipper]

Exactly what I was thinking 🤔 Increased pressure to prevent the formation of voids and then temperatures calibrated to allow for plasticity and pressure to achieve the block and prevent off-gassing from inside the polymer. The 5 tons number makes sense but was still a little surprising 😮 I'm thinking a hot ram would do the trick nicely with a breach plug designed cap for the end to allow for air/gas to vent and then extrude a little polymer as the seal then remove the block and push out the formed, compressed polymer block 😀👍

[@dustbunny2886]

@@EastBayFlipper the 5 tons is on the low side most of our larger molds needed up to 25 ton hydraulic rams , that was for stubs blanks from 400 mm to 1000mm without drying the material he will always have voids all plastics absorb moisture even 3d printing filament

[@doughnut1107]

I wonder if the source for that material is also running it a little wet

[@EastBayFlipper]

@doughnut1107 it wouldn't take mutch to make steam🤔 Putting it into an attic for a few weeks might dry it with enough sun 🌞 A long shot😀😅🤣

[@doughnut1107]

@@EastBayFlipper In the oven at 110c for a couple hours would likely be more efficient

[@martinsto8190]

8:18 Amazing how the workshop is getting more neatly and organized.

[@Kevin75668]

I've machined stuff from homemade recycled plastic blocks, and my best results were blocks that I compressed with a 20 ton press before melting. I was using primarily HDPE milk jugs run through a heavy duty cross cut paper shredder, which gave a fairly uniform size of raw material.

[@srmofoable]

I was going to say the same thing. It's pretty surprising how little plastic is in the jugs.

[@c.a.mcdivitt9722]

Okay- hobbyist 3D printer here. Your railway sleepers are likely HDPE or PET. HDPE I don't know much about, but I've been building a PET pulltrusion system, and I've been researching it. PET loves to draw in water, and your voids might well be caused by steam boiling out from the material. Degassing won't help that much if it's caused by steam. (I know, water boiling out of plastic sounds impossible, right? But I've seen some prints pretty badly messed up by it.) What you need to do is dry your material (probably in an oven) at a relatively low temperature for several hours (or overnight) right before you melt it (or store it in a sealed container with desiccant). You could also put it in the vacuum chamber with a healthy amount of desiccant. Also, those big chunks of starting material are going to be hard to dry. You might want to switch to something like chopped-up milk jugs. Alternatively, you could try 3D printing your part, then re-melting it in salt or plaster to fuse the layer lines.

[@wayoutwest-workshopstuff6299]

Thank you - very interesting

[@bigchrisrogers]

This is a good point. If I have some damp filament in my 3D printer I can hear the water within it boiling as it gets to the nozzle at 200 degrees C, sounds a bit like bacon frying.

[@covishen]

First, thank you for taking me on this journey and kudos to Vevor for being so supportive. I'm in the market for a couple of things and I'm going to be looking at their offerings. It's really nice to see this kind of support from companies for people like you who are experimenting.

[@jamesspry3294]

We studied this sort of thing at uni, couple of observations to help you understand what's going on: 1 - it's not off gassing. Plastics tend to break down and release gasses or vapours at higher temps. All injection moulding and pultrusion is done at the LOWEST temps possible 2 - as plastic cools it shrinks. You always get a void "somewhere" in a moulded plastic part. Keep the pressure on as long as possible (like you did in your second video...) Cheers mate!

[@josephplankinton612]

Sir, I am a retired supervisor chemist for a government research and development lab. We used plastic for making items. First you need to granulate the material. Second, we heated it under a vacuum. You could do the same by adding a lid to your pipe mold and an on/off value. Vacuum it down as far as you can, close value and heat in oven. Don’t open until cooled. This should help a lot in your void spaces. Hope this helps. Enjoy all your videos. Thank You Joseph

[@bugz000]

positive pressure my friend, you can crush the bubbles with high pressure to tiny tiny tiny little capsules of high pressure, but still structurally sound! its how they make clear resins :)

[@wayoutwest-workshopstuff6299]

Thank you - I will try!

[@HamidA-to8vy]

Do not worry Tim, we are enjoying following you and we become smarter by merely watching clever people like you. We appreciate the effort you put to produce these videos. Vibration might help like concrete. It is more like solid but under vibration it becomes more like liquid. vibrating tables are used to cast concrete

[@william5694]

A pressurized chamber is much more effective at resolving voids in a casting. It compresses the bubbles until they are too small to be a bother.

[@jeffschroeder4805]

compressing large bubbles in barely flowing molten plastic is much different that compressing lots of very small bubbles in a liquid. The smaller bubbles are still voids, not suitable for machining.

[@daverolstone5669]

Hi Tim, Have had some success at this on a small scale using plastic containers gallon cans etc. First I cut up the containers into 1" strips then placed them in a baking tray lined with "Silicon" baking paper. and stuck the tray into the Rayburn Oven. Once they where nice and soft I rolled them in to a sausage. Adding more strips until the sausage was big enough to make the block I wanted. The baking paper stopes the plastic sticking to things. To form the block I used a wooden box with a top that would slide inside (a piston), Pressure was applied with a "G" clamp. It was possible to avoid voids during the sausage stage and the "G" clamp just forced the plastic out in to the corners of the box. It's very easy to work the resulting block with woodworking tools.

[@richardball9724]

Brothers make or precious plastics are great resources on you tube for this type of stuff

[@meredithmuller5543]

Ditto on the Precious Plastic community Tim! There might even be a precious plastic workshop near you in the west or at least somewhere in Ireland who could help - maybe even by fabricating the blanks you need when it is time to scale up the car business. If there isn't one in Ireland they have plans and resources for setting up plastics recycling workshops to make the machines you would need!

[@madleech]

I've made machinable wax before which is similarly viscous and similar temperatures. Rather than vacuuming the bubbles out i instead used a painter's pressure pot to compress the bubbles down till theu disappeared. The other difference is I melted the plastic + wax in an open pot and stirred it mix, then slowly poured it into molds. Then I put it in the pressure pot and kept it under pressure until it cooled. You may find that as the material cools it shrinks and so voids will always want to form; keeping it pressurised ensures the bubbles remain microscopic.

[@Demo12345]

You might be able to make the plastic more uniform by either melting it and making it into beads or possibly making/buying a chipper and grinding the plastic into lots of little chunks before putting it in. You could then do like someone else suggested and press this ground up mix with your hydraulic press before putting it in the oven. Also theoretically if you got it hotter so it would flow easier with less surface tension and then put it in the vacuum chamber you might be able to finally get the chamber to help with removing bubbles. Possibly get a large induction heater and wrap the coils around the mold that way it'll heat the steel and if you set it up right then that heat will soak through the plastic. Another thing I've seen some people do when using recycled plastic is add some used motor oil to the molten plastic and mix it in.

[@joethompson11]

Glad Vevor are sorting you out with some cool kit! Really interesting results, enjoyed this 😊

[@gannas42]

I'm glad you are sharing your failures. I think far too often KZbin only shows success and that leads viewers to think they have no hope to do some of these things for themselves once they hit a minor inconvenience or failure. Very much appreciate your videos. 🎉

[@kasbakgaming]

I have experimented with home recycled HDPE plastic myself for making small blanks to use on my lathe for making tool handles, so I also needed to avoid voids to keep the handle solid and not catch my chisels as I shaped it. A few things I learned in my experiments that might help: 1. You do not have to get the temperature too high, and in fact going too high is detrimental because it will just end up burning the plastic and releasing more gasses into the mix. What you want is a low heat applied and removed slowly, in order to maximize the time the plastic is soft and allow the gasses a chance to escape. I worked mine roughly around 250 degrees fahrenheit/121 celsius and depending on the size of the block might keep it heated for several hours. You could go a bit higher than this if you need the plastic softer longer, but I wouldn't recommend going above 300F/150C. 2. Rather than metal for my mold, I used wood. Wood has a much higher R value than metal, so it does take longer for the heat to penetrate, but it also means it takes much longer for the heat to release, giving you more working time for the plastic to stay soft and release the air. 3. Thin pieces of plastic in layers and pressed down on each other worked best for me. The thicker your pieces of plastic are, the longer it takes for the heat to penetrate all the way through and melt to the center. That's fine once it's a solid block but for trying to get the air out to get to that point, you actually want some airflow for the heat to get in. For my sources, I used milk cartons, soap containers, and even cheap grocery bags that we have here in the US (these I often gave a quick once over with a lighter just to get them into a more solid mass than the flowy bag before putting it into the mold). Anything showing the HDPE 2 symbol will work. You don't need to chop it up like it has gone through a blender, just thin sheets to mostly fill your mold. Aside from the melt pattern, or perhaps related to it, this seems to create a sort of damascus effect that increases the end bonding and strength. 4. Be prepared to do multiple cycles of heating, clamping, then adding more plastic and repeating. I would usually start with getting my mold about half way full with loose pieces, would put them in the heat to let those melt down, then clamp for a short while to press the air out and get the pieces to bond. Once it was cool enough to work with but not completely cooled, I would take the clamp out, add more layers of plastic, then heat it again and keep repeating until the mold was as full as I could get it and still clamp. 5. As with many projects, don't let perfect become the enemy of good. Some pockets and voids are going to happen no matter how hard you try, so the goal is minimization rather than elimination. If you end up with any small voids that are a problem in the final product, you can fill it in with small shavings of plastic that you melt in with a heat gun (or just some plastic epoxy if you're crunched for time). 6. Don't be afraid to start over. Sometimes you just get stuck with a run of bad luck and can't get a bubble out no matter how hard you try. Just let it cool, slice up what you got into thin sheets and use it as part of another melt later.

[@wayoutwest-workshopstuff6299]

Thank you - good advice. Except I think this is a different mix of plastics to what you're using.

[@brianshersby8979]

Interesting use of recycled plastics - hope you solve the void problem. Forty years ago I made my 5 year old son a car from scrap wood, powered by an old windscreen wiper motor and the cheapest 12v car battery I could find ( flat out 3mph) the steering systen was almost identical to your wooden cars. I m, ade the steering boxes from 3 inch square section oak post, with half inch axles epoxxyed in. The king pin bearings were made from old.303 brass cartridge cases. Endless fun for yeas! Even had a reversing swith, by reversing the polarity of the motor field windings.

[@buffplums]

Absolutely the best way to design. I love the way you work and think, experiments and trials is the way to go.

[@dfishpool7052]

Thanks for the presentation, Tim. I admire your tenacity, reviewing the results of your experiments and trying all sorts of different solutions. I'm sure that you will meet with success yet!

[@mayoropl1]

You went through standard row of errors for beginners in this area :) HDPE melts at 126˚C (259˚F) - you don't need to heat it much higher, you need to heat it longer (whole crossection). If overheated - it starts to boil and you have bubbles\voids.

[@wayoutwest-workshopstuff6299]

Thanks - makes sense!

[@TheMrWoodsman]

I would try it again after the plastic has been ground down in to a powder, then make a chamber with a heating element around it, put it under the press so you can increase pressure on the mould as the material heats up.

[@lpsowns]

Could see about trying to make a pugmill. Basically a sealed auger that soft material-usually pottery clay-is fed into. The material is mixed and extruded to the outlet size, the heat and pressure reducing the size of any air bubbles.

[@Traderjoe]

I am going to order some things from Vevor after seeing how nice they were to you.

[@AlbertFilice]

I think I see others saying the same but I think, if you chop up the plastic so there aren't any voids in it to begin with, then add it slowly to the container so that it melts as you add it. If you have all those chunks, there is a bunch of air pockets to start. If you're tossing tiny bits onto a mass of molten plastic maybe they'll melt and not suck in air? Cool, and good luck!

[@BRUXXUS]

Your videos are SUCH a delight in creative experimentation and iterating on problem solving. A perfect demonstration on how so many of us learn. This wasn't a failure at all, you learned a lot more about working with this material, even if it's just learning what doesn't work is still learning. :) As hundreds of others have probably already stated, many plastics tend to absorb moisture from the air which expands into bubbles when heated to the melting point. Shredding or pelletizing the plastic first, then gentle heating/dehydrating to remove as much moisture from the raw material before the casting might help. Vacuum drying with the new pump and pot might still come in handy to help with that. :D

[@djmoulton1558]

I think you may be creating the problem of the voids by using large, irregular blocks to start with. What if you were to melt some shallow layers first, and then melt or bond these layers together?

[@tracybowling1156]

Hi Tim! Your experiments are so fun no matter how they turn out! It was all very interesting!! Centigrade is just an old-fashioned term for Celsius. So use whatever words make you happy!

[@tiitsaul9036]

Thank you for taking us along for the journey.

[@martialme84]

Your logic on also showing unsuccessful attempts is sound. Thanks for making this video!

[@wabash1581]

See some good ideas in the comment section. Loving all you projects. Thanks for sharing one that did not have the intended outcome. I like to see the process.

[@tomtruesdale6901]

Very interesting video Tim and thank you for sharing it with us. I see most other have covered what I was going to suggest but I think you are on your way to solving the issues you face.

[@ovalwingnut]

A SUB-Worthy video Now I have the urge to go check out some VEVOR

[@Hellyers]

Forman's inspection at 8:30 did make me chuckle...

[@samsawesomeminecraft]

Casting plastic is usually done in thin panels less than 8mm thick (except at the joints) because otherwise it creates excessive bubbles on the inside. Also thicker parts take forever to cool down after melting. Melting plastic is usually done with shear heating because plastic takes forever to heat up by conduction.

[@ZwilnikSF]

For the bubbles to rise to the surface and release the air, the plastic will need to be more liquid I think. You might be able to retain more heat in the plastic if you put some pre-heated bricks in the vacuum chamber under it but I think much higher pressure compression rather than de-gassing is probably the easier way to go. As others have mentioned, the Brothers Make videos are very informative.

[@backby-anders]

That modified forging fan was the biggest spray gun I've ever seen! :-)

[@bridevalley]

Very interesting! I always learn something from watching your videos even though I don't live on a farm, build railways or design cycle-cars! I do have a small 3D printer and one thing that struck me was how thick and stiff your melted plastic seems to be. I mostly use PET-G plastic for my 3D printed items and that appears to be much less viscous. The temperature I'm using is similar to what you described; around 240 degrees Celsius. I know you'd like to use up your recycled sleeper offcuts but the stuff I use is around 18€ per kilogram from Amazon. In case you weren't aware PET is the stuff used for making plastic water bottles and the G is, I think, glycol that's added to lower the viscosity. It might be worth experimenting with some disposed-of plastic bottles, even though that's PET and not PET-G, but maybe you'd be able to see where the bubbles are as it's much more transparent than the stuff you've been using. Hope that might help... Good luck with your experiment!

[@Averagevideo1029]

I work in PE foam, we always use a round rod heating element usually 200*C embedded in a block of steel to heat our plastic for welding purposes. I would reccomend just drilling a couple more holes in the vacuum chamber lid to run some power inside the chamber and heat while degassing.

[@andyash5675]

A long time ago I worked for a firm that did low production volume phenolic moulding. With that, the mould tool had an electric heater built into it with a PID temperature controller. Overall the machine was like an early manual printing press. It had a heavy old cast iron wheel on top with maybe eight spherical knobs around it. In the middle there was a steel ACME screw perhaps 3/4" in diameter. The wheel was used to apply significant pressure to the mould tool halves. It was slow, but it worked. Basically you need to cross breed a fly-press with an oven.

[@jholmessiedle]

Brothers Make is a good resource as they heat and manipulate 'blobs' of plastic (manipulated to get rid of the voids) and then use a press/ram to get it to conform to the mould. While you may have voids around the mould conformity - you could over-size and machine those off, knowing that the internal portion is relatively 'strong'. The most similar to their process would be silicone baking mats in the oven to melt a thinner layer that you manipulate with silicone gloves into a nice malleable 'gob' - as it retains its heat fairly well (from watching) you can prepare a few at a time and then bring them together. I love Delrin - but this looks super strong too!

[@hartshut]

Make a centrifuge. The centrifugal force will pull the plastic past the bubbles. You can also introduce a heat source that will keep the plastic warm. You could centrifuge multiple molds to balance the spin.

[@JoesWebPresence]

I've been through this Tim! HDPE plastic is the one, as all the other plastics emit dangerous fumes. The key seems to be precise placement of the plastic pieces so it doesn't trap air, and the precise temperature control so it doesn't emit as much fumes. I ended up using heavy weights to press the plastic in the oven, and found that most of the voids were eliminated, but was never able to achieve 100% void free plastic much thicker than an inch or so. I make thick sheets, cut them into lengths and mainly use them as stakes. I also make my own 'L' brackets and the like. Given that you'd like to share this as part of a kit, I can't see any easy way to make those blocks for others to follow using recycled plastics. You've already proved that plywood works well. What about solid blocks? It seems to me that a nice hardwood block may be the answer.

[@Del350K4]

Though this is an enjoyable and fascinating diversion, I can't help thinking that a nice hardwood block might well be the way forward.

[@gonzo_the_great1675]

I use a fridge compressor as my vacuum pump. For vac impregnating wood with resin, for knife scales (handles).

[@Jimfoxyboy]

Heh, ever seen what happens to a marshmallow when you put it into a vacuum chamber? It expands a lot too. I see some talking about compression as well, but then I'd worry about how well the material can contain the compressed gas inside after its cooled down. Injection molding takes small pellet sized material, heating it up slowly while compressing it, to squeeze the air out as much as possible. Then the soft plastic get pushed by a ram or auger to be injected into a mold. Even then, you still can get a little bit of bubbling from air and off gassing but at least its minimized. I hate to ask, but if you are doing this in plastic with molds, does it have to be a large solid block? I get with wood, you wanted to make it simple since it already comes in a solid form. You just cut away what you don't need. Also, as someone else said, be safe out there, specially with plastic fumes.

[@BurnsFilm]

Can't believe i wasn't subscribed, must be on another account. Thank you for the video and great work! I look forward to seeing the next tests

[@redoktopus3047]

i have a much bigger appreciation for injection molded plastic equipment now.

[@totherarf]

I too was going to suggest Brothers Make. Even they had voids though ..... even if small ones. The trick(s) would seem to be 1. Not getting air in at the start (maybe stacking your cut blocks together before melting) 2. Good heat control. 3, Extruding into a hot mould. Remember that even when "liquid" the plastic is very viscus. If you just want to make a cube shape maybe laminating it up would work. You could weld the plates of plastic together by using a metal plate between them heated by running electricity through it to get uniform melting. Again these ideas are worth what you paid for them ;o)

[@beautifulsmall]

As Adam Savage says, Failure is always an option. interesting video, plenty of comments , good luck.

[@filipszatkowski]

You could try to dehydrate the plastic. If it was in an humid environment it could have sucked some moisture out of the air and when heated the water will turn into steamcreating cavities. To do this it would be best to break up the big chunks into much smaller ones and put it into an oven for a few hours at a temperature thats lower than the melting point of the plastic. For Delrin drying temperature would be slightly lower than 175°C (the melting point).

[@arthurschwalm6332]

Would agitation or vibration of the hot plastic help get the bubbles to work their way to the surface, or at least away from the bottom so there would be some usable chunk at the bottom of the block?

[@Sctronic209]

Was thinking the same thing.

[@peterwallace9676]

Like a poker in concrete laying?

[@bobsmith5088]

I think it is just too viscous for that to work

[@daroniussubdeviant3869]

i too have had limited success. using a mix but mainly milk cartons. i mix it with bentonite and activated carbon. i put it in the oven on full to melt it and then treat it like a dough whilst it is still hot and knead the gas out. i then reheat it and press the resultant dough into a silicone mould. this is producing very tough shiny hard black place mats.

[@daroniussubdeviant3869]

my attempts are on a much smaller scale with an old bean can and smaller chunks of materiel. you may have more success by simply using a smaller plastic pellet size.

[@OriginalLictre]

You learn more from mistakes in a process than from immediate successes. One thing that might be worth considering is to use very small scraps of this sort of meltable plastic, and while it's heating, find a way to apply a constant vibration. My thought is that the vibration would encourage the molten plastic to settle, letting the bubbles rise to the top of the mold. Since your mold didn't have any heating elements incorporated in it, the plastic was constantly cooling, and one of the first things that will form is the skin on the top, which would be a major barrier to escaping gasses. However, these are just guesses from somebody with only a high-school shop class experience with forming plastics. (in the early 1980s). Best of luck.

[@tropifiori]

The shop looks very clean and smart

[@pete3897]

At first I was thinking straws into the block inside your vacuum box, but actually what I think you need is a runnier mix so you can pour it. I wonder if more heat or some additive could be used to achieve that... Good luck & thanks for the ride :)

[@broukoid]

3 things: first, you must heat the plastic IN the vacuum chamber (that's not gonna be easy); second, you must put in very small pieces (max. few mm), so the air can escape from every piece as you're heating it up in the vacuum; third - heat up slowly and watch out for overheating - when you overheat, you actually change the plastic properties (like elasticity) and it may become harder for the air to escape not to mention it may be more brittle after cooling.

[@richardball9724]

I have expermented with this idea before. One idea i would surgest is to compress the material as it cools down with g glamps

[@doggfite]

Or the hydraulic press he used in the video several times to unmold the block

[@richardball9724]

That would work

[@rjung_ch]

Thanks for doing all the experimenting for us Tim.

[@kevin-z9s3j]

you need very small bits of plastic to begin with, the smaller the better. like the size of BB's . you also need to form your "block" under pressure to force the material into a solid. good luck with the process. keep on keepin' on my friend.

[@blazinicmischa8196]

Try to put plastic chips in to the mold. And then start to melt them in the vacuum. When its all liquid add the air to the chamber to compress the voids fully and let it cool down

[@charcoal386]

Interesting to see the process of troubleshooting

[@chox2001]

When plastic is extruded it’s normally extruded in slightly larger size than required. It’s extruded by a screw type heated press funnelling in small pellets or similar sized pieces to be compressed by the screw towards the exit tube a short tube the product size that slowly travels into water to cool and solidify the plastic. It’s a science that has to be adjusted for different types of plastic. There is some video on KZbin of plastic extruded in India. Hdpe is probably the best plastic to use and source. Milk carton plastic bottles 👍 The plastic you are using is difficult to work with I know it as timbron it has different names in different locations. Try hdpe but remember the start of the extruded piece and the end of the extruded piece will not be as good as the middle so extrude at least a few inches extra to see what you need to do to get the good consistent stuff.

[@holgerhahn4869]

Really love your presistency in the trial and error process! Really enjoyed the clip! Thank you

[@virtualfather4117]

If you shred the plastic put it in the mold compress it with the hydraulic press put the spring loaded block back on top then heat and cool. Good lock.

[@carlssecondchance]

Could you alter the viscosity of the plastic perhaps by introducing a mixture of different plastics to make them more "workable" so to speak ? All of the above comments are excellent, especially the pellets, I'm sure you will find a path through this dilemma Tim😊

[@MikClarke]

Yes this. It's the one thing that hasn't been mentioned yet... root cause of the problem is the viscosity of the melt, preventing extraction of bubbles by vacuum.

[@AllenKll]

A pressure pot is what you wanted to use. The pressure makes all the bubbles and voids very tiny. then when the plastic cools, it solidifies around them. This is what is used with epoxy resin.

[@jaysparrowhawk9388]

I do a similar thing with bottle tops, to avoid the voids smear the mould with Vaseline to stop it sticking, the mould needs to be polished not rusty, cut your material into small chips and add gradually to the hot mould allowing each layer to melt before adding more. I find the voids appear as the material shrinks but is stuck to the edges of the mould. I use a scraper or a thin knife to remove the plastic from the edges of the mould as it’s cooling, if you can get right down the side all the better, it needs to cool slowly I leave mine to cool on top of the aga

[@sgibbons77]

SUGGESTION: When casting resin, sometimes you use a vacuum chamber to try to get rid of bubbles in the liquid resin before it hardens. More often, you put the liquid resin in its mold, then put all of that into a pressure chamber and bring the pressure up to 40 - 60 PSI. The pressure collapses the bubbles, then the resin hardens, preventing the bubbles from reforming once you release the pressure. For the relatively small blocks you are talking about making, it shouldn't be too hard to make a pressure chamber to try this.

[@thelwq]

As a user of FDM 3D printing machines I would recommend to inject the hot plastic into a mold under pressure and using some kind of nozzle - to lay one, voidless piece o plastic, one layer at the time and then adding another one, fusing them together using force and heat... vacuum is fine but not for stiff and viscous materials like HDPE is.

[@mmheti]

You could try melting it in layers. Create 2-5cm block, suck the air out, add more pellets on top, melt again to create new layer, vacuum, repeat until desired height is reached. The only question is if the layers will melt togeather well.

[@Bigcountry_littlelegs]

Great video mate, that vac chamber looks great

[@chrislee7817]

I do a lot of vacuum infusion to make composites. The other way is to use an autoclave. Put your 'hot block' 😊 in a high pressure vessel to shrink down any bubbles. These small voids could hold grease for bearing lubrication too. 👍

[@amandahugankiss4110]

been said but it is still helpful: dry out your plastic first. super important to drive out any moisture.

[@swingcadillac]

Build a metal funnel above the mold that fits in the oven. The Plastic will heat up and pour into the mold releasing gas as it hits and not leaving voids. I dont think it would work outside an oven because it would cool too fast as its poured but inside the oven it will stay liquid and fill the mold. I was thinking of trying this with a wood fired chamber but your idea of just putting it in an oven is smart because you have to control the temp the whole time, but get a used oven for the shop and put it to an extension cord like the welder has so you dont mess up the wifes kitchen .

[@otastumelis8786]

The issue here isn't gasses in the plastic, those would be smaller bubbles. What's happening is the plastic is contracting as it cools, and since it cools from the outside inwards, you end up with a cavity in the middle. The way to solve it is firstly to cast at the lowest temperature possible to minimise contraction. Another thing that helps (for metals at least) is to have a tall feeding sprue that gives additional material to draw in to fill the cavities. This works for metals because the density of liquid metal is big enough to build up a fair bit of pressure. Liquid metal is also likely not as viscous as plastic. I don't think the same approach would work for plastic, so you'd need another way to add pressure to the casting. I'm not sure if cooling it very gradually to minimise the temperature difference between the core and the exterior would help, but it might

[@stevewilliams2498]

2 things. Split your mould diagonal corners and bolt the two halves for extracting. 2nd .. Pottery clay is similar consistency and must not have air pockets (they explode in the kiln). There is a machine called a Pugmill. If you can keep it warm this is exactly what you need. I don't ask for any royalties, though I probably should 😂

[@sacredsan]

What if you try the temperatures between first and second attempts, but for longer times? around 200 and 220? Also try making sheets, so there is no place for bubbles, and then melting them together with a torch, or one by one in the oven. I suspect that higher temperatures make plastic release gases, and that higher thickness of the object allows for the gases to be trapped. Good luck!

[@assassinlexx1993]

It will trickier. But you have to start with s high vacuum before melting. Make your mold with a small taper to make extraction easier. No air to start means no air to trap. 🤔

[@onkelnb]

My experience with plastic Recycling were similar. I tried to make sheets out of bottle caps. Well, I got some flat blobs that I never used for anything. I tried to force it flat with clamps but it takes ridiculous forces. Grinding down larger pieces of plastic also never worked for me, because i don't have a metal workshop to build a shredder. That's why I ended up with bottle caps as raw material. Ist there any way you can heat the plastic under vacuum? If there ist no air in between the plastic Bits before they melt, there can be no bubbles. But be careful! You will only be able to heat the plastic by conduction, Not by convection! For such a block, it will probably take forever...

[@tomi935]

Dobrze myślisz Tim... 👍

[@OllieWille]

Reading some of these comments, maybe you could heat it while compressing it with the jack? That way you compress the pieces together as they soften, allowing air to escape before it all becomes gooey and bubbly.

[@NicoSmets]

Wonderful video. How about the following: instead of lowering the pressure to hope to release the gass bubbles, how about increasing the pressure to compress the gas pockets to a small and negligable size? I believe this technique is used in epoxy pourings too.

[@xinlu2806]

At this point it wouldn't surprise me if one day you made a spaceship to fly to mars with stuff you found on the farm

[@mergrew0110]

That’s a novel way of derusting the inside of a box tube.😎

[@BrettCooper4702]

You need a heated vacuum chamber to keep the plastic soft you the air can escape. Your pressure container is metal, so it could sit on a hotplate to add the heat needed. Degassing can take a while. the top could be replaced if it's subject to heat issues and the silicon seal should be fine at high temperatures.

[@shinergriff]

Try putting it in a pressure chamber and pump up to 60 -100 psi this will crush the voids down, this method is used in epoxy casting to make the bubbles 'disappear'

[@SW-qr8qe]

The plastic sets from liquid to solid from the outside. The centre is the last place to set. Voids result from internal stress- I think there is a substantial change in volume between liquid and solid state. Injection mouldings suffer from voids if the sections are too large. Every design guide advises constant sectional areas and avoiding large isolated heavy sections - essentially what you are trying to make.

[@RunnerPack]

My first thought: if it's okay for the planks to have voids, maybe it would be okay for your steering blocks to have voids. The tubing a bike is made from is nearly all void, which only makes it lighter weight.

[@georgeross9834]

Easy solution is if a metal cylinder can work for u then use an induction heater around the pipe start at the bottom and move the induction heater up slowly as the pellets melt the air trapped will be at the melting zone . Once you have reached the top allow to cool . A coil induction heater around a pipe. 😊vacuum as well if you can seal the electrical connections

[@deaultusername]

vacuum chamber might work if you could make your own heated vacuum oven to keep the plastic liquid as you pull air on it. Much more likely you need a Bomb chamber (high pressure air chamber) so called as high pressure air is very dangerous but it will work. You should dry your plastic as even though it looks dry and water resistant quite a few plastics are hydroscopic and will pull air from the surrounding environment. As we live in Ireland humidity is quite high and thoroughly drying your source plastic will definitely help. This avoids steam bubbles forming in side the mass.

[@patchvonbraun]

I've had good luck with stuff from Vevor. I don't have a YT channel, otherwise, I'd be begging them for "stuff" for my not-for-profit. We used one of their stick welder/plastic-welder combinations a few months back to effect some significant structural repair work at our observatory. Worked a champ, working hard for 3 days of welding alloy steel structural components. Got it for CAD$139.00 or so on sale. Astonishingly good for the price.

[@mrclaus859]

Thanks for posting

[@MrNoncredo]

you should use very small pieces of plastic the size of grains of wheat, I remember that my father in the 70s, he took me to the factory where they made plastic crates of Peroni beer and there were large bags of yellow plastic mini balls which they tipped into a hopper and after several passes the crates came out in a 50 meter long machine

[@maficstudios]

IF you could draw a vacuum and then heat it, you'd have zero voids. But the chamber lid would melt first. Which would be exciting.

[@liefdegator1]

Instead of putting the mold into the vacuum bucket, you make it such you can suck the mold itself vacuum. (bigger Mold) Also you can then heat up the mold with a flame, making the plastic more liquid. You will not be able to see the process but i think it could do the job.👀👍

[@TgWags69]

From the world of wood resin stabilization and epoxy air bubble removal... most have switch to pressure pots instead of vacuum. You can see if you can find a big old pressure cooker or pressure paint pot. I'd venture to guess about 150 psi or so on that would sheink those bubbles to a very small and insignificant size.

[@aeonturnip2]

Just an idea - how about building up thin layers (not sure if you'd need to degas each one before adding it to the mould), with a final heating to fuse it all together.

[@MassiveDynamic9]

I had this same thought. If, at each moulding, you cut the product into bars (as large as possible without voids), then replace the bars into the mould in their original orientation so that they don't have to be completely melted. Would they be able to be fused together into a solid block if positive pressure were used to maintain full contact between blocks?

[@gustavfenk4021]

I’m thinking that the plastic is still too viscous for any air bubbles to rise to, and break through the surface. A cool crust on top isn’t helping (could an infrared heating lamp help here?). What you are doing is more akin to sintering the pieces of plastic together, rather than remelting - similar to taking the wrappers off a load of toffees and leaving them in a bag in your trouser pocket only to find them fused together into a single sticky mass the next day! If you can’t get the plastic runny enough so that it can be poured into a mould, then you need to work out a way of “kneading” all the bubbles out (rollers of a dough hook/paddle?). Smaller pieces of plastic will still leave voids: there will be more of them but they will be much smaller in size.