Laser hardening has gained significant traction in the United States, becoming a favored method among OEMs and smaller tool and die makers. Each die is unique, requiring the laser to follow precise paths at specific angles and orientations to ensure quality. Robots are commonly used for this process due to their flexibility. This article explores two primary methods of robotic programming used in laser hardening operations and highlights the advantages of one approach over the other.

Methods of Programming Robots for Laser Hardening

Robotic tool path motion for dies is typically programmed in one of two ways:

  1. Tool Path Software Programming – this requires our vendor to supply with CAD model
  2. Manual Touch-up – Moving the robotic head to each point and saving the position manually – this does not require a CAD model from our vendor.

Advantages of Tool Path Software Programming Over Manual Touch-up

  1. Reduced Lead Time

With tool path software, the robotic path can be simulated and tested before the dies even arrive. This preemptive approach significantly reduces lead time for customers. In contrast, manual touch-up requires the die to be physically present, often adding substantial delays. Additionally, Synergy’s capability to run dies in a lights-out operation further accelerates delivery times.

Picture 1: Tool path motion simulated and tested in software prior to receiving the die thereby reducing the lead time. 

  1. Optimized Laser Start, Stop, and Overlap Locations

When laser heat treating circular profiles and circumferential profiles such as draw beads,  the laser often returns to its starting point, resulting in overlap. This overlap can cause a loss of hardness due to annealing at start/stop area. Precise tool path motion is crucial for this optimization, which is difficult to achieve with manual programming. When programmed using manual methods, our OEM customers have seen excessive hardness loss, larger soft spots on the die which reflected on Class A panels after certain duration of time. Synergy has conducted extensive process development and optimized the tool path programming strategies at the overlap regions resulting in minimal loss of hardness. Tool path programming results in retaining extraordinary consistency and repeatability. Synergy’s recipes have been proven over last 6 years of operation with OEMs and eliminated quality issues resulting from manual programming.

Picture 2: Simulation of circumferential paths with minimal overlap regions 

  1. Consistency of Hardness Profiles

Stamping dies often require hardening on male radii, which can range from 3 mm to 25 mm or more. To properly harden these critical areas where metal rubs against the die with the most force, it’s essential to orient the laser beam accurately. Tool path programming ensures a consistent and precise angle of incidence and uniform travel speed of robot motion whereas manual touch-ups rely on the operator’s judgment, potentially leading to poor locational accuracy and non-uniform hardness depth. Tool path programming  guarantees consistent laser beam travel speeds around complex tool motions, resulting in superior consistency in hardness values (+/- 1 HRC). Manually achieving this consistency, especially in complex profiles, is both challenging and time-consuming.

  1. Consistent Overlap in Surface Areas

Laser hardening of binder and cavity surfaces is often necessary for stamping dies, especially when working with materials like aluminum. When hardening large surface areas, overlapping previously hardened laser paths becomes essential. However, these overlap regions can suffer hardness loss due to the next laser pass annealing the previous one. A steep contrast between hard and soft regions can result in a wavy pattern on the stamped part, requiring significant post-processing by the die maker.

Through extensive research, Synergy has developed process recipes that effectively minimize distortion and hardness loss in these areas. Our approach involves precisely laying hardening tracks of the correct size and heat, ensuring accurate placement to reduce soft spots and prevent wavy patterns.

Compared to manually programmed dies, Synergy’s tool path-programmed dies demonstrate significantly less distortion and minimal hardness loss in overlap regions. Tool path programming has also eliminated the need for the extensive stoning often required with manual programming. This level of consistency and precision is only achievable through tool path programming.

 Picture 3: Laser hardening of large surfaces with precise overlap, ensuring uniform hardness and minimal distortion. In contrast, manual programming often results in inconsistent overlaps, and requirement for excessive stoning.

  1. Performance of Trim Dies and Inserts

Laser hardening of complex trim dies and inserts requires precise locational accuracy. Any misalignment in the laser beam placement can result in reduced hardness depth, which in turn affects die performance. Inconsistent or shallow hardness at the trim edge can significantly shorten die life. Manual programming of trim profiles is prone to operator errors, increasing the risk of misalignment and subsequent die life issues.

Over the years, Synergy has successfully laser-hardened numerous trim profiles with virtually no quality issues. Our proven process consistently achieves a uniform hardness depth of 0.040″ to 0.060″ (1 to 1.5 mm) on the cutting surface, ensuring long-lasting, high-performance dies.

trim die laser hardening

Picture 4: Synergy’s optimized tool path programming on trim dies and inserts ensures consistent cutting edge depth and hardness. In contrast, manual programming often leads to variability in hardness and increased risk of performance issues.

  1. Cost Considerations

Manual touchup programming is cost-effective for smaller, simpler tools. However, as die complexity increases, tool path programming and lights-out operations offer substantial value to customers both in terms of cost, quality of workmanship and turnaround times.

Summary

While tool path programming the robots add additional burden to customers to provide CAD data to Synergy, our OEM customers have observed that robotic laser hardening programmed with tool path software can prevent long-term die performance issues such non-uniform wear, wave like patterns showing up on Class A parts, excessive stoning requirements etc. The durability and performance advantages of dies programmed with tool path software far outweigh manual programming the dies.