Data Acquisition for Nozzle Pressure Transducers and Mold Pressure Transducers

Many injection molding customers are asking Sensonetics about data acquisition hardware and software for Shot to Shot Monitoring of melt pressure and temperature using silicon on sapphire transducers. At one time we offered an imported hand-held data logger, DL-380, with PMCIA Memory Card, downloadable to a PC, just for this purpose.

Sensonetics recommends data acquisition of nozzle melt pressure and temperature for comparative studies of before and after control via nozzle melt pressure. Of course, there are specialized companies supplying such hardware and software for plant wide monitoring in the injection molding industry. Examples include: NPE (Nicollet), Mattec, RJG, Synchroshot Systems Corp (SSC), Syscon-Plant Star, and Hunkar. Of these, we naturally prefer companies that don't have their own sensors and transducers to provide the standard 0-10VDC output signals for data acquisition such as, NPE, Mattec, SSC and Syscon Plant Star.

In order to catch Ppeak reliably, pressure transducers with a response time of <1000 u-sec  (such as Sensonetics pressure transducers) are necessary, while a data acquisition system needs to be in the range of 1-4 m-sec. We have approached all the above companies and asked them to use our pressure transducers. We are actively promoting our nozzle pressure transducers based on very favorable results in systems integrated  with Sensonetics pressure transducers.

Some of our customers have engineers and scientists using their own home grown data acquisition systems based on kits purchased from other non specialized sources such as, ADAC Corp, Dataq Corp, Intelligent Instruments, National Instruments, Keithley, Strawberry Tree and others. These generic and general purpose kits are assembled by selecting data acquisition hardware and software components. The user has to adapt the software to injection molding and SPC analysis. Naturally, the cost is lower, but the user has a lot more work to do. Also, these systems are more for individual machine process analysis, rather than full blown injection plant monitoring systems as noted above.

Here is a general way for one to set up a data acquisition system:

First, one has to choose a small and fast system. We recommend a 2 to 8, wire analog channel system; 2 for pressure transducers and temperature transducers, which are essential, and the rest for barrel temperatures, if desired. The data acquisition speed must be selectable up to 1,000/sec, to catch Ppeak properly.

Next, we need a small wiring terminal box to accept the signal from the

0-10VDC pressure transducer and temperature transducer outputs of the transducers to the DAQ system.

After that, there are several different mechanical ways of doing it:

One is to go directly into a laptop computer with a suitable internal DAQ board. Another is to go to a PCMCIA Memory Card to acquire transducer data in ASCII format memory for later downloading and analysis in a desk-top PC or laptop having a good spreadsheet program.

Some companies offer memory card systems with direct and bypass connections to a laptop or PC for use as either memory storage, or direct-to-computer option modes. Other companies offer direct to computer only, without PCMCIA storage. It is important to understand what is desired and needed.

The board level products from kit suppliers are more or less similar, but may not be interchangeable with each other. They can be used inside PC's, and laptops and with various software platforms. They all should do a basic and rudimentary job for similar costs. External boards are sometimes available, when the user can't put them inside the computer.

We don't know enough about any of these kits to state which might be best, but believe them all to be adequate for rudimentary single machine data logging. They have a reasonable degree of portability for machine-to-machine usage.

We strongly recommend that each system be investigated in-depth before purchase by any user to insure that data logging or acquisition will be adequately and completely accomplished with all the necessary parts, software and technical requirements. Because the generalized software is non-specific to injection molding, it will need to be selected and customized by the user.