Beam Production (v4)
We’ve been cranking hard at the Precious Plastic HQ with the development of v4..
The focus for the beginning of the year is on exploring and developing techniques for the Extrusion machine. This topic will be focused on Beam Production, with all the successes, failures and set backs along the way.
Stay tuned for further topics as the development continues..
Test: Polystyrene Beams
Objective: Create transparent beams and explore the control of colour with PS.
@tafnstuff and I tried various beam moulds attached to the extrusion machine. The machine is in good state and using it is very friendly. We screw on each mould, fill the hopper and turn the motor on. The machine was set to 240 C and motor speed varied between 210~250 rpm. Demoulding the beams can sometimes be very hard with PS as it doesn’t shrink as much as PP or PE.
-PS can remain transparent with the extrusion process.
-Quality of finish is high.
-Beams are very hard. (Sound like a peice of rock and take long to cut through)
-One beam developed a large cavity and was completely hollow. We think this could be from the thin gold flakes (coffee cup lids) shrinking rapidly and drawing to the outer layer of black.
Test: Polypropylene Beams
Objective: Create large, strong beams
Shred large flakes into smaller bits. The machine was set to 200 C and the motor speed was varied. For most tests, I used a wooden block attached to a longer piece of wood (plunger). I hung a 1kg bucket onto the end of this plunger to create some relatively consistent pressure to the extruding beam.
-Smoother surfaces can be obtained by using a weighted plunger.
-Smoother surfaces can also be obtained with a warm mould.
-Smaller granules work better than large.
-The end of a beam seems to have better consistency and surface. Possibly due to the heat of mould and surrounding plastic.
Test: PP Beam consistency and speed
Objective: Discover the optimal machine settings
There is an image of this beam above, and I went through the same process however did not use any plunger/resistance and the mould was cold (4 C). I set the machine to a constant temperature of 200 C and ramped up the rpm and changed colour every 10 minutes. Starting with [email protected], [email protected], [email protected], [email protected] and [email protected]
-Initial section of beam was very rough, did not fill mould cavity or fully melt.
-Consistency improved with length. Plastic has more time to melt inside the beam core.
-There was a hollow channel at the end of the beam. Possibly from letting machine run with no plastic.
-With a cold mould, it may be better to start off even slower and ramp up the speeds thereafter.
Test: Polyethylene Beams
Objective: Create stronger beams. I’ve found PE to be an elusive material for the hand powered machines due to it’s viscosity even in molten state. These experiments were to learn about ease of production and the differences between PP and PE beams.
Shred larger flakes into smaller bits. The machine was set to 220 C and speeds were adjusted according to the rising and falling barrel temperatures. The plunger was weighted with 1kg.
-PE can be used to make strong beam.
-After enough time, demoulding is easy.
-Surfaces feel more slippery/waxy than PP or PS.
Test: Large PE Beams
Objective: Make the biggest PE beam possible.
We had some large rectangle and square tubes in the workshop onto which we welded angle iron brackets for connecting to the extruder. It is helpful to clean the inside of the tube before use (image 3). The process of extrusion follows the same steps as before. Machine set to 220 C and speed varied according to the temperature of the barrel. A 1kg bucket was used for resistance on the plunger.
-The rectangular tube mould broke while extruding. This happened when the resistance of the plunger rose as the weight moved further away from the mould. The temperatures spiked to 270 C and the mould bulged (image 2). Closeup of the swollen area of beam also pictured in image 2.
-The square shape worked well too. You can see the shape of the nozzle and initial plastic section in image 3.
-Cooling takes far longer with such large shapes.
-There is a fine line between too much pressure and too little. Only some sections took the shape of the mould, others remained round/organic.
-Temperature on average was 30~40 C hotter than the machine was set.
I’ve had too many bad experiences with extruding pe and ps … that’s why I am trying to develop simple ways of making beams. .. but always looking for getting more information and ideas from other colleagues. What do you think ?https://www.youtube.com/watch?v=gsnsitKldyU
Yo @wolfgang, nice videos! Thanks for sharing your process. Great to see the creative use of “low tech” tools. Quite a lot of hands on work but the results are very surprising, at first I didn’t think they would be strong. A whole new take on making beams.. really interesting!
Looking forward to seeing how your tests go with the hot sand and use of solar power
Hello, any tips about PS demount?
Some times I couldn’t extract beam from metal tube, even with brute force.
Do you use any mould release or oil inside tube?
Hey @copypastestd, for releasing the PS beams we gave the mould at least 30mins to cool. The beams we did make were also not too long.
Circular / square shapes seem to cool more uniformly and are easier to release than the rectangular shapes. So far we’ve had no need for release agent in beam moulds
In description you mention that motor speed varied between 210~250 rpm – it is not clear for me. This speed of motor, or speed of screw after gearbox? What ratio of gearbox do you have in your machine?
Do you have heaters on the mold, or are all your heaters mounted on the side just on the extruder side?
In my case, at some point the plastic gets stuck in the pipe – and the only working way to push it forward is to use heatgun (which in turn is extremely inefficient).
I am satisfied with the quality of my plastic beams (they are strong and smooth) but the process if really difficult takes a long time.
And I’ve never been able to make a bar longer than 50 cm.
Hey @copypastestd, thanks for you questions.
The speed mentioned is the speed of the screw itself, I’ll have to find out what the exact reduction is.
The only heaters are those on the extruder itself. To get a hot mould, I’ve been extruding a beam, demoulding asap and then using the mould again while it’s still hot.
What material have you been using and what temperatures? Your beams look smooth and consistent.
Perhaps the issue of not being able to extrude longer than 50cm is that plastic is not warm enough to maintain the flow or your machine is unable to maintain the pressure
Here’s an inside look at how a beam is born 🙂
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