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There are some sheet metal components which are designed in the bed way bend. The bend radii are stated as sharp or only a small radius is allowed. When we spotted this error, we used to feed back to the component designer asking for a change in design or to enlarge the bend radius.

There are differences between good way and bad way bends. In general, the good way bend is the axis of bend perpendicular to the Grain flow of the sheet metal, the bed way is the bending axis parallel to the rolling direction. A good way bend, the sheet metal can be formed or bent with sharp or small bend radius without having any crack or rupture at the bent edge, but the bad way requires a larger bend radius in order to avoid crack at the bent edge.

The minimum allowable bend radius difference from different material type, as it is just a general guideline, the softer and thinner the material, the smaller the allowable bend radius compare to the harder and thicker material.

A general guideline, a cold roll steel which under 1.5mm thick, the minimum allowable radius is equal to the thickness of the material for 90 degree bend, material from 1.5mm-2.0 mm thick, the minimum allowable bend radius will be ranging from 1.5-2.5 time the material thickness.

 

E ver thought of using disc spring washers as compression springs in tool and die making?

A disc spring is best use in situations whereby the tooling requires higher spring force but constrain by space limitation or when incorporating a nitrogen gas spring is not possible.

A disc spring is a conical shell. It can be loaded along its axis either statically or dynamically. The loads are normally applied to the upper inner edge and the lower outer edge. Disc springs can be used either in a stack or in a single piece.

Disc springs can be stacked in the opposite direction face to face to each other (series arrangement), which means their deflections add up, it allow longer travel length. They can also be stacked in the same direction (parallel arrangement) allowing the force to add up but still remain the same travel length.

 

Disc springs are usually guided with a hardened shaft going through from the centre hole of the disc. The surface of guide elements must always be hardened, harder than the disc springs themselves. A minimum of 55 HRC is usually recommended.

I have tried using disc springs on one of the blank holders of a first draw station in one of a progressive deep drawn tool. This tool had been running for 50,000 parts without any problem arising. The design of the tool is shown below.

 

Disc springs are available in any local hardware stores

 

 

Calculating the correct flat pattern layout is crucial to getting a good quality finished part from your press brake. Yet, many CAD and CNC programmers have no idea how to calculate the required values. Years ago, the real experts created cheat sheets and tacked them to the wall. They only taught the new apprentice how to apply the results shown on the cheat sheet, not how to calculate the numbers. Well, now those experts have retired and it’s time for a new generation to learn the right way to do the calculate the correct flat pattern layout.

Calculating the flat pattern length from the 3D part really isn’t that difficult. Although you may find several different formulas that claim to calculate the Bend Allowance they usually are the same formula, only simplified by filling in the angle or a K-factor. Oh, and yes, you do need to know the K-factor to calculate the Bend Allowance.

 

Let’s start with a simple L bracket. The picture shows that the legs of the bracket are 2” and 3”. The material thickness is 0.036”, the inside radius is 0.125”, and the angle of bend is 90 degrees. The flat length is the total of the flat portion of both flanges plus the length through the arc of the bend area. But, do you calculate that on the inside of the material or the outside? Neither! This is where the K-factor comes into play. The K-factor is the percentage of the material thickness where there is no stretching or compressing of the material, for example, the neutral axis. For this simple L bracket, I will use a K-factor of 0.42.

The formula (See Bending Formulas) is: Bend Allowance = Angle * (PI / 180) * (Radius + K-factor * Thickness). Plugging in our numbers, we have: Bend Allowance = 90 * (PI / 180) * (0.125 + 0.42 * 0.036) = 0.2200999813105009. If you don’t have a calculator handy, try the Bend Calculator.

So the flat pattern length is 2” + 3” + 0.2201 which is equal to 5.2201. So if you add up the flat length of all the flanges and add one Bend Allowance for each bend area you have the correct flat length of the part.

But look at the drawing. That is not how we normally dimension a sheet metal part. The dimensions are usually to the intersection of the flanges or the Mold Line. This means that we have to subtract two times the material thickness plus the bend radius (also known as the Setback) for each bend area. For this set of dimensions, it would be easier to calculate the Bend Compensation value. The Bend Compensation value lets you add up the length of each flange using the Mold Line dimensions and then add one Bend Compensation per bend area to the total. Don’t bother with your calculator. Just go to the Bend Calculator and get the answer. It is -0.1019, a negative number, which means you will subtract this amount from the total of the flange lengths, 5”, to get 4.8981

Found the following chart from the Internet. I thought it is a good idea to share this piece of information with my Blog readers.

This chart comparing the toughness and wear resistance of some common tool steels such as A-2, D-2, L-6, O-1, S-7 and H-13. It provides a guide to the tool designers when comes to selection of correct tool steel.

D-2 tool steel is a high carbon, high chromium tool steel used on applications requiring high wears resistance. D-2 steel can be surface treated such as nitride, titanium nitride if to increase it surface hardness.

O-1 is common oil hardening tool steel that may be hardened from fairly low temperatures with little size change. O-1 can be given standard surface treatments such as hard chrome plating if desired. Nitriding is not generally practical due to a substantial loss of core hardness.

AISI L-6 tool stee is tough, high- strength tool steel that suitable for general purpose applications.

Like wise, L-6 can be given standard surface treatments such as hard chrome plating if desired but not suitable for Nitriding process due to a substantial loss of core hardness.

AISI A-2 tool steel is an air hardening medium alloy tool steel that is heat treatable to HRC 60-62. It has wear resistance intermediate between the oil hardening tool steels ( O-1) and the high carbon chromium tool steels ( D-2) . Because it offers a combination of good toughness along with moderate wear resistance, it has been widely used for many years in variety of cold work applications. A-2 is quite easily machined in the annealed condition and exhibits minimal distortion on hardening, making it an excellent choice for dies of complicated design.

A-2 can be surface treated such as nitriding, titanium nitride coating to further improve it surface harness, hence, improve wear resistance.

S-7 is a shock-resistant air hardening tool steel. It commonly applied for high impact resistance application such as coining, clod forging. It offers good toughness to withstand chipping and breaking, combined with high attainable hardness and good wear resistance.

S7 is not typically suitable for nitriding or similar surface treatments.

H-13 is the most popular and most versatile hot work tool steel that provides a good balance of toughness, heat check resistance, and high temperature strength. It may be used for tool temperatures up to about 1000 F (530 C).

Because of its high tempering temperatures characteristic, H-13can be treated by most surface treating processes, including conventional and ion nitriding, titanium nitriding, and other coatings or treatments to further improve it surface hardness.

 

Precision metal stamping manufacturers are finding metal markets increasingly unpredictable.  The industry has experienced wild swings both up and down — sometimes these swings occurring within a calendar week.  The fluctuations in these markets have been compounded by the uncertainty in the global economy over the past two years.

Commodity markets (copper, gold, silver, oil) fluctuate with the movement of the dollar.  As the dollar strengthens, commodity prices tend to dip.  On the other hand, if the value of the dollar weakens, commodity prices tend to rise.  Since commodities are traded in dollars, they normally follow the up and down movement of the dollar market.

The Steel market, which has been rising since November 2009 (based on the CRU Steel Price Index), appears to have hit a plateau and may even be tracking down in the next couple of months.

Many people in the industry believe that this decline will last for a quarter or so, but an upward trend was seen again in late 4th quarter, 2010.

This pricing fluctuation is as much supply based, as it is demand based.  While the demand for steel may not always be there, many times mills will reduce their capacities so that they can hold pricing, or even see it increase.

Precious metals (gold, silver, platinum, palladium) have continued to rise all year.  Gold, especially, has hit one high after another.  People tend to flock to the safety of gold in difficult times, which has been evident over the past two years.

The only certainty the industry can expect at this point is continued unpredictability in the metals market.

Dies are tools used to process raw material into products via the application and concentration of force. In the case of this lens we focus on sheet metal stamping dies. Sheet metal stamping dies touch nearly all of our lives: the cars we drive, the appliances we use, the shiny cases of our latest iToy, and even the planes and buses we ride in.

Thought to be a dying trade by some, Tool and Die is still a vital part of our manufacturing infrastructure that we should all learn a little bit more about. After all a pound of steel costs less than a pound of butter, a pint of bottled water, and certainly less than a coffee.
Draw dies are the fist tool that processes the flat boring sheet metal into something exciting. A car door, a fender, a hood or roof panel. But also dies make parts that you don’t see; those that keep you safe when during impact, that allow the car to travel fast and safe, that give a place to mount the rest of the mechanical components.

Draw dies stretch and form the sheet into the bulk of what you will recognize of any car going down the street.

After the part is formed in the Draw die, the material used to hold the part as it was formed can be removed. The trimming die removes this material by shearing the edges of the part away from the desirably formed metal. Scrap metal falls away from the part.

Overall any discussion of sheet metal stamping and the Tool and Die trade on the internet is enlightened. After all, most assumed that sheet metal was soon to be left behind for another form of material, such as plastics.

 

Are electric cars the wave of the future?  Ford and Nissan seem to think so.

Ford Motor Co., working to make a quarter of its vehicles run at least partly on electricity, plans to invest $135 million and add 220 jobs at three Michigan facilities to help it introduce five such models by 2012.  The automaker “has said it will begin selling two electric vehicles and three new hybrids by 2012 and that such models will constitute 10 percent to 25 percent of its worldwide fleet in a decade.”

However, the Wall Street Journal notes it is estimated that the growth in fully electric vehicles market will not accelerate. A 2010 study by Deloitte Consulting concluded that these vehicles will constitute no more than 5% of the US market by the end of this decade, citing vehicle high costs and limited driving range.

The Wall Street Journal reports Nissan Motor Co. CEO Carlos Ghosn said the world market for electric vehicles is poised to surge, and if that happens automakers would be unprepared to support demand. The CEO said he is more worried about building more factories to meet the demand than about the $5.03 billion investment that Nissan and Renault SA have committed to the first versions of electric vehicles. Ghosn also noted he is optimistic about the rebound of the auto market in the US, and forecast that sales would get to 12 million vehicles in 2010, up 15% from last year.

I’m pretty optimistic that we’ll see more electric and hybrid vehicles become available.  However, when I was car shopping in 2006, I chose a regular gas engine vehicle.  The reason I chose a regular gas vehicle is because unless I was going to drive a hybrid for 150,000-200,000 miles, it just didn’t save me any more money.  In fact, it would have cost me more.

Now, I haven’t done a breakdown recently.  So that might be a good idea for an upcoming post.  I’m sure the technology has advanced even in the last 4 years.  It seems that the hybrid and electric cars are becoming a bit more affordable for the “average joe”.

What are your thoughts on hybrid and electric cars?  Do you think they are the wave of the future or is there another technology that could be it?  Would you buy a hybrid or electric for your next vehicle?  Comment below.

Before you take the plunge on a new metal stamping design, you need to remove your risk of material failures upfront. Your metal forming supplier should provide you with a formability assessment at the beginning of the quote stage to show any risks and issues before costs are considered.
Formability Analysis Software quickly identifies areas of concern. After entering 3D data, material type and specifications, the software calculates forming stresses.

The engineering team can then simulate the forming process, shown in steps, on a computer.

The software then highlights areas of concern that may cause problems during the form or draw process.

These problems can then be addressed by modifying both the part shape and tooling stations needed to create the finished product. The formability software allows the supplier to communicate problems back to you, early in the quote stage. This, in turn, saves you both time and money.

What may have taken days or even weeks to develop previously, can now be simulated in the software in a matter of minutes, before any material is cut. The ability to provide feedback about your design concepts, instantly, can certainly help strengthen the relationship between you and your supplier.

The Main Advantages of Formability Analysis:

Identifies 90% of forming feasibility issues within minutes

Substantially reduces financial risks during product development

Quickly identifies potential of splitting, wrinkling, and thinning

Accurately predicts feasibility of product geometry, as well as blank size, accounting for material properties, friction and blankholder forces

Saves time during the production and development process

Formability Analysis Software is not only for new designs, but can also be beneficial to existing projects. This software, in conjunction with an innovative engineering team, can find ways to make your current parts better and more cost effective

 

Metal StampingThe metal industry is developing at an incredible rate. Therefore, it’s not surprising that little by little, methods used for manufacturing metal forms up until now are being used less and less, and are now being replaced by metal stamping.  Manufacturers now see the practicality and necessity of changing the methods to be used in the production of metal from casting to stamping.

This is due to the advanced technology that metal stamping offers to the metal industry which makes metal manufacturing and production much cheaper.  Aside from the fact that metal stamping is cost-effective, it offers lifetime durability, uses stronger metal parts and materials and has a capacity for greater volume and mass production which answers the worldwide demand of hundreds and thousands of metal pieces.

It is now considered the best alternative to metal casting. Metal stamping manufacturers believe that the process in metal stamping is more beneficial than casting, the reason why they now choose to use the same in their production. Here below, are the features of metal stamping, which now replaces other forms of metal process like die casting, metal forging, fabricating and also machining.

 

  1. The metal stamping process features a piece of blank metal which is pinned down at the edges and is drawn with the use of a punch to a die in order to achieve a desired specific shape.  The procedures are referred to as shallow drawn stamping and deep drawn stamping.
  2. Stamping can be done depending on the targeted shapes.  Stamping produces a variety of shapes in a variety of metals, too.  Follow-up stamps can be had for the desired complex forms such as holes.
  3. Metal Stamping has two main methods:  the mechanical and the hydraulic.  The mechanical uses a large flywheel for its pressure and runs rapidly for shallow drawn stamping and cutting of blank sheets.  On the other hand, hydraulic press is much slower and exerts more pressure which is great for both shallow drawn and deep drawn stamping.

With these reasons, it is obvious to see the ways in which metal stamping is fast becoming superior to metal casting, especially as it costs less than any other form of metal form processing.