Thermoforming Research

Thermoforming Research

Replacing Glass Fiber and Carbon Fiber Products with the Thermoforming of Thermoplastics and Thermoplastic Composites to Reduce Costs and Increase Time Savings
Harry Koshulsky, Pennsylvania College of Technology, Williamsport, PA

Abstract
In the rally racing industry, light pods are used during inclement weather and during night races. These pods provide more light output and are made from glass fiber or carbon fiber fabric.

This paper illustrates the cost and time savings achieved as well as the improvements in quality found by replacing the current method of production with the thermoforming of acrylonitrile butadiene styrene (ABS) sheet. The paper also explores the possibility of thermoforming thermoplastic composites, in this case, Tegris.

Introduction
Rally racing is a motorsport where highly modified cars race down dirt or tarmac roads at high speeds. The drivers and co-drivers must be able to navigate their way through twists and turns, through towns and forests, as quickly as possible. A single accident could cause irreparable damage to the car causing the team not to finish the stage. The teams race regardless of weather, time of day, or track conditions.

On occasion, the teams need more light for better visibility. To achieve this, the cars are fitted with light pods. Designs for these light pods vary greatly among number of lights, placement on vehicle, and overall appearance. The current method of production is to use glass fiber or carbon fiber fabric. The fabric is pre-impregnated with resin and laid-up manually on a mold. Gel-coat is also used to help with strength and visual appearance. The light pods are thick and heavy for strength and rigidity.

The thesis for this project is that it is more time and cost-effective to thermoform composite parts from thermoplastic sheet than to use the existing process. The four individual performance objectives are as follows: make a prototype; create two molds from the prototype; create a part from both molds; and create a duplicate set of molds.

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Development in Thermoforming Thermoplastic Composites
Robert M. Stack and Francis Lai, University of Massachusetts Lowell

Abstract
Today many thermoplastic resins have entered the foray of composite materials in applications such as aerospace, vehicle and recreational applications. The advantages of thermoplastics are well known and include storage and shelf life, short processing cycles, recyclability and sustainability. In combination with reinforcing materials, synergies in strength, modulus, impact resistance and other properties, thermoplastics can be tailored for a wide range of applications. In this paper, the current state of the composite market, current commercial materials, and various production process used in industry are reviewed. A focus is made on the thermoforming process which is an under-utilized, yet highly efficient manufacturing method, practical for composite applications with limited deformation requirements. A thermoforming technique of layering commingled glass-polypropylene woven fibers with various surface layers is introduced in order to demonstrate this manufacturability.

Introduction
Composite materials are found in thousands of applications across many industries from aerospace, to automotive, to recreation, to packaging. Starting in the 1940s, with the advent of thermoset plastic materials, the fiberglass reinforced plastics (FRP) industry began to develop composites [1]. Today, many thermoplastic-based materials have also been developed to address a wide range of applications. Nielsen [2] listed many advantages of composite materials including strength and modulus, impact resistance, corrosion resistance, chemical resistance, improved mechanical damping and increased heat distortion temperature. Essentially, the advantage of a composite material is the ability to combine the desired properties of its building blocks. To date, the driving force in development of composites has been enhanced strength-to-weight ratios in the aircraft industry [1], but now cost advantages are also becoming a major factor, particularly in automotive applications [3]. There is even a burgeoning industry to incorporate sustainable materials into composite structures [4].

The use of the thermoforming process for smaller scale, higher volume applications is now being considered as it has been proven to be a highly efficient manufacturing method for polymer-based products. A thermoforming technique of layering commingled glass-polypropylene woven fibers with various surface layers is introduced in order to demonstrate manufacturability and the ability create composite materials with synergistic properties. The mechanical properties of twelve composite laminations were compared versus single–ply homogeneous components to present the usefulness and limitations of the process.

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Using Temperature-Controlled Aluminum Tooling
Brett K. Braker, Pennsylvania College of Technology

Previous research has shown that thermoforming high density polyethylene (HDPE) is something that has been shied away from in the plastics industry. This paper will show the differences of thermoforming HDPE using temperature-controlled and non temperature-controlled tooling. In doing that, it will aim to prove that HDPE can be used with success in the thermoforming industry, as long as temperature controlled aluminum tooling is used.

Individual Performance Objectives

  1. Show the importance of temperature-controlled molding in thermoforming.
  2. Prove that HDPE can be a relevant material to use in thermoforming, instead of just amorphous materials.


Introduction

High density polyethylene isn’t usually thought of as a usable material when thermoforming is talked about. It is not a material that seems like it would work with that type of process. Companies in industry have shied away from HDPE, because of its crystallinity and shrinkage rate. The thermoforming industry almost always uses amorphous materials, because they are a lot easier to control than crystalline materials.

Also, a lot of companies use wooden or urethane tooling to run their parts, because it is a lot cheaper to do that than to get aluminum or steel tooling. Instead of heating up their mold with water or oil, and keeping it at a constant temperature, they will just let the heat of the machine and material heat up the mold over time, but will run into problems at the start and end of their runs. The mold will either be too cold for the material and cool it too quickly, or be too hot, which will lengthen cycle time, and increase the chances of part defects.

Increased cycle times and part defects will cost the company a lot of money in the long run, when they could’ve just used a temperature-controlled aluminum mold. A temperature-controlled mold will stabilize mold temperature from the start, and will not have the variation a non temperature-controlled mold will. This will give the company much needed control of the tooling to help give them a chance at producing better quality parts for their customers. With better quality parts coming off of the temperature-controlled mold, there will be much less scrap sheet, stabilized cycle times and oven temperatures, and the company will be paying the cost of the tooling off with material savings.

Temperature-controlled tooling opens the doors to numerous materials that were once thought to never have a place in the thermoforming industry. It minimizes the increase in percent crystallinity that a material goes through when it is heated up and let to relax.

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Thermoforming ABS for Dimensional Consistency:
Effects of Temperature versus Non-Temperature Controlled Tooling

Aaron Lapinski, Pennsylvania College of Technology, Williamsport, PA

This project was a mold comparison project in which dimensions, shrinkage and mechanical properties of thermoformed ABS were compared on two different mold types. The two molds are a temperature controlled aluminum mold and non temperature controlled Ren Shape mold. A design of experiment (DOE) was also preformed on this project. The purpose of this project is to demonstrate to the thermoforming industry that a temperature controlled mold is essential for maintaining dimensional consistency in the finished product.

Introduction

In the thermoforming industry high part dimensional variation has always been a problem. This project will demonstrate that the specification range on thermoformed parts doesn’t need to be near as wide as it is. The scope of this project is to determine the effects of using temperature controlled aluminum mold with and a non temperature controlled Ren Shape mold on an industrial size MAAC thermoformer. The variables being evaluated are part quality, dimensions, shrinkage, and cycle time on amorphous ABS sheets of the same color and thickness.

My project has four basic goals. The first is to determine how a temperature controlled aluminum mold and non temperature controlled Ren Shape mold of the same dimensions will affect shrinkage of a thermoformed ABS part. The second is to gain experience on the set up and operation of the industrial scale MAAC thermoformer. A third goal for this project is to develop a thermoforming lab experiment on the MAAC thermoformer for student education in Pennsylvania College of Technology’s BPS program. The fourth is to demonstrate to the thermoforming industry that a temperature controlled mold is essential for maintaining consistency in the finished product.

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