Why Is My Resin Not Curing In My Silicone Mold?

In the precise world of plastic injection molding, efficiency and dependability are the lifeline to production. When choosing cost-effective silicone molds for resin for small runs, rapid prototyping, or complex designs, you may encounter a tricky problem: mold surface stickiness, undue damage, and even residue that hinders effective molding.

This is a thorn to most professionals. Especially in custom plastic injection molds manufacturing, uncured resin can waste material and extend production.

This article will explain the exceptional value and potential risks of silicone molds in injection molding processes and provide an in-depth solution, from material selection to maintenance, to help you successfully produce plastic injection molds.

Key Answer Summary

Why Trust JS’s Guide? Solving the Problem Of Uncured Resin

Reliable advice is the most important solution to uncured resin issues. JS possesses long-term experience in plastic injection molds business. From fulfilling individual needs of custom plastic injection molds manufacturing to converting silicone molds into high-temperature engineering plastics, we have solved countless uncured resin cases and have full understanding of common defects of silicone molds for resin injection molding.

Whatever it is, reducing plastic injection molds price or reducing trial production lead times, our expertise goes through the entire process, from material selection to process optimization. This guidebook is a distillation of our departmental hands-on expertise, and each suggestion has been tested and proven in production, helping you to detect key problems and errors.

JS has long-term experience in custom plastic injection molds manufacturing. If resin non-curing is a trouble you face, our online plastic injection molds services can help you to optimize the process of production.

Learning About The Silicone Mold Manufacturing Process First Hand

Knowledge of how to create silicone molds is key to resin non-curing troubleshooting, as the quality of the mold directly influences how the resin will behave with respect to the mold and thus how plastic injection molds manufacturing will succeed.

Silicone molds have a niche function in the injection molding industry as an alternative for small quantities of test runs and creating specialty parts, rather than replacing traditional steel molds. Steel molds are suited for large-scale mass production, while silicone molds can quickly respond to custom plastic injection molds manufacturing needs and reduce initial investment.

The production process involves six key steps, and every detail requires attention to detail:

1.Prototype Surface Finish: Maintain the prototype surface to be defect-free and smooth. If small scratches do occur on the prototype, polish the surface up to a roughness of Ra ≤ 0.8μm using 400-grit sandpaper or higher. Failure to do so will directly affect the accuracy of the mold and result in defects in the end product.

2.Release Agent Application: Select a release agent that is compatible with the silicone. Solvent-based release agents are utilized for preventing residue from water-based release agents.Improper release agent may remain on the surface of the mold, and subsequently react with the resin, preventing it from curing.

3.Casting the Silicone: Control the rate of flow to 5-10ml/s to avoid bubbles caused by an over-flow. Bubbles can form holes in the mold and affect resin molding.

4.Vacuum Degassing: The vacuum level should be reduced to -0.09MPa or higher and maintained for 15-20 minutes to efficiently remove bubbles and prevent the creation of voids in the mold.

5.Curing: Control the temperature and time strictly as per the silicone instructions. For instance, platinum-catalyzed silicone should be cured at 25°C for 4-6 hours to achieve mold hardness as per specified standards.

6.Demolding: Carefully remove the mold with a plastic scraper without damaging the mold cavity by pulling.

If you need high-quality silicone molds for resin to ensure production,JS offers professional fabrication services, with strict control from prototype testing to delivery. Orders are ready to be dispatched quickly to fulfill your plastic injection molds parts manufacturing needs.

Silicone Selection: Injection Molding Materials

Choosing the right silicone material is vital in plastic injection molds manufacturing and directly impacts curing performance of resin and lifespan of mold. Tin-cure and platinum-cure silicones are common to injection molds and vary significantly, so the selection should be specific to your application.

Key parameters to remember: Hardness controls demolding and conformal performance, tear strength determines mold lifespan, and handling time and curing time influence production efficiency.

Resin Failure: Determining The Failure Culprit

If resin fails to cure in silicone molds for resin, it’s necessary to identify the culprit from multiple perspectives and address it specifically to avoid costly problems.

Mixing Dilemma: This is the most common reason. Resin often requires the A and B components to be mixed in proportion. Inaccurate or uneven mixing can result in incomplete polymerization of the resin. For example, if the ratio of the epoxy resin mix is out by over 5%, the cure rate will decrease significantly, or fail to cure at all.

Environmental Factors: Temperature and humidity have a direct impact on curing. Below 15°C, the reaction is slowed down, giving prolonged or no curing. Above 60% humidity may influence the curing of moisture-curing polyurethane (PU) resins. Too much moisture can lead to bubbles on the surface or tackiness.

Material Culprits: Aged or improperly stored resins can render them ineffective. Sunlight or excessive heat will cause premature partial curing of unsaturated polyester resin, preventing effective curing. Compatibility problems between the resin and the mold from a silicone material can also affect curing, which must hence be confirmed beforehand.

Silent Contaminants: Surface contamination on the mold or in the resin can inhibit curing. Sulfur-based release agents left behind in the mold, for example, will chemically react with a platinum-catalyzed silicone mold and disrupt curing of the resin. Grease and dust that are brought in during handling of the resin will disrupt the polymerization reaction, so a clean environment is essential.

Solution: How To Solve Problems When They Happen

Once the reason behind non-curing of resin is recognized, specific corrective measures must be taken to reduce loss and bring production back to normal:

For Mixing Problems: Blend the resin according to the exact ratio in the instructions and stir using an electric stirrer for 3-5 minutes. Once stirring is done, ensure the resin is smooth and clear, without streaks or color spots. Allow it to settle for 1-2 minutes to drain bubbles before pouring the resin into the silicone molds for resin.

For Environmental Conditions: Low temperatures can be offset by heating using a heater to maintain ambient temperature at 20-25°C. Avoid exposing the resin to direct contact with the heat sources so that overheating in local areas is prevented. During high humidity, work a dehumidifier to maintain humidity at 40%-50%. Humidity control is particularly stringent when producing PU resin.

For Material Matters: Check the date of manufacture of the resin and storage conditions. Substitute the expired or degraded resin immediately. Also, choose a resin compatible with silicone mold. For example, platinum-catalyzed silicone molds require sulfur- and nitrogen-free resin.

For Contamination Issues: Use a 99% Use a dust-free cloth soaked in pure alcohol to clean the mold thoroughly off all residual release agent or contamination. Dry for use. If mixed resin is being handled, maintain clean tools and prevent grease and dust contact.

JS offers online plastic injection molds services. In case you need new silicone molds or resin products, we will contact you quickly after placing an order, providing quality goods at reasonable prices and avoiding production lag.

Three Core Resin Curing Modes

Understanding resin curing processes can help you coordinate silicone molds better with processing parameters, reduce the risk of non-curing, and ensure the production of plastic injection molds. There are three main core curing methods for resins,which have very different principles and situations where they can be used:

Truth Revealed: Do Silicone Molds Stop Curing?

Many individuals want to know whether silicone molds stop resins from curing. Yes, but it is not an inherent problem with the mold, it is because of some reasons. Once you know the reasons, you can help yourself avoid the risks in custom plastic injection molds manufacturing:

Major reasons for curing inhibition in silicone molds

• Residue of the catalyst: For example, when there is platinum-catalyzed silicone production, if the catalyst is not completely reacted, the excess platinum will react with sulfur and amines in the resin and hinder polymerization of the resin.
• Mold surface contamination: In case a faulty release agent has been employed in mold production or if the mold is not demolded after cleaning properly, release agent residue can seep into the future injected resin and affect the curing reaction of the resin.

Mitigative measures for curing inhibition

• Select high-quality silicone material, ideally high-purity platinum-catalyzed silicone. During production, follow instructions strictly in regulating curing temperature and time to avoid catalyst residue to the utmost extent.
• Wipe the demolded surface of the mold with a dust-free gauze wetted with 99% pure alcohol. If there are stubborn deposits, wipe 2-3 times to thoroughly clean the mold.

The silicone molds for resin produced by JS undergo strict quality inspection to minimize catalyst residue and surface contamination. At the same time, transparent plastic injection molds prices are provided, and mold maintenance guidance is provided after placing an order to help you use them stably for a long time.

Silicon Molds’ Compatibility With Injection Molding

Silicone molds have different characteristics from the usual metal molds, requiring injection molding process alteration to accommodate curing of the resin, extend mold lifespan, and improve plastic injection molds parts quality.

Low-Pressure Injection Molding

Silicone molds are softer and weaker in tear strength than metal molds. Deformation and damage in the mold due to high pressure will further affect resin curing. The injection pressure is to be controlled between 5-30 MPa (usually 50-150 MPa for metal molds), and the injection speed is to be controlled between 5-10 mm/s. This can be optimized based on the viscosity of the resin in order to avoid high-speed shock on the mold.

Temperature Control

Silicone molds contain a top temperature that they can withstand. Even heat-resistant silicone molds must have controlled injection and mold temperatures. The injection molding temperature is 10-20 ℃ lower than that of metal mold technology.

For example, for nylon fiberglass parts, metal mold injection requires 280-300 ℃, while silicone molds require 260-280°C. The mold temperature should be controlled at 40-60 ℃ using a water or oil temperature machine to avoid temperature swings which induce uneven curing of the resin.

Material Choice

Employ resins with good fluidity and low shrinkage to reduce injection pressure and temperature levels, minimizing the demand on silicone molds. For complex components, low-viscosity epoxy resins can be employed, filling the mold cavity at low pressure and minimizing mold wear.

JS has experience with injection molding processes that can be applied with silicone molds and can provide end-to-end services from process design to production implementation. Our online plastic injection molds services ensure rapid turnaround to orders and arrange a separate team to work with you once an order is received in order to ensure optimal process parameters.

JS Case Study: Silicone Molds Overcome Nylon Part Trial Production Difficulties

Client Background

A maker of drones needed to quickly trial-produce 200 nylon glass fiber (PA6-GF30) fuselage brackets. Brackets are structural load components of the drone and must pass dimensional tolerance of ±0.1mm and compressive strength of 50MPa.

The client had three main issues: The cost of conventional steel molds is over $200,000 with an 8-week production cycle, far above budget and schedule demands. 290°C temperature for the injection molding of nylon glass fiber is unachievable using conventional silicone molds. Trial production has to be finished within 5 weeks to display new products in industry trade shows and occupy market niches.

JS Breaks the Game

Adopting JS-9400HT composite material mold, specially designed for high-temperature engineering plastics, with a temperature resistance of up to 320 ℃, it meets the injection molding requirements of nylon fiberglass at 290 ℃, with a hardness Shore A 80, and can resist the wear of fiberglass materials, so it does not damage the mold for trial production.

The innovative “sandwich” structure holds the mold: outer high-strength silicone layer, middle glass fiber reinforced stability layer, and smooth release inner layer. Mold flexibility and dimension stability are both realized, so the fuselage bracket can be precisely produced to ±0.1mm.

With a precision temperature regulation system and optimized injection procedure, the injection temperature is extremely strictly regulated to 285°C. There is also a strict cooling and maintenance regimen requiring a 30-minute cooling of the mold after each injection to avoid mold cracks caused by sudden temperature changes.

Results

JS delivered trial production and mold production in five days, significantly ahead of the client’s five weeks requirement, producing 220 qualified parts at a yield rate of 98% to assembly specifications. Trial production cost was only 3% of what would have been spent with conventional steel molds, saving the client considerable amounts of money.

The client was in a position to display this bracket in an exhibition, attracting prospective partners and earning three orders, achieving market breakthroughs. JS has emerged as the first choice partner for rapid trial production of high-end materials.

FAQs

Q1: Can we use silicone molds to make injection-molded high-temperature engineering plastics?

Yes, but two conditions must be met:

• Select a high-temperature-resistant special silicone material. Such silicone is resistant to high-temperature engineering plastics’ injection temperatures.
• Adjust the processing technology appropriately, reduce the injection molding temperature and avoid long-term damage to the mold in a high-temperature environment,thereby ensuring the production of plastic injection molds pieces smoothly.

Q2: What should the design of gating and ejection systems for silicone molds be?

For the design of gates in gating systems, the gate should preferably be large and smooth. It reduces the flow resistance of the resin, prevents the rapid cooling of the resin upon flow, and reduces abrasion on the silicone mold. Mechanical ejection systems are not usually designed because they have very high flexibility, hence demoulding can be done by simple manual stripping or air blowing with no risk of damaging the mould and longer mould life.

Q3: What are the ways to enhance silicone resin mold lifespan?

There are three significant measures. First, adopt a low-pressure injection process of 5-30 MPa to avoid mold deformation caused by excessive pressure. Second, use a silicone-compatible release agent, uniformly applying it before each injection to reduce adhesion between resin and mold and prevent demold damage. Third, avoid the usage of plastics with sulfur or nitrogen additives to reduce wear on the mold and enable long-term usage of silicone molds for resin.

Q4: How many items can a silicone resin mold typically produce?

There is no one right answer, it is dependent largely on three factors: silicon characteristics, injection molding material, and process.Under normal circumstances, the production of 50-500 pieces using high-temperature silicone gel combined with mild processes is a common range.Sometimes, in the event of good process control and good maintenance of molds, molds can produce over 1,000 plastic injection molds parts.

Summary

Resin failing to cure in silicone moulds for resin is frustrating, but it’s also a valuable diagnostic sign that forces us to thoroughly admire the knotty thinking of materials science. From selecting the right type of silicone to having an incredibly clean working area, successful casting is a matter of attention to detail.

JS is expert in plastic injection molds and offers a full range of services, including manufacturing of plastic injection molds parts. We assure stable product quality and reasonable, transparent plastic injection molds prices.If there is any issue in resin curing or application of silicone mold, we invite you to reach out to us. We will use our knowledge and integrity-based service to support you in overcoming issues and achieving efficient and smooth injection molding.

Disclaimer

The content of this website is for reference only. JS services expressly disclaims any representations or warranties, express or implied, as to the accuracy, completeness or validity of the information provided. Any performance parameters, geometric tolerances, design features, material specifications or processes mentioned should not be considered as any commitment or guarantee by JS for products offered by third-party suppliers or manufacturers on its network or other channels. Buyers seeking quotes for parts are responsible for confirming their specific needs and product suitability. If you have any questions or need further information, please contact JS directly.

JS Team

JS is an industry-leading companyFocus on custom manufacturing solutions. We have over 20 years of experience with over 5,000 customers, and we focus on high precisionCNC machining,Sheet metal manufacturing,3D printing,Injection molding,Metal stamping,and other one-stop manufacturing services.
Our factory is equipped with over 100 state-of-the-art 5-axis machining centers, ISO 9001:2015 certified. We provide fast, efficient and high-quality manufacturing solutions to customers in more than 150 countries around the world. Whether it is small volume production or large-scale customization, we can meet your needs with the fastest delivery within 24 hours. chooseJS TechnologyThis means selection efficiency, quality and professionalism.
To learn more, visit our website:jsmachining.com

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