Multi-Cavity Hollow Blow Molding Oil Drum Solution

1. Introduction

Hollow blow molding is the primary process for producing plastic oil drums, widely used in packaging for lubricants, chemical liquids, food oils, and other applications. Multi-cavity hollow blow molding molds significantly improve production efficiency and reduce unit costs by molding multiple products in one cycle, making them a core technical solution for mass production of oil drums. This article systematically introduces a complete solution for multi-cavity hollow blow molding oil drums.

2. Overview of Hollow Blow Molding Technology

2.1 Principle of Hollow Blow Molding

The basic process flow of hollow blow molding:

1. Extrude parison: The extruder extrudes plastic melt into a tubular parison
2. Mold closing and clamping: The mold closes and clamps the parison
3. Blow molding: Compressed air is blown into the parison through a blow pin
4. Cooling and setting: The product cools and sets inside the mold
5. Mold opening and part removal: The mold opens and the product is removed
6. Post-processing: Remove flash, trim, and inspect

2.2 Main Types of Blow Molding Processes

2.3 Oil Drum Product Characteristics

3. Multi-Cavity Blow Molding Mold Structure Design

3.1 Overall Mold Structure

Multi-cavity hollow blow molding oil drum molds typically use two-cavity or four-cavity designs:

3.2 Cavity Layout Design

(1) Layout Principles

• Each cavity symmetrically distributed to ensure uniform parison distribution
• Cavity spacing meets cooling channel layout requirements
• Consider parison extrusion arrangement
• Mold center of gravity coincides with blow molding machine center

(2) Typical Layouts

3.3 Parison Design

(1) Parison Dimensions

• Parison diameter = Maximum product diameter × 0.6–0.8
• Parison wall thickness = Product wall thickness × 1.5–2.5
• Parison length = Product height + clamping allowance

(2) Parison Control

• Use Axial Wall Thickness Control (AWDS) to adjust parison wall thickness
• Use Radial Wall Thickness Control (PWDS) to adjust parison circumferential wall thickness
• Ensure uniform product wall thickness and reduce material waste

3.4 Clamping and Trimming System

(1) Clamping Structure

• Clamping blades set on the mold parting surface to clamp the parison
• Clamping blade angle: 15°–30°
• Clamping blade hardness: HRC 50–55
• Clamping force must be moderate to prevent parison displacement or cutting

(2) Trimming Structure

• Trimming knives set to remove product flash
• Trimming knife clearance: 0.05–0.1 mm
• Trimming knife hardness: HRC 55–60
• Flash automatically falls off after trimming

3.5 Blowing System

(1) Blow Pin Design

• Blow pin diameter: φ6–φ12 mm
• Blow pin position: Top center of product
• Blow pin stroke: 50–150 mm
• Blow pin sealing: O-ring or conical surface sealing

(2) Blowing Parameters

3.6 Cooling System

(1) Cooling Channel Layout

(2) Cooling Parameters

• Cooling water temperature: 10–20°C
• Cooling water flow rate: 10–20 L/min
• Cooling time: 10–30 s
• Distance from cooling channel to cavity surface: 15–25 mm

3.7 Venting System

(1) Vent Groove Design

• Vent groove depth: 0.02–0.05 mm
• Vent groove width: 5–15 mm
• Vent groove locations: Parting surface, cavity corners

(2) Vent Inserts

• Install vent inserts in areas prone to air entrapment
• Vent inserts use powder metallurgy materials with good permeability
• Vent inserts require regular cleaning to prevent clogging

4. Key Technologies for Multi-Cavity Blow Molding Molds

4.1 Parison Distribution Balance Technology

(1) Runner Balance

• Use balanced runners to ensure consistent parisons in all cavities
• Runner cross-section uses circular or trapezoidal shape
• Runners require polishing to Ra0.8 μm

(2) Mold Flow Analysis

• Use Polyflow or BlowView software for simulation
• Optimize parison dimensions and blowing parameters
• Predict product wall thickness distribution

4.2 Wall Thickness Control Technology

(1) Axial Wall Thickness Control (AWDS)

• Control die gap through servo motors
• Adjust parison wall thickness according to product height
• Wall thickness control precision ±0.1 mm

(2) Radial Wall Thickness Control (PWDS)

• Adjust parison circumferential wall thickness through eccentric sleeves
• Suitable for non-circular products
• Wall thickness control precision ±0.15 mm

4.3 Uniform Cooling Technology

(1) Zoned Cooling

• Divide the mold into multiple cooling zones
• Each zone independently controls cooling water flow and temperature
• Ensure uniform cooling of all cavities

(2) Conformal Cooling Technology

• Use 3D-printed conformal cooling inserts
• Cooling channels follow product contour
• Cooling efficiency improved by 30%–50%

4.4 Automation Integration Technology

(1) Automated Production Line

(2) Control System

• Use PLC control systems</