Compression molding remains a widely used and adaptable plastic manufacturing procedure in many industries.
Large and small production companies employ and adapt this manufacturing process to fabricate plastic components of varying lengths, thicknesses, and complexities. These components range from aerospace parts and medical goods to standard consumer products.
Thus, you will agree that the need to comprehend the principles guiding the compression molding procedure to achieve manufacturing success is not one to overlook.
Hence, this article extensively looks at all you need to know about compression molding.
What is Compression Molding?
Compression molding is a manufacturing process that uses compressive force and heat to fabricate or mold a suitable deformable workpiece to the final product. This technique uses a vertical press and a heated cavity.
More specifically, in compression molding, the selected material gets heated until it becomes pliable. Then the mold is sealed for an adequate time.
Afterwards, the preheated material, also known as the charge material, positioned on the heated hollow or cavity gets squeezed or compressed under the appropriate pressure to produce the desired product.
Compression molding utilizes operating conditions suitable for wide-ranging production volumes.
Moreover, this manufacturing technique is usually compatible with various workpieces like rubber, thermoplastic, thermosetting plastics, and more intricate composite materials.
Likewise, compression molding ranks among the best procedures for producing flat and curved plastic parts.
To a large extent, some compression molded products come with desired properties like additional strength, durability, hardness, corrosion and abrasion resistance compared to other components manufactured from other production methods.
To crown all this, the cost-effective tooling requirements of compression molding make it a suitable go-to procedure for low to medium production and prototyping.
Compression molding applies in manufacturing various products such as electrical parts, casings, knobs, handles, gears, containers etc.
Why Might You Want To Use Compression Molding?
Compression molding remains popular and highly praised due to its unique benefits in fabricating various parts.
Most manufacturers use the compression molding technique to manufacture many products because it is an effective and efficient manufacturing procedure that provides a sizeable production yield within a short period.
Check the benefits of using compression molding below:
1. Low Scrap Rates with Compression Molding
Scrap rates measure the difference in weight between the input material and the total weight of the products manufactured.
Scrapping occurs due to low-quality input materials, reckless procedures, defective machinery, or inefficient production workers.
Compared to injection molding, compression molding scrap rates are 2 to 5% lesser. And this is mainly because manufacturers do not need to use toolings like gates, runners, or sprues for compression molding.
Materials must pass across these tools in injection moulding before moving to the heated mold cavity. In the end, these tools consume extra materials that increase the scrap rates of injection molding.
2. Compression Molding Leverages Repetition & Consistency
Compression molding is a manufacturing method that proffers a high degree of consistency, automation, dimensional stability for many materials, good reproducibility, and shorter cycle time.
The uniformly distributed material over the mold surface during the compression stage usually results in less flow orientation, resulting in higher product consistency.
This explains the reason for the diverse application of compression molding in several industrial sectors, including the automotive industry.
Compression molding is a flexible production technique in that engineers can design compression molds with the aid of the tools like computer-aided design software (CAD) and 3D printing.
Thus, experts use these design samples to fabricate various types of materials. In addition, compression molding is well-adaptable for producing different prototypes before progressing to large-scale production.
This enables manufacturers to detect errors and make necessary modifications to achieve production success.
Compression molding requires little to no additional features besides the cavity’s essential elements that produce the molded parts. Thus, this aids the replication of the details needed for efficient production.
More so, it is ideal for fabricating simple, flat, and large parts.
Compression molding proves a cost-effective manufacturing method for small to medium production runs.
Besides, you’ll find that compression molding requires low capital setup costs and considerably low tool costs. Also, manufacturers can produce the tools from aluminium or lower steel grades, reducing costs.
Compression molding proves an efficient and time-tested resolution for product fabrication compared to other manufacturing techniques.
In most cases, you’ll find that this technique yields components with quality aesthetics and surface finishing.
What Is the Downside Of Compression Molding?
Almost every manufacturing procedure has a few downsides, and compression molding is no exception. Check the limitations of compression molding below:
1. Small Design Errors Have Big Costs with Compression Molding
In most cases, compression molding is less efficient for fabricating components with steep angles, curves or draws. This molding process remains best for manufacturing parts with simple design specifications and large components.
This is because the restricted material flow within the cavity gives room for design errors, air traps, and knit lines when trying to produce intricate parts. Above all, these design errors can incur substantial production costs.
2. Be Ready for High Tooling Costs for Compression Molding
The repetitive nature of the compression molding process means that the molds get subjected to wear and tear over time. Often, molds do not get bolted into a press, so they tend to run loosely.
As time goes by, the trim grooves and fine details deteriorate or, in extreme cases, cause damage to mold faces. As a result, manufacturers must prepare for the higher costs of compression molding tools.
3. Longer Lead Times than Other Technologies
Due to the poor thermal conductivity of rubber and some other materials, loading blanks up to curing temperature by contact with the hot surfaces of the mold require a longer time for larger parts.
This reduces the speed at which parts get cured or de-molded to make a significant change when manufacturing parts in higher volume.
How Does Compression Molding Work?
There are vital steps involved in compression molding. Check them below:
Foremost, the manufacturers select the suitable material and prepare and weigh the workpieces before subjecting them to comminution processes.
Then, the raw materials in the pellets or powdered form get preheated to form the charge material before passing it to the heated mold cavity. Typically, the mold is made from either aluminium or steel.
Next, the engineer covers the matching top plug using a hydraulic press.
Usually, the motion exerts vertical compressive forces. The applied pressure makes the charge material stuff the mold evenly during this time. This, in turn, forms a consistent shape of the desired component.
Afterwards, the expert closes the mold and keeps it closed. Then, the curing process, characterized by moderate temperatures, physically changes the charge material into the final shape and geometry.
Once completing the curing process, the engineer lifts the upper mold to withdraw the final product from the cavity.
The Different Types of Compression Molding
Cold and hot compression constitute the main types of compression molding. The main distinction between the two techniques is that the curing process occurs at room temperature in cold compression.
In hot compression molding, on the other hand, the curing takes place by applying heat and pressure to the mold until the material has cured.
What Raw Materials Are Used in Compression Molding?
The usual raw materials used in the compression molding process include the following:
- Plastic resin (thermoplastic and thermosets),
- Rubbers, and
- Some types of fiber reinforcements.
What Industries Can Use Compression Molding?
Compression-molded components have become a staple in our everyday life. This fabrication procedure applies in many industries, including aerospace, automotive, electrical and electronics, medical, etc.
To a large extent, this aerospace industrial space relies on a solid strength-to-weight ratio and quality surface finishes, where compression molding comes into play.
Manufacturers employ compression molding to fabricate various aircraft components such as wings, blades, engine casings, etc.
Often, experts use composite materials such as carbon fiber reinforced plastics and fiberglass-reinforced plastics to produce most of these parts.
Similarly, the automotive industry’s strength-to-weight ratio is also a design concern as it impacts fuel efficiency. Automakers also use composites to produce several vehicle components using compression molding.
They include engine parts such as brackets and mounts, body parts like bumpers and spoilers, and internal auto parts like seat backs, dashboards, and door panels.
Automakers also use compression molding to make various electrical and mechanical components. Additionally, rubber applies in manufacturing sealants, vibration regulators, and O-rings.
In the medical industry, experts use silicone rubber for manufacturing many medical components through compression molding.
And this is due to its unique biocompatibility with body tissues. These medical parts include orthopedic surgical implants, syringe stops, vibration isolators, diaphragms, cylinder seals and silicone face masks, to mention a few applications.
Manufacturers also use compression molding to fabricate most electronic products. A typical application is the rubber casing for a thermal imaging device. This is due to the aptness of this molding technique for fabricating components with undercuts and irregular thicknesses.
Compression molding provides quality surface finishes and is usually employed in manufacturing cases for smartphones and tablets. It also applies to the fabrication of several internal components of electrical devices.
Is Compression Molding the Right Option for My Project?
Compression molding is one of the oldest processing techniques available. Further, compression molding is the most widely used process in commercial use due to its simplicity and availability.
Nevertheless, resolving whether the compression molding techniques can meet the specifications of your project can get tricky. Look at the top tips below to know if compression molding is the correct manufacturing procedure for your project.
Start with Financial Considerations
Above all, it’s best to consider and assess your financial resilience before employing compression molding. This manufacturing technique incurs high costs from the tools and the grade of material suitable for the procedure.
Thus, when evaluating the economic implication of using compression molding for your project, cost modeling may prove a valuable tool to assess the financial advantage of the technique.
Next, Let’s Talk about Design Considerations
After financial deliberations, you must put the design specifications in mind. To ensure production success, there’s a need to design and fabricate the mold based on the exact product specifications. Anything aside from this will cost you your time, money, and labor.
For instance, you may need to consider if your desired molded part requires design features like holes, ribs, threads, and lettering or dimension variables like section thickness to know if compression molding is well suited for such components.
Getting Production Right for Compression Molding
Before employing compression molding, you need to secure the production right. After getting this right from the appropriate authorities, you can begin manufacturing.
Compression molding can produce about a hundred parts per hour, depending on the shape and size of the desired part. Thin-walled parts will require lesser curing time, unlike parts with thicker walls, thus increasing their production rate.
Compression Molding vs Injection Molding: What’s the Difference?
Even though compression and injection molding techniques share a few similarities, there are still a few distinctions. Check them below:
1. Production Volume
Injection molding is a plastics production procedure involving molten plastic injection into the mold at high pressure.
On the flip side, compression molding is better suited for low to medium production volume, typically compatible with various materials like rubbers, plastics, and silicones.
2. Level of Automation
Generally, injection molding is highly automated and does not require stringent human supervision. Meanwhile, the compression molding technique requires human intervention to load the charge material and withdraw the final products.
3. Cost of Tooling
The compression molding tooling cost is usually less expensive than injection molding.
4. Suitable Applications
Experts often apply injection molding for smaller and highly complex parts. Meanwhile, compression molding is better suited to larger components and simpler geometries.
There’s usually a need to adjust the part’s design considerations with the necessary drafting, parting line and material selection for a productive injection molding process.
Kemal: The Best Choice for Compression Molding Services
Kemal provides diverse manufacturing capabilities, and compression molding services that will meet your design specifications are no exception.
With our top-notch technologies and dedicated experts, we offer other value-added services for all your prototyping and production needs.