Domestic use of plastic hot forming technology for the production of plastic cup about began in the late eighty's in the last century, after more than ten years of development, already in the prosperous stage. Whether from the equipment (sheet production line, heat molding machine - cup making machine, mold, printing machine) or technology has matured.
From raw materials to products are generally divided into three stages, usually used in the production of plastic cup is the main materials: polystyrene (PS), polypropylene (PP), polyvinyl chloride (PVC), polyester (PET), ABS, BOPS etc.. According to different customer packaging requirements, can be divided into single layer structure of HIPS, a variety of colors of CPS (PS, PP, transparent) PVC, PET, ABS, BOPS as well as by one or more material is composed of multilayer composite structure. For example, with high barrier properties of plastic cup and some will need at least two kinds of structure of five layer coextrusion composite material.
The three stage is the:
1 the extruded plastic sheet
This step is the plastic material through the "plastic sheet production line" made of plastic sheet continuous. The equipment is generally composed of: mixing system - crystallizing and drying system with single or multiple Extruder - screen changer melt pump -T shaped head - three roll calender device - edge cutting device - traction device, storing device of coil winding device. Made of plastic sheet thickness between 0.25mm- - 2.5mm, the width is about 300mm-1400mm.
2 hot forming
Hot forming is the production process of plastic sheet made of plastic cup. Hot forming is a special process in the plastic processing. Its characteristic is the sheet heated to high elastic state, and then through the pressure of compressed air and mold pre stretching device makes the sheet laminating die surface, cooling, shaping, obtained after cutting products.
Because the air pressure usually die need molding is positive pressure (0.4-0.8MP), so the cup making process called positive pressure thermoforming, mold used in plastic positive pressure molding production process is called "positive pressure thermoforming of plastics mould".
Method of decoration is also using the printing or labeling the landscaping of the plastic cup appearance.
"The production of disposable plastic cup" positive pressure thermoforming mould applies the structure of integrated and blanking in one.
It has the following characteristics:
On the lower edge of the plate shearing, apart from the blanking effect, some lower edge also molding edge effect.
On the lower edge of the general does not move, can flexibly change the cavity of a mold, plastic cup can produce a variety of specifications. Not only can reduce the cost, but also speeds up the die change speed, while improving production efficiency.
By help of compressed air pressure forming plug tension, pressure.
On the plate shearing, shear knife edge can be 100-500 million. Blunt on shear plate, the lower edge of the sharp grinding, can be used repeatedly. Therefore, in the "disposable plastic cup" production, mold maintenance and repair quality directly affects the production efficiency and product quality. Therefore, maintenance is particularly critical for effective maintenance, to die.
Hot forming die is fixedly installed, the best match in a model of positive pressure thermoforming machine. Because of frequent replacement die not only reduce the efficiency of production and die storage, installation, in the demolition, the debugging process of intangible increased damage may be, inevitably with the precision will be decreased gradually, and then influence the product quality and production efficiency.
Whether imported positive pressure thermoforming or domestic positive pressure thermoforming machine (including domestic cam, homemade oil type positive pressure thermoforming machines), installation, adjustment, disassembly and principle of the die is basically the same.
Installation and debugging method of the following discussion is in cam type positive pressure thermoforming machine for reference.
Installation, debugging steps of 1 mould:
The upper die seat mounting surface of the machine, mould installed on the face wipe clean with a clean cloth wipe, and spraying amount of rust preventive oil, lubricating ointment smearing transparent color food grade in help pressure plug on the pull rod.
The upper mold is arranged on the upper die seat device, don't lock bolt, to facilitate the mold on the edge.
- help die SETI indented cut mouth.
The machine mold base installation surface, down die mounting surface wipe clean with a clean cloth, and spraying antirust oil, in the mold ejector rod coated with grease.
The lower die is arranged on the lower die seat device, don't lock bolt.
And manual barring the lower die to molding position (i.e. the radius arc), by adjusting the machine upper mould seat fixed nut (thick strips with), the machine die holder screw nut or oblique inserting plate (trimming use), so that between shear plate and the lower edge of the distance between the plane used for sheet the thickness of the 1/3-1/5. (some can be sheathed, associated with the cutting edge and the structure of the die)
And manual turning to the cutting position, so that the knife edge into the cut in the plate.
Die - bolt lock on: first on the mold after the mold, from inside to outside, front and rear diagonal. In order to ensure that all the mold is a balanced force, recommend the use of the torque wrench, screw selection according to the use of the proper torque..
And the correct installation of cooling water pipe, pipe.
For cam equipment made in China, open the machine, should first by adjusting the plunger, forming gas, blowing, sheet feeding inductive switch start and stop position, to determine the action program.
For the hydraulic equipment, the starting position should be to determine the induction switch, and then setting, the action program for the length of time adjustment.
For hot forming machine with angle control program imports, should be to determine the action of the program and the time spent by the start angle setting piston, forming gas, blowing, sheet feeding and stopping angle.
And the coarse adjustment program can according to the schematic diagram of the usual procedure control, it is the simulation of a lot of practical production process summed up and come, with a certain degree of universality. Generally only fine-tuning, for individual mold to make necessary bigger adjustment.
And adjustment pressure drop, molding pressure plug depth, width, the width of sheet feeding into the sheet, strip width, the heating temperature, cooling water flow or velocity, or when the control machine mold temperature, cooling water temperature.
- help pressure plug descending depth (H) determination:
To help plug the descent depth (H) = molding depth (H1) -2--10mm (often take 3-5 mm)
The exhaust hole of the lower mould cavity, the bottom edge, under the roof should be kept unobstructed.
In the equipment without material, low speed operation condition or method of dynamic operation through the point check these settings are correct.
And feeding test, fine tuning machines, mold, process parameters to normal production.
Mold cooling, the protection of 2 in production
In order to achieve the maximum possible productivity, it should be possible to maintain the low mold temperature. Of course, with the processing of plastic sheet material, thickness.
When materials processing, the most commonly used, such as PS, PVC, PP, ABS 16--18 C is more typical of temperature.
- but the mold temperature not lower than 10 DEG C, because there will be condensed water, affecting the quality of products, die due to rust.
High temperature will reduce the efficiency of production, such as ILLIG positive pressure thermoforming equipment general provisions can not exceed 30 DEG C.
And cooling water flow a lot of die, it is the key to decide whether to obtain constant temperature throughout the operation of the. Asked the average per minute flow about 80 liters / minute.
Keep the upper die and the lower die body temperature uniformity is very important.