Guide sleeve of injection molding machine before and after injection, guide sleeve of tie rod of moving platen, sliding foot guide of moving platen, connecting rod pin of toggle-type clamping mechanism, guide of cross head and mold adjusting mechanism, etc. , There are various forms of sliding friction pairs, we form a centralized lubrication system by supplying lubricants together.
Centralized lubrication system of injection molding machine should be divided into lubricating oil system and lubricating grease system according to different lubricants used. It is generally composed of (lubricating) pump, distributor, oil pipeline and other accessories. There are two types of lubricating pumps: manual pumps and automatic pumps. Automatic pump is powered by a motor or high-pressure gas. It is divided into gear type and plunger type. Gear type pump has a large flow and low pressure, and plunger pump has a high pressure but a small flow. In automatic pump, its controller should also be involved. Now injection molding machines have all been centrally controlled by computer.

 

Due to many lubrication points of injection molding machine, amount of lubricant required for each point is also different, pipeline pressure loss caused by distance between lubrication points and lubrication pump is different. We must set up a flow distributor between lubrication pump and lubrication point. It is core component of lubrication system. There are three types of impedance type, volume type and progressive type:

Working principle of distributor is to set a small channel on pipeline to increase damping effect. It can only distribute flow proportionally, is greatly affected by pressure of lubricant at the front and rear of distributor. It is the simplest and most economical distributor.
So-called helical impedance type is to insert a small clearance fit mandrel (like a screw) with a helical groove on the surface into standard hole (accuracy can be machined to H7 to H6 level), depth and length of helical groove are controlled to control size of damping; so-called small hole annular gap impedance type is to put a small diameter mandrel in a standard hole, there is an annular gap between hole and mandrel, annular gap is adjusted by controlling diameter of mandrel. Similarly, small hole and mandrel cannot be processed too long, so annular gap can only be controlled to be smaller, so it is also prone to blockage.
Impedance distributors are currently widely used in small injection molding machines because of their compact structure, economy, easy operation and maintenance, and freedom to increase or decrease lubrication points.

Volumetric distributors are divided into pressurized volumetric type and pressure relief volumetric type from working principle. So-called pressurized volume type means that pressure oil delivered by lubricating pump pushes piston in metering part, lubricant that has been stored in metering chamber last time is forcibly pressed to lubrication point. When lubrication pump stops supplying oil, pressure is relieved, piston is reset under action of spring force and is ready for next oil supply.
So-called pressure relief volume type means that piston in metering part stores oil under push of pressure oil delivered by lubricating pump. When lubricating pump stops supplying oil and relieves pressure, piston discharges oil under action of spring force. It can be seen that pressurized volume type can supply oil to lubrication point at high pressure, and reliability is relatively high. It can be seen from the working principle that volumetric distributor can only discharge oil once in a cycle of lubricating pump operation, shutdown and unloading; in addition, spring reset is slow during unloading, which requires high pressure unloading of main pipeline, and its "work efficiency" is low. Especially when injection molding machine is tested for the first time, some parts require a large amount of oil, and waiting time for refueling is long.

 

In addition, due to rubber, spring and other components in distributor, reliability and pressure resistance are not very high, which is its defect. Because of accurate and reliable lubricant supply, volumetric distributor can detect system pressure, and it is convenient to increase or decrease lubrication point, but cost is relatively high compared with impedance type, so it is widely used in medium-sized injection molding machines.

Basic working principle of distributor is use of hydraulic progressive action. It means that each working plunger pair in distributor, after cyclic action of previous working plunger pair, each completes its own plunger stroke and delivers a certain amount of lubricant to lubrication point.
As long as pressurized lubricant is supplied to distributor, working plunger pair operates in a progressive manner and fills with oil at a constant displacement. Then, as soon as flow of supplied pressurized lubricant ceases, working plunger of dispenser stops moving. When lubricant under pressure starts to flow again, working plunger in distributor starts its oil filling cycle again at same point.
Progressive distributors are structurally divided into two types: integrated type and slice type. Integrated distributor is a whole valve body, with a compact structure and convenient installation, but valve body is generally made of aluminum alloy, and threaded port is easily damaged. Moreover, gap between working plunger and valve body will become larger under abnormal high pressure, resulting in leakage, and progressive action will continue incorrectly. Displacement of each hole of distributor is same, and it is difficult to adapt to requirements of various oil requirements of injection molding machine.
There are various specifications for displacement of distribution blocks, which can be matched according to different needs, and have a large degree of freedom. A feature of progressive distributor is that when a blockage occurs at a certain point, the entire sequence action will stop, which brings great benefits to our monitoring of it.