Book and Software

By Paul Nugent

Paul Nugent in Reading, PA wrote the book Rotational Molding: A Practical Guide and created the RotoCycle software.

Rotational Molding: A Practical Guide

Need practical tips on rotational molding? Want to find out about developments in technology and who is conducting it? Want to see real-world examples? Rotational Molding: A Practical Guide is an in-depth study of the rotational molding process, bringing together much of the technical work performed in rotomolding around the world over 30 years. Contributions from nine industry experts and many molders and suppliers, complement the academic and industrial experience of the author. This easy-to-use reference is written in plain, readable English.

“I recommend this book to anyone who is practicing rotational molding”, Glenn Beall, Glenn Beall Plastics, Inc. 

Contents:
1.0 Introduction
1.1 A Modern History of Rotational Molding
1.2 Rotational Molding Applications
1.3 Rotational Molding Markets

2.0 Process Basics
2.1 Four Basic Steps
2.2 Advantages of Rotational Molding
2.3 Limitations of Rotational Molding
2.4 Rotational Molding from Within the Mold

3.0 Materials
3.1 Desirable Characteristics in Rotational Molding Materials
3.2 Range of Materials Available3.3 Polyethylene
3.3.1 General Properties of Polyethylene
3.3.2 Low Density Polyethylene (LDPE)
3.3.3 Linear Low Density Polyethylene (LLDPE)
3.3.4 Medium Density Polyethylene (MDPE)
3.3.5 High Density Polyethylene (HDPE)
3.3.6 Cross Linked Polyethylene (XLPE)
3.3.7 Metallocene Polyethylenes (mLLDPE)
3.3.8 Ethylene Vinyl Acetate (EVA) – Ethylene Butyl Acetate (EBA)
3.3.9 Semi-Conductive Polyethylene
3.3.10 Flame Retardant Polyethylene
3.3.11 Plasma and Radiation Treated Polyethylene
3.3.12 Fluorinated Polyethylene
3.4 Polypropylene
3.5 Nylon
3.6 PVC
3.7 Polycarbonate
3.8 ABS
3.9 Fluoropolymers
3.10 Foaming Materials
3.11 Reinforced Materials
3.12 Other Materials
3.12.1 Acetal Copolymer
3.12.2 Acrylic
3.12.3 Cellulosics
3.12.4 Epoxy
3.12.5 Ionomers
3.12.6 Liquid Crystal Polymers
3.12.7 Phenolic
3.12.8 Polybutylene
3.12.9 Polyester
3.12.10 Polystyrene
3.12.11 Polyurethane
3.12.12 Silicone
3.13 Material Preparation
3.13.1 The Grinding Process
3.13.2 Powder Quality and Assessment
3.14 Recycling of Materials
3.15 Material Standards 

4.0 Molds
4.1 Introduction
4.2 Mold Design Considerations
4.2.1 Reviewing a Part Design 
4.2.2 Mold Elements and Features
4.2.3 Factors That Affect the Cost of A Mold
4.2.4 Heat Transfer Characteristics of Various Mold Materials
4.2.5 Thermal Expansion Characteristics of Various Mold Materials
4.2.6 Specifying a Mold for Ordering
4.3 Fabricated Molds - Sheet Metal
4.4 Cast Molds – Aluminum
4.5 Other Mold Making Methods
4.5.1 Glass Fiber (Composite)
4.5.2 Electroforming
4.5.3 Sprayed Metal
4.5.4 Jacketed Molds
4.6 Mold-Release Systems
4.7 Mold Maintenance

5.0 Machinery
5.1 Introduction
5.1.1 Heating Stage
5.1.2 Cooling Stage
5.1.3 Servicing Stage
5.1.4 Rotation
5.2 Machine Styles
5.3 Operational Parameters
5.3.1 Standard Controls
5.3.2 Internal Air Mechanisms
5.3.3 Mold Swing Charts
5.4 Setting Up a Machine for Operation

6.0 Design Considerations
6.1 Introduction
6.2 Design Development Process
6.3 Computer Aided Design (CAD)
6.4 Basic Design Guidelines
6.4.1 General Considerations – Function, Shape and Size
6.4.2 Wall Thickness
6.4.3 Draft Angles
6.4.4 Corner Radii and Angles
6.4.5 Stiffening of Parts
6.4.6 Holes
6.4.7 Bosses
6.4.8 Tolerances and Shrinkage Considerations
6.4.9 Warpage and Flatness Considerations
6.4.10 Double Wall Parts
6.4.11 Kiss-Offs
6.4.12 Undercuts
6.4.13 Threads
6.4.14 Inserts
6.4.15 Parting Lines
6.4.16 Vents
6.4.17 Heat Transfer
6.4.18 Graphics and Texture
6.4.19 Part Assembly
6.4.20 ESCR Performance
6.4.21 TRIP Molding Technology
6.5 Design Calculations

7.0 Color and Additives
7.1 Introduction
7.2 Basic Types of Colorants and Additives
7.2.1 Pigments – Organic
7.2.2 Pigments – Inorganic
7.2.3 Special Effects
7.2.4 Wetting Agents
7.2.5 Anti-Oxidants
7.2.6 UV Stabilizers
7.2.7 Antistats
7.2.8 Flow Enhancers, Internal Lubricants, Internal Mold Releases
7.2.9 Blowing Agents
7.2.10 Anti-Microbial Additives
7.2.11 Flame Retardants
7.3 Practical Colorant Loading Ranges
7.4 Mixing of Colorants and Additives
7.4.1 Dry-Blending
7.4.2 Liquid Color
7.4.3 Paste Dispersions in PVC
7.4.4 Melt-Compounding
7.4.5 Mixing Equipment
7.5 Effect of Color on Processing and Part Physical Properties
7.5.1 Effect on Cycle Time
7.5.2 Effect on Shrinkage
7.5.3 Effect of Pigments on Physical Properties
7.6 Effect of Additives on Processing and Part Physical Properties
7.6.1 Anti-Stats
7.6.2 Anti-Oxidants
7.6.3 UV Stabilizers
7.6.4 Conductive Additives
7.7 Practical Aspects of Color
7.7.1 Powder Handling Tips
7.7.2 Effect of Changing Material Suppliers on Color
7.7.3 Selecting a Color Supplier
7.7.4 Color Match Request Form
7.7.5 Test Equipment Required to Maintain Quality Color
7.7.6 Dry Smear Test and Bleed Test
7.7.7 Color Standards
7.7.8 Color Problems

8.0 Practical Aspects
8.1 Types of Rotomolding Operations 
8.2 Molding From An Operator’s Viewpoint
8.3 The Process of Material Build-Up in the Mold
8.4 Establishing the Optimum Cure Cycle
8.4.1 Impact Strength vs. Oven Temperature and Cycle Time
8.4.2 Tensile and Flexural Strength vs. Internal Air Temperature
8.4.3 Internal Air Temperature Measurements
8.5 Processing Parameters
8.5.1 Polyethylene
8.5.2 Crosslinked Polyethylene
8.5.3 Metallocene Polyethylene
8.5.4 Polypropylene
8.5.5 Nylon
8.5.6 Polycarbonate
8.5.7 ABS
8.5.8 Foaming Materials
8.6 Bubbles
8.6.1 Bubble Removal
8.6.2 Mold Porosity
8.7 Rotation Speeds and Ratios
8.8 Part Wall Thickness Control
8.9 Venting
8.10 Release Agents
8.11 Cooling
8.12 Shrinkage and Warpage
8.13 Liquid Materials
8.13.1 Polyvinylchloride (PVC)
8.13.2 Reactive Liquid Systems
8.14 Demolding and Reloading
8.15 Multiple Layer Molding
8.15.1 Co-Rotomolding
8.15.2 Foaming 
8.15.3 Reinforcement
8.15.4 Rotolining 
8.16 Quality Control
8.16.1 Quality Control Points in Production
8.16.2 Impact Testing 
8.17 Troubleshooting
8.17.1 Powdered Materials 
8.17.2 Liquid Materials – Plastisols

9.0 Secondary Operations and Decoration
9.1 Basic Part Finishing Techniques
9.2 CNC Operations
9.3 Fixtures
9.3.1 CNC Holding Fixtures
9.3.2 Manual Cutting or Drilling Fixtures
9.3.3 Shrink Fixtures
9.4 Graphics and Decoration
9.4.1 Mold-In Graphics®
9.4.2 Mold-On Graphics®
9.4.3 Post-Mold GraphicsTM
9.4.4 Ink Stenciling and Labeling
9.5 Painting and Adhesives
9.6 Welding

10.0 Process Control
10.1 Introduction
10.2 Basic Control Methods – Heating and Cooling Systems
10.2.1 Heat Transfer Rates
10.2.2 Oven Performance
10.2.3 Cooler Performance
10.3 Direct Temperature Measurements
10.4 Indirect Temperature Measurements
10.5 Cycle Balancing / Scheduling
10.6 Process Simulations 

11.0 Process Economics
11.1 Rotational Molding Capabilities vs. Other Processes
11.2 Costing Elements in Rotational Molding
11.3 Overview of Approaches to Costing
11.4 Comparative Costing vs. Other Processes 

Glossary of Terms
Index

Cost: $350 plus shipping and handling
Also available in Chinese
Please send an email to paul@paulnugent.com for an order form.

RotoCycle

A Windows® based software package that allows the user to determine the output of a machine based on the machine configuration (# of arms, stations, indexing time etc.) and the mix of molding cycle times for each arm. The effect of unbalanced cycles and the bottlenecks created can easily be seen

Program Uses

RotoCycle is intended as an analysis and teaching tool. It can be used for:

• Estimating production output
• Demonstrating the effect of long cooling or oven cycles on individual parts
•   Estimating waiting times in cooling stations
•   Estimating waiting times prior to entering the oven station (operator free time)
• Balancing cycle settings for maximum output - use multiple station independent arm machine more efficiently
• Demonstrating the effect of demolding problems on productivity

 RotoCycle is available from Ferry Industries, Inc. (www.FerryIndustries.com) 

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