 Hello friends, myself Dr. Narendra Kartikar, Assistant Professor Department of Mechanical Engineering, Valschan, the Institute of Technology, Solapur. Today we are going to see the discussion and presentation on design of Compression Mold Part 1. At the end of this session, student will be able to understand the importance feature of design concept for compression mold design, as well the student will be able to apply the design concept for mold design. The content for this presentation are Introduction Compression Molding type of compression mold advantages and disadvantages of compression molds. Let us in brief about the introduction regarding the plastic material need for the particularly plastic material product and various type part manufacturing methods. As we know, the plastic is advanced material being used nowadays not only to build the particularly new product but considering as a replacement for the existing material itself. Considering various type of particularly geometries considering the quantity, quality and so many features, the varieties of part manufacturing methods are developed out of that compression molding is there. This is the general setup for compression mold. With the compression force, the particularly material is going to be flow out into the mold cavity and after the end it is going to get the particularly exactly the replica of mold cavity and thus produce the part geometry itself. In a three stage wise, you can see over here, charge is loaded, force is applied, after the ejection the part can be unloaded. This is the one of the type of compression molding machine. At this stage of this session, are you able to recall, share some of the application products that can be manufactured with the compression molding process. Might be seen or known earlier anywhere in real time, just enlist the varieties of product. I hope that you had enlisted the same. This is the compression mold how it look like. You can see the produced part placed on the same. Compression molds, type of compression molds, hand compression mold and semi compression molds. Semi automatic varieties of types are there, open flash, vertical, fully positive, landed positive and semi positive. These are the three varieties, flash type, semi positive type and positive type. We are going to see in detail one by one. You can see the four different varieties are shown over here in the figure. Hand compression mold, top force, red plate, bottom force plate, bottom force, top force, guide pillar, guide bush and varieties of parts are shown over here. Hand compression mold particularly being used with the manual effort. Hand compression mold are used for smaller production runs or prototype experimental job that require lower mold cost and parts having open tolerance and less intricacy. Many advantages are there, like the materials are used for processing large deep drawn parts of maximum density. The hand molds are less costly. The hand molds with less than 15 kg for easy manual handling and the operations are fully manual. Some of the disadvantages are, the molds are more easily damaged by misalignment, mishandling etc which may result from improper mold operation and closing of the mold. The flash type of compression mold is used to produce a shallow shaped component. Flash formation, in this mold a slight excess of molding powder is loaded into the mold cavity. Unclosing the top and bottom platter, the exceed material is forced out and the flash is formed. Some of the advantages, gas or air can be trapped by closing the mold too quickly and finally powder material can be splashed out of the mold. Some of the disadvantages, moreover because of the excess material loading needed the process is somewhat wasteful as far as raw materials are concerned. Advantage of open flash mold, resins having high melt viscosities can be molded by this process. This is the semi-automatic open flash mold. This is another diagram which shows the semi-automatic open flash mold. Semi-automatic vertical flash mold. These type of molds are suitable for molding the component high density and critical dimensions as related to the cavity and top force. There is a very little clearance between the plunger and the cavity wall. The flash is formed vertically on the type of mold. The flash is removed by filing, sanding and tumbling. Disadvantage of positive type is that after frequent operation the cavity walls become scored and ejection of part is difficult. Advantage it must be measured accurately as there is a very limited means for the excess material escape. This is a semi-automatic vertical flash mold. This is another diagram which shows the semi-automatic vertical flash mold. The flash is flown in a vertical form. Semi-automatic semi-positive mold is a combination of features of the open flash and fully positive mold and allows for excess powder and flash. Flash it is also possible to get both horizontal and vertical flash. A clearance of 0.025 mm per side for the diameter of 25 mm between the plunger that is top force and the cavity is maintained for satisfactory operation of the mold. Disadvantage are more expensive to manufacture and maintain than the other type of compression mold. Advantages semi-positive molds are suitable for producing the component to close tolerance and for better surface finish. Semi-positive horizontal flash type semi-automatic semi-positive flash mold is shown over here. It flows in a horizontal as well as in vertical manner regarding the flash. This is another diagram showing the semi-automatic semi-positive flash mold. Let us see some of the advantages and disadvantages of compression mold from the perspective of technical terminologies. Advantages from tolerance point of view best method for holding the close tolerance over the projected area of flash line regarding the shrinkage. Lower mold shrinkage as compared to the transfer or injection 0.0015 to 0.002 inch per inch less on general purpose phenolic materials. Uniform mold shrinkage due to uniform flow pattern of material. Density More uniform density of molded part. Weld lines Depending on the geometry of the part, no weld lines and fewer mold in strain and stresses because of more uniform fill of the cavity. Venting of the mold may not be needed but not to extend required in transfer or injection molding. Flash Generally flash scrap lower than transfer of injection unless runner less injection considered. Runner system on the shallow draw part maximum number of cavities per bed area due to the less molding pressure and without necessary of link runner system and sprue or plunger location. Suitable products recommended for shallow draw parts. Product Strength Improved impact strength since no degradation of fiber during flow. Cost Generally compression molds are less costly to construct than transfer or injection molds. Landed directly positive may be an exception. Disadvantage Cure time Rate of cure of heavy section or wall thickness may be longer than those for transfer or injection molding. On sections of 0.400 inch that is about 10 mm thickness special compression equipment may be able to equal cure. Mold maintenance part design incorporated undercuts or sidewall are troublesome because high mold maintenance is required. Molded in holes are limited to depth of 2.5 times diameter small diameter holes not recommended. Flash dimensions over flash line limited to plus 0.008 to 0.000 inch that is 0.200 mm. Process Difficult Difficult to mold high bulk materials Some of the references for these presentations are Modern Plastic Handbook, Modern Plastic and Charlize, a Harper editor in chief technology seminars incorporation, McIngrow Hill publication, Fundamentals of Plastic mold design by Prof. Dr. Sanjay Nayak, few of the web references CIPET government website NPTEL study material. Thank you.