Progressive stamping

Progressive stamping is a metalworking method that can encompass punching, coining, bending and several other ways of modifying metal raw material, combined with an automatic feeding system.

The feeding system pushes a strip of metal (as it unrolls from a coil) through all of the stations of a progressive stamping die. Each station performs one or more operations until a finished part is made. The final station is a cutoff operation, which separates the finished part from the carrying web. The carrying web, along with metal that is punched away in previous operations, is treated as scrap metal.

The progressive stamping die is placed into a reciprocating stamping press. As the press moves up, the top die moves with it, which allows the material to feed. When the press moves down, the die closes and performs the stamping operation. With each stroke of the press, a completed part is removed from the die.

Since additional work is done in each “station” of the die, it is important that the strip be advanced very precisely so that it aligns within a few thousandths of an inch as it moves from station to station. Bullet shaped or conical “pilots” enter previously pierced round holes in the strip to assure this alignment since the feeding mechanism usually cannot provide the necessary precision in feed length.

The dies are usually made of tool steel to withstand the high shock loading involved, retain the necessary sharp cutting edge, and resist the abrasive forces involved.

The cost is determined by the number of features, which determine what tooling will need to be used. It is advised to keep the features as simple as possible to keep the cost of tooling to a minimum. Features that are close together produce a problem because it may not provide enough clearance for the punch, which could result in another station. It can also be problematic to have narrow cuts and protrusions.

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Plastic Injection Molding Machine Selection – Why It Is Important

Selecting the right plastic injection molding machine is one of the most important criteria in making quality parts consistently and profitably. The right machine will help keep costs low and make you more competitive. This will allow you to sell more parts, earn more money and at the same time establish a reputation as a quality manufacturer.

Even better, you will have the security of long term customers.

How To Keep Your Costs Low:

  • Minimize reject rate (set a target <1%) Click here to read about how to eliminate warpage quality issues.
  • Reduce energy consumption of all injection molding machines
  • Have faster cycle times
  • Eliminate unscheduled machine downtime –(no breakdowns)

A properly selected plastic injection molding machine will give you all of the above.

Plastic Injection Molding Machine

Common Machine Selection Mistakes And Their Consequences


The best way to appreciate the importance of correct plastic injection molding machine selection is to list the most common mistakes made when selecting machines and the effect on part quality and productivity.

Mistake #1 
Buying Used Injection Molding Machines That Don’t Work

The key to buying a reliable used machine is to find one that has been fully inspected and tested before delivery so that you won’t suffer loss of production due to multiple breakdowns.

Click here to see a case study of how incorrect machine selection can effect part quality Example #2).(opens in a new window)

Mistake #2
Selecting Large Screw Diameters.

Large screw diameters can cause quality problems due to material degradation. When small shot sizes are used with large screw diameters, the plastic material spends more time being heated by the barrel heaters compared to large shot sizes. Material degradation is more likely to occur if the shot size is small compared to the injections units maximum shot capacity especially for heat sensitive materials.

Another problem with large screw diameters are the large shearing forces generated during screw rotation, this can also degrade the material and is likely to lead to reject parts.

Mistake #3
General Purpose Screws

The advantage of a general purpose screw is that they can be used with most plastic materials such as PP, PE, Nylon, PET and PC so they are very flexible and good for moulding companies that mould a variety of different materials.

The disadvantage is that, for some materials, part quality and productivity rates will be lower compared to more advanced injection molding screw designs such as the barrier screw. Click here to learn more about screw selection.

Mistake #4
Injection Pressure Limited.

To consistently make quality parts the molding process must not be limited by the injection pressure. It is advisable to have at least 10% injection pressure in reserve so that the injection molding machine can automatically adjust to normal variation in the plastic material viscosity.

Insufficient injection pressure will produce short moldings.

The injection units screw diameter governs the available maximum injection pressure so it is critical to choose the correct diameter when buying a plastic injection molding machine.

Mistake #5
Inadequate Clamp Tonnage

If clamp tonnage is too low then it will be difficult to produce quality parts. Low clamp tonnage means inconsistent weights, flash, short shots, wall section variation, poor surface finish and size variation.

Machine and mold wear will be excessive.

Mistake #6
High Energy Consumption

Have you ever noticed how there is almost no difference in your cars fuel consumption with 2 people in it compared to just 1 person? A moulding machine is the same. A small mold will require almost as much energy to open and close the platen compared with a medium size mold. A properly selected plastic injection molding machine will use power very efficiently.Click here to learn about how to reduce your energy bill on your existing machinery by changing parameters in the plastic injection molding process.

The type of machine design also plays a significant role in power consumption. There are 3 types of machine designs: fully hydraulic, fully electric and hybrid machines. Hybrid machines are partly electric and partly hydraulically operated. Selection largely depends upon the type and quantity of parts to be molded.

Plastic Injection Molding Machine Selection Process


1. Know the plastic parts you intend to mold
2. Select machine type: Hydraulic, hybrid or electric
3. Calculate clamp tonnage requirements
4. Calculate the injection unit size.

1.Know The Plastic Parts You Intend To Mold

The process of selecting the right machine starts with knowing the particular plastic parts that will be moulded by the machine. Molding parts that are not suited to the machine will result in frustration with on-going quality problems, slow cycle times and machine and mold damage.

If you are planning to buy Cap or Closure Molds then click here to get a quick mold quote from a reputable mold maker. (Opens in a new window)

You should know the part:

  • Plastic material
  • Weight
  • Length x width x height
  • Average wall section
  • Gate location
  • Maximum flow length from the gate
  • Estimated cycle time. Click here to estimate cycle time.
  • Quality requirements
  • Annual quantity requirements. Click here to get to the production calculators used for scheduling.

In addition you should also know the mould size and weight.The correct part information will then allow you to find the injection unit size, clamp tonnage requirements and machine type.

2.Select Machine Type

Types of plastic injection molding machine designs available:

  • Fully Hydraulic
  • Fully Electric
  • Hybrid – combination of hydraulic and electric drive

Fully Hydraulic Machines

The types of hydraulic machines available are defined by the type of clamp design, type of hydraulic pump design and the presence or absence of an accumulator.

Clamp design is either a toggle clamp or by hydraulic ram.

Hydraulic pump design can be a constant displacement pump (also called fixed displacement pump), a variable displacement pump (also called a piston pump) or a servo pump (also called frequency control or RPM control) .

If an accumulator is present then some machine manufacturers use it to drive the entire machine, while others use it for the injection stage only. Accumulators are required for molding of parts which have wall thicknesses in the range of 0.3mm to 0.8mm – this is known as thin wall molding.

Accumulators might also be required for moulding thicker parts but this must be checked on a case by case basis.

Which one is suitable for you?

It depends on your priorities.

Here are some criteria to consider before selecting a hydraulic moulding machine:

  • Buy a new or used machine
  • Purchase price
  • Energy efficiency
  • Plastic material to be processed
  • Part design
  • Mould design
  • Clean room requirement
  • Cycle time requirement
  • Hold time requirement
  • Local service agent capability

If low power consumption is a priority then choose a hydraulic machine with a servo pump as this is the most energy efficient of the fully hydraulic machines. A servo pump will only operate when the machine requires movement, the rest of the time it is using minimal power. However, the purchase price is 10%-15% higher than a hydraulic machine with a constant displacement pump or even a variable displacement pump.

Keep in mind a servo pump control will only save you power if you have long cooling times or machine inactive times such as long take out time for robot.

Fully Electric Plastic Injection Molding Machines

Every movement of the machine is done with direct drive electric servo motors only drawing power when movement is required so they are very energy efficient. Electric machines have excellent repeatability which virtually guarantees consistent part quality.  This makes them suitable for molding medical devices. Click here to learn more about medical injection molding.

Electric machines are suited to clean room operations because there is no hydraulic oil that can leak on to the floor. Click here to learn more about electric molding machines.

Hybrid Plastic Injection Molding Machines

A hybrid plastic injection molding machine uses a combination of hydraulic drive and electric direct drive. The hydraulic drive is used to generate fast injection speeds when moulding thin wall parts. The rest of the machine uses electric drive servo motors and each axis of the machine has its own dedicated motor. For example, the mould opening/closing stroke has its own motor.

These injection molding machines are very energy efficient

3.Calculate Clamp Tonnage Requirements

Clamp tonnage requirements for your plastic injection molding machine can be calculated by:

  • By experience – injection molders and machine manufactures have this information
  • Computer simulation software (Click here to learn more about the benefits of using simulation software.)
  • As a rough guide, a simple calculation Projected Area X Average Cavity Pressure X Number of Cavities. (Click here to find the machine clamp tonnage for plastic parts made from polypropylene).

In order to find the tonnage using the simple calculation the following part information is required:

  • Plastic material
  • Length x width x height
  • Projected area (length X width)
  • Average wall section
  • Gate position
  • Maximum flow length from the gate
  • Number of cavities in the mold

The average cavity pressure is also required and this information is available in some plastic injection molding machine manufacturers hand book for certain materials.

Most injection molded parts average cavity pressures lie in the range of 300-800 bar. Parts with long flow paths and thin walls will have pressures in the upper range while parts with short flow lengths and thicker wall sections will have much lower pressures.

Plastic material selection also influences the cavity pressure.

In addition, you need to know the mold weight and size so that you can check that the mold will physically fit into the machine and that the machine can carry the mould weight. Click here to learn about our mold design services.

4.Calculate The Injection Unit Size

To select the right unit for your plastic injection molding machine you must know part:

  • Plastic material
  • Cycle time
  • Cooling time
  • Shot weight (part weight, cold runner weight and number of cavities)
  • Peak injection pressure requirement
  • Plasticizing rate
  • Injection rate
  • Hold time and pressure

For a specific tonnage machine, manufacturers usually offer 2 injection units to choose from. Both units usually have 3 different screw and barrel assemblies on offer. In order to select the correct assembly, the shot size must be calculated as a percentage of the injection capacity and must lie between 25% and 65% so that good quality parts can be made.

Most screw and barrel assemblies are rated in grams of general purpose polystyrene (GPPS). To calculate the shot capacity for materials other than for GPPS the melt density needs to be known.

Lets assume we have a screw and barrel assembly with a screw diameter of 56mm and the capacity is 510 grams of GPPS. What is the injection capacity for polypropylene (PP)?

Assume melt density of GPPS = 0.945 grams per cubic centremeter

and melt density of Polypropylene  = 0.74 grams per cubic centremeter

(Be sure to use melt density & not room temperature density for this calculation)

Calculation to find injection capacity for PP:

(Density of PP/Density of GPPS)xBarrel capacity of GPPS grams

=(0.74/0.945)x510 grams=399 grams PP

So maximum injection capacity of PP for this 56mm screw diameter is 399 grams.

Next we need to make sure the shot size is within the maximum and minimum limits of between 25% and 65%.

If the shot size for the injection mould is 110 grams (includes cold runner) then the shot size as a proportion of the total injection capacity is:

=(110/399)x100= 28%

which is within limits.

Next, the following 3 criteria must be confirmed to be within limits of the injection unit with the 56mm diameter screw.

  • Injection pressure
  • Plasticizing rate
  • Injection rate

These can be found in one of 2 ways:

The first is by experience – perhaps you have a similar part in production in which case you can read the pressure directly off the screen. Be sure to check the screw diameter is the same.

The second is by computer simulation but keep in mind the results are only as good as the information that is entered. It is advisable to check these results against some real life examples.

Just remember, the screw diameter selected is crucial to long term part quality and productivity.

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How To Learn Metal Stamping

Metal stamping or metalworking is a process where thin sheets of metals undergo different procedures such as bending, embossing and piercing in order to achieve certain images, letters or designs. Usually, metal stamping is done with a machine or a metal stamping tool. You can learn this art form on your own with just a few simple materials.

Learn the art of metal stamping by following the tips provided below:

Purchase metal stamping equipment. First you should have the right materials so that you can start metal stamping. There is plenty of equipment used for metal stamping. You will need a metal hole puncher, metal sheets, needle file, a small hammer, steel block and some stamps and a marker. These are some of the items you will need as a beginner. You can look for these from your local arts and crafts store or you can order a metal stamping kit online from rings-things.com or beaducation.com.
Read and watch. If you purchased the metal stamping kit, you can read the instructions that came with it. These kits are mostly used by beginners just like you. They provide step-by-step instructions and tips on how you can start doing metal stamping. You can also check out online resources for video tutorials on metal stamping. This may be better since you can see how it is actually done.
Enroll in classes. Check local arts and crafts stores if they offer lessons in metal stamping. It will be better for you to enroll yourself in a class if you have the time and the budget since you will be able to learn some techniques that you can’t learn from anywhere else. It is good to see how the process is done to have a good idea on how the process works. If you find that you are good at metal stamping and you enjoy the art, you can purchase more tools and invest so that you can create various pieces.
Practice. The most important thing that you have to do is practice your craft. Metal stamping is not that easy. You may end up with pieces that are not perfect the first time you do it. As you practice and get used to stamping, you will get better at it. For practicing, you can purchase cheap metal sheets from your craft store and use them to practice controlling your hands when stamping. Once you get better, you can purchase better quality metals and even blank charms and pendants that you can use.
Other tools. There are other tools that you can use to enhance your creations. Use the metal hole puncher to put holes on the metal sheet. You can also use different colored markers so that you can change the color of the stamped image on the metal.

When you are already good in metal stamping, you can invest in more tools that you can use. You can create pendants, charms and other items that you can give as gifts for friends or another option is to open up a store or online store and sell your metal stamping creations.

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What Is a Stamping Press

A stamping press is a piece of equipment people can employ in metalworking to shape pieces with the use of a die. The die can punch patterns into the metal, mold it into a specific form, or cut it to a desired shape and size. Stamping presses have an interchangeable design, allowing people to replace the die as needed for different projects. Companies can keep a library of dies around to reproduce products or make future production runs.

The size and speed of this device can vary. Some models are small and relatively slow while others are quite large and capable of handling very high volumes of material per hour. Some require an operator to actually handle the metal and operate the press. Others may use robots and computer-controlled programming so no one needs to be present to run them, with the machine handling operations on its own.

This equipment can be seen on the floor of facilities where people regularly have high volume metalworking needs, like car companies and tool manufacturers. The stamping press may be able to handle cold forging as well as warm and hot production methods to cover a variety of needs. Some machines use a mechanical engine to drive the die while others rely on hydraulic power to squeeze the metal. The best choice can depend on the kind of metal people are working and what kinds of products they plan to make.

The device has a number of moving parts and can be extremely dangerous. The pressure necessary to form metal is very high, and if the limbs of the operator get caught, they can be crushed or severed. It is important to make sure people observe safety precautions around the stamping press, and it is also necessary to maintain the machine properly. The stamping press should be well oiled, with all parts functioning and in place, for employee safety as well as product quality.

Some manufacturers offer stamping press rentals to companies that are not yet ready to invest in buying a press, and often it is possible to buy the machine at the end of the rental, at a reduced price. It is also possible to buy refurbished presses, a good option for companies that cannot afford the market value for a new machine. Another good source for affordable stamping presses can be liquidation auctions, where companies sell off all their equipment when they go out of business.

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Metal Stamping Quality Control

Metal stamping is a form of metalworking that is completed using various levels of difficulty. Almost anyone can form their own jewelry, flowers, numbers and letters out of metal using metal stamping kits or other tools. The higher the quality of the metal used, the longer these personal things will last. Metal stamping is also an industrial fabrication process used to create weaponry, vehicle components, dollar bill changers, vending machines, decorative sheet metal parts, medical life-saving devices, and many other items.

Stamping includes a variety of sheet-metal forming manufacturing processes, such as punching using a machine press or stamping press, blanking, embossing, bending, flanging, and coining. This could be a single stage operation where every stroke of the press produce the desired form on the sheet metal part, or could occur through a series of stages. The process is usually carried out on sheet metal, but can also be used on other materials, such as polystyrene.

When working with metal stamping in the industrial world, material quality is very important. A metal stamping company may work with aerospace or medical industries creating products that can save lives-if the metal used is of low quality, lives can be destroyed instead.

Stamping simulation is a technology that calculates the process of sheet metal stamping, predicting common defects such as splits, wrinkles, springback and material thinning. Also known as forming simulation, the technology is a specific application of non-linear finite element analysis. The technology has many benefits in the manufacturing industry, especially the automotive industry, where lead time to market, cost and lean manufacturing are critical to the success of a company.

Recent research by the Aberdeen research company (October 2006) found that the most effective manufacturers spend more time simulating upfront and reap the rewards towards the end of their projects.

Stamping simulation is used when a sheet metal part designer or toolmaker desires to assess the likelihood of successfully manufacturing a sheet metal part, without the expense of making a physical tool. Stamping simulation allows any sheet metal part forming process to be simulated in the virtual environment of a PC for a fraction of the expense of a physical tryout.

Results from a stamping simulation allow sheet metal part designers to assess alternative designs very quickly to optimize their part for low cost manufacture.

Quality control is important, from verifying the metal when it’s received to complete testing and inspection once the product is completed. Metal stamped parts can be made into fuel injectors for an automobile, engines in an aircraft, bayonet assemblies, and navigation systems used by the military. With components that can take lives if they fail, it’s important to ensure the company you’re working with takes quality control very seriously.

First inspection of the material when it is received is an important quality control process. If the metal company can verify where the materials that will be used in production come from, it is likely they take care to make sure your components do not fail on you. Material identification provides documentation as to where the metal has been before being used in fabrication; it shows where it’s made and how it’s transferred. By using metals from reputable sources, metal stampings are more durable, smoother, and last longer than questionable materials.

Final inspection of the completed component is just as important as material identification. By performing non-destructive testing and other inspection methods on the product, any defaults or other issues will be noticed. A company with high quality standards keeps their rejected products to less than 1%. This shows that quality control is completed during every step of the fabrication process.

Metal stamping prototypes are a great way to ensure that the final fabrication of all parts will be correct in tolerance, size, durability, and design. Whether the prototype is a working part or not, working with companies who offer this as an option can mean the difference between getting exactly what you want and a completed order that doesn’t match your needs.

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What Is Metal Stamping

Metal stamping is a process that is used in all types of manufacturing. It is a highly elaborate system using a combination of machine presses and pure craftsmanship. It is performed in rapid succession and involves various techniques for the type of shapes and designs that are being created. Any type of metallic product sold in the marketplace has been shaped and designed through the use of metal stamping.

Definition
Metal stamping is the industrial process of stamping or shaping designs on sheets of metal. A metal sheet alloy is stamped or pressed on a machine using dies and a hydraulic machine to create the designs.

Designs
Some of these designs are used to create familiar, everyday products such as sheet metal machines, car parts, audio/video devices, aerosol spray cans, pots and pans. Uses also include military tanks.

Types of Metal
Most types of metal are commonly used in metal stamping, though they are generally flexible and can be easily manipulated under the machine process. These metals include aluminum, zinc, steel, nickel, bronze, copper and certain other alloys. The metal is fashioned into sheets of various sizes and thicknesses. Metal presses are designed to shape and design all types of metal sheets regardless of size and thickness.

You can use stamping designs for much more than just scrapbooks and school materials. You can spruce up tired household items, decorate plain clothing and make personalized invitations and greetings cards, to name just a few. There are even various kinds of stamping inks and paints that work better with one material over another. Take a step back and make your own stamps with which to decorate your world. Involve the kids, too, because stamping is easy enough for them to do alone.

Lampshade Decor
Decorate a lampshade with stamps; the light will shine through them and illuminate your stamped shapes, producing great visual effects. Remove the lampshade from the lamp. Dip foam or rubber stamps into craft paint and press them firmly onto the lampshade with a smooth surface. Carefully rock the stamps back and forth to apply the paint around curved shades. Allow the paint to dry thoroughly before replacing the shade and turning on the light.

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The Process Of Precision Metal Stamping

Precision metal stamping is the process of making 3-dimensional metal parts, lettering and other embossing. This is a kind of metal stamping used mostly for decorative purposes. It is similar to normal metal stamping, which is the process of molding metal into different shapes and sizes.

The products obtained through metal stamping are used as components for some larger products in other industries. The most common metals and alloys used for precision metal stamping are copper, aluminum, brass, beryllium, nickel, nickel silver, steel, stainless steel, phos bronze and titanium.

Precision metal stamping is applicable to many industries like computers, electronics, electrical, dental, aerospace, instrumentation, military specs, defense, telecom and automotives. There are many methods in precision metal stamping for producing stamped prototypes. Blank creation is one such method. Blank creation involves the creation of a flat state of the component. The flat blank sheet is then used to make the part’s features. In blank creation, there are many processes
like nibbling, chemical etching, water jet cutting, wire EDM, punch and die.

There are also many methods for producing prototypes by precision stamping. The type of method used depends on the size and intricacy of the parts to be produced as well as the number of prototypes. Single part transfer is one such method in which single parts are transferred from one station to the next for blanking and metal forming.

The main advantage with this method is the cost effectiveness. One single, standard system can be maintained for designing, manufacturing and holding tooling inserts. However, this system is slow because it needs individual prototype parts. The other method is the progressive strip prototyping which involves the automatic transfer of the metal from one stage to the next.

Precision metal stamping can be done at very high speeds and even up to 1,200 strokes per minute. Precision metal stamping gives several advantages like the ability to use any metal or alloy and creation of components with very precise dimensions and shapes. Plating can also be very precise which is helpful when working with precious metals like gold and palladium.

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Stamping Die Process

Metal stamping dies can be used for various sheet metal operations like, shearing, blanking, piercing, bending, forming, coining, embossing, extrusion, deep drawing etc.

Stamping Die Design

Die design is one field of precision metal stamping which gained considerable growth in the recent years. Computers have replaced drafters and drawing boards making the design easier, accurate, unambiguous and faster. Today various computer aided design (CAD) softwares like AutoCAD, Solid works, Unigraphics, Pro Engineer etc help stamping die designers life much easier. Designers also take the help of analysis softwares like Anysis and Nastran to predict the sheet material behavior during various metal stamping operations.

Stamping Die Manufacturing

Tool and Die making is one of most high precision engineering branches. It requires precision machineries and highly skilled work force. Tool and die makers and precision machinists are among the most highly skilled workers in manufacturing industry. Stamping die manufacturing involves step by step operations starting from design study, planning, pre-machining, heat treatment, final machining, bench fitting and assembly. Machining involves numerous operations from raw material cutting, drilling, shaping, milling, turning, grinding grinding, cylindrical grinding etc to modern CNC machining operations like EDM, Wire EDM etc. We will discuss about precision machines and various cutting tools used on these machineries. The precision metal stamping die manufacturing involves lot of bench work and assembly of different parts of dies after the final machining. A number of hand tools and precision measuring equipments are used throughout the process of metal stamping die making.

Stamping Die Maintenance & Trouble Shooting

Precision metal stamping dies require regular maintenance to ensure the quality of the components it produces. Normally the maintenance works involves sharpening of cutting punches, replacing broken and damaged parts, working on dies to ensure the final stamped product meets all the quality specifications of customers etc. With the systematic processes like preventive maintenance consistent parts and enhanced life of stamping dies can be achieved.

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What Is Stamping Die

Sheet metal stamping dies are used to produce high precision metal components which are identical in shape and size. The dimensional accuracy and stability which you can achieve using precision metal stamping dies are very high and thus metal stamping dies are integral part of any manufacturing industry. You can see metal stamping components everywhere. From the electrical switches at your home to the computer you are surfing, from cars to aircrafts, everything needs precision metal stamping parts. A highly specialized branch of mechanical engineering, metal stamping technology has grown considerably with the evolution of sophisticated machineries, CAD (computer aided designing) and CAM (computer aided machining). This site is a resource for all those who are looking for detailed info about precision metal stampings and the manufacturing and trouble shooting of stamping dies.

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