Mechanical Principles of Controlled Gravity and Specimen Clamping
A testing apparatus such as the Qualitest Drop Dart Impact Tester DX-8300 Series relies on a straightforward, gravity-driven plunge to determine if thin plastic packaging will split open under sudden physical stress.
Manual weight drops often introduce frustrating variations from one operator to the next, but this system avoids those errors by releasing a heavy, rounded nose from a locked-in vertical height, delivering the exact same high-velocity impact during every single run. For thin plastic sheets, this high-speed physical crash is a brief, intense event where the polymer stretches, changes shape, and either holds its ground or tears wide open.
To prevent false readings, the test sample must remain completely immobile. If the film slips even a fraction of a millimeter, it absorbs the kinetic energy and skews your data.
This is why the DX-8300 Series utilizes a solid, pneumatic-assisted clamp working with 60 psi dry and filtered air. This setup provides intense, uniform holding pressure in a full circle around the film. Furthermore, the system uses a clean pneumatic dart release to avoid the dragging effect of old-school electromagnetic drops, guaranteeing a true, unobstructed free-fall.
ASTM D1709 Parameters: Method A vs. Method B
Depending on the overall durability of your plastic, standard ASTM D1709 guidelines dictate two distinct testing pathways, which you can run based on the specific DX-8300 model in your facility:
- Method A (Model DX-8385-A): Suited for everyday bags and thinner packaging wraps. It uses a 38.1 mm diameter phenolic or aluminum nose dropped from a strict vertical height of 26 inches (66 cm).
- Method B (Available on Model DX-8385-AB): Built for heavy-duty industrial sheets. It drops a larger, heftier 50.8 mm stainless steel nose from a height of 60 inches (152 cm). The DX-8385-AB combo unit allows operators to run both methods from a single, expandable testing frame.
Regardless of the chosen method, the falling dart must hit dead-center and straight down. Opting for an automated release, such as the optional two-button safety actuator or the electronic footswitch featured on the DX-8300, provides a major operational upgrade over manual setups that can wobble and shift as you let go of the weight.
The Staircase Method: Statistical Calculation of the 50% Failure Threshold
To identify the specific weight limit where exactly half of your plastic sheets fail and half survive, the testing procedure uses the classic up-and-down staircase method.
First, you drop a dart. If the sheet ruptures, you remove a small amount of weight, using the provided incremental sets which go all the way down to 5-gram weights for Method A, and test a brand new sheet. If the sheet survives, you add more weight and drop again. You continue this systematic back-and-forth process until you collect a large enough group of passes and failures, typically 10 of each.
Managing these calculations by hand is a highly tedious task, and any math errors can make your entire dataset unreliable. Instead of manually tracking results, operators use the DX-8300 Dart Drop Software, which links straight to your laboratory PC. The program logs every single pass and fail, handles the math instantly, and calculates the final, highly specific performance score showing exactly how that packaging handles a sudden, concentrated blow.
For anyone producing or purchasing flexible materials, this exact value confirms whether your bags will survive a fall off a retail shelf or a rough trip in a transport truck.
