【107】A precise embrace of three materials in the drone gimbal

【107】A precise embrace of three materials in the drone gimbal

Today, the people from DJI Innovation quietly arrived and directly entered the cleanroom without greeting. They stood in front of the five-axis injection molding machine, watching the mechanical arm take out a drone gimbal bracket - it was a complex component like an art piece, made of carbon fiber, magnesium alloy, and engineering plastic, all integrated seamlessly. The lead hardware director watched it for a full ten minutes, then turned to me and said, "Do you know? We previously considered a joint factory with Panasonic in Japan, but their quote was six times higher, and the delivery time would be three months longer."

In fact, this project began quite by chance. Three months ago, a young engineer from DJI saw our automotive parts at a trade show and, after returning, secretly sent us a damaged gimbal bracket, with a letter stating, "This is our latest model drone's test sample. It broke when encountering strong winds at an altitude of six thousand meters. The original design used seventeen parts to assemble, which was too heavy. Do you have the possibility of making an integrated one?"

When we disassembled that bracket, we felt the desperation of the DJI engineers: the carbon fiber board needed eight screws to be fixed to the magnesium alloy frame, and the frame was connected to the plastic damping component through clasps, with each connection point being a potential failure source. And the user's extreme usage scenarios were astonishing: from the tropical rainforest's humidity and heat to the Qinghai-Xizang Plateau's extreme cold, from the desert's sandstorms to the seaside's salt fog corrosion. Even more demanding was that this bracket had to be equipped with a twenty-thousand-dollar movie-grade camera, any minor deformation would cause the picture to shake.

"The three-material composite, and also the built-in sensor cavity, is equivalent to embedding steel bars in tofu." Senior engineer Chen, the general mold engineer, shook his head after looking at the three-dimensional diagram. But the younger generation of engineers were eager to try. They formed the "Mountaineering Team" and vowed to conquer this Mount Everest.

The first version of the design was brutally rejected by reality - the contraction rates of the three materials were too different, and after cooling, it either warped or cracked. The team tried twenty-seven different pressure retention curves, but still couldn't solve the fundamental problem. Until one late night, Dr. Xiao, a PhD who had just returned from the Shanghai Institute of Materials Research, suddenly said, "Why do we always think about opposing the material properties? Why not take advantage of their differences?" He proposed the "pre-stress gradient design": Let the carbon fiber be in a slightly tensile state during molding, the magnesium alloy remain neutral, and the plastic be in a compressive state, so that after cooling, the three materials would "embrace" instead of "fighting" against each other.

This disruptive idea required a completely new mold structure. The design team boldly adopted the "in-mold folding" technology: The mold itself has movable sliders, which change shape like origami during injection. This sounded like magic, but it was extremely difficult to implement - during the first mold trial, the slider got stuck, and the eighty-thousand-dollar mold almost broke. Mechanical engineers worked through four nights, installing nanometer-level pressure sensors and adaptive lubrication systems on each slider to make them move like joints.

The most stunning part came at the end. DJI required that the internal of the bracket should reserve wiring channels and sensor installation cavities. The traditional approach was post-processing, but that would damage the continuity of the fibers. Our automation team came up with "in-mold wiring": Before closing the mold, the mechanical hand placed the wiring and sensor prototypes into the mold cavity, and during injection, the melt would perfectly wrap them. When the first bracket with a fully embedded wiring was produced, even the experienced Chen couldn't help snapping a photo to commemorate it.

Last week, DJI sent us the high-altitude test video. The drone hovered in a seven-level wind, and the camera on the gimbal remained stable as a rock. In the video's final part, the test engineer said to the camera, "We can finally say that China's drones have the world's top-level gimbal structure."

Now, this bracket is not only used in DJI's flagship products, but also has three variants that are used in their industry drone series.This story began with a damaged part sent secretly, and was achieved through the persistent challenge of a group of engineers to the "impossible". When those drones captured breathtaking scenes in the sky, the three-material composite bracket inside was maintaining the stability of each frame with an accuracy of 0.01 millimeters.

Enabling China's high-end equipment to have a naturally formed skeleton - the Golden Eagle multi-material integrated molding technology redefines structural aesthetics.