3D Printing on the Milsim Field: Our Commitment to Safety and Fair Play
The world of Milsim is constantly evolving, and the advent of 3D printing has unlocked incredible potential for custom gear, unique mission objectives, and immersive props. From specialized "projectiles" for specific launcher systems to uniquely designed throwable "grenades," the creativity of the community is truly inspiring.
At Mjolnir Gelball, we're excited by these innovations. However, our foremost commitment is, and always will be, the safety of every player on our field and the fairness of the game. That's why we've established clear guidelines for the use of 3D printed items, particularly those designed to be launched or thrown. This post outlines our methodology for determining if a 3D printed item is field-safe and game-legal.
The Appeal and the Apprehension: Why We Need Standards
3D printing offers fantastic flexibility, allowing for rapid prototyping and the creation of items perfectly tailored to a scenario. However, this flexibility also brings potential risks if not managed correctly. Poorly designed or printed items can behave unpredictably, cause injury, or create an unfair advantage. Our goal is to embrace the innovation while mitigating these risks.
Our Core Principles for 3D Printed Projectiles:
We assess every 3D printed projectile based on the following key criteria:
Impact Safety: It's All About the Strike Face
The Rule: Any part of a 3D printed "projectile" or throwable grenade designed or reasonably expected to make contact with a player must be constructed from a suitably soft and impact-absorbent material.
Approved Materials:
TPU (Thermoplastic Polyurethane) Filament: We specifically look for items where the entire striking surface or a significant portion designed to absorb impact is printed from flexible TPU. The shore hardness of the TPU will also be taken into consideration – softer TPUs are preferred for impact surfaces.
Foam: Commercially available foam or casting foams securely affixed to the 3D printed body is an acceptable alternative for the primary impact point.
Why: Hard plastics like PLA, PETG, or ABS or Nylons & Resins when used as the primary impact surface, can cause significant pain and potential injury, even at lower velocities. Our priority is to prevent harm. These materials are strictly prohibited as strike face materials.
Aerodynamic Stability & Predictability: No Wild Cards
The Rule: "Projectiles" must be designed for a reasonably stable and predictable flight path. They should not be designed to tumble erratically in a way that could cause the non-striking (potentially harder) surfaces to lead during impact.
Design Considerations: We look for designs that incorporate features promoting stable flight, such as fins, a weighted nose (with the aforementioned soft tip), or an appropriate length-to-width ratio.
Why: Unpredictable flight paths increase the risk of unintended impact areas (e.g., hitting sensitive parts of gear or unprotected skin with a harder part of the projectile). Stability ensures the soft strike face is the most likely point of contact.
Print Quality & Durability: Resisting Delamination and Fragmentation
The Rule: All 3D printed items must exhibit a high standard of print quality. We will inspect for signs of poor layer adhesion, under-extrusion, or other defects that could lead to the item breaking apart during launch, flight, or impact.
Layer Delamination: This is a critical concern. If a projectile or throwable delaminates (separates at the layer lines) mid-flight or on impact, it can create multiple sharp, uncontrolled fragments, posing a significant debris and potential injury hazard.
Our Checks: We will visually inspect for consistent layering and may perform gentle stress tests (with owner permission for non-destructive methods) on samples to assess layer bonding. We look for designs that minimize stress concentrators along layer lines.
Filament Quality & Printing Parameters: Using good quality filament and optimized printing settings (e.g., appropriate temperature, print speed, and potentially increased layer adhesion settings) is crucial for preventing delamination. While we can't verify your print settings, the end product's quality will be the determining factor.
Why: A structurally sound item is a safer item. Fragmentation turns a single projectile into multiple, potentially hazardous, pieces of debris.
Wear and Tear: Ongoing Vigilance
The Rule: Even approved items are subject to ongoing checks for wear and tear. Repeated use can degrade the integrity of 3D prints.
Player Responsibility: Players are responsible for regularly inspecting their 3D printed gear. Look for stress marks, cracking, layer separation, or deformation of impact surfaces.
Field Checks: Our staff may periodically re-inspect items. If an item is deemed to have become unsafe due to wear and tear, its use will be prohibited until repaired or replaced to meet safety standards.
Why: What was safe when new may not be safe after multiple impacts or exposure to field conditions.
The Approval Process:
Pre-Game Submission (Recommended): If you've designed or acquired a new 3D printed projectile or throwable, we encourage you to reach out to us via enquiries@mjolnirgelsim.com.au with photos, design details, and material specifications before game day. This allows us to provide initial feedback.
On-Site Inspection: All 3D printed projectiles and throwables must be presented to Our technology manager at the chrono station for inspection and approval prior to the start of any game.
Demonstration (If Required): For novel designs, we may ask for a safe demonstration of its launch and flight characteristics.
Tagging/Marking: Approved items may be tagged or marked by our staff to indicate they have passed inspection for that day/event.
Our Core Principles for 3D Printed “Sound Grenades”:
Part 1: The Foundational Principles of Safe printed grenades
While the following principles double up with much of the projectile principles we cannot stress these enough. They apply to all 3D-printed grenades that are subjected to any level of force or impact on our field. Failure to adhere to them creates an unsafe device, regardless of its intended function.
1. Layer Adhesion is Everything A 3D print is only as strong as the bond between its layers. This is the most critical factor for safety and the most common point of failure.
A print with poor layer adhesion is a pre-fragmented device. The internal force doesn't need to break the plastic; it only needs to separate the weakly bonded layers.
Causes of Failure: Incorrect print temperature, printing too fast, insufficient cooling, or using moist filament will result in dangerously weak layer adhesion.
Inspection is difficult. There is often no visual difference between a 95% bonded print and a 100% bonded one, but that difference is where catastrophic failure occurs.
2. Material Choice is Critical The material must be suitable for the forces it will endure.
Brittle Filaments (PLA, PETG) & Resins are a Hazard: Hard, brittle materials are exceptionally dangerous for impact or pressure-bearing components. When subjected to a sudden shockwave, they don't bend; they shatter. The result can be a cloud of sharp, high-velocity plastic shards.
Part 2: Applying the Principles – Device Policies
Our policies are based on applying these foundational principles to the level of risk each device presents.
Category A: High-Pressure & Percussive Devices (Gas/Blanks)
STATUS: PROHIBITED
This category includes any player-made, 3D-printed item using compressed gas (CO2, HPA) or a percussive charge (blanks, primers).
For these devices, the principles of layer adhesion and material choice are tested to their absolute limit. The forces are immense and instantaneous. A failure here is not a simple break; it is a catastrophic detonation that turns the device's body into shrapnel.
Because verifying the perfect internal structure required to contain these forces is impossible without destructive testing, all player-made gas or blank-fired devices are strictly prohibited.
Exception: You may use a 3D-printed shell for a commercially manufactured and approved grenade core (e.g., TAGinn, Airsoft Innovations). The core itself must be unmodified, and the shell must not impede its safe operation.
Category B: "Pop Cap" Sound Grenades
STATUS: PERMITTED, WITH STRICT INSPECTION
These devices are the only player-made sound generators allowed. While they don't handle extreme pressure, they must still be built according to the foundational safety principles to prevent cracking, fragmentation, or failure during use.
Inspection Requirements:
All pop cap grenades must be presented at the chrono station for inspection before use. We will specifically assess them based on the core safety principles:
Layer Adhesion: The device must demonstrate excellent layer adhesion, free from any delamination or gaps. Poor adhesion can cause the device to crack or shatter under the small but sharp force of the pop cap.
Material Integrity & Suitability:
The material must be robust enough for repeated percussive force.
Due to their brittle nature, devices made from PLA & PETG require frequent, diligent inspection for stress marks and cracks. Designs that use thin printed plates as firing pins are considered consumable and fail quickly.
Standard 3D printing resins are banned for any component that directly contains or directs the percussive force, as they are prone to shattering.
Wear and Tear: You are responsible for constantly inspecting your device. Any cracking, deformation, or visible stress renders the device unsafe and its use prohibited.
Containment: The design must fully contain the pop cap and direct the sound & ignited powder safely. No part of the cap or device should be able to become a projectile.
Pre-Approved Designs: To streamline check-in, the "Meteorite" by Fulcrum Airsoft and the "Thunderstrike V2" by Isotac Airsoft are pre-approved, provided they are printed to these standards. Other designs will face additional scrutiny.
This policy is not to stifle creativity, but to prevent injury. We appreciate your commitment to keeping our field safe.
Our Commitment to Innovation and Safety:
We believe that with careful design, appropriate material selection, and high-quality printing, 3D printed items can safely enhance the MilSim experience. Our guidelines are in place not to stifle creativity, but to ensure that innovation happens responsibly.
We welcome discussion and feedback from the community. If you have questions about these guidelines or a specific design, please don't hesitate to get in touch.
Stay safe, play hard, and see you on the field!
The Mjolnir Gelball Team
Disclaimer: These guidelines are specific to events hosted by Mjolnir Gelball. Other event organizers may have different rules. Always check the specific rules for any event you attend. The ultimate responsibility for safety rests with every player.