Werkzeugmaschinenbau Ziegenhain – Flexible Gearing of Shafts

For users of machine tools, maximum possible flexibility is without doubt the most efficient answer to constant­ly growing market requirements. This is particularly true for the production of small batches of different workpie­ce variants, because the more flexibi­lity a machine has to offer, the lower the corresponding life cycle costs are to be evaluated. Werkzeugmaschinen­bau Ziegenhain, or WMZ for short, specializes in the development and construction of custom machines for the complete and combined machi­ning of shaft-shaped components. De­pending on the requirement, thread-cutting and deburring work as well as gear cutting using the power skiving or hobbing techniques can be integra­ted in the WMZ complete machining cycle alongside turning, drilling, grin­ding and milling techniques.

Increasing cost pressure combined with shorter achievement times and the de­mand for ever greater manufacturing depth presents both small and large pro­duction companies with new challenges. To be able to survive on the market, invest­ments in new machine tools must be par­ticularly future-proof and flexible. WMZ, a member of the DVS TECHNOLOGY GROUP, offers a wide range of production methods which can be combined for use in one machine thanks to the modular de­sign for the horizontal machining of shaft-shaped components with a length of up to 4500 mm. The resulting combined or complete machining of components leads to significant cost reductions for various reasons.

For one thing, a major share of the ret­ooling, transport and storage times is no longer required, which leads to a signifi­cant reduction in overall machining time. For another, the risk of reclamping faults is almost zero, since the component can ide­ally be made in one single clamping. In ad­dition, the complete machining center has a smaller footprint, which, together with the lower purchasing costs, cuts the capi­tal commitment of the investing company.

Complete machining – save costs

An example: With the machine platform H200 from WMZ, highly efficient turning and gearing work can be done on both ends of a shaft-shaped component by one turning turret and one hobbing unit each. With this example, there is no need to think about how the gearing will be de­burred, because the lathes deal with this. By machining the external contour to­gether with the gearing in one clamping, maximum concentricity of the gearing is achieved. Thus a hobbing or skiving unit can product gearing up to module 7 and quality 6. The milling units on the WMZ machines are equipped with a shift axis to achieve the longest possible service lives. This al­lows the hobbing tool to be used across the entire width without excessive wear. Tool changing should take as little time as possible, which is why the milling cutter holder is equipped with a quick-change system. The time required for hobbing alone can be more than halved by using milling tools with multiple threads.

Power skiving is economical for inter­nal gearing

Hobbing is not suitable for components which require internal gearing or have an obstacle contour. WMZ machines mainly use the power skiving method for cutting gears in such circumstances. The power skiving technology has to measure up to alternative technologies such as broaching or shaping for the requirements menti­oned. Gear shaping proves inadequate, since the technology, which is generally used for machining smaller batch sizes, involves inefficiently long machining times due to the discontinual process.

Broaching of the gearing is extremely in­flexible, because gearing parameters such as the two-ball dimension and thus the quality of the gearing can be exclusively in­fluenced by the geometry of the broach. In addition, broaching tools are very expen­sive to buy. In contrast, the tool costs for WMZ machi­nes with power skiving module are within reasonable limits, since, thanks to a pivo­ting unit, a low-cost roughing tool can be used first for the coarse machining. The subsequent precise machining, which gu­arantees high gearing quality, is then per­formed by a high-precision dressing tool.

In order to avoid high tool costs for power skiving, the parallel tool concept used on the machines from the associated compa­ny PITTLER T&S has proved itself more than once. Good enough reason for the tool concept to be transferred to WMZ ma­chines alongside the gearing technology within the context of constant exchange of technology within the companies of the DVS TECHNOLOGY GROUP.