Mould Cavity Repair Case Study
Steels, especially hard tool steels can be welded conventionally but the heat and the stress introduced with Tig welding make it almost impossible to remove all witness to the repair.
Carr’s carries out dozens of tool repairs daily and has three lasers dedicated to this task.
The increasing consumer demand for cheaper products fashions the need for the manufacturing industry to fabricate tools capable of handling high productions runs. However, these tools are expensive to manufacture, and their high initial cost is usually offset against the unit cost of the products. Carrs Welding Technologies (CWT) has specialized in repairing/modifying Mould Tool components since 1998. By ensuring the use of high-quality filler materials that closely match the customer’s specifications and therefore, allowing our Laser repairs/modifications to be re-machined back to their original form with little or no witness and minimal disruption to production. CWT carry out daily repair & Modification activities on Tooling used in Injection Moulding, Die Casting, Press Tools & Rubber Moulding.
The Context and Challenge
Project background and description
CWT’s extensive knowledge in repairing items by cladding filler material led several well-known plastic injection manufacturers to approach CWT for a solution to repair/refurbish their moulds. Frequently, hot gases from the injection process combined with rapid cycle times caused the shut-out edges and vents to erode resulting in “Flash” on the moulding that then had to be trimmed.
There are several obstacles that need to be overcome when doing this type of repair. Firstly, the defects are, usually, located on edges, which means that the volume of material available to dissipate the heat from any welding operation is greatly reduced. Pulsed Laser Welding is ideal when addressing this issue as not only does it allow for the application of a localised power density, but also leads to a minimised heat affected zone (HAZ).
Secondly, for a successful repair, it is crucial for the filler material to be as close to the base metal’s hardness as possible. This step minimises the creation of softer zones prone to erode (i.e. with lower hardness values).
There are also problems related to logistics and health and safety surrounding the welding and handling of very heavy tools (some up to several tonnes).
Project Goals and Objectives
The main objective for a repair is to find a way to successfully add weld filler material whilst maintaining most of the base material proprieties, i.e. hardness levels, heat conductivity, superficial colouration, amongst others.
The Process and Insight
The first step is to assess the weldability of the base metal and match it with a type of filler wire. This choice depends, entirely, on the final application of the tool to repair. As mentioned before, the starting point is using the same filler wire alloy, but in cases where the carbon content does not allow for a weld free of cracking, the choice involves choosing a filler alloy capable of resisting cooling stresses.
CWT successfully repairs different alloys and grades daily, alloys such as 1.2767 (45NiCrMo16, AISI 6F7), 1.2344 (X40CrMoV5-1, AISI H13) and 1.2311 (3Cr2Mo, AISI P20) are common examples of materials promptly welded by CWT during while-you-wait services. Additionally, CWT has several laser systems and keeps a broad range of filler wires in stock, which allows for while-you-wait services to be conducted with minimum disruption to daily activities on a wide range of materials.
The local addition of filler material allows the end user to locally machine the tool back to its initial dimensions without the need to create a new tool/ part. The following images show examples of repairs done by CWT.
With a very high success rate, CWT always aims to fulfil its customer’s requirements by reworking their tools/parts or by advising if a repair operation is the best course of action. The following testimonials highlight our fast turnaround and quality services.
“…Really helpful and very quick turnaround time…”
Ken Liu, Mechadyne International.
“…Good price, quick turnaround and good quality of work…”
Chris Curnyn, WHS Plastics.
“…Excellent services provided by Carrs, I would highly recommend…”
Kenny Craig, PMP Interplex.
“…Flexible, efficient service – always do their best to accommodate us at short notice…”
Tanzi Besant, Hiflux Ltd.
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