More information please

PVDF, hmm? I'm going to take a guess here. Nozzles of this plastic material could be formed by machining, or by extrusion (such as heating and pulling over a mandrel), or possibly by other methods. Machining could leave striations in the bore of the nozzle, but extrusion would likely leave a smooth inner surface. Can you ask the specifier the reason for this?

tks for the assist but it is quite rare for plastics to be welded,isn't it?

Not that rare. Thermoplastics can be welded.

OK, I take that to mean that PVDF is not a plastic. What is it then? Welding normally implies plastic or metal... Is PVDF a material or a process?

Acronyms should ALWAYS be defined the first time they are used in any document, including posts.

No, welding plastics is very common.

In fact, I have 2 shops east of the Mississippi doing industrial and commercial work.

Fume collecters, exhausts, pickling tanks, etc.

Finally. Used to work for a PCB fab equipment house. (Coates ASI) Nozzles, to me, means devices that amplify/direct fluid onto a surface.

So, I infer that nozzles must be machined from an extruded billet?

I give up.

Looks like the OP gave up some time ago... I sure would like to know what he/she was asking!

As lynlynch mentions, welding of plastics is quite common. One technique consists of a heater-fan-nozzle combination to melt the material, sometimes with filler rod added. This closely resembles oxyacetylene or TIG welding. Another method consists of melting the ends to be joined with a hot knife or blade, and then pressing the ends together. This works for PVC and PU, which I have done, and surely some other plastics.

That said, welding may not be relevant to your needs. It sounds as though you need to shape one piece of material to the given criterion, rather than join two pieces.

Extrusion is a process (Bulk material deformation). Raw material forced through a die of the desired shape. There is direct, indirect, hydrostatic and impact extrusion.

More details of what you need, please.

My kids routinely weld there plastic toy guns when they break them.just heat up a butterknife and go to town

"dkwarner" raises a good point. We can use "PVC" and usually get away with it, but not everyone will be familiar with abbreviations. I try to spell out the more uncommon ones I use, but no doubt I have lapsed from time to time. Good reminder.

I take PVDF to be polyvinylidene fluoride. A thermoplastic. Brand name Kynar, among others.

It can be extruded or injection molded.

http://www.sangirplastics.com/pdf/WeldingConditions-KYNAR-PVDF.pdf

"ALL nozzles are to be extruded."

Why don't you help us by telling us what the hell you are talking about.

What kind of nozzle?

Extrusion is a process which results in a specific shape without the discontinuities other forming methods can leave.

Polyvinylidene fluoride (PVDF) is a thermoplast resin, commonly used for chemical or ultrapurity requirements. Fittings are typically manufactured using one of three methods: mold casting, extrusion or roll-weld. As the name implies, roll-weld leaves a seam where the weld is located. The seam can cause flow turbulence inside the pipe (not a lot, but in a precise chemical process it can be significant). Casting also leaves a seam where the mold halves separate. Extrusion provides a seamless fitting with a smooth, uniform interior radius.

I think he is talking about a requirement or spec. for manufacturing the welding nozzle used on that particular type of plastic welding and the about the actual welding process. I have seen this before on other types of welding where the specification lists that only certain type of fabrication methods are allowed (in this case extrusion) on nozzles, cups, collets and so on.