eSUN PLA mechanical properties and tensile strength specs for functional prints

Diagnosis

The mechanical properties of eSUN PLA+ are significantly enhanced compared to standard PLA due to the addition of impact modifiers and additives that increase the polymer chain flexibility. While standard PLA is notorious for being brittle—meaning it snaps suddenly under stress (catastrophic failure)—PLA+ is engineered to deform slightly before breaking. This results in a higher impact strength and a higher elongation-at-break percentage, making it suitable for functional prototypes that must withstand occasional drops or mechanical tension. To confirm you are utilizing the full mechanical potential of the filament, you must observe the layer adhesion. If the prints are delaminating or "splitting" along the Z-axis under a load of less than 20kg/cm², you are likely under-extruding or printing at too low a temperature. True eSUN PLA+ should exhibit a tensile strength typically ranging between 40 and 50 MPa, depending on the print orientation. If the part snaps cleanly with no whitening (stress crazing) at the break point, the material is behaving like standard PLA, indicating a lack of proper thermal fusion during the printing process.

How to Fix It

To maximize the tensile strength and structural integrity of eSUN PLA+ for functional prints, follow these precise calibration and printing steps:

1. Thermal Optimization: Set your nozzle temperature to 215°C - 225°C. While it can print at 200°C, the higher end of the spectrum increases the molecular diffusion between layers, drastically increasing the Z-axis tensile strength.
2. Flow Rate Calibration: Increase your flow rate (extrusion multiplier) to 102% - 105%. A slight over-extrusion fills microscopic gaps between lines, increasing the effective cross-sectional area of the part and reducing stress concentrators.
3. Wall Density: Set "Wall Line Count" to at least 4 or 5. For functional parts, walls contribute more to tensile strength than infill. Use a 0.4mm nozzle but set the "Line Width" to 0.45mm to force a wider, more compressed bead of plastic.
4. Infill Strategy: Use "Gyroid" or "Cubic" infill at 30% to 50%. Avoid "Grid" or "Lines" as they overlap on the same plane, creating internal stress points. Gyroid provides equal strength in all three dimensions.
5. Cooling Management: Reduce the print fan speed to 50-70% for the first 5 layers, then 100% thereafter. Reducing the cooling speed slightly allows the plastic to remain molten longer, improving the bond between the current layer and the previous one.

If That Didn't Work

• Annealing Process: If the part still lacks sufficient rigidity, perform a thermal annealing process. Place the finished print in a vacuum oven or a controlled oven at 60°C to 65°C for 30-60 minutes. This recrystallizes the PLA polymer chains, significantly increasing the heat deflection temperature (HDT) and overall hardness, though it may cause 1-2% shrinkage in dimensions.
• Orientation Shift: If the part is snapping along the layer lines, rotate the model 90 degrees on the build plate. PLA+ is anisotropic; its strength along the X/Y axis (the direction of the extruded strand) is significantly higher than its strength along the Z-axis (the bond between layers).
• Moisture Removal: If you see "stringing" or hear tiny popping sounds during extrusion, the filament has absorbed moisture. This creates steam bubbles (voids) inside the walls, which act as fracture points. Dry the filament in a dedicated dryer at 50°C for 6 hours before printing.
• Increase Layer Height: Contrary to popular belief, slightly thicker layers (e.g., 0.25mm instead of 0.1mm) can sometimes improve structural strength in PLA+ by reducing the total number of potential failure interfaces (layer lines) throughout the part.

Heads Up

• Temperature Ceiling: Despite the "Plus" designation, eSUN PLA+ still has a low glass transition temperature. Do not use these parts in automotive interiors or near heat sources exceeding 55°C, as they will warp and lose all structural integrity.
• Chemical Sensitivity: Avoid contact with acetone or strong solvents, as they will degrade the impact modifiers in PLA+, leading to surface cracking and a loss of tensile strength.
• Storage: Store the filament in a vacuum-sealed bag with a fresh silica gel desiccant pack. PLA+ is more hygroscopic than standard PLA; moisture absorption directly correlates to a drop in impact resistance.