A Complete Guide of Different Types of Injection Molding Machines


Molding machines, commonly known as injection machines, are special machines that make plastic products. Injection molding machines can be generally divided into several types according to their power mode, the mold opening and closing direction, suitable raw materials, mold clamping structure, and their injection structure. Most injection molding machines are mainly composed of two parts: a bridge, an injection device, and a clamping unit. The holding unit has a mold to enable force for mold closing and clamping. Apart from injection molding, machines offer these two advantages: quick processing and low costs.


What are the types of injection molding machines?

Injection molding machines (simply an injection press) are classified due to their drive system (power unit of their movable parts).


Three main types of drive systems are electric, hydraulic, and hybrid drives, which could be selected in accordance with the specific application tasks. The three types of drives discussed here are the brushed type, brushless type, and stepper drive. Each of these drives has its advantages and disadvantages as well as costs.


Hydraulic injection molding machines

Hydraulic injection molding machines, which are believed to be one of the very first "modern" injection molding machines, were developed in the last decade of the nineteenth century. They tightened the opening and closing of injection mold halves by hydraulic pressure while pouring the melted plastic into the mold cavity. The only parts they consume are hydraulic fluid, which necessitates continuous energy input for both cooling and pumping the hydraulic systems.


The reason why hydraulic injection molding machines are the most prominent ones is that they are an established technology that has been around for decades. These are the cheapest, most rugged, and easiest to source and repair. There is no doubt that hydraulics have excellent clamping forces (3-4 tons per square inch) within their clamping units, so they are very suitable for large mold production.


Nevertheless, the high energy consumption and the high temperatures crucial for molding, which is capable of destroying some heat-sensitive polymers, are the limitations of hydraulic injection machines. The use of both hydraulic pumps and coolant with constant power input adds to the complexity of the system and calls for an extended infrastructure to get over the problem. Moreover, these machines are plagued with a number of problems, being prone to hydraulic fluid leaks and producing more noise compared to other injection molding machines.


It is worth noting that hydraulic injection molding machines are more affordable (from $3,000 - $100,000) than all-electric machines, which are priced based on the size of the machine. They will also incur an increase in maintenance operations and infrastructure expenditure, which, according to estimates of about $17,000/year, would be the labor costs of the workers who are looking after the systems. These systems have a 7-10 year serviceable life expectancy with regular care, but their hydraulic nature makes them susceptible to many complaints, which can speculate and decrease the lifespan. These categories of drive systems, as the name implies, are primarily for application in heavier and thicker-walled parts such as those used by the automotive industry.


Electric Injection Molding Machines

Electrical injection molding machines (also called all-electric machines) are a modification of displacement machines (mainly hydraulic ones) that went into production back in the 1980s in Japan. They implement several digitally controlled servo motors that allow for precise, independent control of the four axes of injection molding: injection, extrusion, clamping, and ejection processes.


Servo motors that are idle when the lifts are not in use will enable energy savings of up to seventy-five percent when compared to hydraulic models that work continuously and, therefore, need continuous pumping power. These injection molding machines greatly minimize the manufacturing processes as they do not require any consumables, which lead to a low level of maintenance and the ability to run, repair, and scale down for smaller applications. The electric motor is the ideal machine for the clean room application, requiring high accuracy while being calm, noiseless, and cost-efficient.


Electric injection molding machines do have some negative points too. The first demerit is the lower clamp power of this class of machines compared to hydraulic injection molding machines. The second drawback is specifically seen in the electric molding machines, as these are costlier and trickier to mend than the hydraulic machine versions.


The price tag for electric injection molding machines amounts to $5000 – $200,000+, more or less, depending on the features and the corresponding machine size. All electric machines stay in spec for producing micro to tiny parts for medical, biochemical, and pharmaceutical products for more than 20 years by maintenance and are usually employed in clean room applications.


Hybrid Injection Molding Machine

Hydraulic–electric hybrids are hybrids of hydraulic and electric injection molding machines.

injection unit 

Combining the advantages of hydraulic and electric injection molding machines, hybrid injection molding machines have recently become the most effective, precise, and energy-saving machines. Hydraulic shut-off valves with servo motor pumps and oil circulators with hydraulic pressure but with variable power, emission, noise, and energy adjustments. It features a low-energy consumption screw that is equipped with a servo motor and a reciprocal screw that saves energy costs as these models expend more energy on the recovery of the screw.


The benefits that hybrid molding machines provide include energy efficiency, reliability, competitiveness, high accuracy, becoming increasingly cheaper, and less maintenance and downtime. Entirely affluent in terms of efficiency, they generate higher ROIs faster than others got than but still give exceptional force and precision.


However, there is one drawback of a hybrid injection molding machine. The design of the machine will be different from that of the other machines, which are the maker or model. For instance, some of the hybrids with hydraulic screw drives are not as efficient as fully electric models. Therefore, this method will experience some downsides of a hydraulic injection.


The hybrid models have varying price ranges that depend on size and application. However, the current rates range just between electric and hydraulic injection molding machine prices. Besides that, there will be cash savings because of the lower maintenance costs, which will result in faster ROI, either for all-electrical systems or hydraulic ones. Unlike other injection molding designs, hybrid machines end up with the same or even longer lifetime if well treated. Notably these applications include high-volume parts for the medical industry, heavy industrial products, varying wall-thickness parts, and many more things greater and smaller whose volumes will be well managed by additive manufacturing.


Are Plastic Injection Moulding Machines Expensive?

Absolutely, injection molding machines are the most expensive component after molds in the injection molding process.


The costs of the injection-molding machines are dependent on their type; the worktop ranges from $2,000 to $20,000, while the industrial model ranges from $50,000 to over $200,000. The prices above do not include the charges for the facility upgrades, qualified workers' pay, service costs, and monitoring equipment. This massive expenditure will disincentivize companies from purchasing injection machines and instead outsource to the subsidized companies with existing capacities. Only the companies focusing on injection molding and having productive and in need of high throughput products would consider buying an injection molding machine. Otherwise, this investment will not be advisable.


What Are the Main Usages of Plastic Molding Machines?

Plastic injection molding machines are used for the mass production of plastic pieces. They can manufacture more than 10,000 parts (depending upon the machine and the part design) in a single working day with no defects or tolerance. Their use is only restricted to the size of the system and the creativity of the designers. Injection molding is so versatile that almost every house in the United States probably has encountered numerous, if not many, injection molded items.


Is it easy to maintain plastic injection molding machines?

It varies from one injection molding equipment to another; however, in most cases, a small volume of maintenance is required from the injection molding machines. It would be a good idea to do daily visual checkups to identify problems early and general maintenance checks every 6 months also. It will be necessary to perform an annual maintenance full day to detect problems, perform readjustments, and substitute old parts.


The areas wherein the supervisor must concentrate the most are oil filters (regardless of indicator status), valves, safeties, hoses, machine cylinders, power lines, lubrication points, nozzle alignment, and control modules. Another thing to note is that injection molding machines are often picky when the seasons change, so be aware of that during the transitional months and during times of extreme temperatures. Not only will a bypass of the preventative maintenance reduce operation speed and affect your profits, and as a result, you will end up with a headache, but the machine lifespan as well, thereby making you lose a great amount of benefit you could have gained from this technology.


What is the difference between horizontal vs vertical injection molding machines?

Horizontal injection molding machines have low weight and central gravity and are more accessible, easy to use, maintain, and develop automation systems. For this long time, DKM has provided a great line of molding machines, from small injection models with 30 tons of clamping force to large machines with 4,000 tons of force.


Vertical injection molding machines are known especially for their compact footprint and easy-to-fit size. Nevertheless, in the completely automated operation interface, it is difficult to remove or discard the substance by hand. The vertical injection molding machine only applies to the production of small-scale plastic parts.


The most commonly used variety of injection molding machines is found in the market.

The horizontal injection molding machine is the most popular in the market. The majority of injection molding machines are horizontal types that are mostly those intended for cylindrical parts and high-volume runs. DKM is the biggest manufacturer of Horizontal Injection Molding Machines. On the contrary, a vertical injection machine is good for little items like pen drives.

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