ᐅ Why does the center divider sometimes bend on the KALLAX?
Created on: 21 May 2024 18:47
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Ottfried61O
Ottfried6121 May 2024 18:47I have noticed that the central divider in some compartments of my IKEA KALLAX shelf sags visibly over time, especially when heavier items are stored inside. My question is: why does the central divider sometimes bend in the KALLAX?
I am especially interested in whether the material is designed to handle this kind of load, if it is structurally intended, or if it could be due to improper use. Are there specific load limits or recommendations that should be followed? Could environmental factors such as moisture or installation errors be relevant?
The shelf is freestanding, not fixed to a wall, and overall it seems well made, but the central divider appears weak to me. I would appreciate technical explanations or practical advice to prevent permanent sagging.
I am especially interested in whether the material is designed to handle this kind of load, if it is structurally intended, or if it could be due to improper use. Are there specific load limits or recommendations that should be followed? Could environmental factors such as moisture or installation errors be relevant?
The shelf is freestanding, not fixed to a wall, and overall it seems well made, but the central divider appears weak to me. I would appreciate technical explanations or practical advice to prevent permanent sagging.
The central dividers in KALLAX units are made of particleboard, which is not designed to support high point loads.
Avoid placing heavy objects in the middle of the compartments and try to distribute the weight as evenly as possible.
Wall mounting adds extra stability to the shelf and reduces stress.
Avoid placing heavy objects in the middle of the compartments and try to distribute the weight as evenly as possible.
Wall mounting adds extra stability to the shelf and reduces stress.
Good morning! I would like to provide a more detailed explanation:
1. Structural Material: The central supports are usually made from MDF or particleboard with a thickness of about 12 mm (0.5 inches). These materials have limited bending strength, especially under heavy loads over extended periods.
2. Load Distribution: It is important that heavy loads do not rest solely on the central support. The weight should be evenly distributed to reduce the span and minimize bending stress.
3. Installation & Use: If the shelf is not attached to the wall, this can lead to higher stresses or twisting in the frame, which places additional strain on the supports.
4. Moisture: Damp environments can cause the material to swell, reducing its stability.
Summary: The central support is stressed due to the relatively thin material thickness, localized loads, and possibly missing wall attachment or moisture. Using a strap or wall mounting, as well as avoiding heavy loads directly on the support, are the most effective measures against sagging.
1. Structural Material: The central supports are usually made from MDF or particleboard with a thickness of about 12 mm (0.5 inches). These materials have limited bending strength, especially under heavy loads over extended periods.
2. Load Distribution: It is important that heavy loads do not rest solely on the central support. The weight should be evenly distributed to reduce the span and minimize bending stress.
3. Installation & Use: If the shelf is not attached to the wall, this can lead to higher stresses or twisting in the frame, which places additional strain on the supports.
4. Moisture: Damp environments can cause the material to swell, reducing its stability.
Summary: The central support is stressed due to the relatively thin material thickness, localized loads, and possibly missing wall attachment or moisture. Using a strap or wall mounting, as well as avoiding heavy loads directly on the support, are the most effective measures against sagging.
I would like to explain in more detail the mechanical reasons why the center panel tends to bend in KALLAX shelves:
The basis lies in the choice of materials: IKEA typically uses a combination of coated particleboard for the large surfaces and MDF for the dividing panels in KALLAX. Both materials have a low modulus of elasticity, meaning they are not very resistant to bending.
The center panels are often relatively thin (about 12 mm (0.5 inches)), and the span within the compartments is often 42 cm (16.5 inches) or more. They can only withstand the compressive and bending stresses from a heavy object placed in the middle to a limited extent.
From a structural perspective, the center panel behaves like a simply supported beam: the deflection depends on the span length (L), the applied load (F), the material stiffness (E), and the cross-sectional moment of inertia (I). Since E and I are limited for the thin MDF, deflection increases with higher load and longer span.
Assembly factors are also important: improper screwing or play between the center panel and the frame can lead to additional movement and earlier bending. If the shelf is not fixed to a wall, the load from tipping moments increases.
Moisture significantly lowers the modulus of elasticity of particleboard and MDF, making the material “softer” and promoting greater bending.
Therefore, my recommendation is always: not only distribute the load evenly but also, if possible, secure the shelf and keep the boards dry. If possible, the center panel can also be reinforced with an additional wooden edge or strip underneath to increase bending resistance.
Do you have a specific usage profile? What kind of loads do you plan to place on the shelf?
The basis lies in the choice of materials: IKEA typically uses a combination of coated particleboard for the large surfaces and MDF for the dividing panels in KALLAX. Both materials have a low modulus of elasticity, meaning they are not very resistant to bending.
The center panels are often relatively thin (about 12 mm (0.5 inches)), and the span within the compartments is often 42 cm (16.5 inches) or more. They can only withstand the compressive and bending stresses from a heavy object placed in the middle to a limited extent.
From a structural perspective, the center panel behaves like a simply supported beam: the deflection depends on the span length (L), the applied load (F), the material stiffness (E), and the cross-sectional moment of inertia (I). Since E and I are limited for the thin MDF, deflection increases with higher load and longer span.
Assembly factors are also important: improper screwing or play between the center panel and the frame can lead to additional movement and earlier bending. If the shelf is not fixed to a wall, the load from tipping moments increases.
Moisture significantly lowers the modulus of elasticity of particleboard and MDF, making the material “softer” and promoting greater bending.
Therefore, my recommendation is always: not only distribute the load evenly but also, if possible, secure the shelf and keep the boards dry. If possible, the center panel can also be reinforced with an additional wooden edge or strip underneath to increase bending resistance.
Do you have a specific usage profile? What kind of loads do you plan to place on the shelf?
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Ottfried6122 May 2024 15:18Filippo schrieb:
Do you have a specific usage profile? What type of loads do you place on the shelf?Good question! I mainly store books, mostly paperbacks and some thicker hardcovers, as well as boxes with photos and smaller devices. The weight adds up to about 7–10 kg (15–22 lbs) per shelf, sometimes a bit more.
Nabla64 schrieb:
Using a strap or wall mounting, as well as avoiding heavy loads directly on the middle support, are the most effective ways to prevent sagging.Wall mounting is currently not an option since I want to keep the shelf flexible.
Thanks in advance to everyone for the replies. I will probably pay attention to load distribution and consider reinforcing the middle support.
Additionally, I would like to explain the statistical background of deflection and offer a practical tip:
The deflection (δ) of a beam under uniform load can be approximately calculated using the formula
δ = (5qL^4) / (384EI)
where q is the distributed load, L is the span length, E is the modulus of elasticity, and I is the moment of inertia of the cross-section.
Since the central supports in KALLAX are narrow and relatively thin, I is small, which significantly increases deflection, especially with large spans and loads.
A simple practical solution is to reinforce the beam by attaching a thin wooden board or strip underneath the central support. This increases the moment of inertia and thus significantly reduces bending.
Using grooved strips (prefabricated “tongue-and-groove” or “slot” strips) can also improve stability.
If the shelf can later be attached to the wall, this also greatly reduces the need for additional reinforcement.
The deflection (δ) of a beam under uniform load can be approximately calculated using the formula
δ = (5qL^4) / (384EI)
where q is the distributed load, L is the span length, E is the modulus of elasticity, and I is the moment of inertia of the cross-section.
Since the central supports in KALLAX are narrow and relatively thin, I is small, which significantly increases deflection, especially with large spans and loads.
A simple practical solution is to reinforce the beam by attaching a thin wooden board or strip underneath the central support. This increases the moment of inertia and thus significantly reduces bending.
Using grooved strips (prefabricated “tongue-and-groove” or “slot” strips) can also improve stability.
If the shelf can later be attached to the wall, this also greatly reduces the need for additional reinforcement.
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