Experiments with Sheetpress outcomes [#V4]
Hello Community, we are currently working on the development of the large sheet-press machine in version #4. Alongside we also started to experiment with the outcomes from it and also explore their different properties. So far it looks very promising and will open a whole different range of design possibilities. We are working with different types of plastic sheets like PP, HDPE, PS, Mixed etc. Here we will be documenting success and failure stories while dealing with them.
We are going to use various tools and machines for cutting, drilling, screwing, bending, welding and for trying different joinery techniques. The goal of this thread is to find out the most efficient techniques to work plastic sheets of different thicknesses.
For more information related to the sheet-press machine follow:
Constructive comments, suggestions, and ideas are welcome. Keep fighting and sharing.
HDPE is definitely one of the most interesting and smoothly manipulable type of plastic to work on. After getting the HDPE sheet from our colleague and friend @markbertbach we started to experiment with different tools and joinery techniques with it. The material is super strong and almost acts like wood. It can withstand more strength and was a good longevity. But it is not so easy to make like other plastic, particularly PP.
The sheet we made is 1000mm x 750mm in size and 13mm in thickness. It was made with 10kg of black HDPE granule. The result has a very smooth finish, almost marble-like texture. It feels really tough and durable. It is extremely flexible. One can easily fold it in any angle with a half cut, without breaking or cutting completely.
The manufacturing process was not very easy. Because of its high viscosity, it takes a lot of time and effort to spread it after melting. We raised the temperature around 225ºC for the melting process. It created a high strength on the walls of the sheet mold and deformed it a little bit. The material is difficult to remove from the mold. It takes longer than making a sheet out of PP or PS.
Cutting HDPE Sheets
Objective: Exploring different cutting tools and techniques.
Tools: Jigsaw, Mitre Saw, Table saw.
I used Jigsaw with plastic cutting blades. Continuous push and faster movement result in a smoother cut. Blades with different orientation of teeth gives different output. Because of its high density, the blade might get stuck in the material if moved slowly. Leaves decent finish after cutting, but needs sanding for a better result.
o Using Mitre saw was a great success. Plastic cutting blade works perfectly. Faster you run the machine smoother the result is. HDPE leaves only a bit of plastic dust due to cutting but no melted or sticky plastic on the machine. The dust can be removed easily. The finishing of the cutting edge of the plastic is already quite nice.
o Table saw worked the best because of its speed. Using Plastic cutting blade is a must. It made a very smooth cut. No fume or melted plastic on the blade. Perfect for the big piece of sheets.
The result generally does not require polishing after cutting it.
o It does not melt at the edge due to the friction with the cutting blade.
o No bad fume while cutting.
o Almost feels like cutting a wooden plank.
o Leaves a little bit of plastic dust on the machine, but it is really easy to remove as it is not sticky.
o The faster the better. Table saw and Mitre saw gives smoother output.
Quite impressive. Do you think that you are close to something that you could market as say a countertop?
With much more rudimentary forming than your sheetpress, I had difficulty with stock warping when I’d attempt using a planer or router on formed #2 hdpe. I’m pretty sure that I could bang together some 6″x6″ tiles out of #2 HDPE and glue them down with some variation of the polystyrene glues. But beyond a certain size there’d be too much warping with what I’ve done. I also had very matte finishes, not exactly the sort of thing that I really wanted. That press has yielded some progress. If you can get to yielding something around a meter deep, 4-5 cm thick, and can hold form in excess of 2 meters wide, then you have yourself a product. Then lets see about coming up with invisible joinery or seams.
I’m kinda jazzed looking at what you’ve done. Very cool.
We still have to experiment with greater thicknesses, but I have my doubts towards reaching 4-5 cm with the sheet-press process. I think we’ll reach a limit enforced by the heat transfer coefficient. Maybe with mixed processes, e.g. extruder + sheet-press, we can reach these greater thicknesses. Other ideas are to weld sheets together, by melting 1 side of the sheet en then pressing two sheets together, forming plastic welds. This could be used to extend the length and width and hopefully also the thickness.
Warpage is a recurring problem that indeed increases with scaling up. nevertheless, we’ve been able to get nice results with manageable warpage.
well balanced cooling, evenly throughout the entire surface and equal on both sides seems to do the trick. It is also important to let the entire sheet cool down under pressure or at least while restricting the warpage.
As to suface finish, the mould finish will copy onto your sheet, so spend a day polishing and your sheets will come out shiney, but for the stool in the picture a structured surface finish was created by using structures ptfe foil
in the other pictures you can see the flatness/straightness of a sheet of PP 105 x 75 x 1,2 cm
Still . . . looking at your display up top, it’s almost like going into a store to shop for a stone for your counter top. I want to run my fingers across the surfaces. The light touches of secondary colors are I think an important touch. Getting into that range where it may not be a naturally formed stone, but it’s close enough to fool the eye and allow the artistic sensibility of the designer or end user to flourish is very compelling. The piece that you worked above has a depth of color I’ve had difficulty trying to produce, that illusion of greater depth than the source material. It’s like an oil painting almost. If you can be where you are afraid to cut it for fear of ruining the original piece, you are now confronted with the artists dilemma instead of the craftsmans grumbling. A far cry from a pile of garbage isn’t it?
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