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Global fastener specialist EJOT has two products which in combination make it much easier for designers and engineers to optimise the strength and speed of automated fastenings into thermoplastics.

EJOT’s DELTA PT® screw is a high-capacity, self-tapping fastener for strong and reliable direct fastening into thermoplastics and DELTA CALC prognosis software has been developed by EJOT to support designers at the pre-engineering modelling stage, by enabling clamp loads to be accurately calculated for thermoplastics applications using the DELTA PT® screw. Its early use produces significant cumulative cost savings.

The rationale for DELTA CALC was that existing similar software tools were geared to the requirements of international engineering standard VDI (Verein Deutscher Ingenieure) 2230, which primarily addresses screw joints in metals. Its guidance has little applicability to self-tapping joints in plastics.

In particular, VDI 2230 has no guidance about how the properties of thermoplastic materials affect the process of thread-forming.

EJOT’s R&D, based on data from many thousands of applications and test assemblies, has shown that reliable clamp load calculations are perfectly possible for direct fastening of DELTA PT® screws into thermoplastic material. From this R&D the DELTA CALC tool emerged to offer optimisation and time-and-cost-saving benefits to industrial designers.

The DELTA CALC® software tool is powerful enough to have multiple applications but its essential characteristics are:

Design of the boss hole

For dimensioning of the boss hole, the default DELTA CALC® calculation applies the design guidelines of the EJOT DELTA PT®. In practice, these often offer scope for variations, the effects of which can be simulated by DELTA CALC (see image II). Its internal database makes around 350 different thermoplastics available for calculation of the joint.

Clamp load design  

Clamp load is the main quality criterion of a screw joint, and so is the primary focus of DELTA CALC®. By specifying the clamp load and the mating and clamping material, the screw dimension and tightening torque required for process reliability can be calculated. A reverse calculation – working from a specified tightening torque to the clamp load – is also possible with DELTA CALC®.

Optimum assembly parameters

DELTA CALC® is able to predict the potential for different failure modes, such as thread stripping or screw fracture, and the exact point of their occurrence – for example, thread stripping at or beyond clamp load. This feature makes it possible to optimise installation parameters to minimise failure risk and ensure process-reliable assembly.

Predicting long-term performance of a screw joint

Clamp loads created by tightening torque can decrease over time owing to the natural relaxation of thermoplastic materials. Changes in temperature can also have an effect. Rates of loss can be predicted with DELTA CALC and mitigated against.

Advantages of DELTA CALC

Use of EJOT’s DELTA CALC software to pre-calculate DELTA PT screw joints can significantly reduce component design, development and testing time. The ability to use data to optimise assembly also prevents over-dimensioning of screw joints.

Cumulatively, there are multiple cost savings in material, weight, error correction and development time. Even these cost savings can be calculated!

DELTA CALC also makes a unique contribution toward quality improvement.

Try DELTA CALC ‘lite’ for free right now

DELTA CALC is available to EJOT customers online.

Simply visit follow the ‘CAD & more’ link and either login or register.

This gives free access to a ‘lite’ online version of DELTA CALC. It is designed for maximum user friendliness so that it can be tried out immediately and independently.

For more complex applications that may be beyond the scope of the ‘lite’ version, simply contact EJOT and ask for advice and support.

Tel: 01977 687040
Fax: 01977 687041

Since 1922 the German owned EJOT Group has grown to become arguably the largest original manufacturer of fasteners and fastening solutions that span multiple sectors and individual markets including Automotive Engineering, Consumer Electronics and the Construction Industry.

Here in the UK the company’s philosophy of market proactivity is evidenced by its product range and its support to designers, manufacturers and OEMs. EJOT has gained widespread approval for application specific products, achieving technical compliance through comprehensive development procedures, gaining acceptance from engineers and procurement alike. Technical testing, development and support is provided by the EJOT Applitec Centre which is based within the company’s UK manufacturing centre in North Yorkshire, with additional expertise provided by sister laboratories around the world.

Advanced fastening solutions for engineering

EJOT’s product and service capability to industrial engineers is based on cost-reduction through intelligent purchase. The realtime cost of managing a fastener impacts in five critical areas; the fastener itself, assembly, quality of joint, procurement and logistics. EJOT’s ability to create either one-sided assembly or part-reduced solutions means its products consistently deliver significantly higher performance resulting in genuine ‘bottom line’ savings. This way, cost reduction does not equate to a lowering of quality.

EJOT’s traditional engineering product portfolio includes high quality fixings for thin sheet through to cast metals, alloys and thermoset plastics. The technology to ‘build lighter, build stronger’ has seen the company develop market leading solutions for fastening into lightweight materials such as EPP foams and honeycomb composites. Leading manufacturers from the automotive industry are now adapting EJOT’s licenced EJOWELD technology for joining high strength boron steel to lightweight aluminium.

EJOT provides sophisticated prognosis and forecasting software bespoke to the company and exclusively for customers to benefit by. Application Engineers assist with project development from concept to production line.

By reducing the inspection required and also the number of unnecessary parts needed, procurement and inventory management also becomes much easier. Pre-engineering, or tear-down analysis can be freely undertaken from the initial consultation. Project management is led by experienced application engineers who are supported by the Group’s unique and highly sophisticated development arm Applitec, with sister laboratories based in Germany and at the Group’s UK base near Leeds.

Applitec research and development centre

Ejot products are high in quality, always corresponding to current technical standards by investigation and development. The competitive market and changing demands require a fast response to maintain this quality and to meet Global standards — often before they are even issued. It is for this reason that EJOT developed its own unique Applitec facility in the UK. It’s here that testing for all aspects of fastener technology, from simple dimensional and three-dimensional analysis to testing the mechanical, structural and material dynamics of properties of the product and performance in application.

Globally EJOT operates 15 manufacturing centres in ten countries, employing over 3,100 people. In addition to the manufacturing operations the Group has 34 subsidiaries in 32 countries, with six research and testing centres in strategic locations. EJOT has also developed partnerships with several academic institutions, aimed at maintaining the development of advanced fastening solutions for the future.

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