Differences in Hygiene Standards Between Food‑Grade Injection Molds and Conventional Molds

Food‑grade injection molds manufacture plastic parts that directly contact food. Mold material, surface condition and maintenance mode will influence food‑contact safety of finished products. Conventional injection molds only satisfy molding, appearance and dimensional requirements. Their differences go far beyond simple cleaning level. Distinct hygiene‑standard requirements cover steel selection, surface treatment, structural design, production operation and storage & maintenance. Mix‑use will cause excessive substance precipitation and foreign‑matter contamination and bring compliance risks.

Differences on Mold Steel and Base‑Material Requirements

Steel selection for conventional molds mainly focuses on hardness, wear resistance, polishing performance and cost. Grades are chosen according to plastic corrosiveness and production volume. No mandatory food‑contact safety constraints apply. General quenched‑and‑tempered mold steels are acceptable as long as service‑life demands are met.

For food‑grade injection molds, mold inserts, runners, gates and other melt‑contact components shall meet food‑contact safety specifications besides wear‑resistance and anti‑corrosion requirements. Martensitic stainless steel such as S136 and 420 are preferred. Material certificates and food‑contact compliance reports must be provided. Steel with excessive harmful precipitating elements is prohibited. Impurity and sulfide inclusion inside steel need strict control to prevent hazardous‑substance migration toward plastic parts under high‑temperature conditions. Non‑melt‑contact mold‑base plates can adopt ordinary mold steel.

Differences on Cavity Surface Treatment and Roughness Standards

Surface treatment of conventional molds is determined by product appearance needs. Texture, etching, sandblasting, nitriding and chrome‑plating are all acceptable. Nitriding and chrome‑plating are applied for better wear‑resistance and anti‑corrosion without strict constraints on plating‑layer composition, as long as appearance and service‑life requirements get satisfied. Reasonable machining texture is allowed on cavity surfaces as long as no sticking or scratch occurs.

For food‑grade molds, non‑food‑compliant plating treatments are forbidden on melt‑contact cavity and runner surfaces. If electroplating or nitriding is adopted, plating materials must comply with food‑contact safety and avoid peeling‑off‑precipitation risks. Mirror polishing is preferred to reduce surface micro‑pores that trap plastic residues and carbon deposits. Cavities shall be free from cracks, sand holes and tiny pits where decomposed plastic and oil contaminants accumulate and continuously pollute products in repeated production. Fully remove polishing paste and abrasive agent residues after polishing work.

Differences on Hygiene Control in Mold‑Structure Design

Conventional‑mold structural design prioritizes molding stability, easy demolding and lower machining cost. Small glue‑trapping gaps are acceptable. Insert‑mating gaps are only controlled for flash prevention without consideration of hygiene risks caused by residue accumulation. Drainage and vent‑groove design merely solve venting and flash issues.

Food‑grade‑mold structural design must avoid hygiene dead corners. Optimize fitting clearance of inserts, sliders and lifters to minimize narrow glue‑trapping gaps. Residual plastic accumulated inside gaps degrades and carbonizes under long‑time high temperature, producing black‑spot debris and small‑molecule precipitates. Simplify runners to eliminate melt‑stagnant dead zones. Design detachable‑easy‑to‑clean vent grooves. Apply food‑compatible sealing rings for mold cooling‑water channels to prevent contamination caused by aging seal‑ring precipitation. Protect threaded holes and blind holes against dirt and cutting‑chip accumulation.

Hygiene‑Control Requirements During On‑Site Production

Before production startup, conventional molds only need simple wiping to remove anti‑rust oil and large iron chips. Various industrial release agents and anti‑rust sprays can be used in production. No mandatory periodic full‑disassembly‑cleaning rules exist. Operators only remove flash and plastic residues in daily work.

Food‑grade molds require complete deep cleaning before startup. Anti‑rust oil, machine oil and polishing residues must be thoroughly cleared from cavities and runners. Ordinary industrial release agents are prohibited in production; only food‑contact‑compliant release medium can be adopted if necessary. Increase disassembly‑cleaning frequency during production. Take apart inserts and runners regularly to clear carbon deposits and plastic residues. Do not pile‑up carbon deposits for long periods. Do not share one mold for food‑grade and non‑food‑grade products. Simple barrel purging cannot eliminate hazardous residues hidden inside gaps. Complete disassembly and washing procedure are compulsory for product‑switching.

Hygiene Specifications for Mold Repair, Maintenance and Storage

Repair work of conventional molds targets wear, scratch and collision damage. Ordinary industrial anti‑rust oil and machine oil can be used during maintenance. Simple wiping is enough before re‑assembly or warehousing. No special cleaning requirements are needed.

For food‑grade mold repair: prevent machine oil and cutting fluid from contaminating cavity working surfaces. Thoroughly clean cavities and runners after repairing work. Only food‑compatible anti‑rust agent can be used for mold maintenance; never apply ordinary industrial anti‑rust oil directly onto melt‑contact surfaces. Fully clean cavities, runners and insert gaps before warehousing then carry out anti‑rust protection. Complete re‑cleaning is required before next production startup. Newly replaced inserts must also satisfy food‑contact material standards instead of directly adopting ordinary mold spare‑parts.

Conventional molds pursue molding performance and cost‑effectiveness, while food‑grade molds add extra food‑contact‑safety constraints on the basis of basic molding capacity. They cannot substitute each other. Even after temporary wiping, conventional molds still hide risks from unsuitable steel, dead‑corner gaps and non‑compliant coating layers and cannot meet food‑production hygiene standards. Only implementing full‑process control covering material selection, design, production and maintenance can avoid substance precipitation and foreign‑body contamination and satisfy compliance requirements for food‑contact plastic articles.