Aluminum Extrusion Joints – Design and Assembly Considerations

IPS Aluminum ExtrusionSome people question whether aluminum extrusion joints can withstand the rigors of life in a warehouse or factory. In fact aluminum extrusion joints can be as stiff and as strong as welded joints, but they must be designed and assembled the right way.

It’s often faster to build a frame or structure with aluminum extrusion and t-slot hardware than by welding. What’s more, with extrusion it’s easy to make alterations when something about the application changes.

Using Aluminum Extrusion

Framing extrusion incorporates slots that hold specially designed nuts captive. This permits rapid assembly with brackets, gussets and other t-slot hardware, making it possible to build almost any structure.

Aluminum has a high specific strength. When extruded as square and rectangular section, it’s very stiff and therefore able to support high loads. This makes it ideal, not only for frames and guards, but also for structures subject to fluctuating loads like machines and handling systems.

The issue that must be addressed though, is ensuring sufficient stiffness and strength in the joints.

Joining Aluminum T-Slot Framing Material

Aluminum extrusion is easily joined by screwing a fastener into the end face of a length of material. This only works though when loads are very light. (A frame for an information poster would be an example.) Any appreciable load placed on such a joint is likely to cause twisting or slip. This is avoided by addressing joint configuration and joint friction.

Joint Configuration: Consider the Load

Strength is maximized by directing the applied load down through an extruded section. This means the horizontal load-bearing piece must rest on a vertical or upright piece, which prevents the load-bearing piece from slipping.

A complication arises when three lengths of extrusion meet at the corner of a frame or other structure. Typically a single upright is supporting two horizontal lengths, but only one horizontal length can rest on the upright.

Here the solution is a reinforcing plate between upright and unsupported length, with a fastener going into the end of the supported piece. With this arrangement the fastener takes the load and resists slip, rather than relying on friction in the joint.

Compression Vs. Tension

Most materials and structures are stronger in compression than in tension, and aluminum extrusion joints are no exception. Try to ensure the loads on a joint go down into the extrusion itself rather than stretching or twisting as this will better resist deformation and slip.

Friction Joints

There will be times when this type of joint is unavoidable. When that happens, remember that each fastener can only apply a limited amount of grip. So, to increase the strength of the joint, use more fasteners. This is achieved by fitting plates on the sides of the two pieces.

Plates, Brackets and Gussets

These three types of accessory are used to stiffen, strengthen and reinforce aluminum extrusion joints.

Flat plates hold fasteners going into two pieces of extrusion at 90°. Gussets are machined or cast pieces that mount at the intersection of two or three lengths and fix them in relation to one another. Brackets are 90° pieces that locate one piece of extrusion against another. They provide some resistance to torsion but don’t add strength like a plate or gusset.

Discuss Your Design With Experts

Making a stiff and durable joint in aluminum extrusion means assembling the right components the right way. If you’re struggling to design a frame or structure with the strength you need, or just want someone to review your design, IPS can help. We provide no-cost engineering to generate a complete list of all the parts you’ll need. Contact us to take advantage of this service.

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