Rapid injection moulding

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Rapid injection molding.

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Rapid injection moulding

  1. 1. RAPID INJECTION MOULDING P R E S E N T E D B Y: A N I L VA R G H E S E G U P TA G A N E S H SANDEEP KURIAKOSE PRADEEP KUMAR D E PA R T M E N T O F M E C H A N I C A L E N G I N E E R I N G S P E C I A L I Z AT I O N : D E S I G N A N D M A N U FA C T U R I N G N AT I O N A L I N S T I T U T E O F T E C H N O L O G Y, S I L C H A R
  2. 2. Introduction 2  Rapid Injection Moulding is the process of making injection moulds and manufacturing using them for the small production run parts in less time and at a reduced cost than full production moulds.  The injection moulds typically made for prolonged production runs are very expensive and time consuming.  Rapid injection moulding techniques can produce moulds better suited to low volume production runs. Design & Manufacturing 1/12/2014
  3. 3. Injection Moulding 3  It is a manufacturing process for producing parts by injecting material into a mould.  Injection moulding can be performed with a host of materials, including metals, glasses, elastomers and most commonly thermoplastic and thermosetting polymers.  It is the commonly used process for thermoplastics and thermosetting plastic. Fig 1: An Injection moulding machine Design & Manufacturing 1/12/2014
  4. 4. 4  Thermoplastics are prevalent due to characteristics which make them highly suitable for injection moulding, such as the ease with which they may be recycled, their ability to soften and flow upon heating and it is safer.  There two types of mould: Single and Multiple moulds.  In multiple cavity moulds, each cavity can be identical or different.  Moulds are generally made from steel or aluminium. Design & Manufacturing 1/12/2014
  5. 5. Injection Moulding Process 5  When thermoplastics are moulded, raw material is fed through a hopper     into a heated barrel with a reciprocating screw. Upon entrance to the barrel the thermal energy increases and the Van der Waals forces that resist relative flow of individual chains are weakened. This reduces its viscosity, which enables the polymer to flow. The screw delivers the raw material forward through a check valve and collects at the front of the screw into a volume known as a shot. Shot is the volume of material which is used to fill the mould cavity, compensate for shrinkage, and provide a cushion to transfer pressure from the screw to the mould cavity. When enough material has gathered, the material is forced at high pressure and velocity into the part forming cavity. Often injection times are well under 1 second. Design & Manufacturing 1/12/2014
  6. 6. 6  The packing pressure is applied until the gate (cavity entrance)     solidifies. Once the gate solidifies, no more material can enter the cavity; accordingly, the screw reciprocates and acquires material for the next cycle while the material within the mould cools so that it can be ejected. This cooling duration is dramatically reduced by the use of cooling lines circulating water or oil. Once the required temperature has been achieved, the mould opens and an array of pins, sleeves, strippers, etc. are driven forward to demold the article. Then mould closes and the process is repeated. Design & Manufacturing 1/12/2014
  7. 7. Injection Moulding Process 7 Fig 2: Schematic of thermoplastic Injection molding machine Design & Manufacturing 1/12/2014
  8. 8. Rapid Injection Moulding. 8  Rapid injection moulds are usually produced from aluminium and sometimes plastic.  It uses techniques such as plaster moulding, rapid prototyping and CNC machining to create moulds which allows for very quick production times.  Although these moulds generally lack the life span or qualities of a final production set, they can produce thousands of parts, are suitable for most materials and colours, and may even be textured.  Modern machining techniques also means that rapid injection moulding can produce ever increasing levels of complexity and size differences which further expands the list of possible benefits the process offers. Design & Manufacturing 1/12/2014
  9. 9. Mould Making Techniques 9 The major mould making method used for rapid injection moulding are as follows: 1. Plaster Moulding. 2. Rapid Prototyping. 3. CNC Machining. Design & Manufacturing 1/12/2014
  10. 10. 1. Plaster Moulding 10  Plaster mould casting is a metalworking casting process similar to sand       casting except the moulding material is plaster of Paris instead of sand it can only be used with non-ferrous materials The plaster is not pure plaster of Paris, but rather has additives to improve green strength, dry strength, permeability, and cast ability First, the plaster is mixed and the pattern is sprayed with a thin film of parting compound to prevent the plaster from sticking to the pattern. The plaster is then poured over the pattern and the unit shaken so that the plaster fills any small features. The plaster sets, usually in about 15 minutes, and the pattern is removed. The mould is then baked to remove any excess water. The dried mould is then assembled. Design & Manufacturing 1/12/2014
  11. 11. 2.Rapid Prototype Moulding 11  Rapid Prototyping Technology is a group of manufacturing processes      that enable the direct physical realization of 3D computer models. This technology build parts on a layer-by-layer basis. First, a CAD model of the mould is designed. Then the model is sliced into layers using dedicated software for this purpose. The To perform a print, the machine reads the design and lays down successive layers of liquid, powder, paper or sheet material to build the model from a series of cross sections. These layers, which correspond to the virtual cross sections from the CAD model, are joined or automatically fused to create the final shape. Design & Manufacturing 1/12/2014
  12. 12. 12 Design & Manufacturing 1/12/2014
  13. 13. . 3.CNC Machine Moulding 13  CNC technology is changing rapidly, and the changes are helping to improve the productivity of machine tools used in the mould industry. Fig 3: A mould made using CNC machine Design & Manufacturing 1/12/2014
  14. 14. 14  Here are some of the CNC features fundamental to many mould 1. 2. 3. 4. machining processes today: NURBS Interpolation:- This technology for interpolating along curves instead of dividing curves into short, straight line segments that deliver improved surface finish, smoother motor performance, faster cutting rates and smaller part program size. Finer command unit:- Some CNCs today offer a command unit of 1 nanometer to machine axes , providing for improved accuracy. Bell-shaped acceleration/deceleration:- Bell-shaped acceleration / deceleration allows a machine tool to accelerate faster than linear acceleration/deceleration. It also provides less position error than various acceleration/deceleration types including linear and exponential. Digital servo control:- Digital servo technology has improved significantly .These advances have combined to allow CNCs to control the servo loops more tightly and thus control the machine better. Design & Manufacturing 1/12/2014
  15. 15. 15 Fig 4 : CNC Vertical Machining Center, Heavy Duty Mould Making Machine Design & Manufacturing Fig 5 : Mould making using CNC machine 1/12/2014
  16. 16. 16 Design & Manufacturing 1/12/2014
  17. 17. When do we require Rapid Injection Moulding? 17  Injection moulding is a production method that delivers low unit costs during production.  Moulds made for extended production may take several months to produce.  This is not always feasible where small numbers of parts are required as prototypes for function and fit testing or marketing tests.  In these cases, moulds identical to the full production examples regarding design and dimension can be made, although they lack the longevity of the final moulds. Design & Manufacturing 1/12/2014 Fig 6: Rapid v/s Conventional Injection Moulding
  18. 18. References 18  http:// www.elsevier.com/locate/mee  http://www.sciencedirect.com/science/article/pii/S0167931709006832  http://www.protomold.com/ProtomoldProcess.aspx  http://www.wisegeek.com/what-is-rapid-injection-molding.htm  http://en.wikipedia.org/wiki/Injection_molding  http://blog.stratasys.com/2013/08/21/3d-printed-injection-molds-rapid- manufacturing/  http://www.mmsonline.com/articles/cnc-technology-for-mold-applications Design & Manufacturing 1/12/2014
  19. 19. Questions ??? 19 Design & Manufacturing 1/12/2014
  20. 20. 20 Design & Manufacturing 1/12/2014

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