Before we understand how stainless steel sinks are made, let's take a brief look at what stainless steel sinks are.
Stainless steel sinks first appeared in Europe and the United States, and China's first stainless steel sinks appeared in Taiwan.
In the early 1990s, Taiwanese merchants brought stainless steel sinks when they invested in mainland China.
In the beginning, there were brands such as “Mantangchun” and later “Molin”.
Stainless steel sinks are manufactured using stainless steel as a raw material.
The main body is processed by integral drawing or welding and then surface treatment.
Stainless steel sinks are used in modern kitchens as one of the essential parts for washing vegetables or dishes.
What equipment is needed to make stainless steel sinks?
Let me show you.
The production of stainless steel sinks requires:
- 2 sets of hydraulic drawing presses (400T and 500T)
- 1 set of hydraulic press (200T)
- 1 set of electric press
- 4 sets of molds
Among them, the wire drawing machine requires a 400T and a 500T wire drawing press.
400T drawing press is used for drawing and 500T press is used for forming.
A 200T hydraulic press will be required for edge trimming.
The electric press is mainly used for punching.
The 4 sets of molds are a drawing die, a forming die, a cutting die and a punching die respectively.
Now that we have a brief understanding of stainless steel sinks and their manufacturing equipment, how are they made?
Let's dive into the stainless steel sink production process.
#1. Purchase of raw material (0.8-1.5mm sheet metal)
The sink factory purchases steel sheets of different widths and thicknesses according to the different sink production needs.
The sheet thickness commonly used in the manufacture of stainless steel sinks is between 0.8 mm and 1.5 mm.
The sheet metal is delivered to the sink factory in coils by weight.
Normally, the maximum width of uncut steel plate is 1220mm and the length is almost unlimited.
#two. Lamination
The ductility of the steel plate is limited.
To prevent cracking and damage to the steel sheet during the drawing process, it is necessary to apply a laminating film to the steel sheet at the initial stage.
The coating only covers one side of the steel sheet, and the side with the coating film will face the mold in the subsequent drawing step.
Film coating can be applied before or after cutting.
#3. Sheet metal cutting
According to the different design lengths of water sinks, the long steel plate needs to be cut into segments by a plate cutting machine to meet the blanking size requirements.
In the image shown below, you can see that workers complete film coating by controlling the roller switch to pass the protective film and steel plate through the laminating zone at the same time.
When the coated steel sheet passes through the guillotine, the worker presses the guillotine switch as needed to cut the steel sheet to the required length.
#4. Corner notch
The sheet, after cutting, now has a regular rectangular shape.
To roughly adapt to the shape of the sink, it is also necessary to feed the sheet into the cutting machine to notch the corners.
Sheet metal, after notching at the corners, is usually polygonal and sometimes has arched edges.
#5. O iling
Apply drawing oil evenly to both sides of the sheet metal after coating and cutting.
Drawing oil will help the sheet be tensioned evenly, reduce the chance of tensile cracking, and extend the life of the mold and pressing machine.
#6. Drawing for the first time
Place the metal sheet on the drawing press work table.
There are openings in the top and bottom laminated plates of the countertop.
The product mold is located in the opening of the bottom plate of the bench (shaded in red in the following figure).
After pressing the motor switch, the top plate of the hydraulic press working table is lowered and the entire working table sinks.
During the sinking process, the horizontal position of the mold remains unchanged, so the steel plate is forced upward to complete the shape design.
The first design depth should be 80% or more of the total design depth.
#7. Cleaning
Dismantle the initially formed basin and clean the contaminated bench with drawing oil.
The water sink after the first drawing process will be sent to the cleaning station to remove the film, and the residual drawing oil will be washed to prepare for the annealing process.
#8. girdling
Why is annealing necessary?
In the drawing process, if the designed depth of the sink is less than 160mm, the desired depth can be achieved in a drawing.
When the depth of the water sink reaches 180mm to 250mm, the probability of the stainless steel sheet breaking in a design increases greatly. To avoid cracks and guarantee the quality of the sink, an annealing process is necessary.
To meet the demand for deep drawing, annealing treatment and secondary drawing are currently required.
Annealing treatment restores the activity of the stainless steel sheet which is highly deformed during the first drawing process.
The annealing line itself is a 20 meter long high temperature line with a furnace temperature of approximately 1150°C.
The inlets and outlets are located on both sides, and the water sinks are transported by a cable-type crane lock or a conveyor belt.
The line can process 30 pieces of water sinks simultaneously.
The annealing process also includes demagnetization, which eliminates the magnetic properties of stainless steel caused by drawing.
Many sink factories do not have their own annealing line and outsource the process to a third-party annealing shop.
Sometimes the sink plant uses an annealing furnace to meet its own replacement needs.
#9. Drawing for the second time
The annealed water sink is subjected to a second drawing process using a mold and hydraulic press.
The second design must be fully stretched to the designed depth.
#10. To trim
After the second drawing process of the water sink, there is no more shrinkage at the edge of the steel plate.
At this stage, it is necessary to remove excess shavings from the finished product.
When cutting the edge, it is essential to reserve the installation position of the reinforcing rib above the countertop.
#11. Drilling
Drainage and overflow holes are punched successively in a special mold by the punching machine.
Depending on the actual condition of the sheet metal and punching equipment, it may be necessary to remove any burrs on the cutting plane.
#12. Welding
If it is a double tank roller welding basin or bottom welding basin, it needs to be welded to the upper plate of the irrigation plate after drilling.
Roller welding is usually done by CNC welding, but it can also be manually welded by workers.
If it is a butt welding basin, it is necessary to carry out butt welding on both sides of the basin.
A distinctive feature of the butt welding basin is the weld line between the two sides of the basin.
#13. Spot welding
The ribs/hooks are welded with a laser welder.
Depending on device settings, each spot weld produces approximately three solder joints.
Strip reinforcement ribs require spot welding multiple times in different locations.
Glue can also be used to join the ribs/hooks together depending on customer requirements.
#14. Surface treatment
Coni clear coating is the exclusive surface treatment technique for the C Series sink.
Additionally, current common surface treatment processes include the following FOUR types:
- sanding (drawing)
- sand blasting (electrolysis)
- polishing (mirror)
- embossing
Here, the sanding (drawing) process is specifically introduced.
Grinding is divided into three or four stages depending on the difference between the basin and the equipment.
The first part that needs to be polished is the bottom of the sink.
Next, the sink wall is rectified.
Depending on the degree of automation of the sink plant, sometimes there is the process to follow to alleviate the need for workers' grinding skills.
Because the two adjacent faces are polished in different directions, chaotic lines are likely to occur at the edges where the textures meet.
A grinding wheel will be used to remove any messy lines between the two vertical faces.
At the end of the grinding process, the top plate is ground to remove spot welding, weld lines and surface flaws visible in the bowl.
#15. Hole opening
Excavation of the tap hole in the position as required by the order.
This process has a high degree of freedom and can be skipped directly according to the needs of the order, or can occur before any process after welding.
#16. Marking
Stainless steel sink marking mainly includes the following two methods: laser marking and embossed marking.
engraving mark
Push the sink fully into the bayonet position to ensure a consistent printing position.
Laser Mark
Laser engraving is used for marking.
In addition to fully automated laser marking, there is also low-cost manual positioning laser marking (as shown in the following image).
Place the semi-permeable membrane with the brand logo at the designated marking position and use a handheld laser emitter to illuminate it at zero distance.
The laser passes through the light transmitting portion of the semipermeable membrane to achieve cauterization on the surface of the stainless steel.
#17. Restoration
Any minor damage that occurs at each stage of production but still has commercial value is manually sent to the repair site before the spraying process.
#18. Spray coating
A bottom spray treatment is performed.
There are three purposes for spraying:
- To make the thin and light sink gain weight;
- To cover the burn traces caused by annealing;
- To avoid condensation in the kitchen environment.
However, most sink manufacturers apply paint only when spraying, and it does not have an anti-condensation function.
In addition to spraying, pickling can also remove burn stains caused by annealing.
#19. Cleaning and packaging
Cleaning work includes removing residual oil, dirt and spills from the front of the sink, as well as any debris from the grinding wheel and stainless steel, fingerprints and other dust.
The sink can be packed in brackets, large boxes or even retail packaging according to the needs of different customers.
#20. Half
Finally, the product is placed in the warehouse and awaits delivery to the location indicated by the buyer.
