PPAP is our standard process in the production of car bumpers.

 

First, the core purpose of PPAP

   - Verify the ability to prove that the supplier's manufacturing process, equipment and quality management system can stably produce parts in line with the design requirements.

   - Risk prevention: identify and resolve potential design, process or material defects before mass production.

   - Standardised Delivery: Ensure that all suppliers submit documents and samples to OEMs (e.g. Toyota, Volkswagen, Tesla) in a uniform format.

 

Second, the 5 key elements of PPAP for injection moulded components

1. Design verification and documentation

   - Material Certification:  

     - Injection moulding materials need to provide UL yellow card (flame retardant), RoHS report (Restriction of Hazardous Substances), if using recycled plastics (PCR), need to additionally submit the composition analysis and batch stability certificate.

     - Case: a car lamp shell using 30% PCR-PC material, need to pass the heat aging (85 ℃/1000h) and light test (UV 3000h).

   - Mould management:  

     - Mould drawings, 3D printed moulds with shape cooling water circuit simulation report (verification of cooling uniformity).

     - Mould life verification (e.g. dimensional stability data after 300,000 injections).

 

 2. Process control

   - Process parameters:  

     - DOE (Design of Experiments) report for injection moulding parameter window (melt temperature, holding time, cooling time).

     - SPC (Statistical Process Control) charts for key parameters (e.g. injection pressure Cpk ≥ 1.67).

   - Process flow diagrams:  

     - Covering the whole process from raw material drying (e.g. PC needs to be dried at 120°C for 4h) to injection moulding, deburring and testing.

3. Inspection and testing

   - Dimensional inspection:  

     - Key dimensions (such as assembly holes, sealing surfaces) of the CMM (Coordinate Measuring Measurement) report, the tolerance to meet the drawings ± 0.1mm requirements.

     - Shrinkage compensation verification for injection moulded parts (e.g. 0.3%~0.5% for PA66-GF30).

   - Performance test:  

     - Functional test: such as automotive connector insertion and extraction force (20N ± 2N), air tightness (helium leakage detection rate ≤ 1 × 10-⁶ mbar-L/s).

     - Environmental testing: high and low temperature cycling (-40℃~120℃), salt spray test (96h without corrosion).

 

4. Quality documentation

   - PFMEA (Process Failure Mode Analysis):  

     - Preventive measures (e.g. mould temperature control ±1℃, regular cleaning of screws) are formulated for injection moulding defects (e.g. shrinkage, flying edge, air bubbles).

   - Control Plan (CP):  

     - Define 100% full inspection items (e.g. visual inspection of appearance) and sampling frequency (e.g. 5 pieces per 2h to measure the size).

   - MSA (Measurement System Analysis):  

     - GR&R (repeatability and reproducibility) of key testing equipment (e.g., digital calipers, tensile machines) ≤10%.

 

 5. Sample Submission

   - Submission Level: Usually choose Level 3 (full set of documents + samples) or Level 4 (partial documents only) according to customer requirements.

   - Retention of samples: It is necessary to keep the injection moulded parts of the same batch with the submitted samples for future quality dispute comparison.

 

 

Third, injection moulded auto parts PPAP special requirements

1. Material traceability 

   - Each batch of raw materials need to record the supplier, grade, melting finger (such as ABS melting finger 220 ℃/10kg for 15g/10min ± 2).

   - The colour difference ΔE between the masterbatch and the injection moulded part is ≤1.0 (detected by spectrophotometer).

 

2. Mould and equipment certification 

   - The injection moulding machine needs to pass the capability study (CMK≥1.67), and the mould needs to complete the T0~T3 trial mould report.

   - If 3D printing moulds are used, additional fatigue test reports are required (e.g. dimensional changes after 100,000 injections)

3. Appearance standard

   - Grade A surface (e.g. instrument panel) is not allowed to have fusion lines, shrink marks; Grade B surface (e.g. hidden structural parts) is allowed to have slight imperfections but need to define the limits

Types of Problems - Typical Cases - Solutions

Dimensional overshoot: Bumper snap hole position deviation leads to assembly difficulties - Optimise the mould cooling scheme, add in-mould sensors to monitor shrinkage in real time |

Material performance discrepancy: PCR material impact strength is insufficient (<30kJ/m²) - Adjust the proportion of recycled material (from 40% to 25%) and add toughening agent. 

Unstable process: Fluctuating injection cycle time (±2s) affects production capacity - Replaced hydraulic machine with electric injection moulding machine to improve parameter control accuracy.  

Incomplete documentation: lack of mould flow analysis report (filling, warpage prediction) - use Moldflow software simulation to optimize gate position and holding pressure curve 

 

Continuous control after passing PPAP

1. Change management (PCR/PCN)  

   - Any process changes (e.g. changing injection moulding machine brand, adjusting masterbatch supplier) need to be resubmitted for PPAP or partial approval.

2. Mass Production Monitoring

   - Daily checking of process parameters (e.g. cylinder temperature deviation ≤±3℃) and monthly updating of SPC charts.

3. Closed-loop customer feedback 

   - In response to client complaints (e.g. batch burrs), 8D report needs to be initiated within 24 hours and root cause analysis provided within 5 working days.

Summary

PPAP for automotive injection moulding parts is not only a tool for ‘handing over work’, but also a tool for systematic verification of manufacturing capability. Enterprises need to focus on material consistency, process stability and data integrity, while combining injection moulding industry trends (such as lightweight, 3D printing moulds) to plan ahead for technical reserves. Enterprises that pass PPAP will not only get orders from OEMs, but also build long-term trust in the competitive automotive supply chain.