Three bases are lined up in a row, their welds still retaining the heat of fabrication. Here, an oven begins to find its footing for the journey ahead.
The base frames for three ovens are arranged side-by-side on the workbench; their four tapered legs have already been welded on, with fresh weld marks still visible at the joints. Workshop welding area. The base frames for three ovens are arranged side-by-side on the workbench; their four tapered legs have already been welded on, with fresh weld marks still visible at the joints. The base serves as the structural foundation for the entire oven. Multi-layer ovens must accommodate numerous sample trays; combined with the weight of the unit itself, this places high demands on the base's load-bearing capacity and stability. Workers cut the legs and base plates from thick steel sheets and weld them into place one by one; every weld undergoes visual and impact inspections to ensure there are no cold welds or porosity.01 Base Welding: The Foundation of an Oven 
From flat sheet to hollow chamber, the stainless steel underwent its first transformation under the heat of flames and welding torches.
The oven's inner chamber has largely taken shape; its stainless steel walls gleam like a mirror, and a port for the hot-air circulation duct is positioned in the center of the back panel. It is a rectangular stainless steel chamber with a mirror-like interior finish and a circular opening in the center of the rear wall—the connection point for the hot-air circulation system. The outer casing retains its raw, untreated metal finish, and with the four support legs already welded on, the entire unit stands firmly on the workshop floor. The inner chamber is the heart of the oven, directly determining temperature uniformity and corrosion resistance. Workers fabricate the sealed chamber by bending and welding individual stainless steel sheets. The welding standards for the inner chamber are exceptionally high; because the unit operates in a high-temperature environment over the long term, even the tiniest pinhole could expand during use. Consequently, every seam undergoes a two-pass welding process: a root pass to ensure a tight seal, followed by a cap pass to ensure a clean, aesthetic finish. After welding, workers use an angle grinder to smooth out any slag and then polish the seams with fine-grit sandpaper. To the touch, the welded seams are virtually indistinguishable from the surrounding surfaces.02 Inner Liner Forming: The Birth of the Stainless Steel Cavity
Those unseen layers of insulation determine just how effectively an oven can lock in the heat.
A neat row of circular holes has been cut into the side of the oven, with five mounting positions for heating elements arranged vertically; workers stand on iron stools to perform the task, and the insulation material packed inside is visible along the edge. A neat row of circular holes has been cut into the side of the oven, featuring five circular ports arranged from top to bottom—these are the mounting points for the heating elements. Nearby, smaller holes serve as access points for temperature sensors and wiring. The insulation layer is crucial for the oven's energy efficiency and temperature control. The gap between the inner chamber and the outer casing is packed densely and evenly with insulation material, ensuring there are no voids or inconsistencies in thickness. Effective insulation ensures uniform internal temperatures and minimizes heat loss; conversely, "cold spots"—areas with lower temperatures—can directly compromise the drying performance.03 Side Openings and Insulation: Locking the Heat Inside 
Behind every shelf lies the patience of workers who have repeatedly calibrated it.
Two workers are installing shelf rails inside an oven—the overhead crane beam bears the slogan "Strengthen Safety Awareness"—while the height of each tier is being precisely calibrated. The oven currently retains its raw metal finish, as the exterior casing has not yet been painted. The framework for the multi-tier stainless steel shelving is already visible, and workers are meticulously securing the rails to the interior sidewalls. The height of each tier has been calculated with precision to ensure that trays sit level and stable, and slide in and out smoothly. The key advantage of a multi-tier fixed-shelf oven is its high capacity, allowing for the processing of large batches of samples at once. However, a greater number of tiers demands higher precision in internal assembly: every shelf must be level and every rail perfectly aligned; otherwise, trays could jam during insertion, potentially even disrupting the hot air circulation.04 Internal Assembly: Precision Installation of Multi-level Shelves 
From metallic gray to pristine white, the oven began to take on the look of laboratory equipment.
The oven has been spray-painted a clean white. Another oven has also been spray-painted. Its originally dark gray-black metal casing is now a clean white, creating a striking contrast with the gleaming stainless steel shelves inside. White is a classic color choice for laboratory equipment; it looks clean and professional, and makes it easy to spot stains or damage. Before painting, workers smooth the surface, remove rust, and apply a phosphating treatment, followed by the application of primer and topcoat. Each coat must dry completely before the next is applied, making the entire painting process a multi-day undertaking.05 Spray Painting: From Metallic Grey to Pristine White 
After nearly a month, the oven finally stood in the workshop as a finished product.
Unlike the previous white-cased oven, the finished product features a blue and white color scheme: the main frame is white, while each layer of the door panels is dark blue, with red sealing strips inlaid along the edges. The ten door panels are neatly arranged from top to bottom, each capable of being opened independently. After placing a sample tray, they are closed, and the red sealing strips ensure that heat does not escape. On the right side of the oven is the control box, housing temperature controllers, switches, and indicator lights. There is an exhaust vent at the top, and sturdy white support legs at the bottom. The entire oven looks professional and robust, and its large capacity of ten layers immediately conveys its processing power. From the first steel plate on July 28th to the complete machine rolling off the production line on August 24th, this oven has undergone numerous processes including welding, forming, drilling, insulation, assembly, painting, and debugging, undergoing countless hands of meticulous work. Now, it is about to be packaged and transported to a laboratory, where it will work day after day, providing a stable and reliable temperature environment for sample drying, heat treatment, and aging tests.07 Finished product: Multi-layer oven with blue and white color scheme
