Injection as an Essential Procedure for Mold Designing

 

Mold designing is a growing industry, and learning this skill can set mechanical engineers apart from their contemporaries in the long run. 

For freshers looking to gain some insight into the field, this article explains the job opportunities for mold designers, followed by a detailed description of injection molding. Further, you can get a glimpse into the different tools required to design a perfect mold. 

So, without further ado, let's delve into the fundamental work dynamics of mold design and how students can pursue a rewarding career in this exciting field.

 

 

A Career as a Mold Designer

Many students might think that opting for mold design as a full-time profession is nothing short of a challenge. On the contrary, the industry features a lucrative opportunity to employ one's technical skills to work. 

Mold designing is an advanced skill that requires a hands-on and practical approach. To fulfill their dream of mold designing and stay ahead of the competition, mechanical engineers must enroll themselves in intensive courses and training programs. 

A vast majority of the mechanical engineers may lack the preliminary know-how to design a mold, even after successfully completing a four-year degree course from a reputed institute. Thus, a mold designing course furnishes adequate theoretical and practical knowledge in this field. 

In terms of current industry trends, Singapore, China, and Thailand feature as primary countries for mold design. Therefore, Indians need to possess appropriate mold designing skills in order to come forward and concretize their benchmark in this field. 

To accomplish the above, a mechanical engineer can learn mold design through a plethora of suitable online courses and diplomas. Students can learn and apply their mold designing skills:

  • To become a good product designer
  • To get hired as a mold designer in the core area
  • To choose the design field as a career option
  • To receive onsite freedom to work as per flexible schedules
  • To engender a start-up in mold fabrication

 

Skills Required to Become a Mold Designer

A mold fabricator must possess a remarkable profile to undertake molding as a full-time profession. You must be mechanically skilled to repair and adjust misplaced molds or manufacture new molds through injection, extrusion, or thermo-formation.

Here is a typical list of skill-sets required to become a proficient mold designer:

  • A passion for manufacturing and technology
  • Strong logical and analytical skills
  • Excellent theoretical and practical knowledge of mechanical engineering
  • Dexterous towards mold-making
  • Technical knowledge (high school diploma or a technical degree) of mold designing
  • Mold designing and injecting experience of around 3-5 years (depending upon the complexity of the mold)
  • Knowledge and experience of the mold designing software

Moreover, interested candidates must also work on developing some essential soft skills, such as:

  • Leadership and team player qualities
  • Time management
  • Decent communication skills to deal with clients
  • Willingness to learn and put that learning to application
  • Excellent listening and thinking abilities to improvise and innovate the already existing mold designs

Injection Molding

Injection molding has varied usages in different industries. Technically, it is used in the medical, automotive, and consumer product industries.

Molders fabricate the molten plastic into rugged and stocky molds under high-pressure conditions. This design is used to manufacture different types of plastics, such as those in cooking appliances, consumer electronics, power tools, etc.

The automotive industry uses nylon molds for better grip and durability, which you can see in constituent parts of dash panel molds and molds used in seat belts. Consumer products, on the other hand, use complex molds for their sturdy structure.

Injection molding takes places through the following steps:

Clamping

  • Before injecting the mold substance, the proper closure of the two clamping units is essential to hydraulically empower the dual halves of the mold, followed by subsequent up force pressure.
  • Further to this, the molder must ensure the proper closure of the clamps to prevent the material from spreading or injecting externally.
  • Large machines have longer clamping duration as compared to smaller ones.

Injection

  • In this, the hopper drops plastic pellets into the mold machine, allowing these pellets to move towards the injection unit.
  • Further, the heat wrapping the injection unit at a pressure of 35-140 MPa forces the pellets to melt.
  • Next, the time of injection stands completed when 95-99% of the mold is filled.

Cooling

  • Cooling refers to the lowering of the temperature of the plastic within the mold machine.
  • This plastic keeps solidifying with time and takes up the desired mold shape.
  • The thickness of the inner walls and the thermodynamic properties of plastic determine the duration of cooling.
  • Finally, only after the elapse of the cooling period should a molder open the mold.

Ejection

  • This refers to the final stage in the injection molding process.
  • The mold designer needs to apply extra force while opening the solidified mold.
  • Consequently, the molding machine forms a complete ready-to-use mold while further allowing the molder to reiterate similar steps for designing similar molds.

 

Mold Tools and Apparatuses

Source

A mold has different components, and each of its parts is dedicated to performing a specific function. The necessary elements of a mold structure are as follows:

Support plate This is the foundational part of a mold. Its purpose is to hold the other components intact in their places.
Ejection box This part of a mold comprises the ejector pins, mechanical lifters, and blades.
Ejector plate It pushes the ejector pins forward to other parts of the mold cavity.
Ejector pin As a constituent of the ejector box, it surfaces as a mediation between the ejector plate and the mold cavity.
Sprue bushing It denotes the point of the ejection of the mold material via nozzles. Its purpose is to fill the mold cavity with the ejected substance.
Runner An efficient runner system supervises the machine to move the sprue to the mold cavity.
Gate Gate refers to the small orifice opening via which the polymer material enters the mold cavity.
Leader pins These pins support the four different edges of the mold and maintain its structural balance. 
Locating ring Its essential function is to locate the mold ring at the center of the plate.
Part A, part B These refer to as the dual half components of the hold where part A indicates the cavity, whereas part B implies the position of cavity formation.

Other Parts of an Injection Mold

The other parts of an injection molder apparatus include:

  • Injection cylinder
  • Fixed platen
  • Rear platen
  • Moving platen
  • Tie bars
  • The front and rear half of the tool
  • Mold height adjuster
  • Travel limit switches
  • Drive unit
  • Carriage cylinder
  • Feed throat
  • Feed hopper
  • Reciprocating screw
  • Barrel heaters
  • Check valves
  • Nozzles
  • Mold half

All the above-listed parts cater to engineering a perfect and long-lasting mold design

 

Plastic Molds

Plastic molding features as a sub-type of injection molding where two plastic materials are molded on plastic models while a plastic brush is attached to one of the mold sides. 

When making plastic molds, the process of polymerization eventually leads to the formation of two types of plastics: Thermoplastics (such as rubbers and adhesives) and Thermostats.

 

The Molding Cycle

The process cycle of injection molding ranges between two seconds to two minutes, depending upon the size and the temperature of the mold material. 

What's important to note about a complete molding cycle is that its duration depends on various factors.

The molding cycle is as follows:

  • Initiation of the molding cycle
  • Mold close (mold safety, tonnage)
  • Injection stroke (injection speed, injection pressure, hold pressure position)
  • Holding period (holding pressure, holding time, gate frozen)
  • Cooling period (start screw back, screw rotation, solidification of the mold, material in the barrel plasticized, finish screw back shot position reached)
  • Mold opening
  • Ejection and Open period (ejection speed, pressure, and stroke)
  • Completion of the Mold cycle

 

Conclusion

Altogether, mold designs feature as one of the most significant manufacturing technologies in contemporary usage. Each mold component serves to perform a particular task, and each task alludes to its multiple ways of performance. As such, mold designers need to exercise these requirements to carve a reliable mold. 

If you're interested in learning about mold designs and its potential to elevate your technical stirrings, go ahead and get yourself enrolled in this mold designing course. This hands-on learning course can stimulate your passion for learning, innovating, and rediscovering something thrifty and skillful.


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