Plastic Processing Guide
From collection to finished sheet — everything you need to know about processing recycled HDPE plastic in the on-country production facility.
Accepted Plastics
The facility processes HDPE (High-Density Polyethylene), identified by the #2 recycling symbol. Each Stretch Bed diverts 20kg of HDPE from landfill.
Accept
- Milk bottles and juice containers
- Detergent and cleaning product bottles
- Shampoo and conditioner bottles
- HDPE pipes and fittings
- Plastic crates and bins
- Bottle caps (often HDPE)
Reject
- PET bottles (#1) — different melting point
- PVC (#3) — releases toxic fumes
- Polystyrene (#6) — incompatible
- Mixed or unlabelled plastics
- Contaminated or food-soiled plastic
- Plastic with metal inserts or electronics
Identification tip: Look for the #2 triangle on the bottom of containers. HDPE is typically opaque and slightly waxy to the touch. When in doubt, set it aside for a supervisor to check — mixing plastic types ruins entire batches.
Collection & Sorting
Good sorting at collection prevents contamination downstream. A clean input stream means better sheets and fewer rejected batches.
Step 1: Collection
Gather HDPE plastic from community collection points, local businesses, and council waste streams. Remove lids and rinse containers to remove food residue.
Step 2: Visual Sort
Check every item for the #2 recycling symbol. Separate by colour if colour-matching sheets are desired. Remove any non-HDPE items, labels, and metal components.
Step 3: Cleaning
Rinse sorted plastic with water to remove dirt, dust, and any remaining residue. Allow to air dry before storage.
Step 4: Storage
Store sorted, clean plastic in designated bins away from weather. Keep different colours separated if needed. Label bins clearly.
Safety
Required PPE
- Shredding: Safety glasses, hearing protection, heavy-duty gloves, closed-toe shoes
- Heat press: Heat-resistant gloves, safety glasses, long sleeves, closed-toe shoes
- CNC routing: Safety glasses, hearing protection, dust mask or respirator
- Sorting: Gloves, closed-toe shoes
Fume Awareness
HDPE at 190°C can produce fumes. Always ensure adequate ventilation when the heat press is running. If you experience headache, dizziness, or nausea, move to fresh air immediately and notify the supervisor. Never heat PVC — it releases toxic chlorine gas.
First Aid
- Burns: Cool under running water for 20 minutes. Do not apply ice. Seek medical attention for serious burns.
- Cuts: Apply pressure with clean cloth. Clean and bandage. Seek help if deep or won't stop bleeding.
- Fume inhalation: Move to fresh air. Rest. Seek medical attention if symptoms persist.
- Eye injury: Flush with clean water for 15 minutes. Seek medical attention.
Shredding
Shredding reduces sorted HDPE to uniform flakes ready for the heat press. Consistent flake size is critical for even sheet quality.
Feed Rate
Feed plastic steadily into the hopper. Do not overload — this causes jams and uneven output. Listen to the motor sound for signs of strain.
Jam Clearing
If a jam occurs: power off the shredder, engage lockout, then clear the jam manually. Never reach into a running or powered shredder. Restart only after the jam is fully cleared.
Output Quality
Check flake output regularly. Flakes should be roughly uniform in size. Oversized pieces indicate dull blades. Dust or powder suggests excessive wear. Both affect final sheet quality.
Sheet Forming
Converting shredded HDPE flakes into solid sheets through the heat press. This is the most time-intensive step in the process.
1. Frame Preparation
Clean the steel frame. Apply release agent to all inner surfaces. Place frame on the press bed.
2. Even Distribution
Pour shredded flakes into the frame. Spread evenly by hand, paying extra attention to corners and edges. Overfill slightly — plastic compresses significantly under heat and pressure.
3. Pressing
Close the press and bring to 190°C at ~5,000 PSI. Maintain for 2–3 hours. Monitor temperature and pressure gauges throughout the cycle.
4. Cooling
Transfer the pressed sheet (still in frame) to the cooling rack immediately. Apply even weight across the surface. Allow minimum 6 hours — overnight is ideal. Rushing this step causes warping.
Tip: Plan production around cooling time. Press sheets in the morning, cool overnight, and route the next day. This maximises throughput.
Quality Control
Every sheet must pass inspection before being routed into bed components. Catching defects early saves time and material.
Inspection Criteria
| Check | Pass | Fail |
|---|---|---|
| Thickness | Even across entire sheet | Thin spots or uneven thickness |
| Surface | Smooth, fully fused | Visible flakes, rough patches, or voids |
| Flatness | Sheet lies flat on table | Warping, bowing, or curling |
| Structural | No cracks when flexed | Cracks, splits, or delamination |
| Contamination | Uniform material throughout | Foreign material visible, discolouration |
Reject Handling
- Sheets that fail inspection are shredded and re-processed
- Record the defect type and probable cause for process improvement
- If multiple sheets fail in a row, check machine calibration before continuing
Waste & Offcuts
The facility operates a zero-waste approach. All plastic offcuts and rejected sheets are fed back into the shredder for re-processing.
Zero-Waste Cycle
- CNC routing offcuts → back to shredder
- Trimming waste → back to shredder
- Failed sheets → back to shredder
- Test pieces → back to shredder
- Nothing leaves the facility as plastic waste
Note: Re-shredded material can be processed through the heat press multiple times without significant quality loss. HDPE is highly recyclable and maintains structural integrity through several re-melt cycles.