Mold machining specifically refers to the processing of forming and blank-making tools. In general, the production process includes: blanking dies, blanking punches, compound dies, extrusion dies, stamping dies, die-cutting molds, etc. However, during the design phase of these molds, a series of problems often arise in subsequent processing. To avoid such losses, we should identify the root causes of these issues. Below, the editor from Zhejiang Precision Stamping Electromechanical Co., Ltd. will briefly introduce the common problems encountered in mold design and processing.
I. Why does the mold have a low number of turnovers?
During the mold-making process, too much silicone oil is added, which destroys the molecular weight of the silicone, resulting in fewer turnovers and reduced durability. If the product is small with complex patterns, using harder silicone to open the mold will lead to fewer turnovers, because overly hard silicone becomes brittle and prone to breaking. Conversely, using softer silicone for the mold also yields unsatisfactory results. Since the silicone is too soft, its tensile and tear strength decrease, causing the mold to deform and reducing the number of turnovers. The mold rubber itself may be of good quality—silicone is not inherently good or bad, only suitable or unsuitable. This situation will not occur when we use silicone with a hardness appropriate for the product to make the mold.
II. Why does the mold experience burning?
Because unsaturated resin and resin products, after adding peroxide curing agents, generate a large amount of heat during the resin reaction. The resin curing time is generally 3 minutes. After 3 minutes, demolding should be done as soon as possible to prevent the silicone mold from burning.
III. Methods for making pour molds and split molds
Operating method for split molds or sheet molds: apply vacuum silicone by brushing or pouring. If making sheet molds or split molds using the brushing method, first apply a release agent or isolating agent on the product or model to be replicated before painting, then apply silicone on the product and wait 30 minutes. After that, stick a layer of gauze or fiberglass cloth on the surface to increase strength, then apply a second layer of silicone. Once the silicone is dry, make the outer mold. The outer mold can be made of materials such as gypsum or resin.
Operating method for pour molds or injection molds: pour molds or injection molds are used for smooth or simple products, i.e., surround the product or model to be replicated with rubber plates or glass plates, and directly pour the vacuum silicone onto the product. After the silicone dries and forms, remove the product, and the mold is formed. The above is the entire process of mold use and operation.
IV. Why does the mold appear dry on the surface but not inside?
The mold is a condensation-type silicone that cures by absorbing moisture from the air. During production, the silicone evaporates water. If an appropriate amount of water is not added, this situation will occur.
5. Why does the mold exhibit poor tensile strength?
This is because during the mold-making process, a large amount of silicone oil is added to the silicone to reduce its viscosity and make it easier to handle. This makes the silicone very soft, resulting in low resistance to tearing, reduced tear strength, and poor tensile performance. Consequently, the mold becomes less durable, has a shorter service life, and can withstand fewer flips.
6. Why does the mold experience oil bleeding?
The mold itself does not bleed oil; this occurs because a compound silicone oil (a blend of silicone oil and white mineral oil) is added during the operation. White mineral oil is a petroleum-based product, not silicone oil.
7. Why do molds produced show surface marks, streaks, or lack of smoothness?
This phenomenon occurs when the product or model to be replicated has not been sanded or polished. In fact, if the model or product itself is not smooth or perfect, no matter how good the silicone mold is, the result will not be aesthetically pleasing or smooth. Another situation is that uneven brushing during demolding can also cause the mold surface to be non-smooth.