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A starters guide on compression moulding and autoclave

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This edition of Knowledge On-The-Go Special Supplement features two key machinery used in the rubber industry viz. Autoclave and Compression Moulding.

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A starters guide on compression moulding and autoclave

  1. 1. Machinery World Rubber & Tyre Knowledge On-The-Go Special Supplement http://rubbermachineryworld.com A Starter’s GUIDE Vulcanizing Autoclave Compression Moulding Press Inside: How To Select?
  2. 2. This edition features two key machinery used in the rubber industry viz. Autoclave and Compression Moulding. Autoclave is a vulcanizing equipment, and the other is the equipment used in your most common rubber moulding technique - compression moulding. These contents first appeared on our portal and witnessed high traffic. This high interest level, prompted us to publish the details in this Knowledge On-The-Go Special Supplement. Our previous issue on Mixing Mills was well-received. Thanks again to each of you - esteemed readers and supportive advertisers. While, the last edition was tracking the advancements of a very popular rubber machinery, this edition is aimed at fulfilling the curiosity of the new generation of business leaders - who are either taking over from their parents or those young entrepreneurs setting up their own venture. Hence, the theme - ‘A Starter’s Guide’. I hope you find this special supplement different and informative. As always, I welcome your feedback on rubbermachineryworld@gmail.com. BestRegards Prasanth Warrier | Editor’s Note | A Starter’s Guide Autoclave is a vulcanizing equipment, and the other is used in your common rubber moulding technique viz. compression moulding. 3 rubbermachineri rubbermachineryworld +Rubbermachineryworld1 grp/home?gid=8252803 rubbermachineri Special Supplement - Rubber Machinery World OCT 2015|
  3. 3. 4 | COMPRESSION MOULDING | Special Supplement - Rubber Machinery World OCT 2015| Image: Bharaj Machineries Make Automatic Compression Moulding Press
  4. 4. 5 COMPRESSION MOULDING MACHINERY Compression moulding is the most common moulding technique you will notice in the rubber industry. The other two are transfer moulding and injection moulding. Compression moulding is a closed mould process and you apply high pressure on the job. It is best used when you have low to medium production volumes for larger parts where tightest tolerances and flawless finishes are not required. Examples may include diaphragms, valves and gaskets, Dampers, O-rings, seals, rubber wear parts, etc depending upon their areas of application. Prasanth Warrier | COMPRESSION MOULDING | Special Supplement - Rubber Machinery World OCT 2015|
  5. 5. Schematic From JW Elastomer Engineering Guide As shown in the schematic here, in compression moulding, you place an uncured rubber profile in a heated mould. Then you soften the uncured rubber by the heat and press them forcing the rubber compound to fill the mould cavity. The rubber is thus made to conform to the shape of the mould and then you cure it to produce your finished article. 6 | COMPRESSION MOULDING | Special Supplement - Rubber Machinery World OCT 2015| Santec Group Make Compression Moulding Machines inside their Plant
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  7. 7. Compression Moulding Press: The machinery you will use is called Compression Moulding Press. These presses are mostly hydraulically driven, where a hydraulic pump powers a hydraulic cylinder (or cylinders) that drive the ram or slide. (Caution: there are pneumatically powered presses too). Hence, the terms that apply to a standard hydraulic press are relevant here. Hydraulic Press Terms Stroke: The amount of possible ram travel. Stroke is the total distance that the ram can travel, from full extension to full retraction. Shut Height: The distance between the bed bolster and the ram bolster when the ram is fully extended. This is also commonly known as the Closed Height. As standard, this dimension is usually within “0.25” due to assembly processes. Daylight: The distance between the bed bolster and the ram bolster when the ram is fully retracted. This is also commonly known as the Open Height. Bolster: The removable plate that serves as the working surface for the bed and ram. 8 Terms & Image Taken from Beckwood Hydraulic Presses and Machinery | COMPRESSION MOULDING | Special Supplement - Rubber Machinery World OCT 2015| The plate is usually bolted to the bed and rams substructures. Bed Height: Bed Height is the distance from the bottom of the hydraulic press structure to the working height or top of the bed bolster. Remote Power Skid: Some press applications may require that the hydraulics be located remotely from the press itself. Others may preclude the power system from being able to be installed at the top around the crown structure of the press. In these cases, the power system and even the controls may be designed into a separate unit capable of being placed adjacent to the press or away from the press. Heated Platens: These are plates that have heating capabilities.
  8. 8. Image: A 60" Mixing Mill With Advanced Features, Controls, and Automation from Bharaj Machineries. | COMPRESSION MOULDING | Special Supplement - Rubber Machinery World OCT 2015| Hydraulic presses are preferred by your peers in the industry because they give Performance, Reliability, and Versatility. This means you can get full pressing force (or tonnage) anywhere in the range of stroke using hydraulic press unlike a mechanical press. By varying the ram speed and other operating parameters, you can optimize cycle time for each of your job. Further, you could customize your bed size; say lower tonnage on a larger work area or higher tonnage on a smaller area of work. You will see that compression moulding presses offered by most reputed manufacturers are vertical and the moulds can be heated using electric rods, steam, oil, water or other medium. Depending on requirement, your moulds may be fixed to both the platens; or part fixed to a platen, or totally free to be drawn out. When you have free loose moulds, your operators need to load and unload them on a press table manually. You call it charging (loading) and stripping (unloading) by hand. On the other hand, the presence of ejector pins or strippers on fixed mould presses will speed up your operation. One of the platens is fixed in your compression moulding press. When the lower platen is raised or lowered in the vertical plane, you call it upstroking; while in down- stroking, the upper platen is the driven plate (moving up and down). Hydraulic presses are preferred by your peers in the industry because they give Performance, Reliability, and Versatility. Bharaj Machineries Make Automatic Vacuum Type Compression Moulding Press10
  9. 9. | COMPRESSION MOULDING | Special Supplement - Rubber Machinery World OCT 2015| How will you decide (select)? Apart from safety and ease of operations, your final choice of a compression moulding press depends on these six important considerations: 1. Calculation of the proper amount of rubber for your product. 2. Calculating the minimum amount of energy required to heat your rubber. 3. Calculating the minimum time required to heat your rubber. 4. Identifying the appropriate heating technique. 5. Predicting the required force, to ensure that stroke attains the proper shape for your rubber. 6. Designing the mould for rapid cooling after the rubber has been compressed into the mould. You try to optimize the Time, Temperature and Pressure – the three critical parameters for your moulding process. Manufacturers compete to offer your robust hydraulic presses with superior drives and controls, advanced levels of hydraulics and instrumentation features. A Reconditioned Press By Pelmar Engineering Your final choice of a compression moulding press depends on these six important considerations. 12 Santec Group Make Compression Moulding Press
  10. 10. | COMPRESSION MOULDING | Special Supplement - Rubber Machinery World OCT 2015| Advantages and Disadvantages of Compression Moulding Process The advantages of compression rubber moulding are lower cost of your moulds, the large sizes of mouldings possible, and the relatively quick changeover between different moulds helping you expedite shorter production runs. Additionally, there are no tooling features like gates, spruces or runners that could increase the time for your mould to enter the cavity or potentially affect the aesthetics of your product. The main disadvantage is your output when loaded and unloaded manually. This increases your cost on skilled labour. There is product wastage too as compression moulding is not precise like injection rubber moulding. Since thermal conductivity of rubber is poor and you often place your profile into the cavity ‘cold’, your cure times are longer. Additional difficulties you face will be from positioning the blank properly in the cavity and the difficulty to control the ‘flash’ that results from the additional material placed in the cavity. Unsuitable for complex moulding, compared to a transfer moulding or injection moulding, your product contamination is also higher in compression moulding. Summarizing, compression moulding is the most common moulding technique that you will find in rubber industry and the common machinery for this process is the a hydraulic compression moulding press. Presses Inside A Plant of Elastomer Engineering Ltd UK RMW 2. PRODUCT ZONE Edition Promoting One Product At A Time...Differently. 3. KNOW YOUR SUPPLIER Edition Advertising One Supplier At A Time...Differently 1. TECHNOLOGY & INNOVATION Edition Communicating One Technology At A Time...Differently RubberMachineryWorld Technology & Innovation MM RUBBER Rubbe r Machinery World Technology&Innovation ProductZoneRubberMachineryWorld ProductZone MM RUBBER Rubbe r Machinery World Know Your Supplier Rubber Machinery Accessories Pracsol Chemicals Machinery MM RUBBER Rubber Machinery World Special Edition In Conversation With Harish Nene, Chief Executive Ofcer ‘Practical Solutions’ on Equipment Simplified KnowYourSupplierRubberMachineryWorld PLUS BUYERs SPECIAL On One Key Topic At A Time ...............Differently MM RUBBER Rubber Machinery World PromoteYourBrandOn REACH 3X...DIFFERENTLY Only on http://rubbermachineryworld.com Thru Buyer-Oriented Editions To Market Your Equipment Solutions Differently. Updated Criterion Checklist To Select Your Two-Roll Mill In sid e Machinery World Rubber Tyre Knowledge On-The-Go Special Supplement http://rubbermachineryworld.com A New Generation Mill FilePictureFromWiki MIXING MILL A Story Of Wows!! Woes To KnowledgeOn-The-GoSpecialSupplement RubberMachineryWorld Top 25 Things You Should Know to Discuss with Mixer Rebuilder HOW TO SELECT YOUR RUBBER TYRE MACHINERY? Jacob Peled Pelma r Engineering Andreas Limper HF Mixing Group Peter Haan Sieme ns AG Arul Shanmugavelu LT - Kobelco Machinery Harish Nene Pracsol Rakesh Sharma AMCL Machinery Insightful Advices From 6 CEOs In sid e MM RUBBER Rubber Machinery World Special Supplement 13
  11. 11. 14 | AUTOCLAVE | Special Supplement - Rubber Machinery World OCT 2015| VULCANIZING AUTOCLAVE You use an Autoclave or Vulcanizer (Vulcanizing autoclave) to convert natural rubber into a cured and chemically cross-linked rubber product. A vulcanized rubber is less sticky and gives you superior mechanical properties. Rubber Vulcanization (a term coined by Thomas Hancock) “process” was discovered accidentally by Charles Goodyear in 1839. If you are curious about history, this is how it goes – Charles Goodyear left a piece of natural rubber mixed with sulphur on a hotplate one evening. Overnight, it turned into elastic rubber and that caught his attention! Since sulphur and heat were associated with the ancient Roman god Vulcan, the process was named vulcanization (or vulcanisation). Your friends in rubber industry use autoclaves to cure tires, hoses, and many other products but not limited to vulcanization and forming of extrudates (like car radiator hoses), rubber mats, sleeves, joints, gaskets and boots. Typically these are products that you cannot achieve on a standard press-based compression moulding process. Depending on the type of your rubber, the vulcanizing process can occur from room temperature (as in Silicone) up to 350°F (170°C) or more like in case of Tire. Image: Bondtech Autoclave Prasanth Warrier
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  13. 13. | AUTOCLAVE | Special Supplement - Rubber Machinery World OCT 2015| The Machinery Autoclaves are predominantly cylindrical pressure vessels with lids or doors to process your rubber parts that require exposure to elevated pressure and temperature. They are available in a wide range of sizes and design pressures in horizontal (or sometimes vertical) configuration. The key component of your autoclave is the door. For a manufacturer, this is also the critical component in cost of autoclave construction. On one hand, your operator must be able to open and close the door quickly and easily; on the other, the door must satisfy stringent safety requirements of manufacturing and usage. Let me explain. Rubber vulcanizing is a batch process. Your autoclave door must be of full diameter to allow easy access to the chamber inside. So you need a fast-acting door to reduce batch change time and increase productivity. Depending on the size of your autoclave and manufacturer’s offered features, there are several types of fast-opening doors. An autoclave design is driven by various safety standards, primary among them being the ASME Pressure Vessel Code. Autoclave Image From Web Tyre Vulcanizing in Autoclaves (Web) Rubber vulcanizing is a batch process. Your autoclave door must be of full diameter to allow easy access to the chamber inside. 16
  14. 14. | AUTOCLAVE | Special Supplement - Rubber Machinery World OCT 2015| Of all safety-related concerns, the most critical are those which relate to the door’s operation. The manufacturer of your autoclave should ensure that the door seals tightly against rated pressure at the highest shell temperature; operate readily and quickly and meets all safety guidelines of a pressure vessel. Regular testing is a must along with fool proof interlock mechanisms to prevent door opening under pressure. Leading manufacturers deploy Solid- Modelling and Finite Element Analysis (FEA) to design and validate autoclave pressure vessels and quick-opening doors. CE Standard in Europe applies to vessels as well as to electrical controls. The process medium in autoclaves may be steam, a combination of steam and air or inert gas, “Dry Heat” produced by electrical heaters, steam or hot oil autoclave jackets, or circulating hot gases. Despite electric heat being 100 per cent efficient, most precise to control, and lowest maintenance; the cost per kilowatt-hour makes them expensive for your use. And because rubber vulcanizing cannot be done in an air atmosphere, you mostly use steam. Two types of autoclaves are in common use – Non-jacketed and Jacketed. In the non-jacketed type, steam is introduced directly into the autoclave chamber. The steam condenses on the walls of your autoclave and on the surface of your rubber products under vulcanization. However, this leaves behind a mark on the surface of your product. And when you adopt preventive measures, you end up getting a dull finish on your rubber products. For some products like Radiator hoses for cars, you can cure in open steam. Inside View of an Autoclave Your manufacturer should ensure that the door seals tightly against rated pressure at the highest shell temperature; operate readily and quickly and meets all safety guidelines of a pressure vessel. 18
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  16. 16. 20 | AUTOCLAVE | Special Supplement - Rubber Machinery World OCT 2015| The jacketed autoclaves has a double wall. Steam is circulated in the jacket to provide heating. There is no direct contact of steam with your rubber products. An inert gas (like Nitrogen) is then introduced in the autoclave to eliminate oxidation. (Oxidation aids polymer degradation and hence you need to eliminate them). Gases are normally poor conductors of heat and thus increases the curing time. You may also come across this process referred to as “gas curing” by technologists. Additionally, if you have brightly colored articles, the jacketed autoclave lends a good surface finish on your rubber product. The vulcanizing process in an autoclave is a function of temperature and time. Traditionally, in most applications there is no indication of when your cure is complete. For this reason, to ensure that all components in the autoclave have been universally cured, your process cycle times are usually longer than is necessary. Modern autoclaves come with PLC controlled systems and offer extended features including variable temperatures, pressures, cycle times, cycle and system alarms, multiple cycle recipe storage and selection. Operator Consoles with HMI provide an operator friendly interface with touch screens, for cycle parameter entry, cycle/ system/alarm status monitoring, operating and diagnostic messages. Separate Images of Controls and HMI Screen (Inset) from different sources on web (Only for representation purpose).
  17. 17. | AUTOCLAVE | Special Supplement - Rubber Machinery World OCT 2015| When you invite offers to purchase an autoclave, you should not be surprised if price variations confuses you or you are unable to comprehend immediately – be it prices among manufacturers and between features. Price is sensitive to some factor and insensitive to others. For eg:, doubling the design pressure might increase the cost of the autoclave by over fifty percent. And doubling the diameter might more than double your purchase price. On the other hand, you may find that increases in length are inexpensive (relatively). So, your purchase price varies as a function of what has been designed and built into your proposed autoclave. Options of features offered by your suppliers has to be carefully decided so as to optimize your overall investment. Operation Cycle Your typical cycle of autoclave curing has the following steps. The autoclave is loaded with your rubber component, and the connections are made to the autoclave. The door is closed and locked. Pressure is applied until the required level is attained. The circulation fan starts. Heating begins and is maintained at a specified ramp up rate. Once the required Price is sensitive to some factor and insensitive to others. 21
  18. 18. rubbermachineryworld@gmail.com Send Us Your Blog Suggestion Or Your Article SELL MORE MM RUBBER Rubber Machinery World WHEN BUYERS VISIT FOR AUTHENTIC INFO ON MACHINERY Promote Your Brand On | AUTOCLAVE | Special Supplement - Rubber Machinery World OCT 2015| temperature is reached, a timed soak at that temperature begins and runs for the necessary duration. At the end of the soak period, the cooling function brings the temperature down to a set value at a specified ramp rate. The vessel is depressurized and the circulation stopped. Steam curing requires a great deal of manual work from one processing stage to the other, and this also contributes to the high cost of your autoclave cured products. RMW Hence, some of your new generation peers advocate the more advanced microwave process. Summarizing autoclaves are pressure vessels for rubber product vulcanization, available in a wide range of sizes. A discontinuous curing method, the curing of your rubber component takes place in a vessel (autoclave) where pressurized steam is the medium of heating. 22
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