Tecnova

The Challenge

Create a low-cost volumetric measuring device to test shrinkage of dental composite and adhesive materials.

The Solution

National Instruments LabVIEW and NI VISION 2009, NI USB 6501 digital I/O device, USB-based camera, and rotating stepper are used to determine 3D volumes from a series of 2D images. A USB based security dongle prevents unauthorized copying of the application.

The Summary

Precise volumetric measurements are usually achieved through liquid displacement methods or expensive 3-dimensional imaging systems such as MRI or CT-scanners. Such devices are often difficult to justify due to the need for a liquid medium or cost.

A major dental materials corporation asked Tecnova to design a low-cost, highly accurate volumetric measurement system. The system is used to test shrinkage of dental polymers and composite filling materials. Unit cost is critical because the company desires to donate or sell the system to universities and/or customers using the companies’ dental products.

The solution allows configuration of measurable parameters. “Uncured” material is placed on a pedestal. The NI USB 6501 digital I/O module controls a stepper motor to rotate the pedestal. A camera is strobed at periodic step intervals and NI VISION routines are used to make baseline measurements. The sample is “cured” using UV light to shrink it and imaging processing is repeated.

LabVIEW vision routines analyze a series of 2-dimensional images to determine 3-dimensional volume within the region of interest. The volume of the pedestal is subtracted from all other volume measurements. Custom analysis algorithms developed by the customer compare the cured sample to the baseline and determine volumetric shrinkage in units of micro-liters. Data is overlaid on the user interface image display, plotted as volume over time, and recorded to a flat-file format for later retrieval.

To prevent unauthorized duplication of system software, the application reads a unique key value from a USB security dongle. Each installation validates itself against this key. Operation suspends if a dongle is not present or if key values do not match.

Tecnova architected the application using advanced object-oriented programming techniques. The user interface employs highly customized controls and indicators with glyphs that modernize built-in LabVIEW graphics and improve the user experience.