Engineering support for direct fastening in light metal 

As valuable support for design engineers and developers EJOT offers prognosis programs for the pre-dimensioning of direct fastening into thermoplastics and light metal. Fastening parameters can be calculated with these tools, by taking the material and design parameters into consideration. Numerous practical examples show that significant savings potential can be achieved with these programs already during the development phase. EJOT ALtra CALC® has been specifically developed for the prognosis of direct fastening into light metal. 

EJOT ALtracs® Plus screws are bespoke self-tapping fasteners for maximum strength of light metal joints up to a hardness of 140 HB (see image I). Based on a comprehensive research and development program, the prognosis program ALtra CALC® (see image II) has been developed specifically for this type of screw. 

On the basis of VDI 2230 many high-capacity calculation programs are available today, but their application range is limited to the calculation of metric screw joints in metallic materials. For the calculation of self-tapping joints the guidelines of the VDI 2230 have only a limited applicability. In particular the process of thread-forming and the specific properties of directly fastened materials are not considered. This also includes various light metals such as aluminium and magnesium. With the development of the ALtra CALC® prognosis program the industry leader EJOT has addressed this problem in order to offer an optimum design aid to the customer. The result is an effective and precise calculation tool, which has already been proven in many applications and is also subject to ongoing optimization and further development. 

Brief characteristics of the possible applications of the ALtra CALC® prognosis program: 

Dimensioning of the screw joint 
For standard dimensioning of the joint, ALtra CALC® calculates with the design guidelines of the EJOT ALtracs® Plus screw (see image III). In practice these specifications often vary. The effect of these variations can be simulated with the program within realistic boundaries. With an integrated material data bank, a selection of many different light metal alloys is available for the calculation of the joint. 

Clamp load oriented design 
The clamp load, the actual "quality criterion" of a screw joint, is the main parameter for the calculation. By specifying the clamp load and information about the mating and clamping material, a reliable calculation of the screw dimension and necessary tightening torque is possible in order to safely reach the specified clamp load in a process reliable way. A reverse calculation, which means the specification of the tightening torque for determination of the clamp load, is also possible. 

Simulation of coating and lubricating effects 
In particular for direct fastening into light metal the screw surface has a significant influence on the resulting torques and clamp loads. The ALtra CALC® prognosis program contains 14 different screw surfaces, which can be optionally combined with various lubricants. Again, in combination with the fastened material and the head connecting surface, the respective friction values are determined which are then used for calculation of the torques and clamp loads. 

Calculation of the optimum assembly parameters 
EJOT ALtra CALC® can calculate different failure modes (e.g. stripping, screw fracture) and the time of occurrence (e.g. clamp load at stripping, pull-out load) - see image IV. With this knowledge it is possible to set the optimum installation parameters with the program in order to minimize the risk for errors and guarantee a process reliable assembly. 

This and other functions for the pre-calculation of screw joints, lead to a clear reduction of development time and thus significant costs savings in component design. Due to the calculation possibilities these savings potentials can be recognized and used early in the process. Over-dimensioning of the screw joint is prevented, material and thus weight is saved. Time-consuming and cost-intensive tests on the component are reduced to a minimum. 

This calculation program is now also available to the customer online under, in addition to other services such as download of CAD data and product information. After the required registration under "CAD & more", design engineers and developers can use the so-called "light version" of ALtra CALC® directly online. "Light", because the tool has been developed for highest possible user-friendliness, so the customer can use it online and independently. For highly complex applications that might not be covered by the light version, the customer can access the complete fastening technology know-how of the EJOT application engineers and of the APPLITEC laboratory. 

Contact Marketing

Andreas Blecher

Team Manager Marketing

Contact Product Management

Rene Gerber

Product Manager Prognosis Programs