Improvements in machinery and moulds
DATE：2022/2/18 8:46:01 / READ： / SOURCE：This station
Improvements in machinery and moulds
(1) Extruder flange reconstruction and start-up and shutdown process control Due to the use of an ordinary 65mm single-screw extruder, the following improvements have been made according to the characteristics of foaming:
1) A built-in heating ring is added to the flange to overcome the uneven heating of the flange during startup, resulting in disordered material flow and uneven foaming caused by the backlog of cold material.
2) Adjust the extrusion pressure by adjusting the mesh size and shape of the splitter plate to match the pressure in the compression section of the mold, so that the flow of the material from the splitter plate to the compression section of the mold remains uniform, preventing melt Disorder and premature foaming. At the same time, the formation of different stream bundles is beneficial to the formation of wood grains.
3) When starting up the machine, first open the machine head, extrude the partially coked or unplasticized plastic that stays in the extruder due to uneven heating, then stop the main machine, quickly close the neck flange, and then start the machine to extrude . This step is not required if a specially formulated starting and stopping material is used when starting up.
4) When the machine stops, stop adding the production material, switch to the starting and stopping material, and stop after the extruding die head is turned on and off.
(2) Design and improvement of mold
1) Refer to the direct enlargement method of the cavity with a larger foaming ratio. The mold produced by this method is prone to melt disorder or rupture caused by unstable extrusion, low extrusion foaming ratio, and high density of extruded products (generally more than 0.7gcm3).
2) Core method. Use the thickness and length of the core, the thickness of the distribution layer and other parameters to control the foaming ratio, and consider whether to build a heating rod in the core according to the size of the mold. The die prepared by this method is relatively stable in extrusion material flow and high in foaming ratio. However, for flat-shaped products, the phenomenon of uneven extrusion flow is easy to occur on both sides and in the middle.
3) Various combined core methods. Referring to the design of the wall plate mold, the core body is divided into several small core body combinations, on the one hand, the extrusion of the product (especially the flat product) is stabilized, and on the other hand, the foam material flow forms the recombination of the material flow beam, so as to have Conducive to the formation of wood grain.
(3) Control of cooling and shaping part
1) Use vacuum water cooling to set.
2) Use a chiller to control the cooling temperature of the mold at 5-40°C.
3) Different cooling water temperature and vacuum are used in different parts of the product, so as to obtain a foamed product with a controllable skin layer.
Author：admin