What is stainless steel wire drawing and polishing?

The difference between brushed stainless steel and polished!

In terms of technology, the wire drawing process is to make a regular and uniform surface pattern on the surface of the workpiece. The general drawing patterns are: thin stripes and circles. The polishing process is to make the surface of the workpiece completely flat, without any flaws, and it looks smooth and translucent, with a mirror surface.

In terms of motion, what the wire drawing process does on the equipment is the repeated movement, while the polishing process is the movement track done on the flat polishing machine. The two are different in principle and different in practice.

In production, professional wire drawing process equipment is used for wire drawing, and there are many kinds of polishing process equipment according to different shapes to adapt to different polishing requirements.

If a workpiece needs to be both drawn and polished, which process should be followed by the previous one?

From this situation, from the effect of wire drawing and polishing on the surface treatment, as well as the process principle, it is not difficult for us to draw: polishing before, wire drawing after. Only after the surface of the workpiece is polished and flattened, the wire drawing can be carried out, because only in this way the effect of wire drawing will be good, and the wire drawing lines will be uniform. Polishing is for brushing and setting the foundation. In a word, if the wire drawing is polished first, not only the wire drawing effect is poor, but the good wire drawing lines will be completely ground by the grinding disc during polishing, so there is no so-called wire drawing effect.

Precautions for sheet metal stainless steel wire drawing

1. Brushed (frosted): Usually, the surface state is straight lines (also called frosted) after being processed by mechanical friction on the surface of stainless steel, including wire drawing, and lines and ripples.

Processing quality standard: the thickness of the texture is uniform and uniform, the texture on each side of the product is natural and beautiful according to the design and construction requirements, and the bending position of the product is allowed to have a slight chaotic texture that does not affect the appearance.

1. The process of drawing:

(1) The grains formed by different types of sandpaper are different. The larger the type of sandpaper, the thinner the grains, the shallower the grains. On the contrary, the sandpaper

The smaller the model is, the thicker the sand will be, the deeper the texture will be. Therefore, the model of the sandpaper must be indicated on the engineering drawing. 

(2) The wire drawing is directional: it must be indicated on the engineering drawing whether it is straight or horizontal wire drawing (represented by double arrows). 

(3) The drawing surface of the drawing workpiece must not have any raised parts, otherwise the raised parts will be flattened.

Note: In general, after drawing wire, electroplating, oxidation, etc. must be done. Such as: iron plating, aluminum oxidation. Due to the defects of the wire drawing machine, when there are relatively large holes on small workpieces and workpieces, the design of wire drawing jig must be considered. , to avoid the poor quality of the workpiece after wire drawing.

1. Wire drawing machine function and precautions

Before drawing, the drawing machine must be adjusted to an appropriate height according to the thickness of the material.

The slower the speed of the conveyor belt, the finer the grinding, and vice versa. If the feed depth is too large, the surface of the workpiece will be burnt, so each feed should not be too much, it should be about 0.05mm.

If the pressure of the pressing cylinder is too small, the workpiece will not be pressed tightly, and the workpiece will be thrown out by the centrifugal force of the roller. If the pressure is too high, the grinding resistance will be increased and the grinding effect will be affected. The effective drawing width of the wire drawing machine does not exceed 600mm. If the direction is less than 600mm, you must pay attention to the drawing direction, because the drawing direction is along the material feeding direction.

Precautions for sheet metal stainless steel polishing

Brightness grade of stainless steel after polishing By visual inspection, the brightness of the polished surface of the parts is divided into 5 grades:

Level 1: There is a white oxide film on the surface, no brightness;

Level 2: Slightly bright, the outline cannot be seen clearly;

Level 3: Brightness is better, outline can be seen;

Grade 4: The surface is bright, and the outline can be seen clearly (equivalent to the surface quality of electrochemical polishing);

Level 5: Mirror-like brightness. 

The general process of mechanical polishing is as follows:

(1) Rough throw

After milling, EDM, grinding and other processes, the surface can be polished by a rotating surface polishing machine or an ultrasonic grinding machine with a rotating speed of 35 000-40 000 rpm. The commonly used method is to use the wheel with diameter Φ 3mm and WA # 400 to remove the white EDM layer. Then there is manual whetstone grinding, strip whetstone with kerosene as a lubricant or coolant. The general order of use is #180 ~ #240 ~ #320 ~ #400 ~ #600 ~ #800 ~ #1000 . Many moldmakers choose to start with #400 to save time. 

(2) Semi-fine polishing

Semi-fine polishing mainly uses sandpaper and kerosene. The numbers of sandpaper are: #400 ~ #600 ~ #800 ~ #1000 ~ #1200 ~ #1500. In fact, #1500 sandpaper is only suitable for hardening die steel (above 52HRC), not for pre-hardened steel, because it may cause the surface of the pre-hardened steel to burn. 

(3) Fine polishing

Fine polishing mainly uses diamond abrasive paste. If you use a polishing cloth wheel to mix diamond grinding powder or grinding paste for grinding, the usual grinding sequence is 9 μm (#1800) ~ 6 μm (#3000) ~ 3 μm (#8000). A 9 μm diamond paste and polishing cloth wheel can be used to remove hair marks from #1200 and #1500 sandpapers. Then polish with sticky felt and diamond abrasive paste, in the order of 1 μm (#14000) ~ 1/2 μm (#60000) ~ 1/4 μm (#100000). Polishing processes requiring precision above 1 μm (including 1 μm) can be performed in a clean polishing chamber in the mold shop. For more precise polishing, an absolutely clean space is required. Dust, fumes, dandruff and drool all have the potential to undo the high-precision polished finish you get after hours of work.

Mechanical polishing: Use an abrasive belt polishing machine to polish the roller frame. First, use a 120# abrasive belt. When the surface color reaches the first, change the 240# abrasive belt. When the surface color reaches the first, change the 800# abrasive belt. As soon as the surface color arrives, change the 1200# abrasive belt, and then throw it to the effect of decorative stainless steel plate.

Precautions for stainless steel polishing

Grinding with sandpaper or abrasive belt in the grinding operation is basically a polishing cutting operation, leaving very fine lines on the surface of the steel plate. There have been troubles with alumina as an abrasive, partly because of pressure issues. Any abrasive parts of the equipment, such as abrasive belts and grinding wheels, must not be used on other non-stainless steel materials before use. Because this will contaminate the stainless steel surface. To ensure a consistent surface finish, a new wheel or belt should be tried on scrap of the same composition so that the same sample can be compared. 

Stainless steel wire drawing and polishing inspection standard

1. Stainless steel mirror light products

After the polishing is completed according to the polishing and polishing process, the qualified surface quality of the stainless steel mirror-finished products shall be carried out according to Table 2; the downgrade acceptance shall be carried out according to Table 3.

Note:

1) The surface area where the defect points are located refers to the surface areas of the A, B and C surfaces.

2) The table defines the number of defect points on surface A and surface B, and the sum of the number of defect points on surface A and surface B is the total number of defect points on the surface of the product.

3) When the surface defect points are greater than 2, the distance between the two defect points is greater than 10-20mm.

1. stainless steel wire drawing products

After the polishing is completed according to the polishing and polishing process, the surface quality of stainless steel wire drawing products shall be implemented in accordance with Table 4, and the degraded acceptance standards shall be implemented in accordance with Table 5.

Note:

1) The surface area where the defect points are located refers to the surface areas of the A, B and C surfaces.

2) The table defines the number of defect points on the A and B sides, and the sum of the number of defect points on the A and B sides is the total number of defect points on the product surface.

3) When the surface defect points are greater than 2, the distance between the two defect points is greater than 10-20mm.

Testing method

1. Visual test, visual acuity is greater than 1.2, under 220V 50HZ 18/40W fluorescent lamp and 220V 50HZ 40W fluorescent lamp, the visual distance is 45±5cm.

2. Hold the polishing piece with both hands with work gloves.

2.1 The product is placed horizontally, and the surface is visually inspected. After the inspection, rotate it to the angle of the adjacent surface with both hands as the axis, and inspect each surface step by step.

2.2 After the visual inspection of the upper direction is completed, rotate 90 degrees to change to the north-south direction, first rotate up and down a certain angle for visual inspection, and gradually inspect each side.

3. Mirror light, matt light and wire drawing inspection refer to standard graphics.