There were two major changes taking place in the 1920s that made factory production more efficient. Both are discussed in detail in the link below.
The first of these was the assembly line system. Henry Ford pioneered the use of assembly lines, which allowed him to make cars much more efficiently than had previously been possible. This system was more efficient because each did just one task over and over as parts were brought to him. This was much more efficient than moving from place to place or doing more than one task.
The idea of the assembly line meshed well with the other factor, which was "scientific management." This trend, also known as "Taylorism," was one in which experts would analyze workplaces to determine where tasks could be done more efficiently. They would break each part of the task down into steps and try to see if any step could be done better, like by having a tray of parts at a different level or by having a certain size of shovel be used by someone shoveling coal into a furnace.
By embracing Taylorism and assembly lines, factories were able to produce goods much more efficiently as the '20s went along.