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Compression molding produces parts by placing a pre-measured amount of material into a mold, closing the tool, and applying heat and pressure. This pre-measured material is called a charge or load, and the mold is usually pre-heated so that the material flows more readily and fills the tool as it’s compressed. When molding is complete, the part is cooled, ejected, and trimmed or de-flashed.

Often, compression molding is used to produce larger or heavier parts – especially ones that are flat or have simple contours. Yet this molding technique can also be used with smaller parts and can produce threads, holes, and grooves. Compression molding supports a wide range of plastic, rubber, and composite materials, but it’s generally used for low-to-medium part volumes.This article explains what part designers need to know about compression molding, one of the many services that we provide. Keep reading to learn more, and partner with Fictiv for complex parts at amazing speeds. Getting started is as simple as creating a Fictiv account and uploading your part drawing. Along with a quote, you’ll receive expert design for manufacturability (DFM) feedback. 

Compression Molds

Compression molds have a movable top half (the core) and a fixed bottom half (the cavity) that are usually made of aluminum or steel. The parting line is where the two mold halves meet. Some compression molds have a single cavity, but most have multiple cavities to help offset the longer cycle times associated with compression molding. To facilitate part release, molds can also use ejector pins and sliders but many are manually removed from the tooling by hand.

How Compression Molds are Made

Typically, compression molds are machined from hardened steel blocks. Manual machining with milling and drilling, or automated machining are used. Compression molds can be die-cast instead, but the dies still require CNC machining. 3D-printed inserts can be used to reduce tooling costs, but they won’t last as long and can’t match the tolerances of metal molds, especially hardened steel ones.

Types of Compression Molds

There are three main types, or styles, of compression molds.

• Flash
• Positive
• Semi-positive

Flash molds

Flash molds are the most common mold because they’re the simplest and least expensive to produce. Before molding, an operator loads the cavity with an excessive amount of charge. When the mold is compressed, material fills the mold completely but flash escapes between the parting line. To control costs associated with waste, flash molds are often used with less expensive materials. 

Positive Molds

Positive molds cost more than flash molds and require an accurately measured charge. Often, positive molds are used when it’s important to control part density, or if a part is molded from expensive materials. Positive molds are also used when parts have a deep draw, meaning that the depth of the compression molded part exceeds its diameter.

Semi-Positive Molds

Semi-positive molds are the most expensive compression mold, but they combine the advantages of flash molds and positive molds. Although semi-positive molds don’t require extremely accurate charge measurements, using an excessive amount of charge can cause the material to escape between the parting line during mold compression.

Compression Molding Materials

There are three main types of compression molding materials

• Plastic
• Rubber
• Composite

Compression Molded Plastic Materials

Compression-molded plastics can be divided into thermosetting and thermoplastic materials.

Thermosets

Thermosets have low shrinkage rates and high durability. They tend to have better mechanical properties, but can only be liquefied once. Consequently, they can’t be remolded. Examples of compression-molded thermosets include:

• Phenolic resins
• Epoxy
• DAP

Thermoplastics

Thermoplastics can be melted repeatedly and are re-moldable. However, they’re generally not as hard and strong as thermosets.  Examples of compression-molded thermoplastics include: 

• Polypropylene
• Nylon
• High-density polyethylene
• Polyester
• PEEK

Compression Molded Rubber Materials

Compression-molded rubber is stretchy and elastic. Depending on the specific compound, it can also provide oil, temperature, or chemical resistance. Examples of compression-molded rubber include:

• Nitrile
• SBR
• EPDM
• Silicone
• Viton®
• Fluorosilcone

Compression Molded Composite Materials

Thermosets and thermoplastic materials can contain fibers for added strength. For example, bulk molding compound (BMC) is a thermoset composite that’s supplied as a dough-like combination of polymer resins, chopped fibers, and a hardening agent. Nylon, a thermoplastic, can be filled with glass fibers and compression-molded into strong but lightweight parts.Rubber-based composites are also supported by compression molding. For example, silicones and fluorosilicones that contain metal, metal-coated, or bimetallic particles provide electrical conductivity and shielding against electromagnetic interference (EMI). These composite materials don’t flow readily enough for injection molding, but they can be compression-molded. 

The Compression Molding Process

Compression molding is a relatively simple process, but it still involves a series of steps:

• Prepare the charge
• Load the mold
• Apply heat and pressure
• Cool or cure the part
• Release the part from the mold
• Trim or de-flash the part
• Clean the mold

Prepare the Charge

Preparing the charge involves measurement. The compression mold type helps determine the charge’s size, but molders still want to avoid excessive trimming or de-flashing. If the charge is too large, compressing the mold will cause excess material to escape between the parting line and produce flash. If the charge is too small, there won’t be enough material to fill the mold completely.

Load the Mold

Loading the mold involves placing the charge in the cavity, the bottom half of the tool. With flat, rectangular parts, the cavity usually has a flat, rectangular opening that approximates the size of the part. For compression molded parts that require a hollow interior, the core combines with the cavity and creates the interior section.   

Apply Heat and Pressure

With rubber materials, compression molds are usually pre-heated to soften the charge and reduce its viscosity, or resistance to flow. With plastics, the pellets put into a mold might not be heated until the mold is compressed. Regardless, the top of the mold (the core) is closed on the bottom half of the mold (the cavity). Heat and pressure are then applied so the charge flows and fills the tool.

Cool or Cure the Part

With thermoplastic materials, lowering the mold temperature causes the molten charge to harden into the final part. With rubber materials, catalysts are used to promote curing, a process that’s also used with thermosetting plastics. With rubber compression molding, there are two main curing systems: condensation curing uses a tin catalyst, and addition curing uses a platinum catalyst.

Release the Part from the Mold

After the part is cooled or cured, the compression mold is opened and the part is released. Depending on part complexity and volumes, part ejection can be manual or automated. Manual ejection is fine for simpler parts and low-volume applications. Automated ejection is used for more complex parts and higher volumes. Typically, a plunger-style ejector pin that telescopes from the underside of the mold is used.  

Trim or De-Flash the Part  

Some mold flash is expected, but excessive flashing needs to be removed so that it won’t detract from the part’s appearance or interfere with assembly or performance.

• Manual trimming is used with simpler parts, larger parts, and lower volumes. Typically, handheld trimming tools such as knives are used.
• Cryogenic deflashing, a semi-automatic machine-based process, can be used with batches of smaller parts, including ones with more complex features.

Clean the Mold

After compression molding is complete, it’s essential to clean the core and cavity to remove any residual material. Regular cleaning is usually done with a  handheld tool, but more thorough periodic cleanings are also required. Technologies include dry ice blasting and cleaning with chemicals, lasers, or ultrasonic immersion. Finally, a release agent is applied to help prevent sticking during future molding cycles.

Compression Molding with Insert Molding and Overmolding

Compression molding also supports insert molding and overmolding, processes that eliminate post-molding part assembly.

Insert Molding

Insert molding compresses a charge over a prefabricated component. The charge then encapsulates some or all of the insert. For example, a metal knife blade (the insert) can be placed into a compression mold with a plastic charge. When the plastic is heated and compressed, it forms a handle around the blade. Insert molding is also used with electrical contacts such as plugs.  

Overmolding

Overmolding compresses a charge over a previously molded component. This provides the advantages of two separate molding materials. For example, a harder material can be compression molded to form a strong, durable handle. A softer material can then be compression molded over the handle to improve its ergonomics and aesthetics.

Compression Molding Advantages and Disadvantages

The advantages of compression molding begin with lower tooling costs but don’t end there. Because compression-molded materials are placed directly into a mold, they don’t need to flow through a complex series of channels and openings as with injection molding. Consequently, compression molding supports the use of heavier and harder-to-flow materials. Because the charge is placed directly in the cavity, compression-molded parts are free of flow lines and residual stresses that can cause defects.

Compression molding isn’t used for fine part tolerances, but compression-molded parts still have good dimensional accuracy. Compression-molded parts also have a smooth, attractive surface finish and can achieve a good level of detail. Because they’re strong and lightweight, compression-molded parts can replace metal ones in structural components and assemblies. Compression molding support for insert molding, overmolding, and a wide range of materials underscores its versatility.

Compression molding is not a good choice for complex parts with sharp edges, steep angles, or intricate details despite its many advantages. Generally, the part geometries are relatively simple so compression molds don’t need to include ejection mechanisms that increase the cost of tooling. Longer cycle times are also a disadvantage, and activities such as preparing the charge, filling the cavity, and trimming finished parts all add costs.

Compression Molding Industries and Applications

Compression molding is used in many industries and applications. Here are a few examples.

Aerospace Compression Molding

Aircraft manufacturers are replacing heavier aluminum parts with compression-molded C-channels, H-beams, U-sections, L-stringers, and T-strings. Aerospace compression molding is also used to produce O-Rings.

Automotive Compression Molding

The automotive industry uses compression molding to produce fenders and large vehicle panels. Compression-molded plastic parts are also used in automotive interiors to protect engine components. Related applications include housings for LED lighting.  

Medical Compression Molding

Medical compression molding is used to produce plastic syringe stoppers and silicone respirator masks. Because this molding process is cost-effective at low volumes, it can also be used to produce dentures for individual patients.    

Compression Molding for Consumer Products

Compression molding for consumer products is used to produce kitchenware such as utensils, boots, scuba gear, and appliance housings. Household electrical components such as sockets, switches, faceplates, and metering devices are also compression molded. 

Designing Compression Molded Parts

DFM is about designing your part so that it’s easy to manufacture and, therefore, less expensive and faster to produce. Here are four things to avoid when designing a part for compression molding.

• Avoid excessively thick walls. Compression molding supports larger, heavier parts, but parts with thinner walls are less expensive to produce. That’s because they require less material and cool more quickly.
• Avoid unnecessary undercuts. Compression molding supports recessed or protruding part features, but undercuts require ejection mechanisms such as sliders that increase tooling costs.
• Avoid sharp corners and sudden changes in wall thickness. Otherwise, the charge may not flow smoothly and uniform cooling may be difficult to achieve.
• Avoid putting the parting line in a highly visible location, especially if you plan to use a flash mold. Even if your part is not cosmetic, it’s important to account for witness lines and the presence of flash.

If your part design is still in development, you may not have considered parting line locations yet. That’s why it helps to partner with Fictiv, a provider of compression molding services that provides DFM assistance. You’ll also gain access to a carefully vetted network of compression molders.

Compression Molding Services from Fictiv

Is your project a good fit for compression molding? Are you considering 3D printing or maybe even low-volume injection molding instead? Fictiv provides all these services and more, so consider us for your next project. Getting started is as simple as creating a free account and uploading your part design. Let’s get started.

What Is the Difference Between Steel Tarps and Lumber Tarps?

 

Steel tarps are made to cover heavier loads, while lumber tarps are more versatile and are used for smaller loads. These tarps are usually sixteen feet by twenty-four feet, or four feet by four feet. While they are both versatile, they have one important difference: lumber tares tend to be larger, making them difficult to use for small loads.

 

While the Steel Tarp is a more expensive option, it is more durable and versatile than its lumber counterpart. The steel flatbed carries loads of steel and other heavy materials and is a good choice for transporting heavy materials. It's easy to use, durable, and reusable. Regardless of what your cargo entails, make sure you have a good supply of steel tares in stock.

 

Steel tares are wider than those used for hauling lumber. The steel tares are used to cover a wide range of heavy loads. They can protect anything from a single pallet to a full truckload of logs. Despite their differences, both types are useful in many situations. Regardless of what type of load you're transporting, there is a tarp for the job.

 

Steel Tarps Vs Lumber Tarps

 

A steel tarp is smaller than a lumber tarp, but it is just as effective for protecting loads. Lumber tarps are more lightweight and water-resistant and are ideal for carrying construction materials, drywall, and stacked wood. The base fabric is waterproof and can protect loads from wind, rain, and sun damage. These tares also make for a sturdy cover for a truckload.

 

Lumber tarps are smaller than steel tarps, but both are useful for protecting large cargo. A steel tarp will protect a smaller load and will prevent moisture from reaching the goods inside. When a wood tarp is too small, it won't cover the entire load. A lumber tarp will provide additional protection, while a steel tarp will protect a lower profile load.

 

Lumber tarps are typically smaller than steel tarps, and are not designed for protection against weather. However, they have the same purpose. A truck tarp is not just for protecting the cargo of a dump truck. It will protect a dump vehicle and prevent the load from getting damaged. A wood tare is a lumber tarp with a flap at the end.

 

A steel tarp is a tarp that covers a large load. A lumber tarp uses a smaller steel tarp to protect a larger load. A lumber tarp has a lower profile. The main difference between the two is the material used for each tarp. The former is made from a heavier material, while the latter is made of a thinner material.

 

Steel tarps are waterproof tarps with a rounded top. Both types are made from heavy-duty PVC-coated polyester. A wood tarp is made from a wood tarp. Generally, a wood tarp is made from an olefin-based paper, which is a common alternative to a wooden tarp. 

 

Steel tarps are smaller than lumber tarps, and are easier to apply and fold than lumber tarps. A lumber tarp can be more difficult to store because it has more layers than a steel tarp. Fortunately, steel tarps can be folded easily. And most truckers can handle folding a lumber tarp by themselves. But if you're a beginner, you should get help from someone who can do it for you.

 

Typical steel tarps have the same width and length as lumber tarps, but the size of the tarp is smaller. They are ideal for flatbed loads, as they don't need to be tall to protect a load. A typical steel tarp is made for heavy loads, but a lightweight tar is better for lighter loads.

Premier League side Watford have had a loan offer with a €16m option to buy accepted by AC Milan for French striker M’Baye Niang, according to Sky Italia.

With AC Milan having accepted the deal, it is now up to the player to decide if he wants to go to Watford. AC Milan had previously accepted an offer from Genoa, but the player rejected it, claiming he only wanted to go to the Premier League.

More undoubtedly to follow in the coming days.

Click Here: Liverpool soccer tracksuit

What pond liner thickness do you need for your pond?  That answer depends on two things:

1. The liner material you use, whether it’s HDPE or RPE

2. What you plan to store in your pond (water vs. waste/chemicals)

Liner Material is Key

Your pond liner material is a critical factor in determining the thickness you need, and its role is often misunderstood.  Quite often we need to convince people that – if they choose the right material – the liner doesn’t need to be as thick as they think.   

We’ve been making pond liners for 30 years.  In our experience, many engineers who call us still want thicker, heavier liners based on a spec they pulled from an old engineering handbook.  That old handbook ignores the huge advances the industry has made in recent years. 

Today the pond liner industry is moving toward materials that are stronger, lighter and thinner.

Choosing the right material means you can achieve your leak tolerance requirements and at the same time have a liner that’s easier to transport, easier to install and whose overall cost is less.

RPE Pond Liners

The key here is choosing an RPE (Reinforced Polyethylene) liner. These liners are the best overall choice for most pond applications.   RPE is a strong film made by laminating two layers of polyethylene with a heavy-duty scrim reinforcement in between. The scrim is made of HDPE thread that makes the liner stronger.  RPE is also coated on both sides to increase its durability and resistance qualities.

RPE liners are 2-3 times more puncture-resistant than a traditional HDPE liner.  That strength allows you to use a thinner liner for your job. 

HDPE Pond Liners

HDPE (High-Density Polyethylene) liners are an older type of geomembrane material. HPDE is thick and strong and has advantages over both PVC and EPDM.  It has a long life and sheets of HDPE can be welded together to make custom liners for larger ponds. 

HDPE contains a loose weave to hold the liner together but is primarily chosen for its denseness. As a dense material it’s also somewhat stiff, even rigid.  

That stiffness can be a challenge when you transport an HDPE liner to the job site. You can’t fold HDPE, so you need to roll it, which increases your shipping costs.  The stiffness of the material also makes it harder to install, which raises your installation costs.  

As a rule, choosing HDPE means that your liner will need to be thicker than an RPE liner and it will be harder to handle.

How Liner Material Affects Thickness

In practice, a 30 mil RPE liner is preferable to a 60 mil HDPE liner for most applications. The superior strength of RPE means you just don’t need the same liner thickness.  

And, while a square foot of RPE costs more than a square foot of HDPE, a 30 mil RPE liner will still be cheaper than a 60 mil HDPE liner.  That’s especially true when you factor in the higher shipping and installation cost of the 60 mil HDPE liner.  

Key takeaway:  Choosing an RPE liner means you can use a thinner liner that’s easier to ship and much easier to install, saving you money.

Pond Liner Thickness Based on What’s Being Stored

As a rule, you can use a 30 mil RPE liner for ponds that store water.  That means that farm ponds, irrigation ponds, stormwater retention ponds and similar applications can use a 30 mil liner. 

Use 40 mil RPE for waste applications. That means if your pond is storing chemicals or biological waste, opt for a thicker RPE liner.  

If you have a particularly high requirement for puncture resistance, consider using a double scrim RPE liner.  These liners are even tougher –  you can literally drive a truck over them without damaging the liner.

Use a 60 mil HDPE liner for applications that are especially challenging, such as demanding oil & gas ponds.  

Call Us For Guidance

If you’re still not sure what liner thickness or material is right for your job, call us at 1.844.202.4241. We’re happy to give you our guidance. 

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The fashion industry is undergoing a significant transformation, driven by technological advancements and changing consumer behaviors. As sustainability and digitalization become increasingly important, 3D fashion design software has emerged as a game-changer. By allowing designers to create realistic and detailed designs, 3D software reduces waste, saves time, and streamlines the production process. However, the cost of commercial software can be prohibitive for many designers. Fortunately, there are several free 3D fashion design software options available for download, offering a range of features and functionalities. One of the most promising free 3D fashion design software is Daz 3D. This powerful tool offers a vast library of 3D models, textures, and characters, making it ideal for designers who focus on virtual try-on, fashion visualization, and animation. Daz 3D is compatible with both Windows and Mac operating systems, ensuring widespread accessibility. Another popular option is MakeHuman, a free, open-source software that focuses on 3D character creation. MakeHuman allows designers to create realistic human models, complete with customizable body shapes, facial features, and clothing. The software is perfect for designers who require realistic simulations and virtual try-on capabilities. For designers who require more specialized tools, Marvelous Designer is an excellent choice. This 3D design software is specifically tailored to the fashion industry, offering features like fabric simulation, pattern creation, and 3D visualization. Marvelous Designer is available for both Windows and Mac, making it a versatile option for designers. Fashion designers who focus on accessories and jewelry may prefer Wings 3D, a free, open-source 3D modeling software. Wings 3D offers a user-friendly interface, making it easy to create complex shapes and designs. The software is highly customizable, allowing designers to tailor their creations to specific needs and preferences. Lastly, there’s SketchUp, a popular 3D modeling software that’s widely used in various industries. SketchUp offers a range of tools and plugins, including a fashion design plugin that enables designers to create realistic garments and accessories. The software is available for both Windows and Mac, making it an excellent choice for designers who work on multiple devices. [3d fashion design software free download]() When selecting a free 3D fashion design software, it’s crucial to consider your specific needs and goals. Beginners may prefer Daz 3D or MakeHuman, while more experienced designers may opt for Marvelous Designer or Wings 3D. By leveraging these tools, fashion designers can stay ahead of the curve, reduce costs, and focus on sustainability and innovation. In the future, we can expect to see even more advanced 3D fashion design software, driven by emerging technologies like artificial intelligence and augmented reality. As the industry continues to evolve, free software options will play a vital role in democratizing access to 3D design tools, enabling more designers to participate in the digital revolution.

• FBH series is our largest heavy duty Continuous Sealer. Designed to handle and seal extra large and/or extra heavy bags.

• Typical products being packaged with these units are Construction Aggregates, Pet Food, Grains, Charcoal, Mulch, Smoking Chips, Rocks, Textiles, Fertilizers, Pellets, etc. Equipped with a sealing system capable of sealing the thickest bag materials.

• Two Pairs of Brass Heating Bars

• One pair of Brass Cooling Bars with Forced-air Cooling System

• You can equip with any conveyor you want to work with this machine.

本教程适用版本：WPS 365 点击免费使用

以WPS 2019版为例，选中数据区域，点击“数据”—>“分列”。

在弹出的界面中点击“固定宽度”，然后根据需要在各字母之间点击插入分列线。

点击完成，即可快速将数据进行分列。