Custom stainless steel lost wax casting downpipe refers to a precision-cast downpipe (often used in automotive, motorcycle, or industrial applications) made from stainless steel using the lost wax casting (also called investment casting) process. This method allows for highly detailed, complex, and durable components with excellent surface finish and dimensional accuracy.
This stainless steel downpipe used in automotive exhaust system, to connect two different components and let the air go through smooth.
Material and Process:
304 stainless steel is perfectly suitable for the operating conditions, so the material selection is confirmed without any
doubt. 3D drawing designed by our customers, but it's important to make a plastic prototype before proceeding with working the mold, it will significantly reduce risks for both sides.
The plastic prototype is made of ABS, milled by a 3-axis CNC machine in two separate layers, then assembled with glue. We sent it to the client for drawing verification, luckily, the assembled prototype got approved immediately, which mean the drawing is correct. The pictures below show the 3D drawing and prototype for reference.
3D drawing of downpipe
downpipe prototype made by ABS
Now we're preparing to manufacture the investment casting molds. Medium-temperature wax by injection molding is used to make wax model.
As the complex structure, our engineers recommend using two molds for the stainless steel downpipe tooling. Because it can not finish well with one mold, so we'll make two wax components, final welded together into one complete wax.
This approach really is a smart design, it splits the casting into more simple parts, which cuts tooling costs and makes the wax assembly more feasible. Welding the two wax pieces also avoids the need for complex mold structures, saving both time and money in production. You can find how the wax model how to make in the following pictures.
downpipe wax casting mold 1
wax model part 1
downpipe wax casting mold 2
wax model part 2
2 wax model part welded together
In this process, medium -temperature wax is used to make wax model. Investment casting commonly uses low-temperature wax (melting point <70℃, suitable for simple castings with low precision), medium-temperature wax (70-100℃, high strength and accuracy), high-temperature wax (>100℃, less used alone), and colored waxes like pink/green (neutral, high fluidity for easy differentiation). Selection depends on casting complexity, accuracy, and process type, balancing strength, thermal stability, and cost to ensure quality.
After this, start the shell making process: dip the wax model into silica sol slurry, coat it with refractory sand, and repeat this process for multiple layers (typically 5-8 layers) to form a shell, with each layer dried thoroughly before the next.
Then remove the wax by heating the shell to 150-200°C, leaving a hollow mold. Next, bake the shell at 1000-1200°C to enhance its strength and remove rest wax.
Meanwhile, melt 304 stainless steel in a furnace to the pouring temperature (around 1550-1650°C). Pour the molten steel into the preheated shell, and let it cool and solidify. Once cooled, break the shell to release the stainless steel downpipe. Then shot blasting, heat treatment, and dimensional inspection to obtain the final product.
For silica sol cast stainless steel products, our dimensional tolerance has reached CT6 (ISO 8062). This means we can consistently achieve high precision, meeting critical requirements for aerospace, medical devices, and high-precision mechanical components.The following pictures is downpipe after shot blasting.
Later Machining the two flanges and drill hole 10mm as well as thread M18&M8.
QC inspection：
Use calipers and 3D scanners to measure outer diameter, wall thickness, and bend angles against drawings, ensuring tolerance within CT6. Visually check for uniform color, bumps, abrasions, or casting defects. Machining surface must to be smooth and inner surface to be smooth without big spot.
Packing：
To prevent damage during transit, each stainless steel downpipe is individually wrapped in bubble wrap for cushioning, ensuring surfaces are fully protected. The wrapped parts then would be packed into wooden case. This packaging method combines shock absorption and structural protection to safeguard the product's surface finish and dimensional integrity.
Ningbo Joyo Metal Metal Parts Co.,Ltd. has the ability of integrate various processes to work complex product. The company excels in end-to-end solutions, from precision casting and machining to surface treatment and assembly, ensuring seamless coordination across technical domains.
Custom stainless steel lost wax casting downpipe refers to a precision-cast downpipe (often used in automotive, motorcycle, or industrial applications) made from stainless steel using the lost wax casting (also called investment casting) process. This method allows for highly detailed, complex, and durable components with excellent surface finish and dimensional accuracy.
This stainless steel downpipe used in automotive exhaust system, to connect two different components and let the air go through smooth.
Material and Process:
304 stainless steel is perfectly suitable for the operating conditions, so the material selection is confirmed without any
doubt. 3D drawing designed by our customers, but it's important to make a plastic prototype before proceeding with working the mold, it will significantly reduce risks for both sides.
The plastic prototype is made of ABS, milled by a 3-axis CNC machine in two separate layers, then assembled with glue. We sent it to the client for drawing verification, luckily, the assembled prototype got approved immediately, which mean the drawing is correct. The pictures below show the 3D drawing and prototype for reference.
3D drawing of downpipe
downpipe prototype made by ABS
Now we're preparing to manufacture the investment casting molds. Medium-temperature wax by injection molding is used to make wax model.
As the complex structure, our engineers recommend using two molds for the stainless steel downpipe tooling. Because it can not finish well with one mold, so we'll make two wax components, final welded together into one complete wax.
This approach really is a smart design, it splits the casting into more simple parts, which cuts tooling costs and makes the wax assembly more feasible. Welding the two wax pieces also avoids the need for complex mold structures, saving both time and money in production. You can find how the wax model how to make in the following pictures.
downpipe wax casting mold 1
wax model part 1
downpipe wax casting mold 2
wax model part 2
2 wax model part welded together
In this process, medium -temperature wax is used to make wax model. Investment casting commonly uses low-temperature wax (melting point <70℃, suitable for simple castings with low precision), medium-temperature wax (70-100℃, high strength and accuracy), high-temperature wax (>100℃, less used alone), and colored waxes like pink/green (neutral, high fluidity for easy differentiation). Selection depends on casting complexity, accuracy, and process type, balancing strength, thermal stability, and cost to ensure quality.
After this, start the shell making process: dip the wax model into silica sol slurry, coat it with refractory sand, and repeat this process for multiple layers (typically 5-8 layers) to form a shell, with each layer dried thoroughly before the next.
Then remove the wax by heating the shell to 150-200°C, leaving a hollow mold. Next, bake the shell at 1000-1200°C to enhance its strength and remove rest wax.
Meanwhile, melt 304 stainless steel in a furnace to the pouring temperature (around 1550-1650°C). Pour the molten steel into the preheated shell, and let it cool and solidify. Once cooled, break the shell to release the stainless steel downpipe. Then shot blasting, heat treatment, and dimensional inspection to obtain the final product.
For silica sol cast stainless steel products, our dimensional tolerance has reached CT6 (ISO 8062). This means we can consistently achieve high precision, meeting critical requirements for aerospace, medical devices, and high-precision mechanical components.The following pictures is downpipe after shot blasting.
Later Machining the two flanges and drill hole 10mm as well as thread M18&M8.
QC inspection：
Use calipers and 3D scanners to measure outer diameter, wall thickness, and bend angles against drawings, ensuring tolerance within CT6. Visually check for uniform color, bumps, abrasions, or casting defects. Machining surface must to be smooth and inner surface to be smooth without big spot.
Packing：
To prevent damage during transit, each stainless steel downpipe is individually wrapped in bubble wrap for cushioning, ensuring surfaces are fully protected. The wrapped parts then would be packed into wooden case. This packaging method combines shock absorption and structural protection to safeguard the product's surface finish and dimensional integrity.
Ningbo Joyo Metal Metal Parts Co.,Ltd. has the ability of integrate various processes to work complex product. The company excels in end-to-end solutions, from precision casting and machining to surface treatment and assembly, ensuring seamless coordination across technical domains.
