There is described an efficient and simple method of billing a client for using a computerized numerical control machine. The invoice amount to be billed is based on at least one trajectory of at least one axis during operation, on a volume of a stock removed from a work piece during operation, and on a processing time information related to working on the work piece. One concept of the method therefore is a pay-per-use concept relating the added value created by the computerized numerical control machine to the invoice amount.

For many clients, purchasing sophisticated technical equipment including computerized numerical control machines such as CNC machines, production machinery, industrial plants, turbines, generators, passenger trains, vehicles, home entertainment devices and many more, an important aspect of their purchase decision is the initial investment necessary for acquiring such equipment. Especially complex and sophisticated computerized equipment tends to be very, costly so that some clients are reluctant to purchase because of the necessary high initial investment.

Even high initial investment can be worthwhile if the projected return-on-investment is high enough. But still the initial investment has to be made by the client, if necessary by third party financing which is not always manageable.

One concept of the present invention is to provide a pay-per-use concept relating an added value or productivity created by the computerized numerical control machine to an invoice amount to be billed to the customer. Such pay-per-use concept makes it easier for the client to acquire the computerized numerical control machine as the machine is paid for according to the value it creates during operation and not according to a fixed purchase price or a fixed leasing rate. So even if the invoice amounts are high, it will be no problem for the client to pay because of the also high added value or productivity created by the machine. It is also thinkable that the machine provider provides the computerized numerical control machine to the client solely on the basis of such pay-per-use concept without requiring initial investment by the client.

Acquiring at least one trajectory of at least one axis during operation of the computerized numerical control machine, acquiring a volume of a stock removed from a work piece during operation of the computerized numerical control machine, and acquiring a processing time information related to working on the work piece by the computerized numerical control machine are all indicators of the added value the machine creates when processing the work piece. Pay-per-use in connection with the present invention therefore means not such taking into consideration a usage time. The stock removed includes material which is being removed from the work piece when working on the work piece using a tool (e.g. milling) thus shaping the work piece according to a desired shape.

Added-value is inter alia indirectly indicated by the at least one trajectory of the at least one axis of the machine during its operation. Computerized numerical control machines usually include a number of controllable axes which are moved according to more or less complex moving patterns to process the work piece as required. The trajectory of the at least one axis therefore is a measure for the degree of difficulty involved in processing the work piece. The more difficult the processing, the more valuable the processed work piece. The processed work piece thus includes an added-value compared to the raw work piece.

Another aspect which may be additionally or alternatively included when determining the invoice amount is a productivity of the computerized numerical control machine. Data indicating such productivity are usually available in a memory of the machine during operation and may include operating time, down time, operation during an (expensive) primary processing time, operation during a (less expensive) secondary processing time and processing time for at least one processing step.