posted August 17, 2006 11:24 AM               

My question to start with involves extruding plastic tubing for a local company.

I do not filly understand the concept of OD in making plastic tubing. We work with vacuum tanks, and sizing sleeves but where or how is the actual control of the OD? The puller, which I understand controls ID and the tubing wall. Also I might add, we are only talking about Horizontal Extrusion here not vertical.

If there is anyone on this list who would like to help a real “Beginner” now’s your chance. I am the type of person that has pride in his work and want to know all I can about it. It seems that the extrusion of plastic tubing is some mystery and it is very difficult to find out exactly how it’s created even with the resources of the Internet. I am hoping this list will help me.

posted August 17, 2006 11:50 AM               

What plastic are you using?
What is the OD and ID of the die?
What is the OD setup on the sizing sleeve?
What is the extruder output rate?
What is the pulling speed?
What are the OD and ID targets?
What is the production rate target?

From this information we can start to build and understanding of how it all works.

------------------
Best Regards,

Tom Cunningham

posted August 17, 2006 12:33 PM               

quote:

---

Originally posted by Tom C:
You will need to collect some facts to help figure this out;

What plastic are you using?
What is the OD and ID of the die?
What is the OD setup on the sizing sleeve?
What is the extruder output rate?
What is the pulling speed?
What are the OD and ID targets?
What is the production rate target?

From this information we can start to build and understanding of how it all works.

---

Plastic is FEP type,die sizing would be for a .125 x .250 tube. Exact size Die and Mandrel not known at the moment because I am home and cannot get actual measurments. The targets would be around 6.5 feet per minute. What I am trying to understand is how or more correctly how to change OD once the setup is running. Thats about as much as I can give from here. Thanks for your prompt reply.

billz

posted August 17, 2006 01:36 PM               

There will be an interaction between the die geometry, draw down, output rate, takeoff speed, and sizing sleeve.

The numbers I ask for are to check to see if the basics are correct.

------------------
Best Regards,

Tom Cunningham

posted August 18, 2006 10:53 AM               

Thanks for the return. You have just hit on the first stumbling block: “Terminology”!

The term “draw down”? What exactly does that mean? I have seen some other terms that I do not understand and will seek your counseling as they come up.

As you can see from my posting time, I am not here in the afternoon, so bear with the time lapse between posts.

On the product, Dupont mostly supplies FEP. We use an FEP Type 160-N, and a Dyneon product, 6301 grade. There are 3 basic material types in use FEP, PFA and FEP UHP, which is the Ultra High Grade.

It seems that in extruding horizontally, we do both, vertical too, the main way that the OD is formed is through the screw speed, then pulling the tube through a sizing sleeve and into the vacuum tank. At that point, the tube is then frozen into what ever size it should be by the temperature of the water as soon as it hits it plus the vacuum applied at the same instant. I should mention also, that in our particular operation, barrel, clamp, head temperatures are all critical to the melt itself as Melt Fractures could result.

The size seems to be somewhat determined by over-all line speed, size of the sleeve used, the distance between the die & mandrel to the water tanks entrance and the amount vacuum applied. All of this assumes that you have chosen the correct die and mandrel and sizing sleeve for the job to be done in the first place, I think? That’s why I am here to learn just how all of these things work together and what you can alter and most important, how you alter it, after the line is set up and running. Of primary concern would be the OD, ID and the wall thickness of the tube itself.

Bill

quote:

---

Originally posted by Tom C:
I have some good familiarity with FEP. If it is a Daikin grade, I know some tech support engineers who work there, so a lot of help is potentially available.

There will be an interaction between the die geometry, draw down, output rate, takeoff speed, and sizing sleeve.

The numbers I ask for are to check to see if the basics are correct.

---

posted August 18, 2006 11:10 AM            

For example . . . http://www2.dupont.com/Teflon_Industrial/en_US/assets/downloads/h26580.pdf

posted August 18, 2006 11:18 AM               

Thanks also for your link, I am on my way over there now.

posted August 18, 2006 11:48 AM               

I am concerned that you are processing these somehwat dangerous materials without any knowledge. Are you aware that materials like FEP can break down and expose you to hydrofluoric acid? This is bad stuff.

Read about it here;
http://www.corrosion-doctors.org/Acids/Hydrofluoric.htm

Dupont MSDS for FEP here;
http://www.mikeholt.com/documents/mojofiles/DuPontTeflonFEP2003MSDS.pdf

Your company should consider more training for you. Courses such as this one;
http://www.compuplast.ca/2006XaloyCPSeminar.htm

I am avaialable for the purposes of training and process development if your company is interested. I live about 1 hours from Tamaqua.

------------------
Best Regards,

Tom Cunningham

posted August 20, 2006 09:34 AM               

Yes, I am aware of certain problem issues that may arise with these products but I work in a very pristine environment and care is taken. The concerns that you have are well founded but the place where I work is not some fly-by-night organization. In addition a previous job I held involved the production of NF3, I’m sure you know what that is, and I was a Maintenance Planner for this organization. Thank you again for your concerns.

posted August 20, 2006 10:26 AM               

I been involved with extrusion for almost 30 years and a company does not need to be Fly-By-Night to have insufficiently trained its operators and engineers.

In a professionally run organization operators and engineers recieve significant training in the extrusion process. Design tools, such as computer simulations, lab testing and support from vendors of equipment and materials is provided. Processing trials are performed to detemine appropriate processing parameters. From all of this operators are provided with processing instructions and corrective actions. Safe startup and shutdown procedures are developed. Finally lab tests and specifications are set into place which insure delivery of a quality product to the customer.

I think it is great that as an operator you want to get control of the extrusion process. But even with all of my expereince I don't think I can successfully and safely develop and control extrusion processes without the aforementioned tools, support, tests and knowledge.

Extrusion is a very complex process. Some professionals have spent their careers trying to understand and control it. You and your company should consider taking advantage of those efforts.

Frankly at this point I am afraid to advise you further because of your inexperience and an inability to communicate properly without misunderstanding.