One of the most common problems tool and die manufacturers and molders encounter is when the core or cavity of their mold tooling begins to crack. Tools are run for months, which means thousands of hours under intense heat and pressure for every single shot of plastic. So, it’s not surprising when small fissures form in the metal after over a million or so shots have been run. And that’s on a brand new tool. Once a crack appears, the mold core repair must be performed, promptly and precisely, in order to maintain flash-free, defect-free parts.
A manufacturer has several options for repairing their mold tooling: send away the cracked cores to be repaired, repair them in-house, or make brand new ones. Most large-scale manufacturers choose to repair cores themselves as it is faster, less wasteful, and allows the producer to stick to its production schedule. As for the repair itself, manufacturers have two options: laser welding and TIG welding.
TIG welding involves a lot of extra steps, with no way to guarantee that the entire crack has been repaired. In a pinch it will suffice, but there’s still a significant chance the repair won’t last very long due to a lack of controllable heat output and poor visibility during the repair process. And because TIG welds can produce too much heat during the welding process, they can actually move the metal and distort the entire part.
Mold core repair welds are already somewhat of a delicate process given how close to the surface the core’s water lines can run. The metal that separates 450-degree injected plastic from cold water can be as thin as .250” thick. Too much heat and its structural integrity is soon compromised.
Where visibility is concerned, the very nature of the TIG welding process impairs your ability to see the crack clearly. The less than optimal lighting conditions mean you will only see what is visible to the naked eye, more than likely missing the full extent of the crack. The microscopic segments of the crack, which have not been repaired, will cut short the usable life of the core. Also, if the repair is incomplete, the core or cavity will continue to leak, making it unusable and requiring another repair attempt.
Laser welding repairs the cracked core or cavity, and also extend its lifecycle after the repair. This is because laser welding imparts less stress on a part and can weld dissimilar metals. TIG welding cannot guarantee that a core’s lifecycle will be extended due to its larger heat-affected zone. Also, laser welding is a low-heat process with a very small heat-affected zone that won’t damage or distort the base metal.
Laser welding is also much more accurate than TIG welding, providing a microscope with at least 10x magnification and a joystick for more precise movement and handling. This is why pulse laser welding allows you to find the crack in a core or cavity even if it’s invisible to the naked eye. Many cracks can propagate past their origin point without leaking or visible damage. If left alone, this invisible section of the crack will continue to grow until the damage is noticeable again. Laser welding gives you the ability to focus laser energy on the crack to find its root, offering a better assessment of the scope of the repair.
At Alpha Laser-US, we understand that certain things are unavoidable and out of a manufacturer’s control. Cores and cavities cracking is one of them, but the mold core repair process is not. With a laser welding system in-house, you can manage repairs the right way and better meet your production requirements.
Talk to us today to schedule a live demo and learn about our training process.