Plastic Production Secondary Operation
Secondary operation Capability Sonic welding Specialty plating and coating Non-destructive Testing Screen printing Coponent assembly Meetmoulds can provide secondary operations listed below: Precision Machining of Injection Molded Plastic Samples Component Assembly Injection Molding Automated...
Specialty plating and coating
Meetmoulds can provide secondary operations listed below:
Precision Machining of Injection Molded Plastic Samples
Injection Molding Automated Assembly
Insert Molding Assembly
Plastic In-Line Assembly
Post Mold Assembly
Specialty Plating and Coating
Hot Plate Welding
Leak Testing and Pressure Decay
Automated Wheel Balancing
These processes and applications give our customers' products an edge in today's competitive product market.
For joining complex injection molded thermoplastic parts, ultrasonic welding equipment can be easily customized to fit the exact specifications of the parts being welded. The parts are sandwiched between a fixed shaped nest (anvil) and a sonotrode (horn) connected to a transducer, and a ~20 kHz low-
amplitude acoustic vibration is emitted. (Note: Common frequencies used in ultrasonic welding of thermoplastics are 15 kHz, 20 kHz, 30 kHz, 35 kHz, 40 kHz and 70 kHz). When welding plastics, the interface of the two parts is specially designed to concentrate the melting process. One of the materials usually has a spiked energy director which contacts the second plastic part. The ultrasonic energy melts the point contact between the parts, creating a joint. This process is a good automated alternative to glue, screws or snap-fit designs. It is typically used with small parts (e.g. cell phones, consumer electronics, disposable medical tools, toys, etc.) but it can be used on parts as large as a small automotive instrument cluster. Ultrasonics can also be used to weld metals, but are typically limited to small welds of thin, malleable metals, e.g. aluminum, copper, nickel. Ultrasonics would not be used in welding the chassis of an automobile or in welding pieces of a bicycle together, due to the power levels required
Before the actual plating process can begin, it is first necessary to mold the plastic part and make it suitable for plating. Proper molding will alleviate stress on the part and eliminate surface imperfections that can reduce overall quality. The molded part should meet specific parameters regarding polishing, drying of the resin and proper melt temperature.
Because plastic is obviously non-metallic in composition, it's essential to "metallize"? the plastic substrate prior to electroplating in order to improve its adhesive properties. This is achieved through electroless plating, which is the process of depositing metal onto the surface of the substrate without the introduction of an electric current into the plating bath. The steps involved in the electroless plating process can vary but typically include some form of the following:
Cleaning – The surface of the substrate should be thoroughly cleaned to remove fingerprints, dirt and other debris. A mild alkaline cleaner will suffice in most cases, although thorough wetting with a chromic acid solution may be necessary in some instances.
Pre-dipping – Pre-dipping the plastic parts in a solvent prior to etching can improve the surface of poorly molded, highly stressed parts. It can also swell the surface of hard-to-etch parts, making it easier for the etchant to reach and attack the surface.
Etching – Etchants typically consist of chromium trioxide or sulfuric acid solutions that increase the surface of the substrate, making it easier for the part to absorb liquids. Etching also produces microscopic holes that facilitate bonding with the deposited metal. Chromic acid etchants are available that provide the low acid concentration that is required for effective electroplating on plastic.
Conditioning – An optional step that can occur after etching is the application of a conditioner to the substrate. This can promote a more uniform absorption during the activation stage. Conditioners are commonly used with certain plastic substrates such as polycarbonate and polypropylene.
Neutralizing – After etching, the part should be thoroughly rinsed to remove any excess acid or other foreign materials. Applying a neutralizer will further ensure that any excess etchant is completely eliminated. The neutralizer can be sodium bisulfite or a similar product designed for the removal of etchants.
Preactivating – A preactivator is a product that is designed to facilitate absorption during the subsequent activation step. Preactivators work well with resins such as polypropylene and polyphenylene oxide. A preactivator should be employed with caution if a conditioner is also used, as this could result in excessive conditioning of the substrate's surface.
Activating – The next step involves the introduction of a low-concentration precious metal liquid activator that serves as a catalyst during plating, while providing the additional benefit of significantly reduced drag-out costs. Typical metals found in activators include palladium, platinum and gold.
Accelerating – An accelerator is used to remove excess stannous hydroxide from the part, which enables the activator to effectively fulfill its role as a catalyst. Accelerators can also prevent the occurrence of skip plating.
Bath immersion – After rinsing the plastic parts, the next step is to place them in the electroless bath to deposit a thin metal coating. In most applications, nickel is the metal of choice, although copper plating on plastic is performed in some instances. Nickel is generally adequate for making the surface of the plastic conductive. However, copper is sometimes chosen for automotive parts because it is less resistant to blistering.
Screen printing is a printing technique whereby a mesh is used to transfer ink onto a substrate, except in areas made impermeable to the ink by a blocking stencil. A blade or squeegee is moved across the screen to fill the open mesh apertures with ink, and a reverse stroke then causes the screen to touch the substrate momentarily along a line of contact. This causes the ink to wet the substrate and be pulled out of the mesh apertures as the screen springs back after the blade has passed.
Screen printing is also a stencil method of print making in which a design is imposed on a screen of polyester or other fine mesh, with blank areas coated with an impermeable substance. Ink is forced into the mesh openings by the fill blade or squeegee and by wetting the substrate, transferred onto the printing surface during the squeegee stroke. As the screen rebounds away from the substrate the ink remains on the substrate. It is also known as silk-screen, screen, serigraphy, and serigraph printing. One color is printed at a time, so several screens can be used to produce a multicoloured image or design.
There are various terms used for what is essentially the same technique. Traditionally the process was called screen printing or silkscreen printing because silk was used in the process prior to the invention of polyester mesh. Currently, synthetic threads are commonly used in the screen printing process. The most popular mesh in general use is made of polyester. There are special-use mesh materials of nylon and stainless steel available to the screen printer. There are also different types of mesh size which will determine the outcome and look of the finished design on the material.
Meetmoulds have experience with lower volume manual assembly, semi-automated assembly cells, and high-volume, fully automated assembly for a variety of mechanical and electro-mechanical products.
These assembly systems are designed on a set of modular building blocks that have been proven and successfully used in a variety of assembly projects.
We will manage your entire project by not only providing the plastic injection molded parts, but also the services to assemble.
Meetmoulds incorporate automated assembly processes at both the press and off-line. We can customize automation to your product.
Your One-stop solution for all your products in MeetMoulds!