PT Blog

To accept pellets or even ground pellets, the feed sections of very small screws need to be proportionally deeper—that is, with a greater compression ratio—to match the output of the rest of the screw. That is due to the restrictive entry dimensions into the screw and lower compaction rates resulting from far fewer particles in the screw channel. Increasing the channel depth in the feed section naturally lowers the torque capacity of the screw.

In additive manufacturing equipment there has been a migration away from heat guns, which feed polymer filaments to supply the melted polymer, to miniature extruders. Miniature extruders increase part buildup rates or output and reduce material cost. Due to the poor heat transfer of polymers, the output of heat guns is limited, and the cost of filament is typically five times or more the cost per pound of pellets. Design of miniature or very small screws, whether used for additive manufacturing equipment or not, requires balancing their output requirements with their torque strength.

For nearly 200 years, Micelli Mold Co. (West Babylon, N.Y.) has supplied the molds chocolatiers use to shape molten chocolate into familiar shapes for some very familiar names. For six decades the chocolate molds it sold were metal, but starting in the late ‘80s, the company switched over to plastic molds that it would injection mold from aluminum tools. The use of aluminum tooling, the fact that many of these molds were created from polycarbonate and the need for flat, stable parts eventually led Micelli to Bole Machinery.

Bole Machinery Inc. (Stow, Oh.) the North American unit of China’s Chunglu Group, itself a subsidiary of Ningbo Shuangma Machinery Industry Co. Ltd., has been in U.S. almost four years, according to its president, Alfred Rak. Rak told Plastics Technology that its main office in Stow was opened in November 2018, created after the company formed its own U.S. subsidiary that spring to handle sales and service directly.

Part one of this series (in March) discussed the importance of proper gate depths and gate widths. Part two (April) discussed two different types of gates, gate land length, and gate-freeze time. This month I will discuss edge gates and runner sizes.
 

Figure 1 depicts a simple edge gate. It is the most commonly used gate type—probably because it is the least expensive to machine. All that is required is an end mill to connect the cavity to the runner. This type of gate is also the easiest to measure its depth, which is critical in multi-cavity molds. However, this design has several shortcomings.

The coronavirus pandemic has caused a big shift in all businesses as everyone adjusts to a new reality. However, for manufacturing, there’s still machinery that needs to be installed.

German waste management company Hündgen ordered a new Lindner Micromat 2500 shredder that was delivered in March and the company’s facility’s retrofitting was in full swing. And then came the coronavirus lockdown.

Having a mold made is a big investment for an OEM or brand owner of any size—a large enough outlay that it needs to be reliable the first time, every time. And once the tool is built and passes all tests, it’s up to the molder to ensure reliable parts are made on every cycle.

Truth be told, some molders are not able to use these tools effectively, devaluing this significant and time-intensive investment. At Performance Plastics in Cincinnati, we frequently see customers looking to transfer their molds because their previous molder couldn’t achieve production goals with the tool.