Extruders - Checking the Gap Between Barrel and Screw

For proper measurement, the barrel needs to be "shot" with a laser in conjunction with a movable target centerline that can be moved to select locations throughout the length of the barrel. This is how to properly install a multi-piece barrel.

The target provides CENTERLINE within any given point in the barrel and the variance is measured by the laser. We installed three extruders for a nylon recycling plant in Augusta, Georgia several years ago; and this is the procedure that we used to accurately "align" the barrel for proper screw clearance.

If you need to contact me so that we can discuss further and in more detail.....email me at charles.miller@earthlink.net and I will be glad to help. I was Mechanical Department Lead on these installations and start-up.

oldgolfer

Thanks MR Old&Experiancedgolfer

May I request you kindly to elaborte bit more about the method you deployed ?

Can you suggest make and model of the Laser and movable target.

I reckon in an empty barrel it may be possible to put the movable target but where does this movable target rest when roating screw is already in the barrel and clearnce is of the order of 0.05 mm . In our case Barrel is single piece having length approx 2000 mm.

From the front end of the barrel gap ofcourse can be checked but how can we check the clearnces in the barrel at diff location in the barrel ?

Thanks in anticipation for your active participation and volunteering to give your Email ID

Regards

Udayan Patel ( udayan121049@yahoo.co.in )

Dear Udyan,

Our practice is to measure the bore of the barrel at 25mm intervals with a bore guage and diameter of the screw at corresponding distances.

overlap the dimensions noted and you will be able to calculate the gap between the barrel and the screw.

It is usually more at the compression zone in the single screw due to high shear & buckling and more at the exit in case of twin screw assemblies where the screws are pushed up and wear off is more on the barrel at 10 O'clock and 2 O'clock portion.

The screw usually is nitride hardened to a depth of 0.20mm and the renitriding has to be done before it wears of beyond 0.15mm to avoid accelerated wear off.

hope this helps.

REgards,

Ragotham

Some tools for measurement of screw to barrel clearance can be found here:

http://www.flitetech.com/measuring.php

Measurement services using those tools are avaialble at:

www.ExtrusionTechnicalServices.com