Problem: Extrude a heavy-walled small diameter pneumatic tube; in this case the wall area composes 75% of the tubing area. The difficulty comes in maintaining wall uniformity while eliminating “lensing,” uneven cooling, uneven shrinkage (curling) and chatter lines. Pictures show the clarity and beauty of properly extruded butyrate. This gem had virtually no extrusion lines, no chatter” marks and no bowing over 20 ft.
Within a .750 OD, we maintained a wall thickness of .187”+-.002.
Solution: For our small-diameter tubing, we use a vintage, thrice-rebuilt Prodex 1.75” vented extruder and our proprietary drying-aftercooling preparation. A new oversized Baldor drive in combination with our proprietary vacuum sizer gives us control that rivals the old air-dried sizing methods. This extruded tube rivals cast tubing.
The final problem we faced was in packing. The tube is so dense, and the nature of amorphous butyrate is to sag at this dimension and weight. Thus, usual shipping containers cannot handle the weight and pressure.
Solution 2: We extruded our own packing tube via a mixture of PETG and butyrate. The 20 ft. packing tube protects the product from normal shipping wear and tear, but also keeps it from sagging and thus, bowing. In addition, the packing tube had such superb light refraction qualities that we are sending a sample of it to Eastman Chemical for its observation. The packing tube itself would glow like a fluorescent bulb when LED lights were placed inside.
This 0.75” OD tube was manufactured for Bartell Machinery Systems, for use in a pneumatic feed line.
We also can fabricate a heavy-walled tube by solvent welding two tubes together. This works well for prototypes and is also very attractive.