INJECTION MOLDING MACHINES: TYPES AND BENEFITS

​There are many reasons as to why the process of injection molding is very popular in the field of plastic production—the most common reason is that it is the best means of producing enormous and identical quantities of plastic parts. ​

There are many different types of molding machines, depending on what you are creating and how the machine affects the product. Machines are mainly classified according to the type of drive system it uses: hydraulic, mechanical, electric or hybrid.

• ​​Hydraulic Until 1983, hydraulic presses were the only option available to mold makers, until 1983 Nissei Plastic Industry Co., Ltd. launched the first all-electric injection molding machine. Although the accuracy of the hydraulic type is not high, it is mainstream in most parts of the world, except for Japan. Here are some of the benefits of a hydraulic injection molding machine:

1. Lower price tag: The base price of these machines are significantly less than its alternatives.
2. Cheaper parts: If a part on the machine needs to be replaced due to damage or the parts life-span reached its limit, the replacement parts are lower cost and easier to find.
3. Stronger parts: The hydraulic parts of the machine are more resistant to wear and tear—they are built to last.
4. Power: Hydraulic molding machines have exceptional clamping force.

 

• Mechanical

Mechanical machines use toggle systems to increase tonnage on the fixture side of the machine. All machines need tonnage so that the clamp side of the machine does not open due to injection pressure (i.e. tool half mounted on the platen). If the tool half opens up it will create flash in the plastic product.

• Electric

Electric presses, also known as motor technology (EMT), reduce operating costs by reducing energy consumption and also solve some environmental issues concerns surrounding the hydraulic press. Electric presses are quieter, faster and have higher accuracy, but these machines are more expensive. Here are some of the benefits of an electric injection molding machine:

1. Energy efficiency: Electric injection molding machines only use energy when in action—meaning the motor output is only equal to that of the load requirements.
2. Less-down time: There is no chance of leakage from oil. Also, no oil use means no filters to be replaced, which means consumable expenses are less.
3. Faster process: These machines are digitally controlled, meaning the process is entirely repeatable and needing no supervision.
4. Clean operation: Since there is no use of oil for this machine, it is safe for use if you are manufacturing medical parts. Typically, these parts should be created in a clean-room area.

 

• Hybrid injection (servo-hydraulic)

The molding machine claims to take advantage of the best features of the hydraulic and electrical systems, but, depending on the injection molding machine, it consumes almost the same amount of electricity as the electric injection molding machine depending on different manufacturers.
A robotic arm is often used to remove the molded components; either by side or top entry, but it is more common for parts to drop out of the mold, through a chute and into a container.
 
To some, the hybrid models promise the best of both worlds by bringing together the benefits of an electric motor and hydraulics. Here are some of the benefits of a hybrid injection molding machine:

1. Diversity: the possible combinations for hybrid injection molding machines open up new degrees of design flexibility.
2. Best of both: Hybrid molding machines combine the energy savings and accuracy of electric molders with the force-generating capacity of a hydraulic unit.
3. Replaced motor: Hybrids have replaced fixed-speed DC pump motors with variable-speed AC drives so the pump only operates when required and uses the necessary amount of oil for process efficiency.
4. Less downtime: These require less maintenance and experience less downtime than an all-hydraulic or all-electric molding machines.
5. Price point: Falls nicely between all-hydraulic and all-electric molding machines, making it an affordable option. Especially for medical device manufacturers.

---

Pros & Cons Comparison Table

​	Pros	Cons
Hydraulic	Lower price tag Cheaper parts Stronger parts Exceptional clamping force	the accuracy of the hydraulic type is not high
Electric	Energy efficiency Less-down time Faster process Clean operation and solve some environmental issues	more expensive
Hybrid injection	Diversity Best of  an electric motor and hydraulics Replaced motor Less downtime Price point	​​consumes almost the same amount of electricity as the electric injection molding machine