Locking force is optimized and the load is evenly distributed in the four pull rods is an important index for evaluating the performance of vertical injection molding machine. Only the load uniformly distributed vertical injection molding machine, in order to ensure the product quality, and can protect the mould and vertical injection molding machine itself, prolong die life and vertical injection molding machine. In addition, the parallelism plays a particularly important role in the process of injection molding. If the template or die is not parallel, each rod load is different, may cause the rod fracture, resulting in damage to the machine, the production disruption. If the installation of measuring device in vertical injection molding machine, can avoid this phenomenon. Traditional measurement methods is to use paste type strain gauge measuring rod strain and thus calculating rod clamping force. This method has many disadvantages, such as difficult sticking, strain gauge is used only once; needs 2 ~ 4H preparations; cannot be used for measuring the die optimization. From a long-term point of view, this method is very expensive, but also high demands on the measurement environment. While the clamping force of new measurement technology is to solve the above problems, not only easy to install, and quick response, strong ability to adapt to the environment.

1 new clamping force measuring device

The clamping force of new measurement technology is the use of strain gauge measuring rod strain to the clamping force, but do not take the strain gauge on the pull rod, but clever the strain piece in a piece of steel shell surface, steel foil protected through magnet absorption rod steel shell, thus the gage pressure at rod surface. The measurement of this new device called the magnetic attached type mould clamping force measuring device (sensor). Stainless steel foil strain gauges were placed between the two magnets, strong magnetic force through a bolt and a nut and a rubber mat the strain sheet firmly affixed to the rod surface, resulting in a strain gauge, between the steel foil and rod surface produced by the interaction of friction force is powerful. When the rod surface stress deformation occurs, due to the interaction of the friction force, under the action of magnetic force firmly attached to the same deformation in the strain gauge and pull rod pull rod surface. During the whole course, magnetic friction and down action instead of usually used for adhesion force strain gauge glue. This means that can be very accurate measurement of cylindrical rod and plane without the use of glue case elongation and strain gauge can be used repeatedly, completely solve the strain gauge used once can not be used again problem, thoroughly solves the strain gauge force consumption consumption when installation problems. It can be said that the magnetic attached type mould locking force sensor is an epoch-making strain gauge measurement transformation technology. But in the process of use, and as paste type strain gauge, is not affected by the rod diameter limit applies to almost all rod diameter.

But this new measurement techniques were used because of mounting strain is the volume and quality of large steel shell, and uses magnetic force to compress, so not too suitable in with online production products occasions large and continuous shock loading on the measurement of the clamping force, only suitable for use in vertical injection molding machine clamping force of debugging and testing the mold.

Aiming at the situation of online production monitoring is a continuous impact load locking force, can adopt another new clamping force measurement technology, namely the strain gauge device in aluminum shell volume and quality of smaller, using steel clamping replace the magnet adsorption, adsorption capacity by pretightening force screw instead of magnet. This measurement scheme using aluminum shell volume and quality of smaller as the mounting base strain gauge, installed more firmly, and can be used in continuous production, able to withstand continuous impact, thereby in the continuous production of real-time monitoring of the change of the locking force. Strip steel but this method of measurement need to customize different circumference.

For vertical injection molding machine R & D and production unit, the new measurement mode locking force the best solution is: in the test machine and mold trial stage, the use of magnetic adsorption type strain sensor for measuring clamping force; in the stage of production, the use of steel strip type strain sensor for continuous measuring the clamping force, and to monitor. The above two kinds of new measuring techniques are submitted a patent application.

2 bar strain and clamping force measuring principle

A lot of methods for measuring rod strain, are deformation occur through the locking rod load were characterized by. Through the measurement of drawbar strain can reflect the following two questions:

(1) rod deformation amount or strain because of mold vary. With a vertical injection molding machine, with a rod, if the mold different, strain pull rod are also different. So through the detection rod strain, to avoid the occurrence of melt overflow from the mold phenomenon.

(2) each rod force to reflect the actual working state of vertical injection molding machine. If the clamping force is too large, will make the machine and mold under high load.

The amount of deformation strain gauge measuring rod directly, the unit is micros-train, with epsilon said. Taking microstrain as the unit of the strain value is very precise measurement of value. Unit output strain gage signal generation is mV/V, then use the signal amplifier into deformation epsilon =1mi-crostain=1 * 10-6m/m.

3 strain and display mode locking force

The above new measurement technology is different from previous stickup method, need not receiving a conversion box from the strain sheet lead, but the same digital point together. In the traditional method, when the strain gauge is more, many cable wiring is tedious, error prone and can only get the relative value. The clamping force of new measurement technology is the direct installation of a cable interface connection is on the sensor, the previous integrated into a 6 pin interface. Then the Y type cable 6 pin is connected with the monitor through. Between the two connected in a half bridge circuit, thus the strain resistance caused by the change of the sheet deformation, in the form of voltage signal changes in performance, and through the signal amplifier monitor in the small voltage change amplification, displayed through the LED panel. The monitor can through the button input corresponding diameter according to the preset value, the young's modulus, can directly obtain the locking force of absolute value.

A new method of measuring the strain is converted to analog the same principle with the old method, namely the strain caused by resistance proportional to changes caused by bridge circuit, a voltage proportional to change, but the new display mode has the advantages that the connection method is changed in the past, has better operability, and the signal through the appearance of high insulation "Y" type double branched polyurethane (PUr) to achieve better cable and 6 pin interface fidelity; two is the absolute value can be directly displayed on the monitor. The two improvement is very good for the improvement of the traditional measuring method.

4 Conclusion

New clamping force measurement technology has the following advantages:

(1) to discard the traditional paste type strain gauge sticking difficult, time-consuming and can only be used once the disadvantages of using the magnetic attached type installation, installation is very convenient and strain gauge can be used repeatedly.

(2) the measurement environment requirement loose.

(3) using the interface technology, the traditional way to avoid cumbersome wiring, has better maneuverability, through the appearance of high insulation of the "Y" type dual branch PUr cable transmission signal to achieve better signal fidelity.

(4) can be read directly the clamping force of absolute value, while the traditional way can only get the relative value.