Excellent resharpening service

Poor cut quality is the most important reason for replacing tools. At the same time, phenomena such as loud operating noises and visible wear indicate that it is the right time to resharpen.

There are various indicators that a tool has reached the end of its edge life. The most obvious is usually the cut quality on the workpiece. If this is no longer acceptable, the user generally decides to replace the tool.

Further indicators include increased noise development and power consumption by the equipment as well as signs of wear (for instance, rounded cutting edges and chipping of the cutting edge) on the tool. The user with corresponding empirical values has the opportunity to establish for himself fixed criteria as the reason for a tool change. This includes, for instance, a specific value for the power consumption.

Standardized replacement cycles for all tools make sense for large production facilities in particular. They prevent machine downtime due to unscheduled tool changes.

Large plants specify a fixed time for a tool change. Doesn't this result in high tool costs when the tools are not used to the end of the edge life?

No, since before a time is specified, test series are used to determine the average edge life. These empirical values then provide the basis for establishing the "most ideal" change point. This tool change takes place before the quality of the workpiece is affected. For large plants with a high output, unscheduled machine downtime as the result of reaching the end of the edge life abruptly costs more than repairing the tool (possibly) prematurely.

The benefits of scheduled tool changes are obvious: personnel can be scheduled and prepare for the tool change, the process planning department can take the tool change into consideration in relation to production planning. In addition, the so-called "overuse" of tools is prevented.

The first step to achieving longer edge life is to select of an optimized tool. Good maintenance also contributes to a longer useful life of tools.

What are the options for increasing the edge life of tools on existing machinery? It is first necessary to check what kind of tools are currently in use and what material mix is being processed. In most cases, it is possible to use tools with a geometry optimized for edge life. For instance, as a rule, the greater the tool's shear angle, the longer is the tool's edge life.

It is also frequently possible to better utilize underused cutting edges on the tool by adjusting the height. Moreover, various versions of adjustable milling tools where unused cutting edges can be repositioned from the outside to the inside to extend the useful life have been available on the market for some time.

However, the quickest and easiest way to extend edge life is to clean the tool regularly. What may erroneously be considered a dull tool can frequently provide good cutting quality again after the cutting edges have been cleaned.

Hoggers impress through their long edge lives at high depths of cut. On the other hand, jointing cutters achieve better surface quality. That is why many machines work with a combination of both tool types.

Hoggers and jointing cutters differ primarily in the way in which they are used, but both are used to size the workpiece. Is it true that hoggers usually have a considerably longer edge life than jointing cutters?

As the name hogger already indicates, this tool is used basically to remove large amounts of material, since the depth of cut does not have an adverse effect on the edge life. This is an advantage over jointing cutters, since the size of the depth of cut has a direct effect on their edge life. This means: The deeper the depth of cut, the shorter is the edge life. If the depth of cut during industrial sizing is always greater than 2 mm, use of hoggers makes sense to achieve a satisfactory edge life.

Because of the way they are used, hoggers usually achieve a better, smoother core layer quality. Jointing cutters, in contrast, achieve a better top layer quality. Since the latter usually has priority in the quality assessment of workpieces, most users favor jointing cutters for finishing.

Therefore, for a depth of cut > 2 mm, double hoggers for pre-sizing followed by a joining unit for finishing in the tenths of a millimeter range can frequently be found on the market. This concept usually achieves the longest tool edge lives.

Using tools beyond the wear limit has adverse effects on tool life. Replacement at the right time and resharpening are worthwhile.

What constitutes overuse of a tool? This expression means that a tool has been used beyond the "healthy" wear limit. Generally, a tool in new condition exhibits almost no wear at first; then wear increases linearly with duration of use. At some point, the wear phase reaches a condition where the degree of wear increases exponentially and significant chipping occurs frequently, since the tool no longer works properly. The phase of exponential wear is designated "overuse".

Can a tool that has been "overused" be repaired again? Usually, yes! It depends on the resharpening area still available. Unfortunately, it is frequently necessary to remove more material from overused tools in order to eliminate the deepest chip. As a result, the tool loses even more resharpening area and the number of times it could be resharpening again than would have been the case if the tool had been changed.

Every time a tool is resharpened, the service life of the tool is extended, thus saving the cost of a new tool. This means that it is worthwhile from a cost standpoint to change a tool somewhat earlier!

The edge life of tools depends on factors such as machine type, processing parameters and quality requirements. This means that plants can affect the useful life of their tools in many ways.

Major factors that affect the edge life include:

Processing parameters: The material type of the workpiece to be processed has a major influence together with the basic sizing concept, for instance, hogging or joining or a combination thereof. Depending on the concept, the depth of cut during processing affects the edge life significantly.

Machine type and condition:
In addition, the machine type, i.e. tradesman model or industrial model, plays a role in determining the edge life. The same holds regarding the machine's condition: Older machines may already show signs of wear and higher tolerances, which can result in shorter edge life.

Type of tool clamping:
The more exact the interface between tool and machine, the lower are the radial and axial run-out, and thus the maximum achievable edge life of a tool.

Type of tool and tool geometry:
The cutting material used on the tool, e.g. tungsten carbide or diamond, has a major effect on the edge life. There are also tool geometries that provide long edge life and others that are more prone to wear.

Degree of tool soiling:
The greater the tool soiling, the shorter is the edge life, since the cutting edge geometry that existed when the tool was new can be used to only a limited extent because of deposits.

Quality requirement of the customer:
The quality requirements that the workpiece being processed must satisfy differ greatly from customer to customer and depend on the use and quality expected of the product produced. Tool life is generally longer when requirements are less demanding than when very high quality standards must be met.

Most of the factors mentioned differ with every user!

That is why no specific value can be given for a tool's edge life. After consulting with the customer, however, the tool manufacturer can offer the best possible tool design for the particular application.

The height of the resharpening area often decides how often a tool can be resharpened. In actual practice, whether a tool can be resharpened depends on the tool and machine. Many offers from tool manufacturers state the tipping height, i.e. the resharpening area, sometimes there is no information whatsoever in this regard.

What information actually helps me as a purchaser further?

The tipping height only designates the height of the HW or DP cutting inserts used, but does not directly say anything about the number of times resharpening is possible. After all, the cutting inserts cannot be used until there is nothing left. From the customer's standpoint, what is relevant is to know the actual resharpening area in order to compare tool offers one to one. If the resharpening area is not stated explicitly, it makes sense to ask, since the height of the resharpening area has a direct effect on the overall service life of a tool.

Why don't all tools have the same, maximum possible resharpening area? The cutting material is generally the most expensive material in terms of the overall costs of the tool. The higher the resharpening zone, the more mm² of diamond, for instance, are needed, and thus the higher are the costs of the new tool. In addition, there are machine types on the market that cannot compensate along the axis of the motor for a severe reduction in diameter as the result of frequent resharpening. This means: a high resharpening area sometimes cannot even be fully used. This can be the case, for instance, on small edge banding machines used in the woodworking sector.

Tools from LEUCO have resharpening zones with various heights. They differ depending on the product line. Industrial tools can be resharpened very frequently.

What is the range of resharpening areas on sizing tools from LEUCO?

In the case of jointing cutters, for instance, LEUCO has various product lines in its program. These differ in their design in terms of shear angle , manner of clamping and resharpening area. The range extends from a diamond introductory model for tradesmen to tools for industrial applications.

The resharpening zones vary, depending on the value of the particular product line, and range from 1.5 mm to 3 mm and 4 mm. Tools such as hoggers, for instance, that are used exclusively in industrial applications all have the maximum resharpening zone of 4 mm.