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Injection Moulding for Phone Case

The manufacturing of mobile phone case covers the mod structure design, injection mould making, injection moulding, spray printing etc, each of which will affect the final appearance of plastic products.

Injection mould structure design for phone case
The phone case usually consists of four large parts of the face shell (top front), the face support (upper back), the back support (lower front), the back shell (lower back) and some small plastic parts, such as the battery cover, buttons, windows, buckles, and anti-scratching etc. These components require adequate consideration of interoperability in the injection mould structural design for phone case, as well as assembly with components such as boards and batteries.
Injection moulding for phone case
There are many related issues to be considered in the injection mould structural design for phone case, such as material selection, internal structure, surface treatment, injection moulding process, packaging and decoration, etc., specifically the following:
  • It is necessary to judge whether the injection mould design for phone case is reasonable and reliable, including the injection moulding process for phone case, the demoulding direction of the phone case injection moulded plastic part, the draft, the core pulling, the structural strength, and the circuit installation (cooperating with the electronic engineering personnel) etc.
  • According to the shape requirements of the phone case injection moulded plastic products, to know whether the moulding process of injection moulding products is suitable, including injection mould manufacturing for phone case, product assembly, shell coating, silk screen printing, material selection, and standard mould parts.
  • Carry out specific structural design and affirm the manufacturing process of each part. Pay attention to the structural strength, installation positioning, fastening method, product variants, component installation and positioning, and definitely the best assembly route.
  • Injection mould structural design for phone case should minimize the difficulty of mould design and injection mould making, improve the efficiency of injection moulding for phone case, and reduce mould making cost and injection moulding cost for phone case.
Injection mould design
Injection mould design for phone case must fully consider the structure and assembly of the phone case injection moulded parts. At the same time, it is also necessary to consider the demoulding of the phone case injection moulded products and the arrangement of water channels and gates. The following is a brief description of the design points of the product ribs, hooks and nut holes.

1. Rib design:
When using PC or ABS+PC materials, the thickness of Rib is preferably not more than 0.6 times the thickness of the shell body. Do not exceed 3-5 times the thickness of the body. The draft is 0.5-1.0 degrees. The spacing between the two Ribs is preferably more than three times the wall thickness.
2. The design of the hook:
The snap-in size of the hook is generally between 0.5mm and 0.8mm. The hook sinks 0.2mm from the parting surface, which is good for injection mould making. The hook has a gap of 0.05 mm with the occlusal surface of the card slot for later modification. A gap of 0.3 mm is reserved at the top of the card slot at the top of the hook as a rebound space for the deformation of the hook. The R angle at the bottom of the card slot increases the strength, so the lead angle is used as the transition zone.
3. Nut hole (Boss) design:
Boss's goal is to connect screws, guide pins and other fasteners or to position the hot-rolled nut during hot pressing. The most important principle of designing Boss is to avoid the absence of support.
In addition, the thickness of the mould iron material needs to be greater than 0.5 mm, and the draft angle of the female mould surface is preferably greater than 3 degrees. Each additional one-thousandth of an inch of the bite depth needs to be increased by one degree of draft angle.

Injection moulding for phone case
Mobile phone cases are usually made of PC (polycarbonate) or PC+ABS materials. Because of the poor fluidity of PCs, high mould temperature and high temperature filling are usually adopted in the injection moulding for phone case. The gates adopted are usually point gates. When filling, it is necessary to adopt graded injection moulding, find the position of the gate and the switching position of VP (injection-holding pressure), which will be very helpful for solving the abnormalities such as gate gas marks and burrs.

The following are the key points of the moulding conditions for the mobile phone case, and the setting points of the moulding parameters such as the melt temperature, the mould temperature, the injection speed, and the back pressure are explained.

1. Melting temperature and mould temperature:
The optimum moulding temperature setting is related to many factors, such as the size of the injection moulding machine, the screw configuration, the mould design and the injection moulding product, and the injection moulding cycle time. In general, in order to gradually melt the plastic, a lower temperature is set in the rear/feed zone of the feed pipe and a higher temperature is set in the front section of the feed pipe. However, if the screw is not designed properly or the L/D value is too small, the reverse temperature setting is also possible.

At the mould temperature angle, the high temperature mould can give a better surface appearance, the residual stress is also small, and the thinner or longer moulded article is easier to fill. The low mould temperature shortens the injection moulding cycle. 40 to 70 rpm is recommended, but it depends on the machine and screw design. In order to fill the injection mould for phone case as quickly as possible, the injection pressure is as high as possible, generally about 850 to 1,400 kg/cm2, and up to 2,400 kg/cm2.

2. Back pressure:
Generally, the lower the setting, the better, but for uniform feeding, it is recommended to use 3 to 14 kg/cm2. The injection speed has a very large relationship with the gate design. When using a direct gate or edge gate, a slower rate of fire is applied to prevent the phenomenon of daylight and wave flow. When switching from injection moulding to holding pressure, the holding pressure should be as low as possible to avoid residual stress in the injection moulded part. The residual stress can be removed or reduced by annealing. The condition is from 120 ° C to 130 ° C for about three minutes to one hour.

Avoid the defects of phone case injection moulded parts
  • Gas mark: Reduce the flow rate of the melt gate and raise the mould temperature.
  • Under-note: Increase injection pressure, speed, material temperature, mould temperature, and increase the amount of glue.
  • Injection moulding flash: Reduce the plastic filling pressure, control the V-P switching point to prevent overfilling, increase the clamping force, and check the mould fit.
Welcome to ACO Mold injection moulding company and contact us. The mould engineers from ACO Mold will give you the best solution, and recommend the suitable materials for you. We are ready and looking forward to cooperate with your next project. You will be happy and satisfied to be our partner in mould making and injection moluding project.

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