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Raising of RPM in twin screw extruders for better processing

Raising of RPM in twin screw extruders for better processing

Raising of RPM in twin screw extruders for better processing

(OP)
I'm working in an industrial company it's main product is wood plast sheets using in automotive industries. Because of processing problems and quality criteria I need to know how can I raise RPM of screws in twin screw extruders without any damage in motor and gearbox.
Our gear box ratio is 63 and motor RPM is 1475 , frequency for long extruder is 45.50Hz and for short extruder is 15.55Hz. Every extruder including of two screws with four motors and each couple of them have a gear box to rotate screws in cylinder. RPM limit has been defined for them is 30 and our technical department scare of any damaging on them and hence banned any manipulating on these factors.Please guide me how can I raise RPM and consider their concerns.

RE: Raising of RPM in twin screw extruders for better processing

What did the extruder manufacturer's application engineer say about your processing problems when you called?


Mike Halloran
Pembroke Pines, FL, USA

RE: Raising of RPM in twin screw extruders for better processing

(OP)
Hello Mike
They don't support us longer after a firing occurred in production line.
Our main problem is using high temperatures in extruders result in lower quality of sheets. I know Raising RPM could affect on quality because of lower temperatures and higher shear stress.
What's the risk of high RPM's for electromotors of twin screws?

RE: Raising of RPM in twin screw extruders for better processing

I'd start by figuring out if the electric motors are being used at 5 pct or 110 pct of their capability, right now.
That requires finding the data sheets for the motors and making a few measurements.
... something that I'd expect the 'technical department' could do.

Which begs the question, since you're not in the technical department, how did you get involved in the alleged problem, and what leads you to conjecture that more RPM is a solution?

Mike Halloran
Pembroke Pines, FL, USA

RE: Raising of RPM in twin screw extruders for better processing

Hi Bahram.
These motors running the screws are VFD run?
If so are they all run on one VFD or do they all have their own?
If VFD what make and model VFDs?

Keith Cress
kcress - http://www.flaminsystems.com

RE: Raising of RPM in twin screw extruders for better processing

(OP)
Hello Mike
I must note that I'm chemical engineer in company and responsible for quality control of produced sheets. I prefer to enter into this case because of an inherent inhibition against any change in machine set up. Anyway according to our experienced records and knowledge, elevation of RPM could lower working temperatures and therefore save energy coincide with promotion in sheet quality. We want to check all of possible risks and convince our conservative technical department for these changes.

RE: Raising of RPM in twin screw extruders for better processing

(OP)
Dear Keith
We have an 90 kW inverter for all of four motors in each extruder by which adjust frequency up to 600Hz and it's brand is Delta.

RE: Raising of RPM in twin screw extruders for better processing

Energy from the drive motors iz not the only source of heat in the product.
That equipment is expensive to fix, so I can understand resistance to experimentation.

Have you got enough instrumentation and labor to correlate product quality changes with normal fluctuations in controlling parameters, without changing setpoints?

Mike Halloran
Pembroke Pines, FL, USA

RE: Raising of RPM in twin screw extruders for better processing

(OP)
Dear Mike
Through control charts for quality parameters I could observe effects of normal changes of control parameters on them.

RE: Raising of RPM in twin screw extruders for better processing

We would like to see pictures of the nameplates on all motors. Current indicated by the display on the vFD and the current drawn by each motor in a set at the same time.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Raising of RPM in twin screw extruders for better processing

Hi Bahram,
Waross is correct, any info that you can provide for the motors and VFDrives is absolutely essential. (ie make / model / ratings / etc)
Also, any (running) load data would be appreciated.(ie rpm (or frequency), volts, amps, real-power)
If I read your opening statement correct; currently you are running the augers at 21.3rpm (45.5hz) & 7.25rpm (15.5hz) and you are permitted to run the augers up to 30rpm (64.1hz). Is 30rpm the max rpm that you desire to operate at?
GG

ps I have run constant-torque loads over the motor's synchronous speed many times, so it can be done, but you need to be carful that all components can handle the additional power.

"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)

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