RAPID INJECTION MOLDING

Presented by: Anil varghese Gupta Ganesh Sandeep kuriakose Pradeep KUMAR

Department of mechanical EngineeringSpecialization: Design and manufacturingNational institute of Technology, silcharRAPID INJECTION MOULDINGIntroductionRapid 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 & Manufacturing13-01-20142Injection MouldingIt is a manufacturingprocess 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 commonlythermoplasticandthermosettingpolymers.It is the commonly used process for thermoplastics and thermosetting plastic.

Fig 1: An Injection moulding machine313-01-2014Design & ManufacturingThermoplastics 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 fromsteel or aluminium.

Design & Manufacturing13-01-20144Whenthermoplasticsare 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 theVan der Waals forcesthat resist relative flow of individual chains are weakened. This reduces itsviscosity, which enables the polymer to flow. The screw delivers the raw material forward through a check valveand collects at the front of the screw into a volume known as a shot.Shotis 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.Injection Moulding ProcessDesign & Manufacturing13-01-20145The 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 & Manufacturing13-01-20146Injection Moulding Process

Schematic of thermoplastic Injection molding machineFig 2:Design & Manufacturing13-01-20147Rapid Injection Moulding.Rapidinjection moulds are usually produced from aluminium and sometimes plastic. It uses techniques such as plaster moulding,rapid prototyping and CNCmachiningto 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 & Manufacturing13-01-20148Mould Making Techniques The major mould making method used for rapid injection moulding are as follows: Plaster Moulding.Rapid Prototyping.CNC Machining.

Design & Manufacturing13-01-201491. Plaster MouldingPlaster mould castingis ametalworkingcastingprocess similar tosand castingexcept the moulding material isplaster of Paris instead ofsandit can only be used with non-ferrous materialsThe plaster is not pure plaster of Paris, but rather has additives to improve green strength, dry strength,permeability, andcast abilityFirst, 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 & Manufacturing13-01-2014102.Rapid Prototype MouldingRapid 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 & Manufacturing13-01-201411

Design & Manufacturing13-01-201412.3.CNC Machine MouldingCNC 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 & Manufacturing13-01-201413Here are some of the CNC features fundamental to many mould 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 & Manufacturing13-01-201414

Fig 5 : Mould making using CNC machine

Fig 4 : CNC Vertical Machining Center, Heavy Duty Mould Making MachineDesign & Manufacturing13-01-201415

Design & Manufacturing13-01-201416When do we require Rapid Injection Moulding?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.

Fig 6: Rapid v/s Conventional Injection Moulding1713-01-2014Design & ManufacturingReferenceshttp:// www.elsevier.com/locate/meehttp://www.sciencedirect.com/science/article/pii/S0167931709006832http://www.protomold.com/ProtomoldProcess.aspxhttp://www.wisegeek.com/what-is-rapid-injection-molding.htmhttp://en.wikipedia.org/wiki/Injection_moldinghttp://blog.stratasys.com/2013/08/21/3d-printed-injection-molds-rapid-manufacturing/http://www.mmsonline.com/articles/cnc-technology-for-mold-applications

Design & Manufacturing13-01-201418Questions ???

Design & Manufacturing13-01-201419

Design & Manufacturing13-01-201420