About the injection molding machine injection and piecewise injection plastic flow theory
More than one, injection plastic flow theory: 1, the first shot low speed into the adhesive, the nozzle to the cold material head away to improve secondary firing rate with cavity in order to shorten the gate of plastic flow to the end of the time, make the filling of plastic viscosity maintain minimum curing, but high-speed injection to control the correct pressure switch point is difficult, slow down so you have to use more sections to be effective control master pressure switch point.
2, shoot the action principle of: using in the electric control hydraulic system flow proportional valve instantly get in the position of the glue speed, subsection firing rate in order to achieve.
Second, the relationship between block injection rate and pressure: 1, section in the injection molding process, filling process whether there are some changes which pressure is only a pressure that is at once, and the holding stage whether some pressure maintaining its speed to keep only one.
2, block shot instances: (1) the same product can use smaller clamping force forming, which can extend the life of the machine, mold;
Diction section to slow down the right pressure switch point can effectively ensure the stability of quality;
(3) the molding of plastic flow is too good, in order to prevent the burrs have to take low rapid-fire glue, but shall not make cooling solidification material for the principle, for the resin melt through the thick meat place to improve the rate of fast full of cavity, flow mark,
Is gradually melting fat gate centered and render striped shape)
Is the initial flow into the cavity within the resin cooling too quickly and with a second flow of resin between the formation of the border.
(4) into the gate (
Parts forming thicker, shot speed is too fast will cause turbulence, cold material residual channel to form a flow mark, reason should slow low pressure into the glue opened the cold head, make the back of the plastic to enter smoothly.
5] nozzle injection molding engineering department is in contact with the mould because the mould cooling water cooling mold temperature was lower than those of nozzle, the part of the heat taken away by the mold, nozzle is easy to produce cold head, the cold head into a mould, will be at the gate block caused by the flow lines or silver strip traces, agent for piecewise injection can improve the bad.
Fine  small precision parts, the size of the gate, and highly difficult of da point gate balance production is not easy, will open the same gate size using multistage injection technology can be overcome.
Once the first injection at low speed and the second section, change the position of switch between the high-speed injection of weld line local displacement can be revised, as in appearance on the obvious place to the less obvious location (
Such as label)
Being sag and fusion of bad phenomena are in opposition to each other in shape, with this method can be improved at the same time;
Product sag area rate drops, filling surface to rapidly improve the rate of filling cavity after cold setting, the weld line positions can quickly shoot rubber shall be taken to prevent bad fusion (
Molding product surface subsidence are commonly occurred in meat thick place, it is the volume shrinkage caused by the time of the molten resin cooling curing
'levies in the holding segment in the process of FRP products will be reduced by reducing residual stress.
⑽ molding product flow thin and long distance conditions need high pressure can complete smoothly, but high shoot rubber easy to cause the gate of the residual stress, which affects quality so take high-speed into the glue, medium-speed filling, pressure to eliminate residual stress at low speed, so as to prevent the deformation of the finished product.
⑾ mold cooling aspects to improve: if the moving mould temperature low mold temperature higher will not occur within the warp moulded, if dynamic mold temperature is higher the moulded part outgoing warping phenomenon may occur.
⑿ scorched (
Is caused by compression combustion gas inside the cavity phenomenon)
Most likely to occur in the parting line or melt it, the surface of the resin is black traces of carbide, and need to make the air gas discharge cavity smoothly, must reduce firing rate.