Learn to buy these universal tension machine is no longer blind
Tensile testing machine is also called material testing machine, belongs to the general industry testing instruments, the market classification of tensile strength machine is broadly divided into two kinds: computerized and economic electronic, many customers feel very blind when buying tensile strength machine, no way to start, now as long as we start from the following aspects, you will be able to find a high quality instrument that you trust, look at it together.
First, the first thing to consider the need to test the range of material tensile strength.
Tensile testing machine is divided into single-column and double-column two, the general single-column load element (capacity / sensor) within 500KG and double-column are more than 500KG, double-column tensile testing machine used in the wire and electric olive, machinery, rubber and plastic industries more tensile range of different, decided to use the load element (sensor) is different, also decided the structure of the tensile machine, but the price of the impact is not significant (Except door type). For general flexible packaging manufacturers, the pull range of 200 Newton is sufficient. Therefore, it is also decided to use the single-arm type can be.
The corresponding structure with the single-arm type is the door structure, it is to adapt to the larger pull, such as a ton or more, flexible packaging manufacturers basically do not use.
Second, the test stroke problem.
According to the performance and requirements of flexible packaging film needs to be tested, the stroke in 500-600mm can be. Material elongation of more than 1000% can be used to choose the stroke of 1000 or 1200mm.
Third, the standard configuration issues.
Intelligent three basic configurations: host, microcomputer, and printer, if the microcomputer function is strong can be printed directly. Also can be equipped with a general computer. With a computer, you can carry out complex data analysis, such as data editing, local enlargement, can adjust the report form, statistical analysis of grouped samples. If equipped with a computer, the manufacturer should be equipped with the corresponding software control system.
Fourth, the output results.
Test results output results can be arbitrarily set: zui force value, elongation, tensile strength, constant force elongation, constant elongation force value, yield strength, modulus of elasticity, zui large test force of 8. This can be said to be the zui comprehensive results of the output when the computer operation. The products of some foreign manufacturers can generally output these 8 items. Some domestic manufacturers can output 5-6, some manufacturers can only output zui force value, the average value, zui small value of three.
Fifth, in the experimental projects can be done.
Flexible packaging requires a multi-use tension machine, that is, on the basis of different fixtures, can do tensile, compression, bending, tearing, shearing, 180 degrees peel, 90 degrees peel test.
Six, the main configuration of the product machinery.
Transmission, there are ball screw transmission and T-screw transmission, the former is expensive, for high precision, high test repeatability; the latter is cheap, for low precision, low test repeatability.
Screws, for tension accuracy measurement has a decisive role. The general ones are ball screw, trapezoidal screw, and general screw. Among them, the degree of ball screw is zui high, but the performance of its performance depends on the operation of computer servo system to play, and the whole set is also more expensive. The use of general screw and trapezoidal screw can achieve the required accuracy of flexible packaging, that is, plus or minus 0.5% accuracy.Sensor, the main cost lies in the life, photoelectric induction is one of the more advanced technology, generally available for more than 100,000 times, imports and some domestic joint venture manufacturers can reach.
Seven, the test speed.
The national standard test speed of 300 mm / min, some of the market equipment in 10 to 500 mm / min, some in 0.01 to 500 mm / min, the former generally use ordinary speed control system, the cost is low, rough impact on the accuracy; the latter use of servo systems, expensive, high precision, for flexible packaging enterprises, the choice of servo systems, speed range 0.5 to 500 mm /min is enough, so that neither affect the accuracy, the price is within a reasonable range.
Eight, measurement accuracy.
Accuracy issues, including force accuracy, speed accuracy, deformation accuracy, displacement accuracy. These precision values zui can reach plus or minus 0.5. But for general manufacturers, to achieve 1% accuracy is enough. In addition, the force resolution of almost all can reach one hundred thousandth (servo system control can reach this requirement)
Currently on the market for the detection of material tensile properties of many tensile testing machines, but not all testing machines are suitable for the tensile test of flexible packaging materials, this paper combined with China’s material testing standards, analysis of the selection of soft packaging materials testing tensile machine should pay particular attention to the indicators.
Tensile properties of plastics and rubber is one of the zui important and zui basic properties of its mechanical properties, which largely determines the use of the kind of plastic and rubber occasions. Tensile properties of good or bad, can be detected by tensile test.
1, the tensile properties of polymers
As a material used when the polymer is required to have the necessary mechanical properties. It can be said that for most applications of polymers, mechanical properties are more important than other physical properties.
Polymers have the widest range of mechanical properties of any known material due to the fact that polymers are composed of long chain molecules and have significant relaxation properties in molecular motion. Such as polymer materials have a fairly high elongation, the general PE elongation at break in 90% to 950% (including the elongation of linear low density polyethylene LLDPE higher), through a special production process, the elongation of some materials can be above 1000%, while the elongation at break of ordinary polymer materials are also more than 50% to 100% between. Usually the higher requirements for the tensile properties of the material are heat shrinkable film and stretch film, etc.
2、Tensile test
Tensile test (stress-strain test) is generally the material specimen ends are clamped on two jigs at a certain distance apart, the two jigs to a certain rate of separation and stretch the specimen to determine the stress change on the specimen, until the specimen damage.
Tensile test is one of the methods widely used to study the mechanical strength of materials, which requires the use of constant speed movement of the tensile testing machine. According to the different ways of load determination, tensile testing machine can be broadly divided into two types of pendulum tensile testing machine and electronic tensile testing machine, the current use of more electronic tensile testing machine.
3, electronic tensile testing machine selection index
As the flexible packaging materials are mainly polymer or its related materials, as mentioned before polymer materials elongation is far better than metal, fiber, wood, plate and other materials, so the detection of polymer tensile strength machine with the usual material tensile properties testing tensile strength machine has certain differences, especially need to pay attention to the effective stroke of the electronic tensile strength machine and the specimen fixture two aspects.
3.1 Effective Stroke
In the tensile test, the size of the specimen used is small, but the elongation of the material is generally high, so the tensile properties of the test soft packaging materials need to be equipped with a larger stroke of the pulling machine, otherwise the fixture may exceed the limit of use of the stroke, causing damage to the equipment.
GB13022-91 “plastic film tensile properties test method” given in the elongation at break or yield elongation (εt, unit is %) of the calculation formula
εt=[L-L0＊100]/ L0
where: εt is the elongation at break or elongation at yield.
L is the distance between the markers at fracture or at yield of the specimen.
L0 is the distance between the markers.