Stamping stencil making method

In the special printing industry, bronzing is a very commonly used method of surface finishing, which allows the product to achieve dazzling visual effects. The bronzing is inseparable from the bronzing on the stencil. How to make bronzing on the basis of the shape of the bronzing surface of the workpiece is crucial for the quality of bronzing. The following describes in detail the production methods of different workpiece stamping stencils.

1. Arc stamping stencil on the workpiece

The bronzing of a standard cylindrical surface, the key to making a gilded upper stencil is to determine the arc radius of the stencil on the bronzing.

For example, a cylindrical workpiece with a radius of 20 mm is to be stamped on its outer surface with a flat stamping hot stamping machine. The structure of bronzing on the stencil is shown in Figure 1.

The bronzing version uses an aluminum base plate and its thickness is:

Δ1=2mm

The thickness of the silicone rubber layer is:

Δ2=3mm

The relationship between the radius R of the aluminum mold and the work radius R workpiece and δ1, δ2 is:

R = R workpiece + δ1 + δ2 = 25 (mm)

The processing step of the bronzing on the stencil is as follows: firstly, an aluminum mold having a shape as shown in FIG. 1 is machined on the milling machine, and then the silicone rubber plate is pressed on the concave surface with an epoxy resin adhesive or a high-temperature adhesive tape.

The silicone rubber layer is elastic, and it will wrinkle after being pressed into the concave surface. It can be polished with fine sandpaper.

In fact, when a bronzing plate with a length of 40 mm and a total thickness of 5 mm is pressed into the concave surface of the upper stencil, the inner edge is compressed, which is a direct cause of wrinkles.

2. Stamping on irregular surface workpieces

The reason why the bronzing of the curved surface is not easy is that the stencil on the bronzing is difficult to be machined to match the workpiece completely, resulting in uneven pressure. Even if it is processed with a numerically controlled lathe, the bronzing silicone rubber plate will appear unnatural after being applied. Where it fits. However, if the bronzing silicone rubber is directly cast onto the surface of the upper stencil to make a bronzing upper stencil, the imperfections in the processing of the aluminum dies can be greatly improved, thereby improving the bronzing quality.

For example, a surface of a spherical ABS plastic workpiece with a radius of 15 mm is bronzing. The hot stamping stencil can be produced by the following method:

(1) Select an aluminum block with a size of 30mm x 30mm x 50mm to machine a concave surface with a shape similar to that of the bronzing plane on the milling machine, as shown in Figure 2.

(2) Evenly coat a layer of QB6203 high temperature silicone rubber adhesive on the concave surface.

(3) Preparation of hot stamping glue. Put TP623 (bronze silicone rubber), T40 (curing agent), 3205 (softening agent), white carbon black (reinforcing agent) into a 1000 ml PP plastic cup, stir well, place it in a vacuum pump and vacuum it. After 10 minutes, remove the glue.

(4)Pour the gold foil adhesive into the groove of the aluminum mold, apply a layer of wax release agent on the workpiece hot stamping surface, put it into the glue solution, keep it for several minutes, and control the workpiece and the aluminum mold at the same time. The silicone rubber layer is between 5 and 7mm.

(5) Curing. The upper mold plate is placed in an oven for curing, the temperature is controlled at about 1200 DEG C., and the time is 30 minutes. After removal, it can be used for hot stamping. The bronzing stencil made by this method has a very good surface bronzing effect.

3. Font bronzing on the template

Gold foil stamping is also widely used in graphic and letterpress fonts, such as copper-zinc plates, photopolymer plates, and rubber plates, which are used for bronzing. Exposure and corrosion are used to separate the graphic and non-graphic areas.

In addition, you can also prepare a simple hot stamping plate to create a hot stamping plate. Here is an example for your reference:

(1) Prepare glue according to the following formula:

Silicone Rubber 75%

Unsaturated polyester resin 13%

Benzophenone (to avoid light exposure) 2%

Softener 8%

Curing agent 2%

(2) Prepare the substrate

Prepare an aluminum plate with a thickness of 3 mm. After grinding and cleaning, apply a uniform layer of QB6203 high-temperature silicone rubber adhesive on the surface.

(3) Making photosensitive media

The prepared mortar was poured on the surface of the aluminum plate to control its thickness to 5 to 7 mm and cured for 4 hours.

(4) Exposure

The negative film was attached to the surface of the silicone rubber, and then placed in an ultraviolet printer for exposure.

(5) Development and corrosion

After exposure, developing and etching with toluene or xylene, a bronzing printing plate is obtained. This stamping relief can withstand temperatures above 200°C.

(author/Bai Songfang)