I got a quota requirement. They ask for flexible PVC tubes with
4.61mm ID and 2.5mm thickness. They also require ID must be concentric with OD with 0.25mm. This is a very tiny tube. Is it possible to use compression air to control the pipe inner diameter? Is the vacuum size tank must? Have anyone tried extruding two or more tubes at the same time? I could not get any good idea about it. Please help, give me some suggestion.Thank you
Depends on what size extruder you are using, and the intended draw ratio, but yes, internal air pressure will do for this (as long as you have good controls). You should be able to get a couple of hundred FPM on a 1.5"-2.5" machine. I would recommend a closed loop control for either die pressure or diameter through a laser gauge.
Two or more tubes will work, though tool design will be critical to balance the flow.
I think your stated tolerances are actually generous.
Thank you for your responds.
The guy who designed all dies has gone. Now I have to take over all his job. I have no experience in plastic die design.
I had a tour to the Follow 2000 software company. The software will help do the flow balance. After I finish the die design, the software will do some correction. I think it will help me lots.
I don't know where I should start. Could you give me some suggestion?
I just finished a package of quote (16 items). We don't have any tooling about hollow profile (including tube). How much is the tooling going to cost? A guy sent me an email about their precison tubing air system:
I can't tell you how much your tooling will cost, as I don't know what you are attaching it to (style of extrusion head) or even what size machine you are using. All I can recommend is to shop around. For PVC, you may want to make it out of something corrosion resistant, like Incolnel or Hastelloy (or use a plating on the flow channels). You may need internal air, and I would recommend On Line Controls in Mass.
I would also think about having a transducer port machined into your head assembly, and get a Eurotherm pressure controller. For lasers, there is Zumbach, Beta-Lasermike and a few others that can offer closed loop controls for puller speed
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