Some challenging bending applications may damage the surface of the tube.Tools are metal, pipes are metal, and in some cases scuffs or scratches are unavoidable.Getty Images
Successful bending is simple for many tube manufacturing applications, especially when using the latest rotary stretch benders.A complete set of tools – bending dies, wiper dies, clamping dies, pressure dies and mandrels – surround and confine the tube along the inner and outer surfaces so the metal flows where it is intended to flow during the bending process .This, combined with a modern control system, provides excellent results for easy to moderate bends.It’s not foolproof, as success also requires proper setup and lubrication, but in many cases the result is good bends, time after time, day after day.
When encountering challenging bends, manufacturers have several options.Some rotary wire drawing machines have a bracket lift function that provides a push force to assist the wire drawing force.In addition to this, toolmakers often have one or two strategies for dealing with difficult bends, such as by increasing the length of the clamp or by machining a series of serrations on the contact surface of the clamp.Longer clamps create more friction; the serrations bite into the surface of the tube.Both provide extra grip to keep the tube from slipping during bending.
Regardless of the specifics, the goal is to produce components that meet customer requirements.In most cases, this means little deformation of the components and a smooth surface.However, this is not ironclad.For tubes hidden from view, customers may tolerate considerable ovality on round tubes, significant flattening of square or rectangular tubes, slight to moderate wrinkling or machining marks along the inside of the bend.Most of this can be quantified as a percentage deviation from the ideal bend, so it is necessary to find out what the customer really wants.Some people are willing to pay quite a bit for the original bend, while others prefer a much less expensive bend with obvious flaws.
Sometimes customers will specify an elbow that doesn’t seem too difficult to produce, it’s made of a moderately soft material with a wall thickness just enough to stretch along the outside of the elbow without splitting, but not so much that it Come together along the inside of the bend.At first it looked like a simple bend, but then the customer revealed one last criterion: no markings.The app is aesthetically pleasing, so customers simply won’t tolerate any damage from the tool.
If the test bend results in machining marks, the manufacturer has two options.One is to take an extra step to polish the finished product to remove all tool marks.Of course polishing can be successful, but it means extra handling and more work, so it’s not necessarily a cheap option.
Removing damage is a matter of removing the surface of a steel tool.This is done by making tools entirely out of heavy duty synthetic polymers or making tool inserts out of these materials.
Both strategies are a departure from tradition; bender tools are often made of metal alloys only.Few other materials can withstand bending forces and form a tube or pipe, and those are generally not very durable.However, two of these plastics have become common materials for this application: Derlin and Nylatron.While these materials have excellent compressive strength, they are not as hard as tool steel, which is why they do not leave marks.They also have some natural lubricity.Due to these two factors, atraumatic tools are rarely a direct replacement for standard tools.
Because polymer molds do not create the frictional forces that steel molds do, the resulting parts often require larger bend radii and are designed to support longer clamps than metal mold designs.Lubricants are still necessary, although usually in small amounts.Water-based lubricants are the best choice for preventing chemical reactions between the lubricant and the tool.
While all tools have a limited lifespan, damage-free tools have a shorter lifespan than traditional tools.This is a key consideration when citing this type of work, as tools must be changed more frequently.This frequency can be reduced by using polymer inserts attached to steel tool bodies with mechanical fasteners, which typically last longer than tools made entirely of polymer.
Damage-free molds are suitable for forming steel, stainless steel, aluminum and copper, and typical applications vary by material.Food and beverage applications are ideal for damage-free tools.Ideally, pipes for food or beverage processing are very smooth.Any scratches, dents or scratches left on the surface of the pipe or pipe can collect debris and become a breeding ground for bacteria.
Other common applications include coated or plated parts.A common misconception is that the coating or electroplating process fills in or masks defects.Coatings and electroplating are very thin, usually targeting a highly reflective glossy finish.Such surfaces will accentuate rather than blur surface imperfections, so precautions need to be taken.
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