# Measuring Pressure of a Press Machine

I am designing a heat press and need pressure feedback of the force or pressure being applied to the product. I need to measure the pressure between to press plates on a hydraulic press. I would like a signal that I can send to an analog input (4-20ma, etc) of a PLC input card. Hydraulic pressure will be applied via a proportional valve. The press operates at around 16,000lbs of force to get around 1000-1500psi at the product being pressed.

I am looking for an "industrial" solution, maybe a strain gage or so that I can insert between the press ram and platen to feedback pressure or force in real time to the PLC.

EDIT: While measuring fluid pressure in the hydraulic system could get me there through calculation, I am looking for actual pressure/force measurement at the platen.

• To get that, you need the object area. Measuring force is easy enough - fluid pressure or calibrated strain gage can tell that. When designing press operations you usually specify the force derived from the desired pressure and the fixture's area. Theoretically you could design a sensor, but if you try to make it generic, I suspect it may end up like a blood pressure cuff. You could make a sensor built into your fixture that outputs pressure assuming it's loaded with parts in a specific way.
– Abel
Commented Sep 11, 2023 at 15:12
• "... and need pressure feed pack." Should that be "feedback"? Commented Sep 11, 2023 at 21:51

Measure the pressure in the fluid applying pressure to the piston, then convert for the piston area and object area.

• I would prefer a sensor measuring actual pressure applied to the plate and not calculated pressure
– Capo
Commented Sep 12, 2023 at 21:19

The press operates at around 16,000 lbs of force to get around 1000 - 1500 psi.

$$\frac {16000}{1000} = 16 \ \mathrm{in^2}$$

$$\frac {16000}{1500} = 10.7 \ \mathrm{in^2}$$

Install an analog pressure transducer (rated at > 20,000 psi) on the press down hydraulic line. Figure out the true scaling factor from the equations above and program this in the PLC.

Note that if the contact area of the press on the product changes and you don't know what the contact area dimension is then you can only calculate the total force (hydraulic pressure × cross-sectional area of the hydraulic piston) on the product. You won't know the pressure (in PSI) on the product.

Product recommendations are off-topic on the SE engineering sites so you'll have to do your own research for a suitable transducer.