ToolGrinding - professional reconditioning of your cutting tools

What are the preliminary requirements for reconditioning a tool?
Around 90 percent of our mono machining tools are suitable for reconditioning. Their suitability depends on factors that include the tool’s geometry, condition and coating. In addition to the technical requirements, we also need to consider whether or not regrinding would be cost-effective. In the case of very low-priced tools, the cost of reconditioning is greater than that of producing new ones in series production. So, as part of our service, we always check whether reconditioning would be more cost-effective for the customer when we receive the tools, by comparing the price of a new tool with the price of reconditioning it. This ensures that the customer gets the most financially sensible option and the tools are not reground if it is cheaper to purchase new ones.

How many times can tools be reconditioned, and are they really “like new” afterwards?
This also depends on certain factors. In my experience, tools can be reconditioned 3 to 4 times. With drills, only the face geometry and the coating are renewed, which reduces the cutting length. They can be reconditioned quite often, depending on how the customer uses the tool. By contrast, milling cutters are reconditioned all the way round – you could almost say they are geometrically scaled. As a result, milling cutters lose both diameter and length each time they are reground, meaning that they cannot go through the regrinding cycle as many times as a drill. The individual geometry of a tool also has a major effect on how many times it can be reground.

For a reconditioned tool to work “like new” again, it is essential to pay attention to every detail. To start with, the user should not keep using the tool in the machine right up to the very last second, as wear increases exponentially towards the end of the tool life. This results in breakouts and cracks in the material’s structure. We all know what it’s like to have a blunt kitchen knife. You have to use more force, and that puts even more pressure on the blade. Micro-cracks in the structure cannot be repaired any more either, which soon leads to breakages when pressure is applied again. As such, to continue using a tool for as long as possible, regrinding is already required when the tool exhibits moderate wear.

The original geometry and the coating have the greatest impact on the tool performance and tool life. Our machining tests have proven that just having a different coating reduces tool life by up to 35 percent. This is also why we only have our tools reconditioned by the manufacturer. If all of the details are kept to, all the way down to the micro-geometry of the blade (where even a couple of micrometres can make the difference), a tool that has been reconditioned can work like new again. However, this is only possible if you have access to the geometric data and the required technical equipment. With coatings in particular, there are often special features that can only be provided when the manufacturer performs the reconditioning. To ensure that we can guarantee this high quality, we have the tools checked by the manufacturer. If reconditioning is not financially worthwhile, then they are sent back to the customer without being processed and with no costs incurred. In this case, purchasing a new tool is the better option.

Roughly what percentage of tools sold are reconditioned during their lifespan?
Not enough, if you ask me. For one, reconditioning saves very valuable resources and raw materials. What’s more, a well-reconditioned tool offers the customer a lot of potential to make savings on the tool costs. At present, less than 10 percent of tools are reground. That said, it’s difficult to come to a reliable figure, as not all of the tools that customers buy from us are reconditioned using our service. But this rate is increasing, in part because the latest generations of high-performance machining tools are not designed to be disposable products.

How are you in the regrinding service responding to the challenges of digitalisation and Industry 4.0?
We will offer a new service from this summer onwards. To facilitate it, we have completely digitalised our processes in recent years. Before being reground, a data matrix code is lasered onto the tools in accordance with the VDMA (German Mechanical Engineering Industry Association) standards. We then create a digital twin, providing the tool with a globally unique ID. We are connected with our partners via a Hoffmann Group cloud solution that has automatic interfaces, enabling us to map the whole value creation chain. This will let our customers track the order status digitally in the future, for example. At the same time, we have laid the foundation for using the tools in other digitalised production processes.