OA screw --- For uniform melting and mixing of resin
Purpose of development
By compressed sub-flight screw, resin material is melted and mixed uniformly using whole length of barrel.
1. Full-length of barrel is used to measure resin. It may be used as larger size of reguar screw and barrel.
2. As composition of melted material is uniform, molding is more stable and repeatability is improved.
3. Less trial shots before actual production saves time and material.
4. Cycle time can be shortened by faster screw rotation with enhanced plasticization and mixing of material.
Comparison of resin temperture distribution of 1 shot
Example 1. Comparison of A4 file case moldings *molding conditions are the same.
MD280W with φ52mm screw Measuring: 180mm (S/D = 3.2), Screw rotation: 240 min^-1
1 cycle: 25 seconds, Material: PP, Red colorant: 3%, Nozzle: open nozzle
Regular screw (left) → NG OA screw (right) → Good
Problems with regular single flight screw
Unmelted resin and uneven coloring. These tend to happen around gate.
Solution using regular single flight screw
①Screw rotation is reduced from 240 min^-1 to 100 min^-1. This changes cycle time by adding 15 seconds; from 25 seconds to 40 seconds.
②Barrel temperature is increased by 15 ℃.
Example 2. Dispersion comparison *molding conditions are the same.
MD75X with φ25mm screw Measuring: 15mm (S/D = 4.6), Screw rotation: 200 min^-1
Material: PP, Black colorant: 0.09%, Nozzle: open nozzle.
Regular screw （top） → Uneven coloring a lot of kneading characteristics are insufficient
OA screw (bottom) → There is little uneven coloring, and kneading characteristics are good