In the field of plastic injection molding, there is always a strange problem. Every time a mold is installed on machine, it takes tens of minutes or even half a day to adjust. It is difficult to produce according to mature parameters of other machines. In the era of standardized manufacturing, this phenomenon is unimaginable, but it comes in detail.

 

Why can't different specifications of injection molding machines copy same parameters?
Can this be done?
Reason, in the final analysis, is that cumulative tolerance of injection molding machine is too large. In the face of precise mold, two injection molding machines cannot achieve same parameter output, so machine-to-mold debugging parameters must be one-to-one.
Where does tolerance accumulate?
Almost every processing parameter and output parameter of injection molding machine has a tolerance. Here are a few simple items:
1. Differences in clamping force. Clamping force of injection molding machine we have seen is rated at 100T and 200T, but what is actual value? Will it be 110T or 95T? It is very likely that error in this piece is very large. Hydraulic press may be better, but pressure attenuation in its production cycle is also obvious, and it is normal to reduce it by 5%.
2. Actual injection temperature difference. Actual barrel temperature of injection molding machine is very different from rated temperature. Now everyone is talking about plus or minus 1 degree or 0.5 degree, and stability of PID control, but what about output of injection temperature? It is two different things from display temperature. Difference is very large. It is not a matter of 1 degree or 0.5 degree at all, but a dozen or even dozens of degrees. Difference is very big.
3. Differences in surface finish of screw barrels.
4. Screw assembly accuracy and clearance differences.
5. Difference in diameter of hydraulic plate.
6. Actual friction and stability variation of slide rails.
7. Actual output difference of pump motor.
8. Difference in parallelism adjustment of two large plates of clamping system.
Okay, so much to say. So many differences can be reduced in industrial technology but are difficult to eliminate. Is there no way to have only one parameter for one machine?
It would be better to use a closed-loop control system or take rifle as an example.
Injection molding machine has cumulative tolerances that lead to inaccurate output, rifle also has cumulative tolerances that lead to inaccurate shooting, so we can't demand that rifle can be very accurate, and we can't demand that gunners have a high level of shooting. Because ordinary injection molding machine here is same as rifle, it is controlled by open loop, that is, I output it, but I don't know exactly how my "controlled object" works.
Controlled object is bullet out of chamber, which is actual output parameters of injection molding machine (temperature, pressure, speed, etc.)
Industry is very particular about standardization. For example, a gun, a soldier holds a bullet of same specification and puts it into a different gun of same model. He certainly does not have to worry about difference between aiming needs this time and last time. But injection molding machine is different. Two injection molding machines of same specification need different parameters for same mold, which is a helpless fact.
To achieve complete stability, closed-loop control is required, that is, what is my actual output.
How process works, I want to monitor and correct deviation in time.
This is a missile. Difference between a missile and a rifle bullet is that actual orientation and operating parameters of the former can be known by reconnaissance. If it is deviated, it is also clear how to correct it in next step. That is to say, even if it is deviated at first, it can be adjustment, this is closed loop control.
Now some high-end injection molding machines can also achieve closed-loop control, that is, how to correct my actual output, information is accurate, and process is controllable.
It is hoped that more and more injection molding machines can achieve same mold and parameters of different machines in the future, which is a great good thing for our injection molding industry.