According to the report, there is a saying that the first test flight of the new aircraft list is the most important. Because it will fall off, people will burn paper to pray for God ’s help. For the same reason, the first trial of the injection mold list is also very important, because the mold will be broken because of the failure. It’s no wonder that the mold factories in the industry have stricter requirements for mold trial process and discipline than during mass production, which is why.
There are many checkpoints for the first test of the new mold. Here we talk about an important parameter between them-the amount of glue injected for the first injection.
The amount of the first shot is the amount of material that should be shot when the list is shot for the first time.
Shooting more will explode the mold, and the mold will be greatly damaged.
With less shots, it may not be possible to push out certain products.
Especially when the product with barrel structure has no thimble or the top plate is pushed out, there is less glue that cannot be ejected, so the top shot is very important.
In the final analysis, how many shots should be shot? What is the problem of the travel distance of the machine screw?
Generally speaking, in the mold design, the weight of the product will be calculated by the software, even if there are errors, it will not be very large. So how do you convert it into the screw movement interval of the machine?
Formula: screw movement interval = product accounting component / screw cross-sectional area / plastic density plastic / compensation factor
Case: The theoretical value of the product weight is 200g, using a 280-ton machine with a diameter of 50mm, the density of the PS material is 1.05, and the compensation factor is 0.85
Then the screw movement interval = 200 / (2.5 * 2.5 * 3.14) / 1.05 /0.85 = 11.4 cm
This is the final total movement interval of the screw. According to the actual situation, if the mold structure allows, the list can shoot 50% full and move 5cm for the first time. If the mold structure needs to be filled at one time, then it will shoot more than 10cm Look. Reply to “Injection Molding”, check more
Several small problems:
Top of the list: The compensation factor is the difference between the density of the plastic at room temperature solids and the actual material used in the screw cylinder. The actual material used in the screw cylinder will be less, mainly due to the volume expansion of the plastic after melting, the screw counterflow, the screw leakage, etc. As a result, generally between 0.80 ~ 0.90.
Second: If the list is going to be full of injections for the first time, you must pay attention to the direction of low-voltage switching to avoid bursting or criticizing.
Third: The mold temperature at the time of trial mold must be equal to the temperature at the time of mass production. The mold temperature is different, and the injection interval is very different. PP at the same temperature moves in the mold cavity of 20 degrees and the mold cavity of 80 degrees Under the same activity, the gap between the activities will reach more than 15%, so we must pay attention to the stability of mold temperature.
In the end, the plastic mold injection parameters must be managed scientifically, and accurate calculation of the parameters, not just feeling, is the first step in scientific management.