Because sales market has put forward ultra-thin, beautiful and lightweight consumer requirements for NOTE BOOK computers, it brings challenges to design and manufacturing. Exquisite appearance, firmness and flexibility of material are two important issues for designers and manufacturers. For manufacturing molders, heat (temperature) is a very important control variable for molding technology and quality control. Influence of temperature on many factors such as measurement size and appearance color is described here.

 

(1)--Sprue (2)--Sprue (3)--Feed point (4)--Cavity
Resin heated to a molten state at high temperature flows from pouring gate
(1) Enter runner. (2) Under pressure from feeding point. (3) Inject into cavity;
This injection process is a gradual cooling process for high-temperature resin heated to a molten state. Part close to cavity wall is first cooled and solidified, then injected part is gradually cooled and solidified. According to shape of mold cavity, molten resin is cured into a specified shape when product is designed. This process is molding process.

Generally speaking, saturation temperature of mold is about 80 ℃. In order to make mold reach saturation temperature quickly, there are following three factors.
A. Ambient temperature: about 14℃ in winter and 40℃ in summer.
B. Warmer (mold temperature machine): It takes a long time to reach 80℃.
C. Molten resin: about 260℃.
As can be seen from above, it is preferred to select molten resin to heat mold so that mold quickly reaches saturation temperature. From perspective of cost, it is one of the most economical and effective ways to heat mold with secondary material.

To select the best temperature suitable for forming a certain part, a temperature should be selected as a control parameter, such as mold temperature or material temperature. Reference value of control temperature point should not be too much. Use mold temperature tester to measure temperature of mold under optimal molding conditions as a parameter to be included in control.
Generally speaking, when measuring, measured size of product under cold mold condition is larger than that of hot mold, so measurement side of the first piece size should be placed in a constant temperature chamber for measurement in hot mold state.

Formula: △L=L*(T2-T1)*∞
Growth amount = initial length * (final temperature - initial temperature) * thermal expansion coefficient (material)
Formula: △L=L*△T*∞
Example: A molded product of ABS+PC has a total length of 320mm when measured at 10℃. When molded product is measured at a temperature of 30℃, what is its total length in mm? (Assuming that thermal expansion coefficient of ABS+PC is known to be 7.5*10 -5)
Growth amount: △L=L*(T2-T1)*∞=320*(30-20)*7.5*10-5=320*10*7.5*10-5=0.24mm
Final length=L+△L=320+0.24=320.24mm
Therefore, when measured at 30℃, the overall length of molded product is 320.24mm.
QC personnel should carry out measurement at a constant temperature, otherwise technicians will be misled due to improper measurement methods. Generally speaking, hot mold will be basically finalized after 6 hours, and size will be stabilized. Thermal expansion coefficient is determined by material. Materials with strong water absorption, such as acrylic, are more prone to deformation and warping in appearance, so it is not suitable for long-term store.
To sum up, temperature has a decisive influence on length (resin product).

In addition to influence of temperature on length of molded product, it also has a considerable influence on gloss of molded product. Generally speaking, gloss of molded product with textured surface will become darker when temperature rises. Conversely, when temperature is lowered, gloss becomes darker.

MI measuring machine or MFI measuring machine is a testing instrument for testing flow properties of materials. Full name is: MELT-FLOW-INDEX.
During molding, when raw material is added to secondary material for production, its fluidity is very good, and bonding line is also good, but when secondary material is used for many times, due to high temperature and high pressure conditions, its chemical arrangement bond changes, that is, molecular structure changes, and density changes. We all know that ρ=M/V, density is related to volume and weight, same weight of raw materials and secondary materials, volume is different, so density is also different.
Change of its density affects its physical properties, and it is easy to embrittle, which will cause harm to safe use of molded product. Therefore, use of MFI testing machine can determine proportion of added secondary material through numerical analysis of fluidity. Customer requires MFI tester as a necessary safety measuring instrument, and MI value is listed as one of important regulatory data.

Use of secondary materials is one of preferred ways for molding manufacturers to reduce costs. However, use of secondary materials has serious hazards to safety of molded products, reasons for which have been explained above. However, under requirement that quality and cost issues must be taken into account at the same time, when adding secondary materials during molding production, first of all, we must actively ask quality control personnel to measure MFI value and conduct a destructive strength test. Quality control personnel and molding technicians should jointly complete degree of grasp of safety factor to ensure safety of product. According to Experience, generally proportion of secondary materials should not exceed 10%, but it should also depend on shape and thickness of product.

Tryout conditions are not optimal molding conditions because temperature is a variable during tryout phase.
Constancy of cycle time requires immobilization and stability of operating program.

Molding technicians and quality inspectors must use professional technology and rich knowledge to win trust and respect of customers, in order to achieve the best combination of quality (Q) and cost (C), so that enterprises can enhance market competitiveness and product reputation, which is goal of technicians and managers.