Numerical simulation of microextrusion: influence of die entry angles and friction on deformation behavior of AA6063 aluminum alloy

ABSTRACT

Micro/meso fabrication techniques have gained significant recognition globally for their advanced manufacturing capabilities. Among these, microforming stands out as a leading process in micromanufacturing. Despite growing interest in microextrusion for industrial applications, the technology remains underdeveloped compared to conventional forming methods, with limited expertise available. To address this gap, it is essential to develop a comprehensive understanding of the microextrusion process, which can guide the production of metallic microcomponents. This research focuses on the numerical simulation of microextrusion to study the influence of die entry angles on the deformation behavior of AA6063 aluminum alloy. Simulations were conducted using die angles of 15°, 30°, 45°, and 60° under varying frictional conditions. Results show a direct relationship between die angle and forming load, while punch displacement decreases as the die angle increases. The role of friction was also found to be crucial in the extrusion process. Numerical results for the 30° die angle were compared with experimental data, highlighting the effectiveness of finite element analysis in predicting microforming outcomes. This study demonstrates the potential of numerical simulation as a powerful tool for optimizing microforming processes in industrial applications.

Keywords:
Microextrusion; FE simulation; AA6063; Die-angle; friction

1. INTRODUCTION

The shrinking standard electronics raise the industry’s demand for competent small part production. Machining has long been renowned for producing small-dimension elements by turning, milling, and polishing. However, these approaches are insufficient to meet the high demand for tiny components. This necessitates searching for new production technologies or adapting existing ones to meet the demand for miniaturization. Microforming is an accepted method of producing small metal parts through forming. This forming technique is distinguished by high output, high dimension precision, same surface smoothness, minimum material waste, and outstanding mechanical qualities of made goods, making it an excellent alternative to machining. Figure 1 shows the TEYFOURI et al. [¹] to microforming technologies. MOGIELNICKI [²] works with cutting-edge metal microforming and numerical simulations. RAN et al. [³] used the ABAQUS simulation platform to perform FEM simulation. Before engaging in costly experimental experiments, FE simulation can be a helpful tool in discovering the best process design conucted by ROSOCHOWSKA et al. [⁴]. For example, Admir ŠUPIĆ et al. [⁵] performed a numerical simulation for aluminium profile extrusion and found that simulation findings aid in forecasting dies damage during extrusion simulation done by ŠUPIĆ et al. [⁵]. Microforming is a plastic deformation technology used to create micro parts with at least two dimensions in the sub-millimeter range and the benefits of high production rate, low production cost, little waste, and good mechanical qualities investigated by GEIGER et al. [⁶]. The size effect is mainly produced by a significant drop in grain quantity in billet material. PICART et al. [⁷] used a tensile test experiment on brass billets to investigate the size effect on material flow stress. The material parameters are applied in a constitutive model for a sheet metal sample to evaluate the stress-strain model based on the experimental data. CHAN and FU [⁸] conducted a rigorous investigation on the effect of size on deformation behaviour and friction variation in microforming processes. In their studies, they produce a series of flow stress curves for decreased-sized samples, and experiments and simulations prove the applicability of these curves. Finally, MESSNER et al. [⁹] and Vollertsen et al. [¹⁰] conducted a wide-ranging review and concisely identified the difficulties to be addressed in developing microforming processes and micro-sized parts to provide the overall research status of microforming. SLJAPIC et al. [¹¹] studied the cold upsetting of brass. The experimental model of the axisymmetric brass forming was created using the finite element method (FEM). The simulation results show that the highest plastic strain coincides with the fracture opening. ADEOSUN et al. [¹²] examined the effect of die entry angle on aluminium 6063 alloy extrusion responses. BUNTE and GOMEZ [¹³] investigate the influence of temperature on different steel epoxy in flexible pipes. QAMAR [¹⁴] used the Finite Element Method (FEM) to investigate extrusion challenges and dead metal zones through numerical simulations of extrusion to confirm experimental findings. On lead and Al-6063 alloy, dies with three different profiles constructed of H13 steel were employed. Metal deformation during plastic flow and the size of the dead metal zone was measured. The variation in die profile symmetry and extrusion ratio was blamed for this event. SRINIVASAN et al. [¹⁵] present a model for numerically investigating the friction coefficient; the model assumes that the flow stress of the extruded material is constant and follows von-mises law. The DEFORM 3D software was used for the FE simulation. For the FE simulation, the DEFORM 3D programme was employed. Based on a typical material model, CHAN et al. [¹⁶] perform a finite element (FE) simulation of micro-extrusion processes with varying friction coefficients to test its relevance in forecasting micro-plastic deformation. KARTHIKEYAN and RAJENTHIRAKUMAR [¹⁷] Simulated the micro extrusion of AL6063 using AFDEX simulation software. The results are scientific and well with in the acceptable range.

Figure 1
Microforming methods [¹].

The following section presents a comprehensive method for the numerical simulation of metal flow in micro-parts, aiming to explore the impact of die angle on the deformation behavior of microextrudates. This study uniquely focuses on die angles of 15°, 30°, 45°, and 60°, employing oil cold steel as the frictional interface. By systematically processing these die angles, the work investigates how varying die geometries influence the deformation characteristics of microextrudates under different frictional conditions. The simulation not only addresses the displacement response of the punch relative to the applied load but also delves into the effects of interfacial friction on the microforming process. A key novelty of this work lies in its detailed analysis of how different die angles affect both the force-displacement relationship and the material flow behavior, providing insights into optimizing microextrusion processes. The study’s approach offers a valuable contribution to the field by enhancing the understanding of microforming dynamics and improving the design of die systems for more effective and efficient micro-part production.

2. MATERIALS AND METHODS

A custom-designed die set assembly was developed and constructed to simulate the microextrusion process using AA6063, focusing on the influence of die entry angle on deformation behavior. AA6063 is an aluminum-magnesium-silicon alloy widely recognized for its excellent properties, making it particularly well-suited for microextrusion processes. AA6063 is highly extrudable, even in complex shapes, due to its balanced chemical composition and excellent flow characteristics. This makes it ideal for microextrusion, where precise control of material flow is critical. AA6063 is known for its ability to produce smooth surface finishes, reducing the need for extensive post-processing. This is particularly beneficial for micro-parts where fine tolerances and finishes are essential. Aluminum alloys like AA6063 are highly recyclable, aligning with modern sustainability goals in manufacturing. The combination of these properties ensures that AA6063 meets the stringent demands of microextrusion processes, delivering reliable, high-quality results for applications in industries such as electronics, automotive, and aerospace.

The geometries for different die entry angles are illustrated in Figure 2. The dimensions of the extrudate were used to determine the appropriate die size, with the anticipated microextrudate measuring and featuring a cylindrical micropin shape. The primary diameter of the die cavity was established based on the available AA6063 specimen size. The corresponding die angles and specimen identifiers are listed in Table 1.

Figure 2
Geometry of die cavity with various semi die angle.

Table 1
Die angle with specimen ID.

SL.NO.	SEMI DIE ANGLE	SPECIMEN ID
1	15°	DA15
2	30°	DA30
3	45°	DA45
4	600	DA60

To meet the extrudate requirements, dies were designed with entry angles of 15°, 30°, 45°, and 60°, and the punch was dimensioned accordingly. Figure 3 presents the 3D model of the die set assembly.

Figure 3
Die set assembly.

2.1. Process configuration

The microstepped pin can be formed through forward extrusion, as depicted in Figure 4. In theory, both backward and forward extrusion processes would yield similar results if friction at the material/tool interface were absent. However, due to the presence of friction, these processes result in distinct material flow patterns and varying process forces. An exploded view of the die set assembly is provided in Figure 5. The extrusion die, a pivotal component of the die set, plays a critical role in shaping the extrudate. A segmented (split-type) die was utilized to facilitate the easy removal of the extruded product, which is essential for testing. The chemical composition of AA6063 is presented in Table 2.

Figure 4
Forward extrusion of micro stepped pin.

Figure 5
Exploded view of micro extrusion.

Table 2
Chemical composition of AA6063.

ELEMENT	Si	Mg	Cu	Mn	Cr	Zn	OTHERS	Al
wt. (%)	0.4	0.7	0.10	0.10	0.10	0.10	0.15	Balance

3. FE SIMULATIONS

Finite element simulation was employed to predict the nonlinear material behavior of the microextrudate. The analysis was conducted using the widely recognized software AFDEX (V20R01). Micro-compression simulations were performed for different die entry angles under oil-lubricated cold friction conditions. Figure 6 illustrates a solid model of the split die featuring various die angles. Cold extrusion was numerically modeled with a punch travel rate of 1 mm/s. The axisymmetric flow behavior of AA6063 was simulated to analyze the extrusion process.

Figure 6
Solid model of spilt die with various die angles. (a) semi die angle 15°; (b) semi die angle 30°; (c) semi die angle 45°; (d) semi die angle 60°.

The simulation parameters for the microextrusion analysis are detailed in Table 3. The process setup includes the workpiece, punch, and lower die. Key inputs such as material type, translational velocity, and friction conditions have been specified. The boundary conditions dictate that the ram moves in the (-) y-direction, while all degrees of freedom of the segmented die are constrained to zero. The stopping criterion for the analysis is defined as the distance between the workpiece and the exit point of the die cavity. The number of elements in the analysis is automatically generated, with the appropriate element count selected based on the complexity of the die geometry.

Table 3
Metal forming simulation parameter.

SL.NO.	DESCRIPTION	SIMULATION PARAMETER
1	Forming Condition	Cold
2	Simulation type	3D
3	System of Units	Newton
4	Analysis	Flow analysis
5	Material Model	Elastoplastic
6	Flash	Regular
7	Material type	AA6063
8	Friction condition	Oil cold steel
9	Punch velocity	1 mm/s

4. RESULT AND DISCUSSION

4.1. Force displacement response of various friction condition

A finite element simulation was conducted using the commercial metal forming software AFDEX to predict the force-displacement behavior during forward microextrusion. For a die angle of 15° (DA15), the maximum displacement was 4.46 mm with an extrusion load of 52.92 kN. Similarly, the maximum displacements for die angles of 30°, 45°, and 60° were 2.49 mm, 1.88 mm, and 1.21 mm, respectively, with corresponding extrusion loads of 45.88 kN, 57.93 kN, and 40.87 kN. Similar result has been arrived by SRINIVASAN et al. [¹⁸] for Al6063 gear at room temperature 37.54 KN, while at elevated temperature of 100°C is 25.21 KN and NANTHAKUMAR et al. [¹⁹] for copper at room temperature (28 °C) is 7451 N, while at elevated temperature of 100°C and 200°C, it is 5440 N and 5091 N, respectively. And also Similarly, a significant improvement in material flow and formability has been observed in micro forming of CuZn15 and X4CrNi18-10[²⁰]. Figure 7 illustrates the simulation results, showcasing the force-displacement responses of the extrudates. During the metal flow through the 0.9 mm die cavity, the punch load stabilizes. The stable load range for each die angle during the simulation is presented in Table 4.

Figure 7
Force displacement responses of various die angle.

Table 4
Punch load range at stable condition.

SL. NO.	DIE ID	STABLE RANGE OF PUNCH FORCE (KN)
1	DA15	50.99 to 52.12
2	DA30	40.58 to 45.49
3	DA45	67.13 to 83.28
4	DA60	50.69 to 52.12

The extrusion force values corresponding to a displacement of 1.24 mm for DA15, DA30, DA45, and DA60 are 3 kN, 7.29 kN, 17.15 kN, and 40.87 kN, respectively. The simulation results indicate that the deformation load increases proportionally with the die angle. DA15 requires the lowest force at 3 kN, while DA60 demands the highest force at 40.87 kN. Figure 8 illustrates the extrusion force from the microforming simulation at a constant displacement of 1.21 mm.

Figure 8
Maximum extrusion forces of various die angle.

DA15 generates the longest pin length with the lowest extrusion force, while DA60 requires the highest load but produces the shortest pin length. As shown in Figure 9, microstepped pins were successfully extruded using various die angles at room temperature. The punch displacements for DA15, DA30, DA45, and DA60, as the metal billet flows from a 6 mm diameter down to the 0.9 mm entry path, are 4.13 mm, 2.14 mm, 1.47 mm,and 0.9828 mm, respectively. Corresponding force values for these die angles are 42.52 kN, 34.97 kN, 30.56 kN, and 28.7 kN.

Figure 9
Force displacement response of microextrudate. (a) Die angle 15°; (b) Die angle 30°; (c) Die angle 45°.

4.2. Billet extrudate at 0.9 mm die cavity

The metal flow initiated at the die cavity’s 6 mm entry diameter and concluded at an exit diameter of 0.9 mm. The micropin was extruded through the die chamber with a 0.9 mm diameter. Table 5 presents the punch displacement from the 0.9 mm die entry to the exit. Notably, DA45 exhibited the highest punch displacement at 0.1532 mm, while DA60 had the lowest punch displacement at 0.0772 mm during the microextrusion process. This is attributed to DA60’s shorter slope height and larger metal flow area compared to the other die angles. Figure 10 illustrates the billet extrudate formed with the die cavity.

Table 5
Metal flow at die cavity.

SPECIMEN	METAL FLOW START FROM ENTRY AT DIA 0.9 MM TO EXIT AT DIA 0.9 MM				PUNCH TRAVEL DISTANCE
	PROCESS	STEP ID	PUNCH DISPLACEMENT (mm)	FORCE (KN)
DA15	Start	52	4.1191	39.1921	0.1207
	End	66	4.2398	50.343
DA30	Start	55	2.1303	33.7253	0.1164
	End	78	2.2467	41.6866
DA45	Start	25	1.4706	38.1164	0.1532
	End	43	1.6238	54.1233
DA60	Start	87	1.055	38.7669	0.0772
	End	130	1.1322	40.4503

Figure 10
Billet extrudate at die cavity. (a) Entry; (b) Exit.

4.3. Flash loss

During the microforming process, the simulation may lead to the formation of flash (17), which results from the clearance between the punch and the die. Flash loss occurs when material flows into unintended gaps or clearance between the die components, such as the die and punch interface, due to forming pressure. Regulating extrusion force, temperature, and material flow to reduce excess material displacement. Flash formation was observed in all four scenarios. Figure 11 illustrates the flash loss in the microextrudate for different die angles.

Figure 11
Flash loss in microextrudate (simulation and experimental). (a) Die angle 15°; (b) Die angle 30°; (c) Die angle 45°; (d) Flass loss.

5. CONCLUSIONS

The study provides valuable insights into the behavior of forward microextrusion for different die entry angles, simulated using AFDEX software. The following conclusions emphasize the practical implications of the findings and their relevance to industrial applications:

1. The results show that a die entry angle of 60° leads to higher effective stress and extrusion forces due to significant metal flow constraints in the die cavity. For industrial applications, this highlights the importance of avoiding larger die angles for materials prone to high flow resistance, as it can lead to increased energy consumption and wear on tooling.

2. The 45° die angle (DA45) exhibited the highest punch displacement of 0.1532 mm, indicating improved material flow and deformation efficiency compared to other angles. In contrast, 30° die angles (DA30) offered a balanced reduction in extrusion force while maintaining effective material flow, making them suitable for processes prioritizing energy efficiency and tool longevity.

3. Flash loss was observed across all die angles due to the clearance between the punch and the die. This finding underscores the need for precision tooling design to minimize clearance and reduce material wastage in industrial microextrusion. Die angles of 30° and 45° are recommended for industrial microextrusion processes due to their ability to balance deformation efficiency and lower extrusion forces. This reduces operational costs and tool wear, particularly in high-volume production.

4. The study emphasizes the importance of precise tooling to address issues like flash loss. Implementing tighter tolerances and advanced surface treatments can minimize material waste and enhance productivity. For industries such as electronics (e.g., IC connectors) and medical devices, where dimensional accuracy and material integrity are critical, these results provide clear guidance on die design and process parameter optimization.

By focusing on die angles that optimize deformation behavior and reduce extrusion forces, manufacturers can enhance efficiency, reduce costs, and improve the overall quality of micro-extruded components.

6. SCOPE FOR FUTURE WORK

The study relies heavily on finite element simulations, which may not fully capture real-world complexities like thermal effects, material anisotropy, or variations in lubrication. Investigate advanced die and punch designs with reduced clearance to minimize flash loss. Explore coatings or surface treatments to further reduce friction and enhance die life. Conduct more detailed studies on the influence of grain size and texture evolution during microextrusion, particularly for materials with varying compositions and heat treatments. Analyze the effects of alternative materials to AA6063 to expand the applicability of the findings. Improve simulation fidelity by incorporating more advanced material models, such as anisotropy and strain hardening effects. Validate simulation results with extensive experimental testing to ensure accuracy and applicability.

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Publication Dates

• Publication in this collection
  17 Feb 2025
• Date of issue
  2025

History

• Received
  26 Nov 2024
• Accepted
  07 Jan 2025