Thin wall HDPE extrusion
Thin wall HDPE extrusion
(OP)
I am trying to extrude a single lumen thin wall tube for medical application. I cant figure out how to maintain any type of tolerance. Is there anyone out there with experience in this area that could point me in the right direction? Thanks






RE: Thin wall HDPE extrusion
What is a lumen other than a unit to measure light output or intensity.
Twin wall HDPE is not exactly a new or novel process.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Thin wall HDPE extrusion
RE: Thin wall HDPE extrusion
That has been around even longer.
And? are you a designer trying to specify tolerances or an extruder trying to maintain them?
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Thin wall HDPE extrusion
RE: Thin wall HDPE extrusion
Tooth 1) What wall section.
Tooth 2) What dia tube.
Tooth 3) What MFI HDPE.
Tooth 4) What size extruder.
Tooth 5) What output are you running vs maximum for that extruder.
Tooth 6) Depending on what sort of drive and screw design of which I have no idea at the present so I don't even know what direction to take when asking questions are the amps steady and what is the compression ratio and length to diameter of the screw.
Tooth 8) Are any temperature zones over riding.
Tooth 9) What temperature is the water in the vacuum tank.
I give up
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Thin wall HDPE extrusion
Dimensions: .018" ID, .034" OD. Material is petrothene, I dont have the grade in front of me as I am at home now. Machine is a 1.25" 24:1 LD with a Zenith gear pump. I am not having any feeding or amperage problems. All heat zones are steady. I am only able to turn about 8 RPM on the screw because of the size of the tube. Water temp in tank is around 80F
RE: Thin wall HDPE extrusion
Also I was irritated by yet again a prospect of having to ask 30 questions. It happens quite a bit and frankly gets tedious so I will cough to irritated rather than condescending.
OK that is a very thin small tube on a machine that is really much to big for the job. The gear pump is all that makes it possible I think. Even so you may get pulsations from the pump but at least hey will be small and regular. If you have an option for a smaller pump running faster that might help as would a pump with a greater number of smaller teeth.
Your residence time in the barrel must be extremely long, so I would keep the temperatures as low as possible for the back 70% or so of the barrel to avoid degradation, but don't overdo it or you will have inconsistent melt temperature and just as much trouble as if it was degraded. It might be wise to try to source material with extra processing aid/stabiliser added.
Sorry but it's a bit late to think clearly and I have a full day tomorrow. Do you know anyone who specialises in extruding drinking straws. They are bigger dia, but I expect will still tend toward similar problems and solutions.
Do you have a selection of screws to choose from. What does your raw materials man say.
Your torpedo and its adjustment and taper in the die will be very sensitive.
I am thinking you need more lik a a film blowing grade rather than an extrusion grade.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Thin wall HDPE extrusion
RE: Thin wall HDPE extrusion
Your tube is almost a thickish blown film.
When making fibre, HDPE likes very high draw down ratios. 10:1 vs 6:1 for nylon seems to spring to mind, but don't trust me on that as it is a bit on the hazy side.
Spectra fibre is made by drawing down HDPE in very hot water, hence the term gel spun. It would be fairly easy to increase bath temperature and increase draw down I would think. Of course tube is harder to grab and stretch than is fibre. Hot water might really slow down your already low output and create melt consistency problems. I guess you cant draw by stages with multiple tanks.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
RE: Thin wall HDPE extrusion
And I think you need a fractional MFI grade with no nucleating agent and possibly 3 to 5% Vinyl Acetate to allow more stretch and a bit less crystalisation.
Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules