MACHINING AND METAL FORMATION

The predecessor of the enterprise is the third branch of the Chongxin General Factory,which was founded in1990.With rich experience in sheet metal processing and mold manufacturing, we are well-equipped to meet your needs and provide high-quality solutions.

Metal Processing Services

EMPDA’s machining and metal formation team has a wealth of experience working with many different types of materials such as aluminum alloys, steel and plastics, in addition to countless hours of completing designs for our customers.

EMPDA's Metal Forming Expertise

Common metal forming techniques include stamping, bending, drawing, and extrusion. Choosing the right metal material is crucial for ensuring the performance of the final product. Common metal materials include but are not limited to steel, aluminum, copper, and their alloys. Each material has its unique physical and mechanical properties, making them suitable for different application scenarios.

Stamping

Starts with sheet metal, and through sets of dies (stages), the metal is struck once per stage to deform the metal piece. The metal piece is transferred from stage to stage and through this progression, the metal is formed to the desired shape. Each stage normally performs a small amount of transformation which is why it is common to see 3-4 stages in stamping.

Forging (Steel and Aluminum)

Forging starts with stock metal (rod, bar, sheet) and through rapid localized impact force, metal is formed into a desired shape. This can be done when metal is cold, warm or hot. The resultant piece of metal normally becomes stronger than the stock piece. Forging produces a stronger piece of metal than other processes, such as casting.

Extrusion

Bar or Rod stock is forced through a die, of desired end part cross sectional shape. Starting stock piece will typically have a larger cross sectional area than of the resulting part.

Rolling

Metal stock is passed through one or more rollers (dies) to elongate (reduce thickness) the metal to the desired shape. The end result of the part will have a much more uniform thickness and cross sectional.

Bending

A stock metal sample in pressed between a lower and upper die (U shape, V shape or L shape) to deform the part to a desired angle. Typical bending operations are only preformed once, however, a series of bends can be applied to create more complex parts.

Welding

Two metal pieces of metal are melted together with a filler metal at high temperatures. The resulting weld joint will be stronger than the base metal. Because of this advantage, welding is used to join parts that would typical break from other metal processes, stamping, bending, etc.

EMPDA's Machining Expertise

Metal machining is the process of taking a larger piece of metal and removing material until a desired shape and size is reached. The machining process achieves accurate dimensional results and is typically used on parts from other metal forming processes that require strict tolerances.

The 3 main machining processes are: turning, milling, and drilling. Other processes include cutting—used in a verity of applications and stages of completion—as well as grinding/polishing, done post machining to achieve a specific type of finish.

Turning

Performed on a lathe, a workpiece is spun on an axis while a blade tool removes material from the workpiece at the desired locations. The blade works along the other two axis to create precise features. This process can be automated (CNC) or performed manually.

Milling

Milling machines rotate the cutting tool instead of the workpiece. This allows the workpiece to be stationary on a fixed or movable table. Milling allows the workpiece to be machined along three dimensions. Milling machines offer the most flexible form of machining as they can perform a wide verity of cuts with on small or large workpieces using a single machine. Modern automations now allow some milling machines to automatically change cutting tools.

Drilling

Drilling is used to cut cylindrical holes in workpieces. Despite its simplicity, drilling is a highly important process as it aids in assembly of the finished piece and is used to form locating features when used in tandem with other formation process. Most fiducials—0,0 origin of the part—will be produced by drilling. Drilling can be done manually or through an automated process.

Chemical Etching

Chemical etching is a process that removes material. A stencil of chemical resistance material is applied to the top and/or bottom of the surface of a metal sheet. The metal piece is dipped into a chemical bath or chemicals are sprayed onto the metal. If both sides do not have chemical resistance paper, the acid will penetrate the whole piece. If only one side of the sheet metal has the chemical resistant film, only partial of the metal will be removed. This creates very accurate clean cuts in the metal.

Cutting

Cutting involves taking a large piece of metal and breaking it into smaller pieces or parts. The end shape is typically similar to the desired end piece. Cutting is used to get stock metal closer to the desired end result in timely manner before transfer the workpiece to another machining operation for final finishing. The most common cutting machines are: saw/blade, laser/plasma, water jet, and wire EDM.

Grinding / Polishing

When parts come out of a metal formation process, they typically lack the finish or surface appearance desired. Grinding and polishing are used post process to remove access material from previous processes. A very thin top layer of material is removed off the part to achieve a smooth or textured finish.

A Sampling of Finishing Processes

For smoothing work piece surfaces, a polishing and buffing process is needed. Polishing uses an abrasive that is glues onto another object, like paper or wheel. through rubbing or grinding, the surface of the part becomes the desired smoothness. Not all polishing results in a smooth surface, the smoothness depends on the abrasive size. Buffing, the abrasive is applied either to a wheel or to the surface and through rubbing the surface of the part becomes shiny, or mirror like.

A decorative finish, similar to paint but more durable, it applied to the surface of the metal. The powder is a dry plastic which adheres to the metal by melting the powder.

Brushed metal finishes pull material away in a uniform, parallel grain texture. This is a very effective way to remove surface imperfections.

There are two main types of plating, electroless and electro. Electroless plating uses a chemical bath that employs an autocatalytic process when the metal part is dipped into the bath solution. Electroplating uses electricity to coat the part with the desired finish.
For a uniform matte finish, sand blasting is the preferred process. Abrasives like sand, steel shots, or metal pellets are forced into the part at high speeds. Similar to polishing, there are specific ball sizes for different smoothness.
Parts are put into a large bowl with media, which can be small or large. The bowl is vibrated at a frequency in which the parts are passed through the media. As the parts pass through the media they vibrate with the media creating a polished finish on the part. This type of process is most common for de-burring parts (with larger media). For a more smooth finish, the media will be small (sand). This is one of the few finishing process that have the ability to create a finish on the inside of holes as the media surrounds the whole part, not missing any tight space.
For high abrasion resistance, blackening is a superior finishing technique. The part goes into a series of tanks with cleaners, caustics, and coolants. Through this process, a thin layer of black oxide is layered onto the part.
Most notably used for hardening and protecting against corrosion in metals. An unknown feature of anodizing is the ability to dye the part afterwards. This method is best used to get bright vibrant colors for the finished part.