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Ocean Cooling Process
We just let the thing sit in the breakers for 15 minutes. The beam slides out with a few taps of a hammer.
Beam production is going along fairly smoothly.
We had some minor setbacks with our extrusion machine. Back pressure from a clog shattered our motor mount, so we had to rebuild the frame.
Shout out to Reliable Workshop (portside in Male) for machining the faceplates for the motor.
Make sure your machine has been heating for a fair amount of time before pushing any plastic!
With that we are back to extrusions. Here are some logistics:
Mold Size: 40×40 – 22 gauge
Melting temps: 200 / 220
40 minutes run time
15 minute ocean cool (see photos)
In an effort to try to increase production time, we tried increasing melting temps to 220 / 240. This did not change anything, with run time still at 40 minutes to fill the mold.
Mold Size: 40×40 – 22 gauge
Melting temps: 200 / 220
23 minutes run time
15 minute ocean cool
HDPE is much faster, and produces a much smoother product.
We are not plugging the beams with wood blocks / any resistance in fear of busting our very thin walled tubing. HDPE’s results are very consistent, and produce a smooth enough product where it feel unnecessary.
PP would benefit from some mold resistance; the beams are still strong, but potentially unappealing for a certain aesthetic. We still think they are very usable / if anything communicate the material more clearly than something super smooth.
So far we have used the 40×40 beams to make some comfy Maldivian hammock chairs. They can be viewed in the Product Design Topic
We will now be moving onto making a bench, using long 50×25 beams sitting on a rebar frame. Other molds we are going to be working with are 25×25 square, and 20mm round. We hope to make some planters from the square, and want to experiment further with warping / bending the round beams.
That’s all for now. Thanks for tuning in!
Our machine here in the Maldives is not what we were operating and testing with during v4. That being said, we are semi limited in several categories:
Width and Lengh
I like to think the setup we are using here is more aligned with the extruder build most people are running, which is the current model PP has released.
So far, we have found that it is hard to find thick gauge steel tubing / and or does not exist here. Tubing is also almost always galvanized here, which means welding it without grinding is unadvised, due to zinc poisoning.
With those things in mind, we have already begun production of a 40×40 by just shy of 2 meter length. We purchased a 3 meter length of 22 gauge tubing from a local metal distributor and got to work.
Due to sketchy stick welding setups on thin gauge tubing and using scrap steel for bolt connections to the machine, we are getting the beam out of the mold from the non machine end, so we dont have to worry about any weld splatter / extra material getting in the way of removing the beam.
(Past beam molds were removed from the machine end, but with the upgraded v4 machine, we were able to keep the mold on the machine, and after a cooling period, restart extrusion which would push the old beam out of the mold.)
By extruding just to the 2 meter length, after a quick 10 min ocean cooling, the beam slides right out real easy. We are not producing extremely smooth beams, like ones seen in our v4 production, but they are also not extremely haggard, and very usable.
We have found that extruding a beam over 2 meters results in difficulties removing the beam from the mold. We believe this has to do with inherent pressure build up over length. We prefer not to use mold release if we can.
That’s all for now!
I leave you with a photo of our current little setup.
photos of the beam mold(s) will come within a week 🙂
Take it easy!
Did you end up making this?
Any info on sun exposure to your benches / stairs? Any warping?
Glad to see the beams being put to good use.
Nice! looking good / nice fix for the screw coupling, makes sense. We have essentially the same thing (hex hole) but with some set screws, just to make sure.
We have sectioned every beam we produce to check out the inside. We have mixed results, but this can be the product of many different variables, such as plastic used (because beams require bulk amounts, we use what we can get, this is sometimes mixed material / material that has non plastic things in it), speed is another variable, as is heat and pressure.
But pressure in my opinion is the greatest factor. If you can put resistance on the plastic as it forms in the mold, you get less air bubbles. We just use a wood plunger that fits the mold, and hang weights on the tail that sticks out.
I am happy to see lots of interest in the current development. This last month has been spent working on upgrading the machine with a new motor 1.8KW >> 3KW, and trying to develop continuous extrusion with water cooling.
Originally when we were doing beam extrusions, we were using 3 meter lengths, and waiting for the plastic to cool before being able to slide it out of the mold.
These days we are using a water pump system which sprays cold water on the entire mold, and slightly slower speeds, to be able to continuously extrude out of the mold without taking it off the machine.
This has had varied success, with 30x30MM square tubing it works well, and produces smooth beams after the inital 1/2 a meter or so.
When you try to move up towards 50x50MM the material becomes to thick to cool the center (the plastic flows through the center and hits the walls over and over as it fills the beam mold) and fails as soon as it reaches the end of the mold.
So maybe water cooling is not the option. This is where our new setup comes in.
The new motor has a higher gear ratio, so we are able to get much faster output. At max speed, we are turning the extrusion screw at 440 RPM. We are outputting material into molds at that rate.
This has resulted in filling meter long lenths of 65MM round tubing in 10-15 minutes. They weigh in at 9 kilos.
With larger mold filling at high speed, we are not water cooling. We wait for the mold to fill, then stop the machine for about 10 minutes, then turn it back on; The new material pushes out the now cooled material, and we can just pull it out after a few seconds. This makes workflow easy, as there is no water, and no need to pull the mold off of the machine.
Thats all for now, see y’all soon!
Both PP and HDPE, however, HDPE was not shrinking as much, and was breaking molds. Continuous extrusion development has been going along well, so we hope to have tackled that small issue.
Were are still getting numbers for kilo output, but Mattias sheet I previously linked has some handy information for extrusion times / beam sizes that you could get that from.
I think either motor is a fine choice, really whatever you want to part with.
Still working on air bubbles. If you have very fine shredded plastic going in (1 – 3MM) and no pause in material flow (power shortage, materials gets stuck going into barrel from hopper) we get limited / no air bubbles.
I will do a photo dump here in a few days of how things are looking / any updates we have.
In the mean time I can answer your questions, thank you for your patience.
– The extrusion screw we have is 23mm, and the barrel ID is 24.
– Glad to hear you have a well equipped shop / are pumping out machines.
We just upgraded to a much larger motor, but for V3 we had a 1.5Kw motor, or about 2HP. Max RPM at 50Hz was 138.
This setup handled everything fairly well. Beams were a little slow, but no issues with filling molds until we tried large beam fills (110MM x 110MM).
We now have put the same extrusion screw setup on a larger motor, 3Kw…
Max RPM is 400 at 60Hz, though we will not be extruding anything at that speed.
Key way is the way to go. The old setup was extrusion screw to coupling > coupling to 24MM key way shaft. Now it is the same, but we have the 24MM key way shaft coupled to the new motor, which has a slightly larger key way shaft. We use a jaw coupler for this.
Sit tight on the CAD drawing, I will find the best email for you to shoot it over to, and then we can discuss further.
Take it easy in the mean time, and goodluck with the build!