Strip layout design concept for metal stamping dies

Strip layout design concept for metal stamping

All metal stamping designs should start with the basics. A solid foundation is required with both a visual and technical guide to progress further. The strip layout is the starting point of a metal stamping design which is the foundation or plan to manufacture and build the actual tool.

The strip layout design has several purposes. Once complete, it gives a visual representation to the manufacturing facility and to the client to have a good idea how the tool will work and how each progression or step will be made once the strip or coil is inserted into the die. The stamping can then begin.

This visual guide is the most important aid for the metal stamping die designer. It reveals details to clearly see how each feature must be made at each progression as the strip advances into the tool. Then important decisions can be made to simplify the final design or make it fit for automation and most importantly to improve it before it even starts.

The strip layout should include punches, form blocks, pilots, and some die blocks in order to make it clear how the tool will work and produce the parts. It is to ensure that the tool will do exactly what it is supposed to do.

Tool and die designers who neglect putting enough effort into this process, often end up with design errors. As a result, the manufactured stamping tools don’t perform well enough or don’t work at all. In that case costly modifications are necessary to correct mistakes before production can start. Usually these tools are notorious for break downs and require maintenance more often than others.

The proper tool and die design of a strip layout gives a piece of mind to the tool and die designer to proceed in the right direction. It is insurance for the end user or those who finance the project and want to be sure that their investments are in good hands with the tool working efficiently for a long period of time without breaking down. This is what it is all about. The sole purpose of a metal stamping tool is to produce as many identical high quality parts as possible at the shortest amount of time without stopping. Every time the tool requires maintenance and is not producing, it takes money away and becomes less efficient.

A good metal stamping die starts with a solid foundation, a good strip layout that gives the chance to eliminate future nuances, and to build world class tools that you can count on.

Vortool Manufacturing Ltd.

Unit 240 19358-96 Ave.

Surrey, BC V4N 4C1 Canada

Call: 604-239-7218 | Email

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Design considerations for stamping tools and dies

Design considerations for metal stamping tools and dies

Metal stamping die design considerations or decisions are driven by a number of factors in tool and die design.

However there are a few mayor points that should not be missed and must be included in the decision making process. You could design and build an inexpensive fabricated tool or you could make one that is a top of the line master piece.

How do You Decide Which One to Make?

Your customer will tell you what they need, what material the stamped parts are, how many parts should be stamped, when they want the finished parts, and how much they are willing to pay and so on.
These are important guide lines toward the metal stamping die design. They tell you what you can do and what you can’t. They set some boundaries.

The part itself is one of the major contributors that guide you through what the minimum requirements are toward the tool. It will help you with what you need in order to produce the particular part.
You may raise questions that need to be answered. How efficiently will the parts be produced? How long will the tool last? How user friendly should the tool be? What are the variables that can be implement in the design?

The Above General Guide Lines Should be Specified More in Detail

• How many parts will be produced per run, monthly or in the lifetime of the tool? If the amount of production is low, you will know that the tool will likely be manually operated and be budget oriented. If e.g. 5,000 parts are to be made every week for the next two years, than you know it is a high demand tool and automation and continuous operation is required. The tool must be designed accordingly. More time and money can be spent to make the suitable tooling.
• Low production rate equals inexpensive tooling components, unsophisticated guides, supports, etc.
• On the other hand if the metal stamping tool is running all the time, then you will need to build a tool that lasts. It will require less frequent tool and die maintenance, and be built for high speed automation. The tool steel should be higher quality, and more suitable for extended use. In this case instead of using e.g. A2 or D2 material, consider using M2 with coated surfaces or Vanadis 4 Extra or comparable. For the extra cost, these tool steel will last many times longer before sharpening is required. Use a ball bearing guide system, instead of standard bronze plated bushings and standard die pins. The ball guided system is better for high speed punch presses and high speed stamping.
• Pressure plates require springs behind them to generate enough force. Consider using gas springs. They are generally suitable for high speed stamping, and about 250 spm and rated about 1 million strokes before servicing. They are also more powerful than conventional die springs with the same footprint. You can use punches with ejector pins in them to push off slugs that are serious obstacles in automated stampings. You can also use die buttons with slug control that keep the slugs in the die button, preventing slug pulling. Slugs pulled back onto the die surface area can jam the strip and cause the feeder to buckle the coil. If this happens, your tooling may be at risk for serious damage.
• Bending is generally done using a wipe form method. The parts eventually gull and have heavy marks. The form sections constantly require polishing, causing downtime and quality issues. Ready benders can eliminate most of these problems, where the bends have simple straight features. This method completely eliminates parts sticking into the form die, as they require less pressure and will not mark the part as much or just simply eliminate it altogether. It is a perfect solution for pre-painted strips to stamp.
• Stock pushers are designed for automated stamping and have a superior feature that make their use a preferred choice.
• At upstroke of the press, they release the force applied to the edge of the strip or coil entirely, allowing a resistance free strip advancement. The applied pressure is adjustable, and you can design the engagement timing as you need it. The pilot punches can locate the strip perfectly before you lock its position for the duration of the cut.
• Another contributor to your metal stamping tooling design is to know what press or presses will be used for stamping. Your tool must be compatible and fit the desired press or presses. You may want to consider making 3D models of the presses with the vital features that are necessary for your tool design.
• The general requirement toward any stamping tool and for their design is that it should cost as little as possible, yet produce the most amount of parts at the best quality, should not break down, and will last longer than the anticipated life span of the tool. This perfect scenario should be achieved at all times. Compromises sometimes must be made and accepted, but not be part of your design.
• The guide lines or restrictions that are set by your client, your tool and die manufacturing facility or your ability, will have an impact of the outcome of your design and ultimately of the stamping tools and the produced parts.

Vortool Manufacturing Ltd.

Unit 240 19358-96 Ave.

Surrey, BC V4N 4C1 Canada

Call: 604-239-7218 | Email

Made in Canada

Custom specialty bench top, portable and modular presses

C frame press

AirHEAD 5 - 4 ton benchtop pneumatic box frame press

AirHEAD 5 - 4 ton benchtop pneumatic box frame press

Custom portable air-oil cylinder / shop air punch press station

AirHEAD 12-16-7 - 6 ton air to oil cylinder portable punch press station

Custom precision benchtop three platen flatbed die cutting press for steel rule die

Custom benchtop pneumatic swaging press

Custom air-oil punch press station for modular long mandrel die

Benchtop, portable and modular presses that operate with shop air

Modular press using multiple punch stations

Vortool Manufacturing Ltd.

Unit 240 19358-96 Ave.

Surrey, BC V4N 4C1 Canada

Call: 604-239-7218 | Email

Made in Canada

Optimum cutting clearance for blanking sheet metal

At optimum cutting clearance for blanking sheet metal at any given thickness, the sheared edge or the shiny band should be about 1/3 of the material thickness. The ripped or break away surface is 2/3. 

This is an indicator that the bur does not exist or it is at its minimal.

When the band is too small, it indicates that the cutting clearance is too much. The bur is generally larger than normal, and the part may not be as flat as should be.

When the band is too large, it indicates that the clearance is too small. The bur is large and uneven, so the punch may stick in the strip and stripping is difficult. Die and or punch edges chip often. It is because the strip is extremely tight on the punch, and as it pulls out, the edge (weakest point) may rip off, especially when the ground surface is not as smooth as should be.

Generally I use 10% clearance per side between 1- 2.5 mm and 12-15% for thicker material. The thinner the material, the clearance gets smaller as well. Over time I collected data from cutting clearances and results, and I use this data as average in my calculations. There is a variable of soft, medium or hard material to be blanked. I developed an iPhone app to simply type in the material thickness and hardness of the stock that gives me the calculated clearance per side and diameter.

There is a misconception among toolmakers that absolute centered alignment of the punch and die is less critical when the sheet (stock or coupon) is thicker. This is wrong. When the components are misaligned, the bur is generally larger on one side and the other not. What happens is that the pressure required to blank, e.g. 40 tons, will force the punch out of its position and try to get back to the center. This deflection creates more problems than most people would think.

• Excess bur on one side.

• Flex, or movement while cutting. This movement will cut the life span (between sharpening by ~70%. Any side movement is the cause for most tooling problems.

• Excess strain on die components, guide pins and bushings.

• As a result of the above, the parallel movement of the die set is compromised and slightly tilted. This would compound the initial problem.

• The punch press will also suffer. The blanking pressure is shifting sideways and will wear off the press components sooner. The improper clearance also affects the tonnage required and is greater than usual. Used punch presses are generally worn and always have a little slack. It means that even a 200 ton press’ RAM could be pushed back for a moment before it can go down with full power. This slight hesitation also creates movement while cutting, and it is, again affecting the life of the punch and die edges. If this happens, the cut edge will look different. Sometimes the bottom edge can measure about the same as the upper part and the edge may have horizontal lines, small bands.

When I design metal stamping dies, it is important for me that the tool stays in production as long as possible. It makes money. When the tool is off the press, it does not only require labour, time and money but will not produce anything either, and this is an even bigger loss. So, I always ensure that the clearances are correct and the alignment is absolutely centered, regardless of the thickness of the material. I use a similar precision for alignment between punches and dies, regardless if the thickness is 0.025 mm or 13 mm.

Vortool Manufacturing Ltd.

Unit 240 19358-96 Ave.

Surrey, BC V4N 4C1 Canada

Call: 604-239-7218 | Email

Made in Canada