High strength sheet metal joints
- One-sided accessibility
- Removable and high quality screw joint, without part preparations, such as pre-drilling or punching
- No tolerance problems with clearance or threaded holes
- No material waste and no swarf
- Use with various sheet surfaces
- High loosening torque and vibration resistance, no need for additional safety elements
- Easy removal and recycling
- Repeat assemblies also possible with metric screws
High strength sheet metal joints
Especially in the fast automotive industry, where the used components have to withstand high stress, the demands on fastening technology are high. For example in the car body construction the composite design is on the increase where different materials have to be fastened securely and lastingly. In addition to one-sided accessibility, the removability of the fastener is also very important, especially with regard to recyclability. These complex conditions are a case for the use of the EJOT FDS® (FlowDrill) screw, which fastens thin sheet metals made of steel and aluminium without the need for a pilot hole and in excellent quality. Work steps such as pre-drilling or pre-punching are no longer necessary. Due to the increased thread engagement in the formed draught a high-strength screw joint is created - without the undesired metal chipping. The screw joint is able to transfer high pull-out as well as shearing forces.
Assembly without holes
With the FDS® screw EJOT developed an alternative for the common practice of pre-drilling of the components to be joined. Through an optimisation of the fastener layout the joining of a body-in-white in space frame structure can be carried-out completely without pre-drilling. For this the fastening parameters where adjusted and the geometry of the FDS® screw below the screw head was optimised, since a small amount of the material flows against the fastening direction. While in the past the clearance hole was used for taking up the displaced material it is now absorbed by the increased space below the screw head. Process steps of the FDS® assembly without pilot hole: 1. Warming up2. Penetration of the material3. Forming of the through draught4. Thread forming5. Full thread engagement6. Tightening
Fastening tool selection
A higher screwdriver speed and a defined end load is needed for flow drilling, thread-forming and tightening of the screw require a high torque. The suitable screw drivers have been developed in cooperation by a EJOT and different manufacturers. For exact specification of the suitable tools the FDS® product management will gladly assist you, for determination of the selection criteria we can also carry-out assembly tests in the EJOT® APPLITEC laboratory.
FDS® Application Check
The EJOT FDS® is a flow drilling screw for detachable, high-strength sheet metal joints, which gets by without component preparations like drilling or punching. The online-tool FDS® Application Check enables the user to determine the relevant benchmarks for the screwing task, by naming the sheet metal components that shall be joined. These benchmarks are i.a. the needed pressure force, as well as a recommendation for tightening torque for various surfaces. Comments about the joints feasibility complete the tool.
FDS® WN 21 Head Styles and Drives
WN2141 round washer head with cross recess Z (or H)
WN2142 pan head with cross recess Z (or H)
WN2143 flat countersunk head with cross recess Z (or H)
WN2147 hexagon head with washer
WN2151 round washer head with TORX®
WN2152 pan head with TORX®
WN2153 oval countersunk head with TORX®
FDS® Flow-drill screw assembly with additional sealing function
A pre-assembled embossed aluminium sealing washer, ensures an under-head seal of this special version of the FDS® screw. Current applications can be found in e-mobility in the area of the battery box fastening, where the sealing washer prevents water from entering. The waterproofi ng function (1 m water column / 24H) is achieved by the sealing surface of the aluminium washer. Pre-drilling of the clamping part is necessary for this application.
The diameter of the underside of the washer is smaller in size than the clamping part hole and is therefore outside of the sealing area. Due to the automated feeding, the sealing washer has to be 1 mm smaller in dimension than the head diameter. The captive washer is assembled fully automated, but remains rotatable.