Designing with TSlot Aluminum Extrusions
Tslot aluminum extrusions generally enable quick design and manufacturing of structural frames, but their design can have a huge effect on overall structural integrity. Below are our three top design tips for creating reliable, rigid, and industrialgrade tslot aluminum extrusion structures.
1. Choosing the right extrusion profile
Not all extrusion profiles are created equal. Two profiles might have the same outer dimensions—45 x 45 mm, for example—but very different rigidity, depending on their area moment of inertia.
Another key aspect to consider is the crosssectional area, which affects the overall weight of the assembly. Since the best profiles are highly rigid and lightweight, the best performance indicator is the area moment of inertia to surface area ratio. The table below lists some key parameters for five wellknown extrusion models.
VENTION V2 
Extrusion A 
Extrusion B 
Extrusion C 
Extrusion D 


Profile Dimensions (mm)  45 x 45  45 x 45  45 x 45  45 x 45  45 x 45 
Material (aluminum)  6005T5  6560T6  6105T5  6063T5  6063T5 
Profile area (mm2)  761  563  757  571  737 
Area moment of inertia (mm4)  162,325  107,780  139,310  109,635  141,720 
Torsional constant (mm4)  31,851  19,394  31,042  19,836  39,719 
Weight per meter (kg)  2.06  1.63  2.05  1.55  2.03 
(Area moment of inertia) / (Surface Area)(mm2)  213  191  184  192  192 
Max deflection (500mm cantilever) at 1500 N force (mm)  5.58  8.28  6.50  8.25  6.30 
Stress (500mm cantilever) at 1500 N force (MPa)  103.96  156.57  121.05  153.48  117.11 
Torsional displacement (1m length) at 50 Nm torque (degrees)  3.46  5.68  3.55  5.55  2.77 
Vention currently offers six extrusion sizes. Our 45 mm series of extrusions suit many applications, from industrial furniture to robot range extenders. There are three sizes of extrusions using 45 mm increments—45 x 45 mm, 45 x 90 mm, 90 x 90 mm and 180 x 22.5 mm—all share the same mounting hardware.
Our lightduty extrusion profile, 22.5 x 22.5 mm, is useful for applications with low loads and low weight limits. See the following table for a detailed breakdown of each profile’s properties.
Part Number  Length range (mm)  Yield strength (MPa)  Area moment of inertia (mm^4)  Torsional constant (mm^4)  Weight per 45 mm  Fastener size  

STEXT006XXXX  45–1,530  140  8,885  2,043  20.1 g  M8 x 1.25  
STEXT101XXXX  452,295  240  103,180  29,000  63.87g  M8 x 1.25  
STEXT001XXXX  45–2,295  240  162,325  31,851  92.5 g  M8 x 1.25  
STEXT002XXXX  45–3,330  240  1,111,757 Ix 287,967 Iy***  189,708  149.4 g  M8 x 1.25  
STEXT005XXXX  45–3,330  240  1,850,913  941,414  228.6 g  M8 x 1.25  
STEXT009XXXX  45–1,530  240  77,150 Ix 3,783,293 Iy*  52,788  162.9 g  M8 x 1.25 
45 x 45 Light Duty Extrusion
The new 45 x 45 mm Lightduty (STEXT101XXXX) is Vention’s newest offering extrusion profile, allowing for an alterative 45 x 45 profile that is perfect for applications with lower loads and weight limits. With a profile area reduction, and in turn weight per 45mm length, of 31% the 45 x 45 Lightduty offers a best in class balance between the lightweight nature of the profile and the structural rigidity based on weight. 45 x 45 Light duty extrusions are identified with a Light Duty informative label.
Tabletop Extrusion
The 22.5 x 180 mm tabletop aluminum extrusion is perfect for workstation table tops, CNC worksurfaces, machine tending workstations, and more. It provides a large mounting surface with evenly spaced tslots, which are ideal for modular jigs and fixtures.
The tabletop extrusion tnut profile, vgrooves, and spacing follow Vention standards, making it compatible with all gussets, assembly plates, and frame accessories.
Although only 22.5 mm thick, this extrusion is still capable of supporting robots that produce 1800 Nm of estop torque (Yaskawa HC10 for instance). That is, as long as support extrusions are installed running perpendicular to the tabletop. For maximum strength these joists should be placed a maximum of 315 mm apart (distance L) and attached firmly attached to the machine frame.
When simply supported a table top extrusion of 1530 mm length can support a load of 100 kg. For increased load capacity add supports at consistent intervals.
To mount the tabletop extrusion flush with 45 mm extrusions, use the 67.5 mm gusset (STHP0030007). In order to achieve the proper spacing, a 45 x 90 mm or 90 x 90 mm extrusion is required.
Tabletop extrusions have a total of nine tslots, which allow many different mounting options.
Calculate the safety factor
You must always add an adequate safety factor (SF) for your situation. For instance, if a structure will theoretically fail at 1000 N of force, a safety factor of two would establish an allowable load limit of 500 N. Safety factor is a measure of how confident you are of your calculations.
Safety factors should be based on (but not limited to) the following variables:
 Calculation accuracy and thoroughness.
 Environmental conditions.
 Consequences of failure.
 Cost of overbuilding.
⚠️ Important: Determine safety factors according to your industry’s standards. Always increase the safety factor if there is any risk of injury occurring due to system failure.
Calculate bending stresses
To evaluate whether a profile meets your design requirements, use free body diagrams and basic static calculations to estimate the applied load on the structure. Do the same for each individual extrusion.
Once determined, use the formulas below to calculate the maximum deflection and bending stress for each of your applicationcritical extrusions.
Where:
Variable  Description  Value  Unit  Notes 

Vmax  Maximum deflection    mm  
L  Extrusion length    mm  
F  Applied force    N  
E  Young modulus  68,900  N/mm^2  Aluminum 6063T5 
I  Area moment of inertia  see table  mm^4  
σmax,bending  Maximum bending stress    N/mm^2  
c  Distance from neutral axis  22.5  mm  Applicable for 45 x 45 mm profile 
Compare the max bending stress with the material’s yield strength to estimate your extrusion’s capacity to withstand the required load. For Vention’s V2 6005T5 aluminum extrusions, for example, a calculated bending stress of 65 N/mm2 is well below the material’s 240 N/mm2 yield strength.
Remember, however, that this is only an estimate, since it does not account for other important factors like the extrusion’s own weight and shear stress.
Calculate buckling strength
When calculating the strength of a structure it is important to consider buckling. Buckling occurs when a long vertical beam is compressed by a force. The beam tends to bend outwards, which further reduces its structural integrity, leading to sudden failure. This failure is most likely to happen with vertical beams, because the load due to gravity is larger than the other forces acting on the structure.
Calculate the max allowable buckling load using Euler’s critical load formula. First, determine which end conditions match your scenario based on the joint types. Then use your chosen extrusion profile’s column length factor and area moment of inertia to calculate maximum load capacity.
Third, compare the max load capacity to your expected force from a free body diagram, and determine the safety factor. Your safety factor should exceed standards for your industry.
2. Choose the right joint configuration
Selecting the right extrusion profile is only part of an effective structure. The assembly joint configuration can also substantially change the rigidity and structural integrity of a design.
Avoid relying on frictionbased joints to support the load. Instead, position one extrusion on top of another, as shown below. Force is transmitted directly from the horizontal extrusion to the vertical extrusion increasing strength.
❌ Friction joint (not recommended): Lower strength; force transmitted through friction between plate and extrusion.
✔️ Reaction forcebased joint (recommended): High strength; force transmitted directly to the frame via contact with vertical extrusions.
When frictiononly joints are unavoidable, the strength of the joint is dependent on the number of fasteners multiplied by each fastener’s friction force. Each Vention M8 fastener (the type used in extrusions) can support 2100 N in friction.
In the friction joint example above, each fastener can generate 2,100 N of friction when tightened to 13 Nm, the horizontal beam can support a maximum load of 12,600 N (that is, 2,100 N per fastener x 6 fasteners). Consider the total amount of force needed to support your desired load, and divide it by 2100 N to find the number of fasteners you will need. This number will tell you which size assembly plate to choose, from onefastener plates to eightfastener plates.
Calculating the necessary assembly plate size is a great way to optimize the cost of your design. You might be tempted to choose the strongest assembly plate available, but you can save costs by going with one that only fits the amount of fasteners you need (and no more). Our application engineers routinely reduce costs by up to 15% just by replacing six, seven, or eightfastener assembly plates for ones with fewer fasteners.
If possible, transform a frictiononly joint into a stronger threeway joint by threading one of the fasteners directly into the extrusion’s end. By uniting three different extrusions in such a configuration (i.e., one vertical and two horizontal), none of the plates depend on friction alone.
✔️ Strong threeway joint: one bolt threads directly into the end of the extrusion.
❌ Weak frictiononly joint, bolt does not thread into the extrusion end. (These are sometimes unavoidable.)
In some cases, joints may undergo a force that pulls the bolt and tnut out of the extrusion. The extrusion’s resistance to this force is what we call “pullout strength.” This “ultimate strength”—the point at which complete failure occurs—is given on a perfastener basis.
For Vention V2 extrusions, the ultimate strength is 16.7 kN. However, designs should not be based on this value, because even much lower values can permanently damage the extrusion.
We recommend a design value of 7.2 kN per fastener. This value is lower than the material’s yield point, so no permanent deformation will occur. As with all design values, remember to apply a safety factor.
Ultimate strength is also affected by the direction of load. Whereas bolted connections under tension will fail when the pullout strength is exceeded, compressed connections can withstand much higher loads, because the force is directly supported by the extrusion. As shown below, placing the assembly plate correctly with respect to the load will maximize strength.
Max load is 2 x 7.2 kN, because two bolts are sharing the tensile load.
Max load is just 1 x 7.2 kN, because one bolt is supporting the entire tensile load.
3. Use highstrength extrusion systems for demanding applications
Combining effective assembly joints with the appropriate extrusion profile can improve the structural integrity of your assemblies. For heavyduty or precise applications, Vention’s highprecision assembly plates (part numbers STHPXXXXXXX) feature a patented Vshaped boss (protrusion) on the plate underside.
 Eliminates angular misalignment, because it is no longer necessary to locate plates by their screw’s loose clearance holes.
 Increases slippage resistance, by converting frictionbonded joints to structurally bonded joints.
Many plates come in GP (general purpose) and HP (high precision) variants. Your choice depends on whether you want to optimize for lower price (GP) or higher strength and precision (HP).
4. Structural joint design guide
Use the following tables to determine the strength of single sided jointed connections when subjected to moment, torsion and friction forces. The values are valid for the following assumptions:
 For moment loading, the load is created by a vertical force applied on a beam 1000 mm from the joint.
 For friction loading, the load is created by a vertical force directly on the joint, with negligible torsion or moment.
 Given values for strength are valid for structural extrusions: STEXT001XXXX, STEXT002XXXX, and STEXT005XXXX.
 Values for strength are the force at which plastic deformation begins to occur. This is the point where permanent damage starts, and should be avoided by using a safety factor.
 Values listed for “GP” / “HP” correspond to gussets that are either Generalprecision or Highprecision, respectively. More detailed information about these components can be viewed in Section 3 of this document.
** Important: Determine safety factors according to your industry’s standards. Always increase the safety factor if there is any risk of injury occurring due to system failure</strong>. A minimum safety factor of 2 is recommended.
Gussets 
STGP0030001 / STHP0030001* 
STGP0030001 / STHP0030001* 
STGP0030001 / STHP0030001* 

Friction, F (N) GP / HP 
2100 / 2100  2100 / 2100  Buckling Failure** 
Moment, M (Nm) GP / HP 
127 / 127  112 / 112  127 / 127 
Torsion, T (Nm) GP / HP 
0 / 10  0 / 10  0 / 10 
Plates 
STGP0010005*** 
STGP0030001*** 
STHP0010001*** 

Friction, F (N)  6300  6300  4200 
Moment, M (Nm)  235  725  325 
Torsion , T (Nm)  70  85  45 
Other 
STGP0020001 
STGP0010004*** 
STHP0010001 
STHP0010001 

Friction, F (N)  4200  4200  2100  2100 
Moment, M (Nm)  100  215  100  500 
Torsion, T (Nm)  165  65  390  390 
*: These configurations assume no contact between the extrusions, which is common in assembled structures.
**: This configuration is more dependent on a buckling failure mode than friction. Use the calculation methods for buckling shown in Section 1 of this document.
***: The values for these configurations are for joints fixed by an assembly plate on a single side.
Conclusion
Aluminum tslot extrusions have become a compelling alternative to welded steel for many applications, but they require a few design considerations. If you need any help with your project, or simply want to confirm some design parameters, you can ask our team of application engineers for free using Vention’s live chat or email us at: support@vention.io
Vention V1 extrusion properties
Part Number  Length range (mm)  Yield strength (MPa)  Area moment of inertia (mm^4)  

V1 45x45mm Aluminum Extrusion  STEXT001XXXX  45–2,295  140  154,260 
V1 45x90mm Aluminum Extrusion  STEXT002XXXX  45–3,330  140  1,105,496 Ix*** 
V1 90x90mm Aluminum Extrusion  STEXT005XXXX  45–3,330  140  1,840,143 
*Area moment of inertia (or the second moment of area) describes a profile’s resistance to beam bending. A higher value indicates less deflection.
***Note: The 45 x 90 mm and 22.5 x 180 extrusions’ moment of inertia depends on the extrusion’s orientation.