Materials and Processes
ChinaSavvy, an ISO 9001:2008 registered firm based in China, offers a variety of manufacturing processes working with a number of materials to deliver high quality products.
Capable of setting up both high and low volume manufacturing processes, ChinaSavvy ensures that only the best quality end products, meeting Western quality standards, are produced.
Some of the manufacturing processes offered by ChinaSavvy include:
- Metal Fabrication
- Aluminum Extrusion
- Metal Injection Molding
- Metal Sintering
Working with a number of materials in the fabrication process, ChinaSavvy specializes in aluminum and stainless steel fabrication processes, as well as steel fabrication.
Our fabrication shop specializes in:
Including cutting and burning, forming, machining and, welding and assembly.
Working with a number of aluminum alloys, ChinaSavvy offers press bending, rotary bending, roll bending, heat-induction and hot-slab forming.
- Anodized Aluminum FabricationNote here that, because certain alloying elements decrease aluminum’s resistance to corrosion, certain grades undergo anodizing processes in order to increase the thickness of the natural film on the aluminum itself. In doing so, the metal’s resistance to corrosion and its surface hardness increases. Anodizing is also used to allow for the coloring of the aluminum, giving the added benefit of an improved adhesion and lubrication.
Our specialized aluminum fabrication shop is capable of using a non-consumable tungsten electrode to produce a weld. The welds produced using this process are clean, mechanically strong welds that requires no other finishing processes (such as grinding).
Stainless Steel Fabrication
Our stainless steel fabrication shop offers a number of stainless steel fabrication processes ranging from work hardening and machining, to welding, soft soldering and brazing.
In terms of stainless steel tube fabrication, ChinaSavvy offers both welded stainless steel tubing and seamless stainless steel tubing. Stainless steel tubing requires that the alloys be melted according to certain specifications depending on the grade used, the stainless steel strips from which the tube will ultimately be formed, is produced using either cold formed coil or hot formed coil.
Seamless stainless tubing is however manufactured through piercing, gun drilling or extrusion processes.
ChinaSavvy also offers TIG Welding services for stainless steel, more commonly used to weld thin sections of stainless steel. Using TIG welding processes, on stainless steel offers a variety of benefits including the creation of pore-free welds that are sound, a very low electrode wear and a narrow fusion zone, to name but a few.
Working with steel, ChinaSavvy offers fabrication services that meet the highest quality standards. Offering cutting and burning, drilling, welding and assembly services, our steel fabrication shop works to ISO 9001:2008 standards, delivering high quality, steel fabrications.
Steel fabrication involves various processes, including:
- Cutting and Burning: Here, the steel plates need to be cut to size. This is most commonly done through shearing techniques. CNC cutting torches (commonly laser, plasma or fuel gas powered) is also used here to cut large sections of steels.
- Drilling: This process involves the use of a drill line – a way to drill holes and mill slots into steel beams, sections and channels. CNC Drill Lines are also commonly equipped with position sensors and feed conveyors. These sensors and conveyors are responsible for moving the steel into the correct position for drilling.
- Welding: In this process, machined and formed steel parts are assembled and tack welded into place. Checked for accuracy, the weld is then completed to the project’s set requirements. Do note however that special precautions are required when welding steel, as warping may occur due to the heat caused by the welding process.
- Final Assembly: Once cutting, drilling, welding and other finishing processes are complete, the fabricated steel part will undergo final assembly.
The sand casting process is divided into different stages which includes:
- Pattern Making: The pattern, a replica of the finished product, can be made of various materials and can be used for more than one mold. These patterns also have to be extremely precise – ChinaSavvy employs computer aided designs (CAD) to produce patterns.
- Mold Making: Here, a flask (or mold box) is used to produce the mold, which is typically constructed in two halves.
- Pouring: Once the molten material reaches the desired temperature, it is poured, using the gating system and runners to fill the mold.
- Cooling and Shakeout: After cooling and solidification has taken place, vibratory tables are used to shake the refractory material away from the casting.
- Reclamation: During this stage in the process, the sand used can be reclaimed using various techniques including vibration, thermal reclamation and wet washing.
- Cleaning, Fettling and Finishing: Abrasive cut-off wheels are used to remove the gating system and the parting line is usually grinded or chipped. Here, flash, oxides and refractory materials that remain are removed and the casting can further be polished or grinded.
Permanent Mold Gravity Casting
The permanent mold casting process can be divided into 6 steps:
- Mold Preparation: Mold used in this casting process is preheated, allowing for a better metal flow and a reduction in defects.
- Mold Assembly: This step entails the application of a ceramic coating the mold cavities, which will allow for an easier part removal. Mold used in this process also consist of two halves and, if any cores are present, they are inserted at this stage.
- Pouring: Molten metal is poured, at a slow rate, flowing through the runner system and filling the mold cavity.
- Cooling: The molten metal is now allowed to cool and solidify.
- Opening the Mold: Here, the two halves are opened and cast removed.
- Trimming: The runners and sprues also solidifies in the process and has to be cut away from the casting.
Lost Foam Casting
Generally more expensive than other casting processes, lost foam casting does offer a set of advantages ranging from tighter tolerances to a reduction in the weight of the parts casted.
The lost foam casting process can be summarized in the following steps:
- First, using the foam molding press in most cases, the foam pattern is produced.
- Next, the gating systems and pattern is glued together in order to produce the cluster. Note that the pattern can either be a single molded piece, or made up of various parts.
- The cluster is coated with a permeable refractory coating, muck like the one seen in lost wax casting, and left to dry under controlled conditions.
- Once this coat has dried, a hard shell and supportive mass has formed around the pattern.
- The cluster, now coated and dried, is invested in a foundry flask with loose, unbound sand. It is then vibrated in order to achieve a tight compaction, the result being the pattern shape left behind in the sand.
- The molten material is now poured, making use of the gating system to direct it through the cluster. This step also causes the pattern to immediately vaporize.
- Once the mold has been sufficiently filled, it is left so that the molten material can solidify.
- After solidification has taken place, the sand and shell mold is broken. It is also in this step where the risers and gates are removed.
The final casting can now undergo other finishing processes and heat treatments.
The investment casting process at ChinaSavvy entails:
- The designing and building of the wax injection mold.
- This wax injection mold is then used to create the wax pattern. Note that multi-cavity tools are used in higher volume productions in order to accelerate the production of wax.
- Pattern assembly then takes place. Note here that treeing and gating systems are vital as they allow for optimal filling during the pouring process.
- The wax pattern, fully assembled with gating and treeing systems in place, is then dipped into a ceramic slurry and coated with a refractory. The pattern is allowed to dry (using an atmospherically controlled area) and dipped again in order to meet the desired strength and thickness.
- Next, an autoclave reclaims the wax from the ceramic patter shells. These shells are then preheated and cured.
- Thee ceramic molds are then filled with the molten material, left to set and then broken off.
- The finished casting produced is then cleaned. Note that it is also here that the gating and runners are cut off.
Metal Die Casting
ChinaSavvy uses a number of processes for zinc, magnesium and aluminum die castings. These processes include:
- Cold-Chamber Conventional Die Casting
- Hot-Chamber Conventional Die Casting
- Multi-Slide Hot-Chamber Die Casting
Cold-Chamber Conventional Die Casting
In this process, the die is closed and molten material is ladled into the shot sleeve. The molten material is pushed into the cavity of the mold using a plunger. This plunger is held under pressure until the solidification process is complete.
After solidification, the die is opened and the hydraulic plunger advances in order to ensure that the casting stays in the ejector die. F any cores are present, they will react in this step of the process. Finally, the ejector pins will eject the casting and the hydraulic plunger will return to its original position.
Hot-Chamber Conventional Die Casting
Here, the die is closed and the piston raised (which in turn allows for the molten metal to fill the cylinder). Next, the plunger is moved downwards. This allows for the port, which is pushing the molten material into the cavity, to seal.
The plunger is held in place until the molten material solidifies. Once solidification has taken place, the die is opened – it is also in this step where cores, if present, will react. The casting will stay on one half of the die. The plunger will return to its original position and the casting will be ejected.
Multi-Slide Hot-Chamber Die Casting
This process uses four, perpendicular slides within the tool itself, allowing for accurate and complex castings. Learn more about multi-slide hot-chamber die casting.
Casting zinc, aluminum, bronze, iron and steel, Shell-Mold Casting, also known as Shell Molding, is an expandable mold casting process that involves the mold being formed using a resin covered sand.
The shell casting process can be simplified into the following steps:
- A fine, silica sand, which is covered in a thin thermosetting phenolic resin and liquid catalyst, is shot, dumped or blown into a hot pattern, which is heated to between 450°F (230°C) and 600°F (315°C). Patterns used in this process is commonly made of cast iron.
- The sand, shot onto the pattern, is allowed to sit for a few minutes, allowing for the sand to partially cure.
- Next, the sand and pattern is inverted – this allows the excess sand to drop free of the pattern - leaving just the shell. The temperature of the pattern and the time allowed for the sand to sit on the pattern, influences the thickness of the shell formed. This can be anywhere between 0.4 inches (10 mm) and 0.8 inches (20 mm).
- The sand will now be allowed to finish the curing process. This is achieved by placing the pattern and shell in an oven. After the sand has cured, the shell is stripped from the pattern.
- Finally, the mold can be formed. This is done by combining two or more shells using either clamping techniques or a thermoset adhesive as a glue.
When this shell is used in casting processes, it is placed in a flask and surrounded with sand, shot or gravel, which acts to reinforce the shell.
Precision CNC Machining
Computer Numerical Control (CNC) Machining entails the use of computer controlled machine tools to remove unwanted material from the workpiece. Used in both plastic and metal manufacturing, precision machines are capable of producing larger and deeper cuts.
Other advantages associated with CNC Machining includes:
- Two- and three-dimensional contouring abilities (because CNC machines are capable of simultaneous movement).
- Productivity is increased as a high pressure coolant is used in order to cool and clean the cutting zone.
- Because the process is consistently repeated, the mass production of identical parts is achievable through CNC machining processes.
Note that, in CNC machining, good jigs and fixtures are crucial in order to ensure productivity, efficient costs (in terms of waste materials, productivity and a reduction in manual labor requirements), interchangeability and quality.
Lathes are machine tools that allows for workpieces, mounted horizontally, to be rotated along various axis.
3 Axis Machining involves the workpiece being moved in two directions (the X and Y axes) and the tool being moved up and down (the Z axes). With 5 Axis Machining, there is the added capability of two additional rotary axes, the fifth axis being responsible for the tilt of the tool.
Axis of movement is implemented by either moving the tool itself, or by moving the table onto which the workpiece is mounted.
ChinaSavvy employs multi-axis machines to create parts that have extremely complex geometries, with a CNC lathe being capable of creating a fillet by moving the cutting tool around the corner of the part.
In the aluminum extrusion process, the desired shape of the die is designed and created. The aluminum billet is then heated and transferred to the loader, where a lubricant is added to prevent the billet from sticking to the parts of the extrusion machine.
Pressure is then applied to the dummy block, resulting in the billet being pushed into the container, forcing it into the die. The extruded part passes onto the run-out table in the form of one, long piece in the same shape of the die opening.
It is then pulled to the cooling table where fans are used to cool the newly extruded aluminum. The extrusion then hardens and moves to the saw table where it is cut to length. Age ovens are then used to heat treat the extrusion, hardening it and speeding up the ageing process. Take a more detailed look at the aluminum extrusion process at ChinaSavvy.
With a full service manufacturing department delivering services ranging from sand and gravity die casting, to injection molding and metal sintering processes, ChinaSavvy is at the forefront of high quality manufactured parts and cost efficiency.
Metal Injection Molding
The metal injection molding (MIM) process consist of the following steps:
- Feedstock Preparation: Typically between 60% metal and 40% polymer, this feedstock is produced using a powdered mixture of metal and polymer. Here, the powdered metal is mixed with a hot thermoplastic binder and cooled. This cooled mixture is then granulated into a fine powder.
- Injection: The feedstock is melted and then injected into the mold cavity, where it is left to cool and shape.
- Debinding: Pre-sintering or thermal debinding involves the green molded part to be heated in a low temperature oven, allowing for polymer binding removal through evaporation.
- Sintering: The final step, it involves the sintering of the brown part in a high temperature furnace. This process allows for a reduction in empty spaces, resulting in a high density part
The metal sintering process can be divided into the following three steps:
- Blending: The sintering process starts with the blending of powdered metals, based on the properties required. Mixes here also contain a solid lubricant. Blending enables the creation of a uniform mixture, required material properties and ensures minimum friction during compaction.
- Compaction: The powder is delivered to the cavity of the die, using a filling shoe, and then compacted with force.
- Sintering: A heat treatment process, the sintering step allows for the powder grains of the green part to grow together through a diffusion process. This allows the powder to bond.
Further Suggested Reading:
- A Guide to Materials Used at ChinaSavvy
- A Guide to Production Costs
- A Guide to Tooling Costs
- A Guide to Surface Finishes