View Full Version : Plastic extrusion

03-15-2008, 05:20 PM
Does anyone know anything about plastic extrusion, ive just bought a lab size extruder, but i need to sort making the dies , watercooling bath etc

the dies look quite easy for simple things, im just looking at things like 1/8 and 1/16 inch rod so the actual hole for the plastic cant be difficult, its the bits/dies to make it straight as it cools that im not sure on

03-16-2008, 01:54 AM
Do you have the tanks that go with the extruder? You will need tanks about 10 feet long, maybe two of them back to back. You will need a puller at the take off end after the tanks. The tanks will need to be filled with recirculating chilled water too. Now what are you going to do with the finished product? A fly knife or coiler is needed at the end of the line. Overall your extrusion line will be about 40 - 60 feet long depending on what you are extruding. How big is your extruder? (screw size? How many lbs per hr?). Material input is just as critical as the take off, you don't want to run out of material after you are up and running.
We run poly pipe on our extruders, 200 lbs per hr, 1000 foot coils in 3 minutes! This set up requires vacuum tanks to keep the tubing from collapsing after it leaves the die.
Tubing also runs 24 hours a day, 6 days per week.
What specifically do you want to know? Maybe I can steer you in the right direction.

03-16-2008, 09:32 AM
Its only a small extruder, sold as a lab extruder a betol 2520, it is listed as 25mm screw size, the guy with it was doing 1/4 inch rod from hdpe, he said it was running on that a few kilos per hour, so its only slow, but he said he was running on about 1/4 speed of the motor

i only need low production levels as its to go in model kits that we produce, about 10 inch in each, we already make all the plastic links and other parts so ive decided we need the tube components as then we need to buy no parts other than plastic

the only info i have is from the listing for it

> BETOL 2520 Lab extruder, 3.8Kw Scott DC motor, 75 - 1500 RPM variable speed,Water cooled barrel with 3 independently controlled heater zones. 2 Controllers for External heating zones


i have no tanks, or puller , im going to make them

I have tool chillers for the injection moulders and a system set up for our cyanoacrylate distillation with a cooling tower so cold water feed isnt a problem

i have a few books on plastic tooling and it seems quite easy to do a simple round rod, as long as i accept that its going to shrink so i need to work the size out for that

What im looking at making , one part is easier than the other, i need a 2mm rod inside a tube with 2mm bore, it needs to be sliding fit but the ones you can get are not that good fit , for control rods for model aircraft as well as just small sections of various shaped rods for art/craft from various plastics

Allthe info i have is on doing shaped extrusions such as windo frame sections, on that it looks to me like after it goes through the shaped die, it then goes to another shaped die in the water spray tank

would i need to do this on something like a 2mm rod, i was thinking, it comes out of the die with 2mm hole in, then its going to flop downwards,

do i need to support it straight from the die in another watercooled section, does the die have unheated die straight from the heated die to the waterbath

would feeding it over something like a teflon coated alloy angle into a tank of water with water flowing onto the top of the angle work?

At the other side of the tank i was going to feed it between 2 rubber wheels with a notch in the center to pull it along,then over another alloy piece, to cut to length i was going to trigger with light sensor at about 1 meter away from the wheel puller end , the light sensor will trigger an air guilotine to cut down just after the rubber wheels to cut to length

With the tube section i have more info on dies, it looks difficult on the sizes i need, 2mm id, as i need to fit a center rod with airfeed to blow it outwards to the sides of the die as it cools ?