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By Kenny Pravitz | May 3, 2018
Value-added assembly is a process where the value of an article is increased at each stage of manufacturing.

There are typically a variety of pieces and processes involved in making a complete part. As a result, customers sometimes require several different suppliers to make each specific component of the assembly. Even smaller products can have a long list of components and suppliers. During the manufacturing process, costs can vary greatly and the time it takes for products to be completed depends on a range of factors, one of them being how long the supply chain is. In general, a shorter supply channel means your products will get to market quicker, with fewer costs. A great way to shorten your supply chain can be to partner with suppliers that offer value-added processes, or can provide multiple different services or aspects of production.

Value-add can be defined as a process where the value of an article is increased at each stage of its manufacturing, bringing an enhanced benefit and cost savings to the customer.

As a value-added supplier, GM Nameplate’s (GMN) plastics division in Beaverton, OR created a video that demonstrates the value-added assembly process of a medical part. In this video, you can see the stages that these molded parts go through to reach the completed subassembly. Similar to most projects at GMN’s plastics division, the process begins with injection molding. Once that part is molded, it can be decorated, depending on what the customer wants. Offering different decorating options, such as screen printing or hot stamping, after a part is formed is an example of a value-added benefit.

In the video, an operator can be seen placing 17 brass inserts in different bosses of the molded part. To make sure the inserts are properly installed every time, the operator places the molded part in a poka-yoke (Japanese term for “mistake-proofing”) fixture. The molded part will only fit in the fixture one way, so the operator installs the inserts into the correct bosses. These inserts are then heat staked, where a heating element makes contact with each brass insert. The insert then transfers heat to the boss, melting the plastic around the screw. This enables the screw to be removed without stripping the plastic.

Next, the video shows the part being placed in another fixture where a three-camera vision system verifies all the inserts were properly installed. This vision system also has a poka-yoke fixture to ensure consistent verification. Once the vision system notifies the operator that all inserts were properly installed, the part moves to the next value-add station. We see the molded part moved to an assembly fixture where a blue latch-spring component (which is also injection molded by GMN) is assembled to the main plastic enclosure. After this, an operator installs gasketing to the perimeter of the part. Finally, the part is inspected and then packaged for shipment.

From beginning to end, multiple different components and processes were used to make this part, all under one roof. This added value allows customers a cost savings as well as a streamlined supply chain, as several components were completed by one manufacturer, instead of multiple vendors for each individual operation. GMN takes a holistic approach to building your device, and the breadth and depth of our internal capabilities bring increased control, predictability, and reduced costs to your supply chain.

To watch this process in action, click play on the video below. 

By Kenny Pravitz | Mar 27, 2018
A softer plastic resin can be over-molded to a rigid plastic all within the same process with two-shot molding.

When you look at or feel a plastic component, you would usually assume that it’s made of one type of plastic. However, some plastic products are actually made using two different types of resin, sometimes more. You are probably familiar with this application which can be seen in plastic toothbrushes that have a rubberized grip. The main body of the toothbrush is made of a rigid plastic, while the grip is made of a rubberized plastic. Even though there are two different types of plastic present, both were formed at the same time using two-shot molding.

GM Nameplate’s (GMN) plastics division in Beaverton, OR recently created a video that demonstrates this two-shot molding process. The process is called two-shot molding because there are two different resins being injected by two separate barrels. There is a primary barrel, which injects the first resin, forming a rigid substrate in most cases. The secondary barrel then injects a different resin on top of or surrounding the region of the first substrate.

Depending on the size and intricacy of the part, you can design the tool to make several parts in each cycle. In the video, we see that two parts are completed during each cycle. On the left side, the rigid substrate is injected by the primary barrel and forms the backbone of the two components. The tool then rotates 180 degrees, and the rubberized plastic is injected onto those two pieces by the secondary barrel. While this is being done, two more rigid substrates are made at the same time again by the primary barrel on the left side. After the pieces are injected by the secondary barrel, an end-of-arm tool picks up the completed parts, and then the tool rotates 180 degrees once more, ready to start a new cycle.

Two-shot molding is ideal for higher volume projects, as more engineering is used in designing the two-shot molding tool. The tooling used for two-shot molding is intricate because it must inject two different plastic resins simultaneously, but only in certain features of the part. Two-shot molding is a much more efficient process for high-volume projects compared to conventional over-molding, where you use two separate tools to manufacture parts with different resins. Due to this efficient output, two-shot molding is frequently used in the automotive and medical industries.

Click on the video below to see the two-shot molding process for yourself!

By Kenny Pravitz | Jan 30, 2018
IMD allows different graphic overlays to be used in the same molded shape, giving  you customization.

Many industries require the decorative elements of plastic to be highly durable. For example, the aerospace, automotive, and medical industries have many high-wear applications that require strong, durable parts where printed icons won’t scratch off or fade away. Products that are decorated using first-surface decorating processes, where graphics are placed on the outermost layer (such as pad printing, screen printing, or hot stamping), wear out over time and aren’t suitable for these industries. Depending on the materials and processes used, the inks on plastic pieces can fade out over time, making it difficult or impossible to read indicators on those pieces.

In-mold decorating (IMD) is a plastic decorating method that ensures the durability of the graphic overlays and allows for multiple design options for the overlays. In brief, IMD is a process where a graphic overlay is physically fused to injection molded plastic to form one piece. Molten resin is injected either in front or behind the graphic overlay to form a bond between the two. Unlike pad printing, screen printing, or hot stamping – where inks and overlays are exposed to the user that can deteriorate over time – IMD parts have a layer of plastic that encapsulates the ink, protecting it from users and the outside environment.

GMN Plastics, GM Nameplate’s (GMN) plastics division in Beaverton, OR, recently created a video that demonstrates the IMD process. In the video, we see an end-of-arm tool pick up a graphic overlay and place it in the injection mold using a vacuum system, while simultaneously removing a part that was just molded. Both of these functions are completed in one cycle, allowing for faster and more efficient production. Locating pins in both the end-of-arm tool and injection mold itself allow for consistent placement of the overlay in the tool, which is critical for functional parts in regulated industries. If the overlays are not correctly and consistently placed in the mold, some portions of the overlay may not be fully encapsulated by plastic during the molding process.

IMD is ideal for higher volume projects that have stringent durability requirements, as there is more design engineering required up front than with a standard injection molded part. However, one advantage is that once the graphic overlay and molded part is designed, printed graphics on the overlay can be changed at any time to allow for customization and unlimited design options.

To learn more about what the IMD process is, read this blog.

To watch the IMD process, click play on the video below. 

Bruce Wold, GMN
By Bruce Wold | Aug 4, 2016
Designing for manufacturability

A very important aspect of project planning is assessing the design and providing design considerations for part manufacturability. During this phase, GMN Plastics program managers and engineers are looking for anything that might cause problems in the molding process including both cosmetic and dimensional issues. Typical issues include wall thickness, wall to rib ratio, draft angles, boss diameters, undercuts, weld line locations, and texture choices. GMN Plastics solves this problem with years of experience and state-of-the-art software simulators that allow engineers to get a closer look at the part by dissecting it into smaller pieces. These tools can help identify these issues so that they can be solved prior to production.

One of the main issues faced during project development is wall thickness. The wall thickness depends on many factors and there is no density that works universally for all projects, so it must be customized per part. Wall thickness is important because it affects processing of the part and depending on how far the material needs to flow, this can affect both cosmetics and dimensions. If the walls are too thin than the melted plastic moves slowly through the tool, which makes it difficult to fill. On the other hand, if the walls are too thick than it takes longer for the plastic to cool, which can cause part shrinkage. This happens because the areas of plastic on the outside cool more quickly than the inside, which can cave in. Where possible, there needs to be even wall thickness and smooth transitions for the material to flow through correctly.

Wall to rib ratios are another important consideration during part design.  Ribs are commonly used in plastics manufacturing as a way to increase the strength of the part structurally. It’s important to note that rib thickness must be 60% or less than the wall thickness of the part or the ribs will sink and be seen through the other side of the part. 

One of the main considerations during injection molding manufacturing is the part draft angles. This is because the part needs to be able to get out of the tool and to do this there cannot be a 0 degree, or exactly perpendicular, draft. A 0 degree draft angle would cause the part to get stuck inside the tool. A part with heavy texture will need to increase the draft angles even more because the plastic is more likely to stick to the tool. The key takeaway here is that correct draft angles will make the part look good without getting stuck.

Boss diameters, the holes where screws are inserted, are important to consider too. The boss diameter needs to be the right size because it typically holds a metal insert which needs to fit in correctly. If the boss wall is too thick, there will be sinking on the other side of the part. If the diameter is too small, the insert will not fit in the hole. There are industry specific standards based on each manufacturer.

An undercut can be defined as a recessed area of the part, and in terms of molding this means that the undercut area makes the part unable to release out of the tool. The plastic is injected around the undercut feature and the part cannot be ejected because the shape curves inward. The part is stuck because the plastic has formed around the tool which causes problems during production.

Weld lines are a cosmetic issue for consideration. A weld line occurs when the material wraps around a feature and comes back together around an obstruction while filling the tool. When this happens, a small line is formed called a weld, or knit, line. This needs to be considered during part design because the weld line is tricky to hide. When determining the location of a weld line it is important to look at the plastic temperature, gate location, speed of flowing plastic, gate thickness, gate location, and gate height.

Texture can be used to hide molding flaws. For example, when the part design will give you sink a heavier texture can help to hide this. Using texture like this has a lot of tradeoffs in design and many customer negotiations occur.

During the stage of project planning when part design occurs, all of these factors are critical to build a successful part that meets customer specifications. The main issues to consider in regards to part design include wall thickness, wall to rib ratio, draft angles, boss diameters, undercuts, weld lines, and texture.