Results from initial process testing with mentioning of properties and remaining challenges.

Deforming during cooling process

Depending on the material used, the shrinkage during the cooling process can be significant. We realized that it is best to let the plastic cool down in the mold under constant pressure.

Uneven melting

Due to the machines we used for the heating process, we experienced uneven melding. The T-Shirt press heats only from the top, meaning it takes a lot of time to penetrate to the bottom. We tried burning the mold around with a lid but it still does not result in perfectly evenly melted plastic.

In the oven, the distance to the heating elements makes a difference. The close the dough gets to the heating rods, the higher the chance that it will burn while at the same time, the center may still be granular.

Burning

Burning must be avoided! It can cause toxic fumes and will cause the polymer to change its structure so that it can no longer be recycled (at a good quality).

Granular patterns

Shredding material and heating it to a minimum melting point can cause interesting granulate patterns. But air pockets have to be considered, depending on the application.

Marble patterns

To obtain the marble pattern, the dough like heated plastic has to me mixed and folded. This caused colors to mix and once pressed and cut, it reveals a marble like structure. The more the dough is mixed, the more the colors combine from rough to fine patterns and eventually to one solid mixed color.

Time to completion

The melting process takes a long time. Different methods for a higher throughput have to be considered.

We are considering two options:

a) Melting larger quantities at a time and pressing the material into a big block. Once cooled down, it can be sliced into individual sheets.

b) Continuous melting process via conveyor belt oven in a thin layer of polymer material. Material can then be worked on a heated tale top to avoid settling before enough mixture is transferred into the mold.

Air enclosures

While sigle air enclosures can be filled during the refining process, it is better to avoid them during the production process.

Quantity and technique

The exact quantity to produce one unit output should be defined for serial production. Guessing does not yield solid results and causes waste.

Also, the technique of how to insert dough into a mold makes a big difference. Since the dough depends on the flow rate of the polymer type that is used, some materials will spread less than others. The more base area covered, the better. Cutting the dough into several elements yields good results but it has to be hot enough and under enough pressure to combine / connect to the remaining elements.

This technique can also be exploited for the creation of patters.

Uniform size

During the refining process, it is important to focus on a uniform size and appearance.

Maximum dimension

We worked with a table saw to cut the tiles to size. The blade is not big enough to separate a large cube into individual slices. A bandsaw or other types of saws could potentially solve this problem.

Overview of some prototype specifics

So far melting cut/shredded pieces (>500g) of PP,PE in the oven @ 250C at least 40minutes (not including preheating, folding) then pressing in between heat-resistant fabric and mold gives base tile.

Cut/shredded PP,PE (<500g) can be placed under heat press @240-250C for heating and folding between heat-resistant fabric (only), to be transferred to a mold(with fabric in between) and press.