Nozzle Pressure Measurment- Is it the right place to measure?

Anonymous(emotional attention) ??what?? I wouldn't have signed that remark either!!

As far as nozzle pressure measurement, I think it is the best indicator of "actual" injection pressure. The system that I work with uses a pressure transducer in the nozzle tip as the control measurement of injection rather than the velocity control / transfer to pressure control. This allows pressure control for the entire injection sequence, eliminating the hesitation at transfer.

If you were to use a transducer in the last place to fill you will not see pressure until the cavity is FULL, as opposed to a post gate sensor which will give some pressure fluctuation during cavity fill.

Concerning cavity sensors and the wittness marks - There should be no difference than an ejector pin wittness unless it is installed improperly. Of course this is regarding flush mount transducers. If you are concerned about wittness marks - consider a under the pin type sensor.

Regards
Dave

Without a doubt measuring the pressure in the mold is the most desirable. Best case would be a post gate sensor and an end of fill sensor which will allow you to transfer using cavity pressure as well as using the end of fill sensor to help determine part quality. If you can only have one sensor and are not worried about transferring on cavity pressure, place the sensor in the area last to fill or as close as you can get to it.

RPG

If it is for the switchover point, the ideal location for a pressure sensor is at around the 75% fill point of the mold.So that the flow front is sensed prior to hitting the end of the mold.

The nozzle measurement suffers from variation due to freeze off in the mold as it fills.

This can vary much more due to changes in fill speed and temperature between one set up and another.

The closer you get to the melt flow front gives you much more accurate measurement.

You can pick a rise point on the sensor output which allows for the delay in switchover to hold and the component of dynamic flow pressure drop which starts to equalise as the shot decelerates.

It is not rocket science but, it need a degree of experience to pick the ideal setup.

Bob Burns

JD,

Typically the pressure sensor is at the machine nozzle. However it depends on what you want to conclude out of the measurements.

If you really want to be accurate on your switch over point (if this is what you are looking for), then you can place a sensor at the end of your cavity. This will however make your complete mold quite more expensive.

Product finish is critical to the part. Witness lines would be very visible. Trying to keep the mold as clean as possible.

Product finish is critical to the part. Witness lines would be very visible. Trying to keep the mold as clean as possible.

JD,

Im just wondering why you need to measure the pressure at nozzle. You want to correlate with your dimension?I would suggest put it in the mold. RJG has this technology that can measure pressure at different area of the mold. They can install sensor wher you want your pressure to be measured.

Kuyakut