Rooster's Revenge

I was involved with a formability analysis project recently. Here are the facts:

1. The automotive OEM had performed incremental simulations on eight stampings;
2. The Tier One die shop sent out three RFQ packages to three Tier Two die shops;
3. The Tier One die shop requested one-step simulations from each Tier Two shop.

This makes no sense. It is economically irrational. Why have three companies replicate each other’s work?

And why settle for lesser quality results from a one-step when the OEM has full blown incremental simulations available for quoting purposes?

It is a quote, not rocket science. Why spend the time and money doing something inferior to something that already exists that closer to reality? Not once, not twice, but three times?

Even the Tier Two company said “you can’t fix stupid”.

httpv://www.youtube.com/watch?v=0gxKStPXyn8

Like Ron White says, “stupid is forever”.

I am pleased to announce that Die Guy is now featured in the top 25 engineering sites at Alltop! You will notice the badges to the right as proof that Die Guy not only kicks ass, but is on Alltop.

Alltop is the mastermind of my acquaintance Guy Kawasaki. I am a big fan of Guy and have been fascinated with Alltop since its inception. In fact, I originally gave Guy the idea for their new “My Alltop” page functionality. That kicks ass too!

Alltop’s Chief Evangelist, the one that got this blog in Alltop, is Neenz Faleafine. Like Die Guy, she kicks ass and is one of the cool kids!

Please visit her blog at faleafine.com.

And remember, if you are ever in Hawaii, say aloha to Neenz. She kicks ass.

It amazes me how technical people turned management have trouble communicating their ideas.

I received a three page document the other day that had to be read three times to be understood.

Once I cut through the technical jargon and management buzzwords, the message could have been boiled down to one simple sentence with three simple bullet points:

If the customer asks about Issue X when using our software, please tell them the following:

• We are aware of this isolated issue;
• Please send us your file so we can attempt to replicate Issue X;
• There is no current workaround, but Issue X will be resolved in our next release by the end of the year.

When communicating with your crew, boil it down so the message is clear, concise, and precise.

Having been forced to use Comcast for television and internet since 2006, I am not a big fan of their service. Customer service sucks. Technical support sucks. And their prices have doubled in three years.

For these reasons, I simply love the DirecTV commercial about “Blamestorming”.

httpv://www.youtube.com/watch?v=7Z-tHzc7VXU

Having worked in a variety of companies from the Fortune 500 to the Mom and Pop backalley hillbilly metalhead shops, blamestorming occurs all the time. Unfortunately.

I blame management.

Progressive dies must be engineered to take No Stock Movement (NSM) into account. This is the time during the press upstroke that the feeder has to wait for the die components to be clear of the coil.

Feeders have a limited amount of time to index the coil one progression. This time is measured in crank angle degrees. Most feeders have 180° of time to feed. The faster the press runs and the shorter the press stroke, the less time is available to feed material one progression.

No Stock Movement is a simple calculation. It can be expressed as:

• NSM = UDT + LDT + P +ESM

where (all values are inches or millimeters):

• NSM = No Stock Movement
• UDT = Maximum Upper Die Travel (along press stroke vector)
• LDT = Maximum Lower Die Travel (along press stroke vector)
• P = Distance Pilots extend past stripper pads
• ESM = Engineered Safety Margin (dwell time after pilots are clear of coil before feeding starts)

For example, a progressive die with an upper pad travel of 50 mm, lower lifter travel of 25 mm, pilots extending 6.3 mm past the stripper in the open position, and 3.7 mm engineered safey margin requires:

• NSM = UDT + LDT + P +ESM
• NSM = 50 + 25 + 6.3 + 3.7
• NSM = 85 mm

In other words, the feeder cannot start feeding until the ram is 85 mm from bottom dead center on the press upstroke. The feeder must have the capability to index the coil one progression before the ram is 85 mm from bottom dead center on the press downstroke.

Otherwise, the press will have to operate slower or a faster feeder will be needed to run the die free from tooling interference with the material.

In the spring of 1998, we witnessed an epidemic of commercial aerial cam unit failures in the field. These off-the-shelf cams were relatively new to the automotive industry, replacing the time-honored practice of engineering and constructing home-made aerial cams.

We discovered that the cams were failing because the dies were engineered with no cam pad for stripping the cam steels. The slide return spring had to do all the work. In many cases, the spring was inadequate and the cam failed.

I personally contacted every supplier of commercial aerial cam units in the industry world-wide seeking an equation to quantify slide return force in aerial cams. The response was universal: there was none.

My personal mantra is find a way or make one. I had to make one.

I created an equation to quantify slide return force in aerial cams. This equation works regardless if there is a cam pad or not.

The equation for aerial cam slide return force is:

• Fasr = [Fs / cos(α + β)] + {(0.00981 • ms) • [0.20 • (cos β - sin β)]}

where:

• Fasr = aerial cam slide return force (kN)
• Fs = stripping force (kN)
• α = upper driver angle from horizontal (degrees)
• β = work angle from horizontal (degrees)
• ms = working slide mass (kg)
• 0.20 = coefficient of friction
• 0.00981 = force due to gravity

NOTE: if there is a cam pad, then the stripping force (Fs) required by the aerial cam slide is equal to ZERO.

For example, assume an aerial cam has a working slide with 40 kg mass with an upper driver angle of 30° from horizontal. The work angle is 20° from horizontal and 4.65 kN stripping force is required. There is no cam pad.

The required slide return force is:

• Fasr = [Fs / cos(α + β)] + {(0.00981 • ms) • [0.20 • (cos β - sin β)]}
• Fasr = [4.65 / cos(30° + 20°)] + {(0.00981 • 40) • [0.20 • (cos 30° - sin 30°)]}
• Fasr = (4.65 / 0.6428) + (0.3924 • -0.1541)
• Fasr = 7.17 kN slide return force

If the aerial cam slide return spring does not have the required force capability, then either a supplemental pressure system or a cam pad will need to be added to the cam.