On the outside, blow molds are provided with support surfaces to prevent damage to the cutting edges, especially in set-up mode, i.e. when closing the mold without plastic. The mold support also serves to transfer excess clamping force.
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ROLE OF AIR IN BLOW MOULDING
In a blow molding machine, air has multiple purposes: pre-blow and inflation air expands the parison until it contacts the mold wall to reproduce the shape of the blow mold. The inflation air presses the material against the mold wall to reproduce surface details such as lettering, surface textures, etc. Furthermore, the inflation pressure promotes good and permanent contact between the mold wall and the polymer, since the polymer starts to shrink during the cooling period. In addition to these functions required directly with the actual blow molding process, air is required for pneumatically activated functions in the machine, such as the insertion of a blow needle to move molded parts (core pulls) or doors in the machine’s safety guard.
Wherever possible, the blow air should be introduced into the parison through the largest possible opening. In this way, sufficiently large airflow can be provided to quickly inflate the parison. In most cases, this is done using this blow pins which are inserted into the parison from above after the blow mold has closed, or are inserted into the open parison from the below before the mold closes.
However, not all applications have openings as large as most packing applications, so that in such cases so-called blow needles are inserted into the parison. This can be done during or after the mold is closed.
In most cases, compressed air systems with 8 to 10 bar air pressure with clean and oil-free air are sufficient for the applications mentioned above. In some cases, for example for safety reasons or to reduce cycle time, blow molders install two different compressed air circuits: one compressed air circuit for the blow air with 16 bar and a second circuit, not necessarily absolutely oil-free, with 6 to 8 bars for the pneumatic functions.
In contrast to injection molding, blow molding only allows heat to be dissipated from the molten plastic on side via the cooled blow mold surface. To keep the cycle time as short as possible, there are several methods of dissipating additional heat from the plastic via the blow air.
One possibility is the so-called “interval blowing”. This means that in a sequence of short intervals, blowing air is blown into the blow mold, followed by short intervals in which the heated air is released (vented) from the blow mold. The volume of air exchanged is relatively small here, another cooling method using a larger volume of air is the so-called “reverse purging”, where air can flow continuously through the blow molded part. The air blown into the hollow part is vented through a second opening, creating a constant exchange of blow air inside the mold and cool air from outside of it. In any case, it is important to design the outlet opening so that a certain internal pressure is maintained in the blow molded part. The advantage of this method is the doubling is the cooling front. The heat does not have to be discharged exclusively to the outside. The method is also limited in the volume of the articles. For an article the size of a bung drum, approx. 210 m3 air per minute would have to be compressed and introduced from ambient pressure (1 bar) to 5 bar blowing pressure to achieve an average heat transfer coefficient of α1 = 50W/m2 K.
Another way to reduce the cycle time is to use dry, cryogenic air with temperatures as low as -450 C. With e.g. Beko Blizz air treatment units the air is dried and cooled. In combination with water cooling of the mold, a considerable amount of heat can be removed from the blow molded part by using cryogenic air in combination with interval blowing or reverse purging. The use of this cryogenic purge air achieves a cycle time reduction of 20 to 30%. Since the blow mold surface tends to “sweat” (condensation of humidity on the mold surface) when using very cold water and cryogenic blow air, the use of dry air curtains is recommended. Another variant is the use of cold and humid air, as the heat capacity of humid air is higher than that of dry air.
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DESIGN GUIDELINES FOR BLOW MOULDING MOULD
Guide pins and guide bushings from common standard parts suppliers are usually used as blow mold guides. The guide length should not exceed 1 * D. This is particularly important for mold movement machines to avoid damaging the parallel guidance of the clamping unit and the blow mold guide. The bore for the bushing must be drilled towards the rear of the mold or be cleared laterally to be able to easily remove pressed in material and ensure a clean closing of the blow mold.
HOW TO SELECT TOOLING IN BLOW MOULDING MACHINE :
With a basic understanding of the differences in the types of head tooling
available, we can now look at calculations that will help make our tooling
choices. It is important to keep these points in mind:
Parison diameter is dependent on head tool size, resin characteristics,
regrind content, temperature, and punch-out speed.
Head tooling diameter is determined by part shape and size.
PLC in EBM
Until the late 1970s to early 1980s blow molding machines were primarily delivered with contractor control. This type of control offered the advantage that the electrical components could be checked by appropriately trained maintenance personnel and easily replaced in the event of a fault. Changes in the machine control system could be made with the help of simple auxiliary devices. However, the disadvantages were the susceptibility to faults and short service life due to wear of mechanically moving parts, the large number of components (up to 150 contactors, 12 temperature controllers, etc.), the size of the components, and how these elements were connected. This type of control was called “hard-wired programmed logic controller”.
CLAMPING UNITS IN EXTRUSION BLOW MOULDING
In all extrusion blow molding processes, a blow mold consisting of two halves closes around the parison once it has reached its full length. These two halves of the mold are mounted on the so-called mold mounting platens, which from part of the clamping unit (or closing unit).
RADIAL WALL THICKNESS DISTRIBUTION IN BLOW MOULDING
In blow moulding, the wall thickness distribution of the finished article is essentially determined by the wall thickness distribution of the parison, its position in relation to the blow mould cavities, and the local stretching paths.
SWELLING BEHAVIOUR OF THE PARISON
The visco – elastic behavior of the thermoplastics (here the memory effects) in conjunction with the flow channel geometry in the head causes the diameter of the parison to change after leaving the die. The wall thickness also changes and thus the length of the parison. This phenomenon is called ‘; die swell’’.
MANDREL HEADS IN EBM
In mandrel heads (also referred to as ‘’heart – shaped – curve heads’’, or cardio did heads) the solid core part is massively integrated into the basic structure of the head. These heads are also called side-fed heads.
SPIDER HEADS IN EBM
The main task of parison heads (blow heads or even just heads) is to divert the compact melt flow as supplied by the extruder into a vertical downwards flow movement and to form melt tube with a uniform circumferential wall thickness distribution.
EXTRUDER WITH GROOVED FEED ZONE
Blow moulding machines with grooved barrel extruders are universal machines for all types of polyolefin; the grooved barrel system is,however, indispensable for high molecular weight, high viscosity raw materials. In these extruders, the cylinder wall in the feed section features tapered longitudinal grooves.
SMOOTH BORE EXTRUDER
Blow molding machines with smooth – bore extruders are more or less limited to the processing of low to medium molecular weight polyolefin types. Smooth bore extruders are less expensive than those with a grooved feed zone and show less screw wear.
Is a Blow Molding Machine Used to Make Anything Other than Plastic Bottles?
For manufacturing plastic bottles, experts rely on a state-of-the-art blow molding machine. With this particular process, a manufacturer produces a broad range of finished products in varying sizes and shapes. Because of that, multiple industries depend on a professional company to make a specific type of plastic bottle needed.
What Are the Future Trends of Plastic Molding Machines?
Although the plastic molding industry took a hit this year due to the instability within the automotive industry, it’s still on target for breaking records. After all, the plastic molding machine is something that a broad range of industries rely on for both internal operations and the making of consumer goods. As demand increases, you can expect to see some exciting changes for plastic molding machines.
Can Extrusion Blow Molding Produce Complicated Shapes
When it comes to extrusion blow molding capability, most people think of standard plastic bottles, tight-head containers, jars, and larger water containers. However, the extrusion blow molding process can do much more. In fact, when using a technologically advanced extrusion blow molding machine, it can produce finished products with complicated shapes, and in varying sizes.
Rotational Molding: Advantages and Disadvantages
Rotational moulding offers a number of benefits, but it’s not the best production process for every part. So how do you decide if it’s a fit for you? Understanding the advantages and disadvantages of the process is the first step toward making a decision with confidence.
Importance of Extrusion Blow Moulding Machine in the Pharma Industry
Nowadays plastic is the reliable and most effective form of packaging for different industries and pharmaceutical domains. In the pharmaceutical sector, two types of polymers are used, thermoplastics and thermosets.
HOW TO START A TOY-MAKING BUSINESS WITH EBM IN INDIA?
Before starting the toys making business, it is important to do market research. It is important to collect as much information as possible about this business so that you get the knowledge of exactly what kind of toys are in demand in the market.
WHY INDIAN GOVT. ENCOURAGES TOY MAKING BUSINESSES MAKING BUSINESS
Indian government motivates and urges the Indian startups in the toy sector to maximize manufacturing and increase the reach of Indian made toys to the world. After holding a meeting with senior officials and ministers, the Prime Minister make a statement and urge the start-ups and young blood to innovate in the toy sector. Also, PM has given the suggestion to the educational institutions to arrange competitions in toy technology and design.
Biodegradable vs. Recyclable Plastics
Biodegradable plastics undergo digestion by microbes to form natural bi-products and what is known as humus (a sludge that makes an excellent plant fertiliser). It also produces gas which is officially known as biogas. Biozone’s landfill-biodegradable plastics have proprietary additives that help them biodegrade naturally in landfills. Once the biodegradable packing ends up in a landfill, it attracts the necessary microbes that break down the plastic into its natural components.
The Future of the Extrusion Blow Molding Machine
Everywhere you look, competition among different industries has exploded. Thanks to a thriving market, companies that once struggled now see incredible success. Just as businesses need ways to stay ahead of the competition, so do extrusion blow moulding machine manufacturers. Because of that, they continually push to come up with more innovative solutions.
Why CMP Machines are the BEST?
Innovation is at the heart of any successful company. Innovation keeps an organization at the top of their game, allowing them to flex their competitive muscles and take pride in the work they do.
What is Multilayer Extrusion Blow Moulding Machine?
Nowadays literally all humankind use plastic products 24/7 all over the world. It is super easy to get access to all kinds of plastic products. You might have come across bottles that have a shiny layer on the outer side, or different colours on the outer and a different one in the inner. So, what it is? It is a multilayer extrusion product. Well, let me explain to you how what it is exactly.
Exterior Surface (Mold Cavity) Design
The inner and outer walls of the part are formed simultaneously and integrally, but interior and exterior designs are essentially independent so we review them separately. As the design develops, the designer should begin thinking about the interaction of the plastic and the mould that will produce the part. The visual exterior of many products is formed in one half of the mould called a cavity. Following are some of the features of mould cavities the designer will want to consider.
Interior Surface (Mold Core) Design
The inner and outer walls of the part are formed simultaneously and integrally, but interior and exterior designs are essentially independent so we review them separately. As the design develops, the designer should begin thinking about the interaction of the plastic and the mould that will produce the part. The interior surface of double-wall blow moulded parts is normally formed by a mould core. Since the mould core must fit inside the cavity, there should be no question it meets the same core blow ratio = W>2D overall size requirement as the cavity.
About Parison and Parison Control
Parison blow moulding of intricate plastic bottles and other plastic parts requires air pressure control that is precise, repeatable and rapid responding. Proportion-Air offers electronic closed-loop pressure and flow control used to improve processes in the plastics blow moulding industry.
Why CMP Blow Moulding Machine?
Multiple industries and outside manufacturing companies depend on advanced extrusion blow moulding machinery. Without the right machine, there would be no way to produce superior quality products and we, at CMP, provide quality over quantity. Let us go through the advantages you will get for using CMP’s machine.
Information about the series of Extrusion Blow Moulding Machines in CMP
Have you ever seen a person at the fair or the mall during the holidays, blowing glass to create beautiful, artistic designs? It’s mesmerizing how a random piece of coloured glass can be manipulated by precisely placed hot air and become such a masterpiece. This art form inspired the current method of manipulating plastics to form many of the items we use every day, from water bottles to toys and so many things in between. This artful method is called Extrusion Blow Molding and it’s a common and inventive way of mass-producing hollow, lightweight products that are also durable and waterproof
How to select a Blow Moulding Machine?
The reputation of the blow moulding machine manufacturer you do business with has a lot to do with the quality of the equipment it sells. The right company takes great pride in offering its customers top-of-the-line products at a competitive price. Buying a blow moulding machine can be a nerve-racking experience for fresh entrepreneurs.
Types of products manufactured in Extrusion Blow Moulding Machine
Blow moulding is a manufacturing process for forming and joining together hollow plastic parts. In general, there are three main types of blow moulding: extrusion blow moulding, injection blow moulding (one stage), and injection stretch blow moulding (two stages). In the extrusion blow moulding process (EBM), plastic is melted and extruded into a hollow tube (a plastic parison). This plastic parison is then captured by closing it into a cooled metal mould. Air is then blown into the parison, inflating it into the shape of the hollow bottle, container, or part. After the plastic has cooled sufficiently, the mould is opened and the part is ejected. It is designed to manufacture high volume hollow plastic products.
Types of material used in Extrusion Blow Moulding Machine
When choosing a material for blow moulding; cost, density, flexibility, strength, and other factors should be considered into what resin is best for your part. If the elastomeric properties of the material are exceeded, a hole will tear through the material resulting in a defective part. Other relevant properties are largely based on your application and might include mechanical, physical, chemical resistance, heat, electrical, flammability or UV resistance.
Extrusion Blow Moulding Machine VS Injection Blow Moulding Machine
If you operate a business that requires specially formed plastic bottles or containers, such as juice and water bottles or liquid soaps and shampoos, it’s to your benefit to understand the various manufacturing processes for making those bottles and containers.
What are the 2 types of Extrusion Blow Moulding Machines?
Blow moulding is a manufacturing process used for the production of plastic bottles, containers, and custom shapes. At Central Machinery and Plastic Products, we use extrusion blow moulding (EBM). EBM bottles are easily identifiable by their pinch line across the base of the bottle. This line is created as the mould cavity closes on the parison and the tail is trimmed off.
The process of Extrusion Blow Moulding Machine
Extrusion Blow Molding is the simplest type of blow moulding. A hot tube of plastic material, called a parison, is dropped from an extruder and captured in a water-cooled mould. Once the moulds are closed, the air blown through the top of the neck of the container. When the hot plastic material is blown up and touches the walls of the mould, the material freezes, the container now maintains its rigid shape.
What is Extrusion Blow Moulding Machine?
Blow moulding is an umbrella term for forming hollow plastic parts by inflating a molten plastic tube or parison until it fills a mould and forms the desired shape. Think of it as inflating a balloon inside of a water bottle. The blow moulding process begins with melting down the plastic and forming it into a parison. The parison is a tube-like piece of plastic with a hole in one end through which compressed air can pass. Water channels are carved into the mould to assist in cooling.