HALAO Kitchenware Co., Ltd.
Add.: 63 Xinxing Road, Suixiang Industrial Zone, Ronggui Town, Shunde District, Foshan City, Guangdong Province, China
Tel.: +86-757-28881782
Fax: +86-757-28881782
Contact Person (Supervisor): Cherry Feng

Stretch Formed Sink Production Process

At HALAO, we are keen to innovate and strive to take care of each and every production process down to the last detail. Durable, versatile and eye-catching, our ergonomic kitchen sink is what raises us a notch above the rest in the steel sink industry.

HALAO passed the TUV certification and received ISO9001 certificate in 2000. There has since been a new management system in place, which is commonly known as the 9S---Sort, Straighten, Sweep, Sanitary, Sustain, Save, Safety, Service, and Speed. This system requires that every worker and manager should join in management, build self worth, and develop self management in order to overcome any potential drawbacks in the sink production.

More than 20 processes are used to produce our kitchen sinks. From the initial raw material quality check by using a spectrograph, to the stretching process, each stage of production process is closely tracked by our technicians. Every subsequent process is also closely linked to the former one. In addition, there are quality inspectors who carry out routine checks on every process. Prior to receiving the next operation, all the workpiece is rigorously tested. When quality problems do occur, inspectors should notify our dedicated team of 20 technicians and ask for solutions.

Production Process

1. Raw Material (stainless steel)

Presently, we are using 0.6mm-1.2mm thick SUS304 or SUS201 stainless steel in the manufacture of our stretch formed kitchen sinks.

SUS304 and SUS201 steel blanks typically come in coils.

SUS 304 stainless steel has a sleek surface. It is easy to stretch, and resists rust. SUS201 stainless steel is generally priced lower than SUS304. It is suitable for middle market, with a rust-resistant ability second only to SUS304.

Each steel coil has a label stuck on it. The first batch of steel material entering our factory will be tested by an ultrasound thickness gauge to ensure that the thickness tolerance falls within the range of ±0.02mm.

Special liquid chemicals are used to determine the grade of the steel. If the green liquid turns yellow, then the material being detected should be SUS304 steel. If it turns red, the material being detected should be SUS201.

The label on the steel coil lists the name of its manufacturer, the grade of steel, thickness, weight, and the date of manufacture.

The diameter of steel coil should be around 1 meter. To ensure a uniform thickness on both sides of the steel as well as in its middle, a micrometer should be used to measure its side thickness while the ultrasound thickness gauge measures the center thickness. In addition to measuring thickness and the grad of steel, we need to test its tensile strength too. Tensile strength is a crucial factor to consider if you don’t want your steel to crack, deform or crumble during stretch forming process.

a. Steel Grade Measurement

The liquid chemical might be useful for determining the grade of stainless steel, but it can also cause irreparable damage on stainless steel surface.

b. Tensile Testing

A standard 0.28mm-thick stainless steel should be able to withstand a pressure of 370MPA. If it can not, it will fail the test.

c. Steel Processing
film application and cutting

Film application is a process whereby a thin layer of film is applied to the surface of steel. The film layer would protect the steel from being scratched, or damaged by heat in the stretch forming process.

After you stick a layer of film onto the steel surface, the sheet steel would be cut to the required size.

2. Stretch Forming Process

a. Applying protection oil

Stretch forming is thought of as the core process in the sink construction. First, protecting oil must be applied to the part that needs to be stretched. The purpose of oil application is to make sure the steel is well lubricated so that it won’t break due to high tensile force during stretching. Steel thickness after stretching should be between 0.8-1.0mm.

b. Stretch Forming

A hydraulic press is typically used to perform this process. The steel is clamped along its edges over a die. A punch is brought down to press part of the steel into the die cavity. After this process, the initial shape of the sink can be formed. However, the sink can not have its final shape if you only punch it once. More times of punching are needed to stretch the steel and make it thinner until the required thickness, depth and shape is formed.

c. Inspection and Un-sticking the Film

After the stretching process is done, workers should visually check up on the sinks. Quality inspectors also need to select a small number of sinks for close inspection to ensure they get no cracks, wrinkles, or other surface defects on them. After inspect, un-stick the film from the sink and send it to the next process.

3. First-Time Cleaning

The greasy sink needs to be washed to remove nasty stains on its surface. This washing process is to get the sink ready for the heat treatment process. If washing is not done well, the remaining oil on the sink surface would burn the sink surface when it is heated in a furnace.

4. Heat Treatment

The purpose of heat treatment is to reinforce the molecular structure of the stainless steel and prepare the sinks for the second-time stretching process. However, heat treatment might also cause undesired damage to the stainless steel surface.

5. Second Time Stretching - Trimming and Flanging

The second-time stretching process is the same as the initial stretching. It is just to make sure the sinks reach its final desired depth. The sink needs to have rims. That is why the flanging process is necessary.

6. Second Time Cleaning

This cleaning process helps get rid of the surface stain formed during the second stretching process, and get the sinks ready for the following production process.

7. Surface Treatment---Sandblasting

Sandblasting is a process that shoots fine sands at a high speed against the surface of the sink. It helps form the micro-grooves in the sink surface. Of course, you can not see these grooves with your eyes. Sandblasting process creates fine lines on the sink surface, making it extremely smooth. In addition, this treatment also improves the hardness and the ability to withstand scratch of the stainless steel sinks.

8. Surface Treatment: Polishing

Use flexible polishing tools, abrasive particles or other polishing media on the stainless steel sink surface to create a mirror finish

9. Hole Punching : Holes for Faucet, Soap Dispenser, and Sink Drain

Holes are punched into the sink when a top die comes down on the bottom die. The overflow hole should be punched separately from other holes due to its special position. Sometimes, overflow holes get punched into the sink even before the stretching or polishing process.

10. Overflow Hole Punching Process

This process relies on the same working principle as the faucet hole punching process.

11. Sticking Pad onto the Underside of the Sink

This lightweight, black pad does not contain Formaldehyde. It is used to dampen the noise during use of sink.

12. Spraying Painting

The spray painting process is carried out in two steps. The first step is to apply a layer of coating to the sink while the second step is to let it dry. Coating thickness is generally 0.1-0.2 mm. The paint used in this process is typically colored, eco-friendly water-soluble paint, which has no unpleasant odor and is free of formaldehyde. After the drying process, the paint will form a protection layer on the place where it has been sprayed. This process can be customized to your specific requirements.

13. Final Sink Cleaning

Prior to packaging, the sinks nee to be polished for two times. At each time, talcum powder is used to rub on the sink surface in order to restore its shine. Some fine talcum powder will be left on the sink surface as it can be cleaned off with water before use.

14. Packing

The packing process includes sink and accessories packaging, as well as the overall packaging.