# Sheetpress Experiments - Cassandra - 650 - EDC - RC1

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## 10 mm

A one-stage process, suitable for up to 10 mm thickness, requires careful setting and timing to avoid warping effects.

### Description

One-stage process for plastic sheet pressing.

### Settings

- Temperature: **155-160°C**
- Cool-down temperature: **130°C**
- Duration: **1 hour** for mold closing, **30 minutes** for cool-down

### Requirements

1. Place a stainless sheet inside the mold.
2. Fill with plastic, carefully pressing.
3. Avoid contact between the mounting edge and the mold.
4. Wait **10 minutes** before full pressing.
5. Wait **1 hour** for full mold closure.
6. Cool to **130°C** and wait **30 minutes**.
7. Remove the mold and access the formed sheet.
8. For shiny/flat finish, press again with a harder surface.

### Results

- Small flatness errors (0.5-1 mm) based on press quality and plastic characteristics.

### Problems

Warping and material shrinking, especially in corners.

### Proposed Solutions

Add reheating steps at **140°C** and press again to minimize shrinkage and warping.

| | |
|-|-|
| Mould | ![Mould](cas-650-hdpe-10.jpg) |
| Top-side | ![Top-side](cas-650-hdpe-10.jpg) |
| Back-side | ![Back-side](cas-650-hdpe-10.jpg) |

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## 20 mm

A two-stage process for thicker sheets with a more controlled heating and pressing cycle.

### Description

Two-stage process for enhanced material control and heating distribution.

### Settings

- Temperature: **155°C**, cooling at **130°C**
- Duration: **90-100 minutes** for initial heating, **30 minutes** cool-down with die insertion

### Requirements

1. Reheat the plastic to **130°C**.
2. Insert a die with **3-4 mm** thickness once melted.
3. Cool the mold for **30 minutes** before opening.
4. For thicker molds, ensure the press has **20 tons** of power.
  
### Results

Reduction in warping and improved flatness by using intermediate dies.

### Problems

Requires a significant amount of time to ensure proper penetration of heat.

### Proposed Solutions

Incremental heating and die insertion at controlled temperatures to minimize air pockets.

| | |
|-|-|
| Mould | ![Mould](cas-650-hdpe-20.jpg) |
| Top-side | ![Top-side](cas-650-hdpe-20.jpg) |
| Back-side | ![Back-side](cas-650-hdpe-20.jpg) |

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## 40 mm

A challenging process with long melting times, leading to potential warping and deformation.

### Description

3-stage process for very thick sheets. Manual handling needed to prevent air pockets and deformities.

### Settings

- Temperature: **175°C**
- Duration: **2 hours** of heating, **3 hours** cool-down
- Mould: **55mm**
- Die: **10mm**

### Requirements

1. Heat to **175°C** for at least **2 hours** to melt the thick plastic layers.
2. Insert a die (10mm) to ensure no air pockets form.
3. Let the plastic cool with a **3-hour** rest while engaged with the die.
4. Reheat corners at **140°C** and press again, for 15 minutes, with no mould (careful).

### Results

Height differences up to **5 mm** on die-engaged side.

### Problems

Long melting times, air pockets, and corner deformities leading to warping on one side.

### Proposed Solutions

Intermediate reheating and more controlled cooling periods to mitigate height differences.

| | |
|-|-|
| Mould | ![Mould](cas-650-hdpe-55.jpg) |
| Top-side | ![Top-side](cas-650-hdpe-55.jpg) |
| Back-side | ![Back-side](cas-650-hdpe-55.jpg) |

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