The profile question: Even more options than the connections?!
You’ve got the general idea of what you’re building. Now comes the next big decision: which profile is going to carry the load?
Let’s start simple: bigger is of course stronger. But it is also heavier, more expensive, and takes up more space. You might already know one of my golden rules: don’t overcomplicate things. Keep your inventory simple, and don’t try to use a different size for every specific application. One size fits most. That is why I like to stay within two “lines”. Lines define the base dimensions of the profile and the slot size. First a quick diagram of what these profiles look like:
Line 5 - 20x20 base, 5 mm slot
Line 5 is the compact choice. It works well for small frames, light enclosures, panels, sensor mounts, and compact systems where space matters more than brute strength. Think of 3D printers, small storage units, or transporting lightweight items like paintings.
Use it when:
- The span is short.
- The load is light.
- The frame is mostly for support, not for impact or motion.
Line 8 - 40x40 base, 8 mm slot
Line 8 is the all-rounder. It is the first choice when you want a frame that feels solid, stays stiff, and can handle real use without overthinking every load path.
Use it when:
- The frame carries meaningful weight.
- The structure is larger or deeper.
- You need better stiffness against bending and twisting.
- The build may include drawers, doors, motion, or mounted accessories.
If you’re not sure where to start, or you do not yet know the final requirements, go for line 8. It offers the best cost-per-strength ratio and comes in many variants.
Light or standard
What does light or standard mean? Each profile has a certain cross-section.
You can clearly see: light means less material. That makes it lighter, but it also reduces strength. Here is an easy way to understand the effect. Imagine your aluminium profile resting on two supports while you stand in the middle. How much does the profile bend?
| Profile | Dimensions | Type | Force [kN] | Deflection | Limit [kN] | Deflection |
|---|---|---|---|---|---|---|
| 2020-S | 20x20 | Standard | 0.1 | 4.2 | 0.5 | 22 |
| 4040-L | 40x40 | Light | 1 | 3.34 | 3.5 | 11.6 |
| 4040-S | 40x40 | Standard | 1 | 2.1 | 5.5 | 10.7 |
| 4080-L | 40x80 | Light | 1 | 0.44 | 13 | 5.6 |
| 4080-S | 40x80 | Standard | 1 | 0.3 | 19 | 5.6 |
As you can see, for a 1 m long beam the 2020 profile is out of its league for load-bearing applications. The equivalent of just 10 kg already makes it bend visibly, and at 50 kg it reaches its limit. With line 8 profiles, loads around 100 kg are no big deal.
To keep things simple again: light profiles save weight and cost, standard profiles save headaches. If the part only needs to exist, light is fine. If the part needs to hold shape, use standard.
4080 and other heavy members
4080 is for the serious stuff. Use it when one direction needs much more stiffness than the other, or when a member carries the main bending load over a long span.
Good cases for 4080:
- Long horizontal beams.
- Table or machine bases.
A heavy member does not need to be everywhere. Often, the best design is to use 4080 on the long load-bearing sides, then smaller profiles for cross members, braces, and accessories. That keeps the frame strong without making the whole build bulky.
Back to keeping it simple
- Use line 5 for small, light, compact parts.
- Use line 8 for all-round applications.
- Within line 8, start with 4040 and choose according to the job.
- Use light profiles for non-critical support.
- Use standard profiles for load-bearing members with moderate demands.
- If things really get heavy, use 4080 light for long spans, high loads, or parts that must stay very stiff.
- Use 4080 standard for the most demanding applications.
So ready to get started? Check out the profiles here: