Bob Want is a technical tooling sales and application analyst with Tools For Bending Inc.
Telephone: 800 873-3305
web site: www.toolsforbending.com
Editorial on his TPJ Article: "Avoiding Common Bending Problems with Common Sense"
Bob published an excellent article titled Avoiding Common Bending Problems with Common Sense in the December 2006 issue of TPJ. In the article he presses the point that proper understanding of the importance of choosing proper bend tooling cannot be understated.
Psychology of Choosing
His first deals with the psychology of the choosing bending equipment, and its impact on making poor decisions regarding how to fabricate a tube. Bob has noticed that fabricators are often tempted to "go with the the gut instinct and...the flashiest solution." His point is that fabricators should resist that gut instinct and "try to use a methodical, calculated approach."
The Method of Choosing
The rest of the article dicusses the method that he suggests. You'll find ideas like keeping the solution as simple as possible (not any more complex or bigger and more powerful than necessary) are the constant themes through this article. That approach makes this article a gold-mine of information for engineers trying to learn the mysteries of tube fabrication.
In the BENDER BASICS section, he has a short discussion regarding choosing benders. This discussion is more brief than I prefer - but it is a start. I recommend that a few other variables be introduced regarding bender types. For example, any fabricator of mulitple bend parts that must change between parts periodically on the same machine should almost always choose a full three-axis CNC rotary draw bender rather than a one-axis NC bender (that controls only the bend arm).
Any application that has two bends or more per part with rotation (twist) between bend planes is a prime candidate for a FEED / ROTATE axes on a carriage. One of our customers purchased an SMT Industries conversion of several NC machines to full CNC benders. At first, they tried one of these conversions. They had anticipated productivity gains, but had underestimated the gains actuall made. Converting from one-axis NC to a three-axis CNC was a huge investment - and a bit risky for them.
Well - now they've converted at least six of these NC benders to CNC. They have at least tripled output with the same number of benders. They are getting more orders from customers because their total output capacity is tripled.
But this came with a problem (a good one): "How do we handle all of this increase in material flowing through our shop?" They ended up re-routing the flow of material through the shop to reduce movement of the product from start to finish. And they added more shop space - lots more.
Selecting a Bending System
His rule of thumb regarding centerline radius to centerline height is interesting: "if the centerline radius of the bend die is the same as or less than the centerline height of the bend die, the bend die stability under load in the bend cycle witll be compromised." TFB has solutions for this problem, but it is more costly. The job quote should be increased accordingly. Also, he discusses the idea of why at least two benders (CW AND a CCW) of the same capacity can be necessary. To newcomers, the term CW and CCW may be a little confusing at first: A CW bender is also called a RIGHT HAND bender. If you stand in front of the bender and reach out with your right hand to pull on the bend arm, your right hand will touch the part that swings outward. CCW benders are also called LEFT HAND benders. If you extend your left hand to the bend arm, then your left hand will touch the part of the arm that swings outward.
He finishes with this advice: "Before casually requesting all the bells and whistles when comparing tooling quotations, consider the simpliest solution to your needs first." I like that advice, and think its practice saves a lot of headaches for fabricators.
Link to the Article
Mike Cone - 09:14, 7 February 2007 (EST)