Sep 24, 2020
A length measuring device consisting of a fixed and a movable measuring surface, which is adjustable with a fine thread, is called a micrometer screw.
The measuring sample is held against one of the two parallel measuring surfaces and the thread is turned up or down by an adjusting screw until both measuring surfaces touch
the testing sample.
The thread is turned by means of a ratchet in order to avoid falsified measured values due to different measuring forces.
If the measuring force is too high deformation of the testing sample or the micrometer can happen.
The occurring measuring forces should be constant and reproducible. The ideal measuring force is between 5 and 10 Newton [N].
The roundness of a testing sample cannot be measured with a micrometer screw.
Almost all micrometers are equipped with plastic handles or shells for insulation.
In order to obtain optimum measuring results, the micrometer must be held on this sheathing.
Otherwise, the surfaces held in place may expand due to the body heat and falsify the measurement result.
The room temperature for the most accurate possible measurements is 20 °C.
There are analogue micrometers as well as those with an additional digital display of the measured values.
Different micrometers are required for internal, external and depth measurements or for measurements on gear flanks.
Depending on the requirements, micrometers can be tested internally by the quality assurance department or
by external certified calibration laboratories, as well as by the respective manufacturer using linear standards, gauge blocks or setting rings and plane-parallel test glasses.
Measuring Technology: Depth Micrometer for depth measuring
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This glossary of plastic industry is provided by PLEXPERT Canada Inc.
Sep 24, 2020
The composition of a mixture is determined via the so-called mixing ratio. It indicates how many parts or % by weight of two or more components are mixed. The mixing ratio is mandatory and can only be achieved by an exact weighing with a digital scale.
Different mixing ratios, for example in polyurethane foams, have a significant influence on the properties of the final product.
Measuring technology: Weighing of the
mixing ratio between
masterbatch and basic material.
Related topics:
Xscale
This glossary of plastic industry is provided by PLEXPERT Canada Inc.
Jan 11, 2019
It is a surface sensor whose contact surface is formed in the form of a paddle.
This allows a good contact also e.g. on a curved cavity wall.
Normally the temperature sensor is a K-type (NiCr-Ni) probe with a temperature range between -50 °C and +400 °C.
It should be noted that a contact measurement always influences the measurement result and hence is less accurate.
The mold wall temperature can only be measured at one-point in order to obtain useful information.
It is important that the duration of the measuring is sufficiently long.
Nov 4, 2019
A cuboid block with a very high length accuracy is called a parallel gauge block. They are used for testing and calibrating measuring instruments, as well as for direct measurement. By sliding the blocks together, also called wringing, different length can be made. The adhesion force holds the gauge blocks together. Steel gauges should not be joined together for more than eight hours as they tend to cold weld.
The total deviation is composed of the dimensional deviation of each individual gauge block additively, therefore, combinations should
consist of the least possible amount of individual gauge blocks.
Gauge blocks are linear gauges with the smallest measurement uncertainties. Calibration at a National Metrological Institute
(NMI), in Germany this is the Physikalisch-Technische Bundesanstalt (PTB) in Braunschweig, uncertainties of a measurement of approximately 20 to 50 nm are achieved.
Measuring technology: A
parallel gauge block with a nominal size of 75 mm.
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This information and services are provided by:
This glossary of plastic industry is provided by PLEXPERT Canada Inc.
Jun 14, 2019
The temperature in fluid, gas, powder or plastic is mostly measured with a penetration probe.
This is a thermocouple that consists normally of two wires out of different metals.
The temperature difference induces electrical voltage inside the metals (thermoelectric circuit) which can be calculated backwards to temperatures from the connected measuring device.
Dependent on the materials, the penetration probe can be used for different temperature ranges.
Penetration probes from type K (NiCr-Ni) can be used in a temperature range between -65 °C to 400 °C.
In the plastic industry, penetration probes are used to check the temperature of the melt that is injected directly out of the nozzle.
