Miami University

Instrumentation Laboratory Project Page

Project: Microcompression System

Department: Chemical, Paper, and Biomedical Engineering

Primary Investigator: Dr. Steven Keller

Purpose: The behavior of low density fibrous webs, such as paper towel and polymeric nonwoven materials, under localized compressive force is of considerable interest for end use performance, especially
the durability of embossed features and for softness to the touch. Related to, but not the same as micro-indentation of ductile and plastic materials, micro-compression seeks to characterize the compression
of embossed and through air drying features with in-plane dimension of several mm and out-of-plane height of < 1mm. This instrument was developed to measure a wide range of compressive forces from
10 mN to 2 N while simultaneously imaging the collapse of the structure. The design requires a unique tandem configuration of low and high range load cells to which the probe tip is affixed. The probe and
backing plate are controlled to 0.5 μm steps for smooth strain rate and precise measurement of Z-directional separation distance. In-plane (X-Y) positioning of the probe tip is controlled to 1 μm within a
100 mm square operating window. A sophisticated user operating system based on NI LABView allows complete control of experimental execution, data and image collection and storage, and protection of
the delicate sensing hardware. Videos showing force as a function of probe position are easily compiled from the acquired results. The instrument is primarily for graduate research, but has been operated
by undergraduate students as independent research projects.

IL Comment: Researcher required a way of detecting extremely small forces being exerted during the compression of paper towels to study their compressibility characteristics, using a stage movement system
that is already in their lab (stage movement steps are in the micro-meter range). Their previous system was unreliable, as it did not have any safety mechanisms in place to prevent damage not only to their test
samples but also the expensive load cell sensors being used for these experiments.
Our design uses a LabVIEW based approach that monitors and controls the position of each stage (front and back) on 3 different axes (X, Y, and Z). The Z stage (where the load cells sit) also includes force based
limits that if the set limit is exceeded at any time the stage retracts away from test sample protecting both the test sample and the load cell from overloading damage. This one improvement has and could potentially
save thousands of dollars in load cells. The load and position data is saved to disk for further analysis.
The design also includes an automated movement mode which will run through a user defined program of machine movement and data acquisition (DAQ) which allows for experiments that could last several days.
To make everything work with the stage controllers that the researcher already has, a custom hardware interface box was required to be designed and constructed by the I\L.

Cost to researcher: $644.72

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