There are several main problem in the cable tie manufacturing: short shot, flashing, bubbles, gets yellow, brittle, and we will tell you why:
China is the main production area for cable tie, with up to 50% of cable tie are made in China and exported to all over the world. We started developing nylon cable tie injection molding machine in 2005, shaped in 2007 and keep improved in the following years. Now we have been in this field for 14 years and have 70% market share. As the leading cable tie injection machine manufacturer, we widely evolved in cable tie production, including moulding machine, mould, material and auxiliary machines. In this article, we’ll overview the common problems for nylon cable tie manufacturing.
The selection of injection machine, mould and raw material dominate the injection moulding process. And poor selection will ultimately affect cable tie quality, productivity and profit.
Cavity of cable tie is long and narrow, to fill fully, so much more attention is paid to injection pressure and injection speed by upgraded motor and pump. To sustain stable processing condition, injection molding machine also needs to have strong clamping force. Clamping force depends upon the material& design of clamping unit. For example, our designed clamping structure based on the characterize of cable tie production, all platens, toggles and tie bars enhanced.
The normal injection molding machine
Below we take K358F machine of F series, which is special for the cable tie manufacturing, compared with K320VT normal machine
|Tie bar diameter||100mm|
|Fixed platen thickness||285mm|
|Moving platen thickness||557.5mm|
|Tail platen thickness||765mm|
K850L machine of L seris, which is special for the cable tie manufacturing, compared with K800VT normal machine
|Tie bar diameter||165mm|
|Fixed platen thickness||455mm|
|Moving platen thickness||490mm|
|Tail platen thickness||525mm|
And for L series cable tie injection machine, the actual maximum clamping force is much higher than rated clamping force.
|Rated max clamping force||Actual max clamping force|
Selection of raw material is critical. Poor flowability will have a negative impact in injection moulding. It’s necessary to check with supplier about that.
Pre-warming the mould to reach the correct temperature will reduce the reject rate at the machine starts up. Connecting mold temperature controller will help cut down pre-wraming time and save material cost.
Customers observe cable tie appearance firstly. Bad appearance will be counted out right now. Very often clamping unit will be overlooked. However, insufficient clamping force will generate flashing. Inexperienced operators always attempt adding injection pressure to reach quick moulding. High injection pressure is one of the probable reasons of flashing. Beyond that, mold design is crucial as well.
PA 66 is a relatively complex resin, and absorbs water from air easily. Dry material is the first step to be done. Insufficient dry results in the high temperature water vapour, screw and barrel special for PA will exhaust part of them. But fast injection speed traps air. Poor exhausting design of mold intensifies air trapping.
4. Nylon cable tie gets yellow
To optimism productivity, some cable tie manufacturers try to increase temperature to reduce cycle time. As we know, for some American producer, their cycle time is 4.9s, but material temperature reaches to 380°C. Melting point for PA 66 is approximately 280°C. Cable tie gets yellow because of high temperature. For injection machine suppliers who have poor experience for cable tie production pay limited attention to L/D ratio of screw. Weight for each shot of cable tie is very small, the melted resin stacked on the front of screw by using the normal screw.
In-appropriate screw diameter, L/D ratio will lengthen the time resin stayed inside of barrel, which leads to PA 66 degraded and cable ties get yellow& brittle. PA 66 price increased dramatically since 2018, producer pushed to add more PA 6 and granulated resin. Keep temperature, screw &barrel set same as before, cable tie get yellow. So, did constant improvements base on the market situation.
To inspect cable tie quality, tensile strength is the main point. As we mentioned above, high temperature will degrade PA 66, and finally tensile strength lowered. Too much recycled material and PA 6 affect tensile strength negatively too.