1. Designing and Manufacturing of a hand operated plastic injection moulding machine envisioned for the mesoscale range.
Freddy Travieso
Project Supervisor : Dr. Paul Ewart
Methodology/Results
Bachelor of Engineering Technology (Mechanical)
Abstract
Design Evolution
After a secondary research to identify design parameters and existing technologies a logic flow chart to aid with the process was put together (Fig. 2).
The design was an iterative process. Constraints on budget, material and the availability of manufacturing process prompt changes and the creation of three versions parting from an original concept. The design evolved from a apparatus that uses custom built hand lever capable of 24 MPa of injecting pressure to a more simple machine that uses an existing arbor press and capable of up to 68MPa of injecting pressure.
This project entitles the design and manufacturing of a hand operated plastic injection molding machine capable of processing up to 4 cm^3 of thermoplastic material.
The final design and analysis of the machine is done by using a three dimensional software and the use of FEA (Finite Element Analysis).
 key words: plastic, injection, moulding, polymer.
Different parts sections were identified and verified by hand calculations first. Safety factors for the different parts of the design versions can be seen tabulated in table 1 and 2. Estimate values show that the parts under load conditions are not expected to fail.
Assemblies and the final assembly were verified using FEA (Finite element Analysis) (Fig 3). High stress areas were identified. As a result modifications of size and shape done as required.
Mould provided by stakeholder
CAD Model.
Any Bearing to be used?. If so check forces & stresses
Nozzle considerations
Clamping unit (What kind?)
Determine Heat required to heat cylinder + polymer
Determine stresses on shaft and/or plunger
If ram type, determine if risk of buckling for given material and loading condition
Knowing pressure in cylinder. Use formula from pressure vessels to find outdoor diameter based on yield strength of given material
Determine from sketch and FBD reactions, forces and internal pressure.
Consider thermal expansion of plastic
Determine cylinder dimensions from volume
4 cm3 of melt
Heating up to 240C
Check FEA
Introduction
New Zealand’s Industry have managed to gain an important presence in the global market of electronics, space and healthcare products with innovative companies like Rocket lab and Fisher & Paykel Healthcare among others.
The products created in these companies frequently require components with very small dimensions which conventional machining processes are not capable of producing economically. One processes that have been able to adapt to the challenges that miniaturisation brings is Plastic injection moulding (Fassi, 2017) however, the the micro and mesoscale manufacturing of products is an area that has not been well advanced which opens a niche for more research and development in this area.
The purpose of this work is to design a simple and economical a machine that could allow further research in the mesoscale injection moulding process and that could be used as a tool to reinforce the knowledge gained in the lessons imparted in Wintec.
Limitations and Future Work
Designed to be used with Arbor press.
The apparatus was designed Max. of 4095N so steps need to be taking to limit force.
The design was analysed under Static conditions only.
Future work redesigning of clamping system.
Future work Fatigue Analysis
Next phase
Prototype Construction and Testing.
Conclusion
Fig.1 Model (3D) using Autodesk Inventor. Version 1.1 (Top). Last version V1.3. (bottom)
Fig. 2. Methodology Flowchart
The apparatus is not expected to fail under the design loading conditions (Statics). However since the apparatus would be used under heat and cyclical stress a fatigue analysis should be performed as future research.
Table 1. Safety Factors for V1
Cylinder
15.7
Piston
12.6
Handle lever
2.1
Pins
6.1
Post-Base 39
Table 2. Safety factors for V1.3
Cylinder
5.1
Piston
4.6
Bracketwall 2
Lifting bolt Compression 74
Lifting bolt shear
12.5
Crushing of base thread 53
Base Threading shear 44
Acknowledgment
Special thanks to:
Fig.3 Analysis of the holding assembly using Autodesk inventor FEA. As a result of the high bending stress under the loading condition the section of the Column was changed from 25x25mm to a 50x20 mm. Also the holding arm span was increased in the vertical direction to provide more support against bending. its thickness was increased from 8 mm to 10mm. These changes brought the safety factor of the assembly from a minimum of 0.39 to 3.2.
References.
Fassi, I. &. (2017). Micro-Manufacturing Technologies and Their Applications : A Theoretical and Practical Guide. . Cham, Switzerland: Springer