The misconception that is prevalent in the packaging industry is that the can is a commodity that is standardized. A can to the consumer is just a vessel, often competing with plastic bottles or cartons. It is a line item to the procurement department that is specified in terms of cost per thousand units. But to the production engineer and the plant manager, the material composition of a can is the underlying variable that determines the whole behavior of the filling and seaming line.

What are cans made of is not a chemical question, but a mechanical question. The decision to use aluminum or steel cans changes the physics of the packaging process fundamentally. It alters the behavior of the container to the axial loads during filling, the flow of the metal during the double seaming process, and the calibration of the machinery to avoid disastrous downtime or piles of scrap metal.

This guide goes beyond the periodic table to discuss the engineering consequences of material choice. We will look at the way the unique mechanical characteristics of aluminum and tin-plated steel work with automated equipment and what this implies for your production efficiency.

The Basics: Aluminum Alloys vs. Tin-Plated Steel

We need to determine the metallurgical differences and their common use in the market before we analyze the line performance. When engineers ask what are cans made of, they are looking for the specific alloy and temper properties.

Алюминиевые банки are not pure aluminum. They are complex aluminum alloys that are meant to be highly formable. Aluminum beverage cans are the most dominant in the beverage industry (carbonated soft drinks, beer, energy drinks) because of their lack of rigidity but high ductility. They are also being applied in high-end nitrogen-flushed snacks and ready-to-drink (RTD) coffees, where internal pressure helps to hold the structure. Interestingly, recycled aluminum plays a key role here, as it can be remelted and reformed repeatedly with minimal loss of properties.

• The Body: It is usually composed of 3004 alloy, containing manganese (around 1%), and magnesium (around 1%). This composition offers the required strength-weight ratio and permits the sheet metal to be drawn and ironed into a thin-walled, two-piece cylinder.
• The Lid (End): This is typically made of 5182 alloy which contains more magnesium. This renders the lid more rigid and tougher than the body to give the rigidity required to hold the rivets and the score line to the opening tab, often eliminating the need for a traditional can opener in modern convenience designs.

Steel cans, formerly known as tin cans, are mostly made of low-carbon steel. It is necessary when the food products need high-temperature retorting (soups, tuna, vegetables, meat) or vacuum sealing (milk powders, infant formula, dry nutraceuticals), and the container should be able to retain its shape under vacuum or thermal pressure.

• Tinplate (ETP): It is a sheet of steel that is covered with a thin layer of tin (usually achieving the desired thickness of the tin plating via electrolysis) to prevent corrosion of the metal. It is still the benchmark of metal food cans because of its structural strength.
• Tin-Free Steel (ECCS): It is an electrolytic chromium-coated variant. It is a great adhesive for lacquers and polymers, but does not have the aesthetic brightness of tin.

To visualize the engineering distinctions, refer to the comparison below:

When discussing what are cans made of, we must also consider the insides of the metal food cans. To prevent the corrosion of the can or interaction with the food, a hard film of resin or a polymer coating is often applied. This acts as an effective barrier, ensuring the exterior surfaces of the metal food can remain pristine while the interior resists acid and dry salt.

The chemical composition is interesting, but it is subordinate to the operational reality. The manufacturing process depends on these mechanical properties. The factors that make the difference between a production line that operates at 99% efficiency and one that has a 5% scrap rate are the yield strength, ductility, and strain hardening coefficient of the metal. Machine dynamics are determined by raw materials.

Material Stiffness: Impact on Filling and Seaming Dynamics

Siffness is the most important operational difference between metal cans made of aluminum versus steel. This variance demands radically different methods of handling, filling, and sealing. A machine that is adjusted to the rigidity of steel will squash aluminum; a machine adjusted to the compliance of aluminum will not seal steel.

Aluminum Challenges: Low Rigidity and Axial Load Buckling

The aluminum can of beverage in the modern world is an engineering wonder of lightweighting. Manufacturers have increasingly made the can body walls thinner, typically to about 90 microns (about the thickness of a human hair) to minimize the cost of materials and the weight of the shipment. Although this is cost-effective, it poses a major structural weakness.

Before being pressurized, aluminum cans, especially 2-piece beverage cans, are low column strength. The can should be able to hold the vertical pressure during the filling and seaming process, particularly at the bottom end. This is referred to as Axial Load or Top Load.

• Filling: The filling valve descends and seals against the can rim to create a vacuum or manage counter-pressure.
• Seaming: The seamer lifter plate pushes the can body up against the chuck to engage the cover.

When the force of the filling valve downward or the force of the lifter plate upward is greater than the yield point of the aluminum, the sidewalls will collapse. This is known as Buckling. A buckled does not only lead to the loss of products, but it also tends to jam the turret, which means that the machine will have to be manually reset.

In order to alleviate this, accuracy control is necessary. Conventional cam-driven lifters tend to use linear and unyielding force. When there is a slight change in the height of the can, the mechanical force spikes and crushes the container.

Steel Challenges: High Hardness and Springback Effect

The reverse engineering problem is steel. It is inflexible, tough, and uncompromising. Although you will hardly squash metal food cans when filling it, the material resists when forming.

The modulus of elasticity of steel is high. When the seaming rollers bend the steel flange to form a seal, the metal will tend to spring back to its original form. This effect is referred to as Springback.

• Sealing Integrity: To defeat springback and provide a hermetic seal, the seaming machine needs to exert much greater force than is needed with aluminum. Without rigidity in the machine, the force that is supposed to bend the metal will bend the arms or shafts of the machine. This diversion causes a False Seal, a seal that appears right on the eye but does not have the required compression to keep out bacteria. This is critical for food cans containing acidic foods, where leakage could spoil the freshness of the food product.
• Tooling Life: Hardness of steel is a machine component abrasive. Seaming rollers and chucks wear much more quickly when handling steel than when handling aluminum. The seam profile is changed by worn tooling, resulting in loose seams and possible leakage.

The work with steel requires brute force and accuracy. The equipment should be designed to resist high-cycle fatigue and high-load processes. This is dealt with by high-performance equipment in two main ways:

1. Structural Rigidity: The machine frame and head should be made of heavy-gauge materials. As an illustration, the frame can be made of 1.5mm to 2mm thick 304 or 316 stainless steel to make sure that the machine does not bend under the heavy load of seaming steel.
2. Hardened Tooling: In order to fight wear, the seaming rollers should be made of high-grade tool steel with special heat treatments or ceramic finishes. These components should be machined accurately, typically to 2um (micrometers) to provide the roller profile with pressure at the correct location to provide the necessary force to push the steel to its yield point without harming the coating. This is the only means of overcoming springback consistently, by means of this combination of rigid structure and hardened, precision tooling.

Double Seam Formation: Sharp Seams vs. Loose Seams

The hermetic seal is the double seam created by interlocking the can body (Body Hook) and the lid (Cover Hook) at the end of the tube. This is where the ends meet. Although the geometry of a double seam is standardized, the route to the same varies radically depending on the ductility of the material.

The Risk of Sharp Seams: Aluminum is very ductile; it easily flows under pressure.

• The Phenomenon: Aluminum is soft, and therefore, it is easy to over-tighten the seam. When the second operation roller exerts excessive pressure, it may flatten the metal to form a sharp edge on the top of the seam.
• The Defect: This is referred to as a Sharp Seam or even a Cut-over. The sharp edge may crack the metal or peel off the protective lacquer, exposing the metal to oxidation. The aluminum seaming curve should be accurate but smooth.

The Risk of Loose Seams: Steel resists flow. It requires persuasion.

• The Phenomenon: In case the first operation roller fails to exert enough force, the Body Hook will not tuck under the Cover Hook sufficiently.
• The Defect: This causes a Loose Seam or Low Overlap. At the visual examination, the seam might appear thick and rounded, but inside, the hooks are not hooked. The steel seaming curve needs a high-pressure first pass to press the rigid metal into the proper geometry.

This difference is the reason why a universal seaming arrangement can hardly be effective. The roller profiles and the cam attack angles have to be aligned with the willingness of the material to deform.

Production Reality: Switching From Steel to Aluminum

The competitive advantage in the present market is versatility. SMEs and co-packers frequently have to alternate between steel cans (e.g., pet food or powder) and aluminum cans (e.g., beverages or nitrogen-flushed snacks). Some are even exploring hybrid containers or hybrid cans of aluminum composites. Nevertheless, this switch should not be treated as a mere change of mould, which is a formula of failure in operation.

Critical Adjustments: Seaming Clearance and Turret Speed

Switching between steel and aluminum means that the machine will have to be recalibrated in terms of physical settings.

The Clearance Factor

The Pin Height (the distance between the base plate and the chuck) and the Seaming Clearance (the distance between the roller and the chuck) are important. Aluminum is thinner. When you use aluminum cans with settings that are set to compress thicker tinplate, the rollers will not compress the metal enough to make it leak. On the other hand, operating steel in aluminum environments will clog the machine and break the bearings.

The Physics of Mass

Another important production variable is the weight difference. A steel can is heavy; it is firmly placed on the conveyor and the lifter plate. A can of aluminum is a featherweight when it is empty.

• Toppling: When the machine is spinning at high speed, the centrifugal force and air resistance of the spinning machine can easily cause an empty aluminum can to become unstable.
• Transfer Stability: The transfer star-wheels should be in perfect synchronization. Any slap of the guide rail that a steel can would absorb would shoot an aluminum can flying. The turret speed usually requires modulation when changing to aluminum, and the acceleration ramp-up should be less jagged to be more stable.

The Solution: Automated Recipes for Rapid Changeover

The manual adjustment method, which involves the use of feeler gauges and wrenches to adjust the clearances, is slow and subject to human error. It causes prolonged downtime that kills profitability.

The current production requires Intelligent Servo Integration. Rather than mechanical adjustments, the sophisticated metal packaging lines are controlled by PLC-based systems to control these variables.

• Digital Recipe Management: Operators are able to store particular torque settings, speed profiles, and servo-lifting heights in the HMI (Human-Machine Interface). In changing the recipe of “3004 Aluminum” to Tinplate Steel, the operator chooses the recipe.
• Servo Precision: The servo motors will automatically regulate the lifting speed and pressure to the profile stored. Although physical tooling (chucks and rollers) might still require replacement, the manual process of calibration of forces and speeds is computerized. This guarantees that the first off the line following a changeover is as good as the last, and the startup scrap and changeover time is greatly minimized.

Conclusion: Matching Machinery to Material Science

A complex engineering decision tree begins with the question what are cans made of. Aluminum is lightweight, efficient, and requires delicate handling and accurate axial load control. Steel is structurally rigid and requires strong machinery that can withstand high wear and resist the strong forces of springback. Whether you are dealing with a different material or a variety of shapes, the best way to understand the principle remains the same.

Effective production is not achieved by making a machine work with a material, but by choosing equipment that is sensitive to the special mechanical characteristics of the material.

В Левапаке, we believe that exceptional packaging machinery starts with a profound understanding of the package itself. We don’t just assemble components; we engineer solutions that respect the distinct physical behaviors of aluminum and steel. This material-first philosophy is why we insist on using heavy-gauge 304/316 stainless steel for our frames—not just for durability, but to provide the absolute rigidity required to seam steel without deflection. It is why we machine our components to 2μm precision and integrate intelligent HMI and servo systems—because handling lightweight aluminum demands a delicate, programmable touch. With over 18 years of experience, we translate material science into mechanical reliability, ensuring your equipment is not just a tool, but a perfectly matched partner to your packaging needs.

Are you struggling with high scrap rates or complex changeovers? Don’t let material properties dictate your efficiency. We can help you analyze canning food processes to a greater degree. Contact our engineering team to assess which machine configuration will maximize your line’s performance.