Class Code 4478
Plastic Goods Mfg
Class code 4478 covers California employers who manufacture plastic goods using processes such as injection molding, extrusion, blow molding and thermoforming. The September 1, 2026 approved pure premium for this code is $4.866 per $100 of payroll, a key input in calculating workers' compensation costs for these operations.
What Class Code 4478 Covers
This classification applies to businesses that convert raw thermoplastics and thermosets into finished or semi-finished plastic products and components. Typical operations include injection molding, extrusion, blow molding, rotational molding, thermoforming, trimming/deflashing, and secondary assembly of plastic parts. It covers employees who operate and maintain molding and extrusion presses, set and change molds, run downstream finishing equipment, perform product inspection and packaging, and handle raw resin and additives. Shops that manufacture domestic items (containers, fittings, housings, consumer goods) and industrial components primarily from plastic materials fall under this code.
Who It Applies To
- Injection molding machine operators and mold setters
- Extrusion and blow-molding technicians
- Thermoforming and trimming/finishing crews
- Plastic parts assembly and packaging workers
- Quality control/inspection staff in plastic product plants
- Maintenance technicians servicing plastic processing equipment
Common Job Duties
- Loading resin, colorants and additives; measuring and batching materials
- Operating injection, extrusion, blow molding or thermoforming presses
- Installing, aligning and changing molds and tooling
- Trimming, deflashing, machining or tumble-finishing molded parts
- Performing in-process inspection, dimensional checks and documentation
- Packaging, labeling and preparing finished plastic goods for shipment
- Routine preventive maintenance and troubleshooting of processing equipment
Common Injury Risks
Understanding the $4.866 Rate
The pure premium $4.866 per $100 of payroll is the WCIRB-approved base cost to cover expected claim losses for this class. Insurers apply this rate to your payroll to calculate base premium, then adjust it for your insurer's expense loads, state assessments, your experience modification (X-mod), premium credits/discounts, and any deductibles or retrospective rating plans. Accurate payroll coding, safety performance, and claims history are the primary factors that affect the final premium an employer pays.
Cal/OSHA Compliance Requirements
California employers in plastic manufacturing must maintain a written Injury and Illness Prevention Program (IIPP) and follow Cal/OSHA General Industry rules for machine guarding, lockout/tagout where equipment is serviced, and hazard communication for resins and solvents. When processes generate fumes, dusts, or high noise levels, employers must implement engineering controls, proper ventilation, respiratory protection programs, and hearing conservation per Cal/OSHA requirements. Training, up-to-date Safety Data Sheets (SDS) and documented medical surveillance where exposures occur are also required.
How Key HR Helps Employers Under Class Code 4478
A PEO like Key HR helps plastic goods manufacturers by centralizing payroll classification, managing claims and return-to-work programs, and delivering targeted loss-control services such as machine-guarding audits, respiratory and hearing conservation program setup, and lockout/tagout procedures. Key HR can also help optimize experience modification, administer safety training, manage vendor networks for medical care, and implement cost-saving alternative rating options that reduce workers' comp expense.
Get a QuoteFrequently Asked Questions
How do I know if my shop should be coded as 4478?
If your primary business activity is manufacturing finished or semi-finished plastic products using operations like injection molding, extrusion, blow molding or thermoforming, class 4478 is typically appropriate. Payroll should be allocated by employee function; office staff and non-manufacturing employees may be coded separately. Misclassification can lead to premium adjustments and audits, so document job duties and processes.
What practical steps lower workers' comp costs for plastic manufacturers?
Focus on engineering controls (machine guarding, ventilation, automated material handling), standardized lockout/tagout and permit procedures, a written IIPP with expedited injury reporting, early return-to-work/modified duty programs, and routine training on chemical handling and ergonomics. Consistent documentation and proactive claims management reduce lost-time claims and improve your experience modification over time.
What should I do immediately after a workplace injury in a molding or extrusion area?
Provide or arrange prompt medical care, secure the area to prevent further hazard, notify your supervisor and your PEO or insurer, and begin an incident investigation to identify root causes and corrective actions. Timely reporting, appropriate medical direction and an organized return-to-work plan help contain costs and improve recovery outcomes.
Quick Facts
- Class Code
- 4478
- Classification
- Plastic Goods Mfg
- Pure Premium Rate
- $4.866 / $100 payroll
- Effective Date
- September 1, 2026
- Source
- WCIRB Approved Filing
Manage Workers' Comp Through a PEO
Key HR provides pay-as-you-go workers' comp for California employers — no large deposits, no audits, better rates.
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