Why Injection Molds Need Repair
Injection molds are used repeatedly under high pressure and heat. Over time, this constant use naturally causes wear. Even well-maintained molds can develop small issues such as worn edges, minor cracks, or less-defined engravings.
At first, these problems may seem minor. However, if they are not repaired early, they can affect product quality and production efficiency. Parts may lose accuracy, surface finish may decline, and unplanned downtime can occur.
Traditionally, mold repair has been done using manual welding or grinding. While these methods are still widely used, they have limitations. Excessive heat can damage the mold surface, and the results often depend on the operator’s experience. Repairs may take longer and, in some cases, shorten the mold’s lifespan.
Modern Solution: Laser Welding
Laser welding has become a key part of mold-making and injection molding processes. Compared to traditional methods, laser welding allows manufacturers to repair molds faster, safer, and more reliably.
Advantages of laser welding:
- Targeted precision: Only the damaged area is affected.
- Minimal heat: Surrounding material stays safe, preventing distortion.
- Semi-automated operation: Technology and software assist the operator, ensuring consistent, repeatable results.
With laser welding, you can restore worn edges, rebuild faded engravings, or fill cracks without disassembling the entire mold.
How Laser Welding Works
Laser mold repair uses a pulsed laser welding process, commonly performed with YAG or Fiber laser systems. In this process, filler material is used to rebuild worn or damaged areas of the mold. The laser delivers controlled pulses of energy that melt the filler material and the mold surface together, forming a new layer slightly higher than the original shape.
This pulsed approach allows precise control of heat, protecting the surrounding mold material while achieving accurate repairs. Filler material can be added in two ways:
- Manual: The operator guides the filler wire directly into the repair area. Slower but offers highly precise.
- Automatic: The machine feeds the filler wire automatically. Faster, more consistent, and easy to repeat.
Repair Locations on the Mold
Laser welding can repair any area visible to the laser. This “line of sight” requirement means that as long as the laser can reach the damaged spot, it can be repaired.
Common repair areas include:
- Corners: Both outside and inside corners.
- Engravings: Worn or unclear markings.
- Small holes or cavities: Even holes as small as 1/8 inch.
- Damaged areas on sloped or angled surfaces.
Some areas are more challenging to reach. In these cases, special optics or techniques may be needed. Even with restricted access, laser welding can often restore worn surfaces without disassembling the mold.
Filler Wire Size and Type
The size and type of filler wire depends on the area being repaired and the material of the mold.
Wire Size:
- Smaller wires (0.003–0.010 in.) are used for fine details or thin areas to minimize heat and prevent distortion.
- Larger wires (0.010–0.020 in.) are used for larger or thicker repairs, where more material needs to be built up.
Wire Type:
The type of filler wire depends on:
- Mold material
- Hardness required in the repaired area
- Condition of the repair (cracks, plated surfaces, previous welds)
- Cause of the damage
Hardness of the Welded Area
The hardness of the repaired area depends on:
- Mold material
- Type of filler wire
- Laser settings, which affect how the filler mixes with the mold
Proper selection ensures a strong, durable repair, and reduces the risk of cracks or future damage.
Mold Materials That Can Be Repaired
Laser welding can repair a wide range of mold materials, including:
- Steels: S-7, H-13, P-20, D2, A2, A6, M2, 410 SS, 420 SS, 440 SS
- Special alloys: NAK-55, Elmax, Aermet, CPM9V, aluminum alloys, copper beryllium, Amcoloy 940
Some materials, like high-carbon steels, are more prone to cracking. Aluminum and copper alloys are highly reflective, requiring special techniques. Understanding welding metallurgy is essential to prevent cracking and ensure durable repairs.
Recommended Laser Welding Machines
1. Sisma SWA 300F/450F Fiber Laser Welding Machine
The Sisma SWA 300F/450F series is a high-precision laser welding system designed for mold repair and maintenance. It enables distortion-free welding without preheating, even on complex geometries such as narrow grooves and sharp edges. Powered by an energy-efficient, maintenance-free fiber laser and supported by intuitive advanced software, the SWA delivers high-quality welds, increased productivity, and easy operation for a wide range of materials.
2. Sisma SWT 150F/300F/450F Fiber Laser Welding Machine
The Sisma SWT Series Fiber Laser Welding Machine is a semi-automatic, maintenance-free solution for efficient and precise mold repair. It offers high productivity, smooth and accurate axis movement, and consistent welding quality supported by advanced, easy-to-use software. Available in open Class 4 or enclosed Class 1 versions, the SWT series combines performance, durability, and safety in a compact, ergonomic design.
3. Sisma LM Series YAG Laser Welding Machine
The Sisma LM Series YAG Laser Welding Machine is designed for high-precision micro-welding, achieving spot sizes down to 0.1 mm. Equipped with SmartSpot™ technology, it ensures stable laser pulses, a wide depth of field, and repeatable welding results from the first shot. Featuring an ergonomic, low-noise design and ECO mode for reduced energy use and extended consumable life, the LM Series delivers precision, comfort, and reliable performance for mold repair applications.
Sisma Laser Distributor in Singapore
LFC PTE LTD is the authorized distributor of Sisma Laser Welding machines in Singapore. Contact us to learn more about laser welding and how these machines can support your injection molding applications.
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