Once bolt connection in mechanical equipment is loosened, it will cause bolt to fall off and cause major safety hazards, or bolt slack pre-tightening force will decrease, which will greatly shorten fatigue life of bolt connection. Therefore, appropriate anti-loose measures should be selected in design to ensure that bolts do not loosen in actual use.
Commonly used anti-loose measures in design are as follows:

Anti-loosening of double nuts is also called anti-loosening of counter nuts. When two counter nuts are tightened, there is always interaction pressure between the two counter nuts, and any one of the two nuts needs to overcome friction between screw threads to rotate. Even if external load changes, pressure between top nuts always exists, so it can relax.

 

 

 

 

 

Self-locking nuts generally rely on friction. Principle is to press embossed teeth into preset holes of sheet metal. Generally, hole diameter of square preset holes is slightly smaller than that of rivet nut. A nut is used to connect with locking mechanism. When nut is tightened, locking mechanism locks bolt thread.
Embedded nylon self-locking nut

 

 

Deformed thread locknut

 

Two-in-one nut with wedge and hammer

 

Wedge action lock nut

 

Thread locking glue is an adhesive composed of (meth)acrylate, initiator, accelerator, stabilizer (polymerization inhibitor), dye and filler in a certain proportion.

 

After nut is tightened, insert cotter pin into nut slot and bolt tail hole, open tail of cotter pin to prevent relative rotation of nut and bolt.

 

Slotted nuts are used in conjunction with screw bolts with holes and split pins to prevent bolts from rotating relative to nut.

 

 

Tandem steel wire anti-loosening is to insert steel wire into hole of bolt head, and connect bolts in series to restrain each other. This way of relaxation is very reliable, but it is troublesome to disassemble.

 

High-strength bolt connections generally do not require additional anti-loosening measures, because high-strength bolts generally require a relatively large pre-tightening force. Such a large pre-tightening force generates a strong pressure between nut and connected part. This pressure generates friction torque that prevents nut from rotating, so nut will not loosen.

 

After nut is tightened, bend single-ear or double-ear stop washer to side of nut and connecting piece to tighten nut to lock nut. If two bolts need double interlocking, a double brake washer can be used, and the two nuts brake each other.

 

Open spring washer

 

Conical elastic washer

 

 

 

 

 
What are benefits of injection speed?

 

The most important process conditions in injection molding process are temperature, pressure, speed and corresponding action time that affect plasticizing flow and cooling. These factors influence and restrict each other. For example, if temperature of melt and mold is increased, injection pressure and speed can be reduced, and vice versa, injection pressure and speed need to be increased.
Core of influence of various process conditions is change of viscosity of plastic, which is very important for reasonable selection of parameters during injection process and their mutual influence.
Characteristics of injection speed
(1) High-speed injection has following advantages in injection process:
⑴ Reduce injection time and shorten molding cycle;
⑵ Improve plastic process, which is conducive to forming of thin-walled parts;
⑶ Improve surface gloss of products;
⑷ It can improve strength of welding line, so that welding line is not obvious;
⑸ Prevent cooling deformation, etc.
(2) Low-speed injection has following advantages in injection process:
⑴ Prevent flashing of molded products;
⑵ Prevent generation of jet lines and flow lines;
⑶ Prevent burning marks;
⑷ Prevent air entrapment in plastic melt;
⑸ Prevent deformation of molecular orientation.
Advantages of high-speed injection are also disadvantages of low-speed injection, and vice versa. Therefore, combination of high speed and low speed in injection process can make full use of their respective advantages and avoid their respective shortcomings, thereby ensuring product quality and process economy. This is what we usually refer to as multi-stage injection technology, which has been commonly used on modern injection molding machines. At present, most of medium-sized injection molding machines have five to six levels of injection pressure, speed changes, and three to four levels of holding pressure changes (due to holding stage, melt has filled cavity. At this time, feeding material of melt flowing into cavity under holding pressure is already limited, so pressure holding speed has little effect)