Keypoints of transparent soft hose extrusion

First, consider the intended outcome in an environment bounded by these four statements:

a) The extruder is responsible for continuously pumping plastic at a prescribed temperature and pressure

b) The cooling station (water, air, vacuum, etc) is responsible for continuously holding the plastic in the intended shape from the extruder until cool

c) The take off unit is responsible for continuously pulling the extrudate down line through the "magic foot" represented by the interaction of the extruder and the cooling station elements

d) The cut off device is responsible for intermittently cutting good parts to length

Since you don't mention a cut off device, the thought process is simpler -

1) Decide if the extruder is pumping continously - aka every so many (milli)seconds is the same output exiting the die at the same melt temperature.

2) Decide if the cooling station is holding the extrudate in the same way (and applying any continual cooling medium) second to second in the "magic foot" - that area between the time that the melt exits the die and is generally set.

3) Decide if the take off is pulling the product away at a consistent rate.

If 1) and 3) are squared away, look to the cooling station - perhaps you are "free extruding" into/onto water or air and you may need some suggestions to maintain a constant cooling application at that magic moment or kiss -

Just our two cents -
Skippy and Buzz
http://skippyandbuzz.blogspot.com/

Not so easy. If you control ID and OD, you have controlled wall thickness, except for the concentricity. The question implies the control of extrusion variables such as feed consistency and die temperature, as well as managing second-zone surge in the beginning of the compression zone. The tolerable tolerances will vary also with the application, the materials, the market area, and the price. Best way to find acceptable variation in a given market is to buy some of the competitive product and measure it.
As for the extrusion books, I wrote the first of these (1962) and am still writing, and would not put into print such tolerances without further defining materials, markets, etc.
Allan Griff, Forum Moderator, April 13, 2011

Any book on extrusion will give you these answers. Tube extrusion have ID OD and Wall Stock. You pick two you want to control and 'float' the third.

Do your homework or call and expert: Paul Waller of PlasticsTouchPoint. He's in Toronto