A brief introduction to pencils
Pencil is a kind of pen used for writing and drawing. It has a history of more than 400 years. Among them, pencils for drawing can be divided into three stages of development: graphite, wooden penholder and capped pencil. In addition, its color has red-white, black-white, yellow-black stripes.
The hardness mark of pencil lead is usually “H” for hard pencil, “B” for soft pencil, “HB” for soft and moderate pencil, and “F” for pencil with hardness between HB and H.
Arrangement (from soft to hard) 9B, 8B, 7B, 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H, 7H, 8H, 9H, 10H and other hardness grades.
The bigger the number in front of H, the harder the lead core, the lighter the color. The bigger the number in front of B, the softer the lead core, the darker the color. The classification of pencil rods is based on the weight of graphite in the pen core. Among them, H pencil has relatively high hardness, which is suitable for objects with relatively hard or clear interface, such as woodworking lines, field drawing, etc. HB pencil has moderate hardness, which is suitable for writing or outlining under general conditions; B pencil has relatively soft core, which is suitable for drawing, and can also be used for filling and painting some machine-recognizable cards. For example, we often use 2B pencils to fill out answer cards. In addition, there is also a common color pencil rod, that is, people often say that the color pencil, mainly used for drawing.
It is divided into two parts: pencil cap and pencil rod. The main decorative material of pencil cap is polyester material. The manufacturing process can be divided into moulding, offset printing, assembly and other processes to complete it. Pencil rod exterior decoration materials mainly include nitrocellulose pencil paint, printing ink, electrochemical aluminum foil, rubber head and aluminum hoop, etc. The manufacturing process can be divided into pencil board, lead core, pencil rod, finished product decoration and other process.
Pencil board processing will open and cut logs, square sawing into blocks, after hydrothermal treatment, through the cutting machine into pencil board. The plate is 184 mm long, 73 mm wide and 4.8-5.2 mm thick. The pencil board is softened and easy to roll by heating (60 ~ 120 C) drying and denaturation at high temperature (130 ~ 200 C).
The lead core is made of graphite and clay in a certain proportion. After mixing by kneading machine and three rollers machine, the lead core with a certain size (such as HB~3H lead core diameter 1.80~2.10mm) is extruded by core pressing machine. The lead core is dried by heating (50~150 C) and roasted at high temperature (800~1100 C), so that it has a certain mechanical strength and hardness. Finally, the lead core is made by oil immersion treatment. The processing of color lead core is similar to that of graphite lead core, but it does not need sintering. There are two kinds of processing methods: one is mixing clay, talc powder, adhesives, colors, grease and wax evenly, then forming and drying, which is called mixing method; the other is extruding ceramic clay, talc powder, colors and adhesives evenly into lead core or putting the dried lead core in the oil core container to absorb grease adequately at a certain temperature. Oil immersion method.
The pencil rod is machined by slotting machine. The thickness of the pencil board is 4.1-4.2 mm, and the slot board with the core slot is suitable for the diameter of the lead core. Then the lead core and the pencil board are glued together by a binder. After being heated in clamping state (50-120 C) and dried for 1-8 hours, the white pencil with the length of 178-180 mm is machined by the planer.
Appearance decoration process uses white pencil for painting and printing decoration, as well as cutting light, printing trademark, rubber head, pen cap and other processing, making it a finished pencil with certain specifications, appearance color and pattern patterns.