The can industry is full of good ideas – some come from OEM’s, others from aftermarket suppliers or a variety of other sources – just about anywhere.  And in the end, what’s important is that they get developed properly and made available to customers.  At Stolle we think there’s room for all – as long as the customer always comes first.  That’s why Stolle offers a wide array of upgrades and retrofits designed and tested to provide optimal performance and safety in our existing product lines.

To be fair, many third party suppliers are at a distinct disadvantage as they don’t have the in-depth knowledge that results from the investment of years to develop and perfect the equipment and its components.  Simply knowing the dimensional characteristics of a part doesn’t tell the whole story.   Some upgrades from third party sources, while filling a need, can also have unintended consequences that may not be in the best interest of the equipment – or the customer – over the long haul.   Recently, we came across just such a situation.
 

A third party supplier came across an idea for a product to use as an upgrade to our Stolle Ragsdale Bodymaker, a popular machine that currently boasts over 1000 units operating around the world on any given day.  The assembly in question was our Parallel Motion Assembly, or PMA. 
In a Stolle Ragsdale Bodymaker, the PMA converts the rotational motion of the crankshaft into the linear motion of the ram.  The goal of the supplier was to sell a product that would lessen the weight of this assembly.  Unfortunately, to install the new device, the customer was required to cut a piece out of the main frame, a procedure that set off alarm bells for the professional engineers at Stolle.
 

Karl Fleischer, P.E., Chief Engineer, says, “The plate that has the cutout in it is a structural member that ties the two sides of the main frame together in an area near the crankshaft.  Making a modification to a structural member of the main frame can have two effects: 
 

View from ram area showing main bodymaker frame with
a large cutout to accomodate third party motion assembly
 

First, it can reduce the rigidity of the main frame thereby reducing the frame’s ability to react machine (inertial) and process (can making) forces.  This implies greater running deflection in the frame, increased wear rates in machine components, and lower can quality.” 

And Karl continues, “Secondly, because the main frame manufacturing steps are weld, stress relief and then machining, there are some residual stresses in the frame induced during the machining process.  Cutting a structural member can relieve these residual stresses resulting in loss of dimensional stability of the frame.

Reverse view of same cut in bodymaker frame

Also, if the cut is made using atorch, the heat put into the frame can produce distortion that also will result in loss of dimensional stability. The potential consequences are the same.” 

He concludes by adding, “Additionally, the loss of metal in this flywheel support area could contribute enough distortion to shorten the life of tear drops and cranks due to continuous stroke deflections during canmaking operations.  I saw an example of this recently in a rebuilt crankshaft.  There were signs of fretting corrosion between the face of the redraw cam and the mating face of the crank teardrop.  Because of the extremely high cycle nature of the bodymaker, the results of this frame cut could have the effect of reducing the fatigue life of the given parts.”