Pipe corrugators used to manufacture endless parts

The following ideas are posted for your review about existing technology and other interesting thoughts about corrugated pipe cooling systems. These are our opinions, and no doubt other people may have ideas that are contrary to ours. Please review and read these and use the ideas to help you in your decision making process when buying technology to manufacture corrugated pipe.

Low pressure injection molding using continuous extrusion.

I’ve often wondered why the use of a continuous caterpillar style take off / puller, or modified pipe corrugator has never been adapted to perform continuous extrusion injection molding or sophisticated profile extrusion.

I can think of many products that would benefit from a continuous extrusion process: architectural trim, corner molding, foam pool noodles (imagine a snake design for your kids), possibly even specially profiled gasket designs with indents and detents not suitable for traditional profile extrusion.

Pipe corrugators when fitted with molds can many make shapes suited for a straight open close mold mechanics, it is even possible to fit molds with special inserts that can be retracted prior to opening.

Pipe corrugators by their name pigeon hole themselves into a very narrow technology niche, rename them and a pipe corrugator is a very sophisticated continuous extrusion takeoff system capable of moving molds past a fixed injection point, at high speed, great precision while supplying vacuum to the mold cavity for even filling and having very controllable cooling or heating systems.

Over the past 40 years pipe corrugators have evolved in the light weight profile walled pipe extrusion industry with tremendous mechanical advances over the traditional Reifenhauser / Corma vertical chain carrier air cooled style machines. Today very high speed liquid cooled or heated molding systems are available and could easily be adapted into a multitude of possible continuous extrusion or continuous filling applications.

Low pressure injection molding on a continuous extrusion system has already been proven with the development of the Ultra Rib design of pipe first invented by Uponor. While this process is relatively slow in line speeds, it resulted in a new design of pipe not previously possible with traditional profile vacuum tank extrusion s in tremendous pounds throughput and was a significant advance on pipe forming technology at the time.

With rapid development of the composite extrusion industry, more conversion of traditional building materials, the penetration of foaming technology into the extrusion industry it seems imminent that development groups will be looking for more advanced systems to perform high speed continuous mold filling of infinite length products.

So, what would one look for if evaluating a technology supplier for a continuous injection molding extrusion process.

• How does the material flow, does it pour or extrude. Material with low viscosity at exit of the injection nozzle are likely best run in a vertical process using gravity to their favor. Materials with high viscosity are likely to handle the more typical horizontal extrusion filling orientation. - What is the mold cooling or curing temperature needed. Molds typically are cooled, and water cooling systems are well proven and advanced. Heating systems, which are really higher temperature operating curing systems are also available, but more expensive due to the oil heat transfer system used.
• What is the tolerance in the product design for flashing? As a general rule, the less tolerance for flashing, the more expensive the machinery. The function of the mold mechanics requires mold halves in repeating increments typically called the mold length. This characteristic of the extrusion filling process requires thorough evaluation of not only the product design, but the capabilities of the machinery, and the ongoing maintenance to maintain the required flashing specification.
• How does the technology manage thermal expansion and contraction of the mold set? This is a critical component of setup and efficiency. When a mold train running in an endless loop changes in length form thermal expansion or contraction it affects the drive gear train, it’s important to review how this is accommodated in the machine design.
• Can the continuous extrusion device be easily changed in mold train length? In many applications a discreet part will be made and later cut, when dealing with a continuous mold train of a fixed length you must design the discrete part length to result in an integer quotient when divided into mold train length. This relationship should always result in a review of the finest gear pitch increment that the mold train is driven by. Resulting in the possible mold length variations for part design.
• What is the line speed you can get to. In the corrugated pipe industry line speeds approaching 200’/min have been talked about. In the 4” corrugated drainage tubing technology line speeds of 120’/min are known. IN the end the line speed is governed by the contact time the product needs to cool or heat prior to be released from the mold. Continuous extrusion technology for pipe corrugating has been made with a mold – product contact distance from 12” top as long as 20’, it very quickly becomes a ROI calculation.
• Are changeovers important? If it’s a one product line likely not, but with the outputs of this technology that’s unlikely. A complicated area to discuss, but intuitively the faster you can change a line the more money you can make. Make sure you understand the complete changeover process: die, molds alignment, height adjustment.

When looking for break through technology your mind has to stretch, and a thorough evaluation is always smart. Advanced takeoff system allowing continuous filling of molds at high speeds under tight temperature control is highly developed in the pipe industry, we need to find technology cross over opportunities to improve on industrial energy and productivity efficient.