Coiled Steel Straighteners

The next auxiliary machine involved with a punch press set up, isn’t always necessary. Material straighteners are used in a hand full of situations, however, aren’t always necessary and their usage depends heavily on the condition of the material and amount of stations within a die.

Coiled material will always have a slight curvature to it, due to its tightly wound and banded state. To neutralize the curvature in coiled steel, straighteners have to really make a mark on the material. In the picture above, there are 9 straightening rollers. The pressure from each roller bends the material in different directions to eventually even out the material. As the material enters from the right, the first rollers apply the most force, and as the material moves to the left and towards the press, the rollers weaken in force applied allowing for the deformations to gradually even out, making the material straight.

The other common situation where a material straightener is required is when the material is being ran through a progressive die of more than three stations. Running material through multiple stations means that there are multiple forms, hole piercing, or cutting that needs to be done to create the desired part. Because of the multiple operations that need to be done, ensuring that the raw material that is being fed into the press is as straight, and flat as possible is paramount. Having the material be consistently straight helps ensure that the die will run as it is designed, and eliminate any backing up of material or malfunctions that could be detrimental to the die and stamping press.

Next week, we’ll take a look at feeders, the ever important auxiliary equipment that keeps the material churning into the stamping press.

Punch Press Un-coilers

Punch press un-coilers are rather self explanatory, as their main function is to hold coils of material, and allow the material to un-coil as it is being fed into the press. While somewhat of a simple task, there are a couple of variations that allow some flexibility and bonuses for metal stamping operations depending on what kind of parts are being stamped out. The five main styles of material un-coilers include a standard reel, a motorized reel, a pancake un-coiler, a cradle, and a tandem un-coiler. We’ll start off with the most basic of un-coilers, the standard reel:

Standard Reel Un-coiler

Standard reel un-coilers have no motor or any control device that limit or dictate how much material is being un-coiled at a time. Standard reel un-coilers come in a variety of sizes, holding lite to medium sized coils. Since there are no controls to the standard un-coilers, the amount fed out at a time depends on the feeder attached to the press. While not the most technologically advanced of all the un-coilers, standard reel un-coilers will always have a place in a stamping operation due to their low cost and maintenance requirements, and ease of moving from one press to the next.

Motorized Reel Un-coilers

Motorized reels are very similar to standard wheels, with the exception that material is fed intermittently by a motor within the un-coiler itself. Motorized un-coilers will either feed material with the aid of an actuating arm, or sensors. The more economical end of motorized un-coilers will feed material based on a time out put, i.e. feed for five seconds, where as some of the higher end un-coilers equipped with sensors will give a continuous feed depending on the material height within the view of the sensors. Motorized un-coilers are typically preferred to non-motorized un-coilers as it helps reduce wear on feeding mechanisms.

Pancake Un-coilers

Pancake un-coilers are similar to the standard reel un-coilers, with the exception that the material lays horizontally on a flat surface, as opposed to being elevated on the un-coiler vertically. Pancake un-coilers are great for coils that aren’t perfectly round, or to be able to stack multiple coils on top of each other, speeding the process of getting a new coil set up and reducing press down time.

Cradle Un-coilers

Cradle un-coilers are another option for managing material, especially larger coils. Cradle un-coilers are better to use for larger coils as the weight of the coil isn’t resting on an extended arm like it would be with either a standard or motorized reel. Most cradle un-coilers will feed material with some sort of motorized function since there would be too much weight needed to be pulled by a feeder.

Tandem Un-coiler

Tandem un-coilers are immensely helpful in reducing press down time. While possessing two separate arms to load coils on to, a second coil can be loaded on to the open side while the press is running the last bit of the original coil material. Once that first arm’s material is all used, a motor allows the main body of the tandem un-coiler to rotate and use the full coil of steel already on the other side. The only down fall of the tandem un-coiler is its price, as the tandem un-coiler tends to be the most expensive of all of the un-coilers we’ve looked at today.

Additional Equipment for Punch Presses

Now that we’ve covered the basics with punch presses, ranging from frame and power differences, we look to the outside of the press before we look to the inside. There are a handful of machines that are required to have along with a punch press to run a punch press to its full capabilities. Today we’ll take a look at three of the main auxiliary equipment pieces to add with a punch press, and in the coming weeks we’ll take a closer look at each individual machine.

Punch Press Un-Coilers

Punch Press Un-Coilers are very important, as this is where the raw material begins its journey into the press. Coils are loaded into the un-coilers and are fed into the press by a variety of techniques. Some un-coilers are motorized and control the amount of material that is fed at a time, whereas some have no electrical or motor functions and feed out as much material as is being pulled. All styles of un-coilers have their strengths and weaknesses based on their set-up that we’ll take a more in-depth look at next week.

Material Straighteners

Material straighteners are needed depending on what thickness of material is being used, and how far the material is being fed. Since the coils of material have been bound in their wrapped position, some heavier gauge materials tend to have a curvature to it that will need to be straightened out before hitting with a die. The same goes for a die with more than two or three hit progressions. If material is needed to travel through so many progressions, it is important that the material is as straight as it can be going into the press.

Feeders

Material feeders are vital to a smoothly running punch press. A feeder determines the amount of material that is fed into the press, so having a consistent set amount of material specified for each product is very important. There are a couple of different styles of feeders, and determining which feeder is best for your situation can vastly improve run time efficiency.

Next week we’ll start off by looking at the different styles of material un-coilers.

What’s the Difference Between a Mechanical and Hydraulic Press?

While serving the same purpose and having, mostly, the same general anatomy, there are some key differences between mechanical and hydraulic punch presses. The main structures that we discussed two weeks ago (Straight Side and C-Frame) can still be applied to both mechanical and hydraulic presses, however the difference lies with how the energy to cycle the ram is created.

Mechanical Power

A mechanical press generates its power, mechanically, meaning that a motor is connect in a variety of ways to a crankshaft that cycles the ram for one complete operation. The motor that generates the momentum is connected to a flywheel via belts, and in simple punch presses, is connected to the crankshaft and controlled by an attached clutch. In some bigger punch presses, the flywheel will attach to a pinion that attaches to an additional gear that rotates the crankshaft. In Straight Side presses, there will typically be two pinions and gears that run the singular crankshaft.

Benefits of Mechanical Punch Presses

• Speed. The speed in which mechanical presses can be ran are higher than hydraulic presses. This allows for higher production and efficiency.
• Consistency of tonnage at bottom of the stroke. With a mechanical press, you’re maximum tonnage delivery happens in a smaller window as compared to a hydraulic press. However, this again helps attribute to the speed at which mechanical presses can be ran because you know the absolute limit of what your press will be hitting at the bottom of its stroke.

Hydraulic Power

Hydraulic punch presses run off of pressurized hydraulic fluid, just like any hydraulic machinery would. The ram of a hydraulic press is hooked up to a cylinder that receives hydraulic fluid via a motor that pumps the fluid.

Hydraulic presses tend to be used for slower, deep draw parts. The reason hydraulic presses are used for deep draw parts is because the hydraulic power allows for a more consistent source of pressure in a larger range of the stroke, as compared to a mechanical press. Hydraulic presses may be used for faster running parts as well, however, the ability to run deep draw parts is diminished the faster the press is ran. Ensuring that the proper amount of force is applied at the bottom of the stroke is crucial as well, to avoid over exertion of the material causing ripping and potential damage to the die and press.

Benefits of Hydraulic Punch Presses

• Better forming and drawing capabilities. Hydraulic presses have a wider window within the stroke path of the stroke because the compressed air requires less motion to exert its full force compared to a rotating motor and flywheel.
• Better for smaller runs.
• Shut height variations don’t affect the force that can be applied.

Both mechanical and hydraulic presses have their strengths and weaknesses, but factoring in the different parts and functions you can create with a die, both styles of presses will always have a place to be used.

Anatomy of a Punch Press

Last week we familiarized ourselves with the two main styles of punch presses (C-Frame and Straight Side), so now we want to touch on some of the key interior parts of a punch press. We’ll focus on the main working pieces that are most commonly found with mechanical presses.

Mechanical Flywheel

Highlighted here is the mechanical flywheel. this area is critical for the operating of a mechanical punch press. Belts are attached to the lower and upper sections of the flywheel to connect the motor to the crankshaft. The yellow cage is a non-operating, yet critical component of the flywheel as well. Since the motor is running the flywheel at relatively high speeds, it’s important, and is the law, to keep the moving parts covered to keep employees safe.

Ram and Bolster Plate

Above we have a picture of a general operating area of a punch press. A die is installed and ready to be run in this picture. Both the ram and the bolster plate are on display here. These two parts are key to any punch press operating correctly.

Bolster Plate

In this picture, the bolster plate is highlighted. The bolster plate is important because it is where the die is placed and secured on. It is absolutely crucial that the bolster plate be a flat surface. Insuring that there is no left over scrap or any debris on the bolster plate before installing a die is very important. If there was any mis-alignment on the bolster plate, the die could run crookedly and potentially break and damage the punch press.

Ram

The ram is rather self explanatory, as it is the moving part that rams the punches of the die into the material. The die is also attached to the ram to insure that the die is running as smoothly as possible. During the set up of a die, the ram is manually adjusted to the correct height. If the ram is set too high, the die doesn’t cycle through properly, and does not perform its functions correctly. If the ram is set too low, the die can bottom out and become stuck, creating heavily damaged dies, a stop in production, and many headaches.

These three pieces are what make a mechanical punch press go. While there are a lot of pieces that make everything run, if the ram, bolster plate, or flywheel are malfunctioning a punch press is not going to run efficiently, if at all.
Next week we’ll take a look at the differences between mechanical and hydraulic punch presses.

Punch Press Basics

What is a Punch Press?

A punch press is a machine that creates a certain amount of pressure, measured in tonnage, to be able to bend, pierce, form, and shear all types of materials. Some punch presses are operated by a hand lever that works with smaller, and lighter materials, while other punch presses are ran with electricity and hydraulics to improve the speed at which they are ran, and the tonnage they can create. Many of the punch presses we use are ran via electricity to power a crankshaft or flywheel to generate the speed and tonnage for the ram to cycle through an operation and create a part.

Today we’ll be going over the two main styles of punch presses, as it is important to understand the two main body types of punch presses before we get to their inter-working parts.

C-Frame vs. Straight-Side Punch Press

There are two main forms of punch presses, the C-Frame and Straight-Side. Just like anything in life, there are benefits and dis-advantages to both. Both styles can be used with hydraulic and mechanical power sources, and both have similar options for the amount of tonnage they can generate. Here are the differences:

C-Frame Punch Press

The C-Frame punch press, also commonly referred to as a Gap-Frame punch press, is characterized by the body of the press wrapping around the area of operations, resulting in the form of a “C” around the bolster plate. C-Frame punch presses main advantages are the three access points to the die, and generally speaking, lower costs as compared to most Straight-Side punch presses. However due to its shape, the motion derived to the ram will always create a slight mis-alignment under load, and the steps to counter-act the mis-alignment can lead to extra costs.

Advantages:

• Three access points to the operations area, allowing easier die maintenance and adjustments, along with evacuation of scrap metal and finished parts.
• Generally less expensive than a Straight-Side punch press.

Dis-Advantages

• Un-avoidable, mis-alignment due to body construction.
• Added costs and operations to counter act mis-alignment.

Straight-Side Punch Press

Straight-Side punch presses look as they are described; straight, with two main sides. While Straight-Side punch presses provide less areas to make adjustments to dies and evacuate scrap metal and finished parts, Straight-Side presses do not have the mis-alignment issues that come with a C-Frame press. This makes them more accurate, and best to use when tight tolerances are required.

Advantages

• No issues with mis-alignment, better for high tolerance parts.
• Less requirement for die maintenance due to accuracy of press.

Dis-Advantages

• Higher costs of presses, and moving costs due to larger size and weight.
• Less access points to work area, making adjustments and scrap evacuation more difficult.

Next week we’ll take a look at some of the inner working parts of a punch press that allows a stamping operation to produce parts.