Drawing stamping and stretching stamping are integral in the metal stamping industry, yielding various metal parts for a vast array of the machinery and manufacturing sector. However, it’s not surprising finding clients confuse the two processes and mistake one for the other. While both approaches fall in the metal stamping category, they utilize various metal forming processes, yielding metal parts with minimally similar streaks. This article compares the two metal forming techniques to help you better understand the differences and the similarities that may exist.
Drawing Stamping and Stretching Stamping
A few similarities, as well as differences, exist between drawing stamping and stretching stamping. But, understanding each metal-forming technique will help you set them apart by their formation process and eventual products. Here’s an insight into drawing stamping and stretching stamping processes.
Drawing stamping involves punching through a metal blank to create deep shapes. With drawing stamping, manufacturers use measured punching forces to permanently create a seamless metal flow to distort a blank. Usually, no heating is involved, and the blank takes the shape of the lower die, resulting in sturdy and symmetrical forms. These formed metal parts are helpful in a vast array of applications, mainly automotive, aerospace and electronics.
The Drawing Stamping Process
Metal drawing stamping is procedural and considers numerous aspects of the formation process, including the ideal forces and materials. That ensures producing metal parts has the correct sizes and projected quality. The process becomes relatively seamless with everything in position and when the various elements strike a balance.
Most manufacturers use software to determine the measurements for the finished metal parts depending on the available blank material and sizes. Simulation software like Autoform and NG Engineering are the go-to options for most manufacturers when designing the dies. These software usually recommend the ideal metrics of the drawing stamping process depending on the suitability of the metal to the sheer forces. Once the design is in place, and the dimensions are available, manufacturers feed them into the forge ahead with the formation process, involving:
- Securing the blank on the die – The lower die holds the metal blank for drawing, and it must ensure a proper grip to prevent potential slips. The blank holder is usually the best part for the job and grips the blank sheet before the upper die applies further pressure and administers a punching force.
- Punching the blank – As the blank sheet stays in position, the punch comes down in a measured force. And right as it’s about to administer a punch, the blank holder firmly holds it in place. That allows it to seamlessly flow into the metal, resulting in the projected shape, size, and design. The punch usually draws the blank sheet into the hollow, leaving just a little room to accommodate the metal thickness. The blank usually takes the shape of the die cavity and ensures that it doesn’t scratch the outer surface.
- Withdrawing and finishing touches – After the drawing, the punch usually retracts to its original position to prepare for the next punch. Meanwhile, an operator needs to be around to withdraw the drawn part and place another blank sheet for the following drawing procedure. The operator then lubricates the punch to minimize friction, and the process picks up again. A little finishing touches may come in handy to add an aesthetic touch to the final metal part.
Types of Drawing Stamping
Two types of drawing stamping operations exist, all defining the final parts and outcomes. Both use tensile forces to stretch and elongate parts of a metal sheet. However, the manner in which they subject the metal parts to the formation process varies. The drawing stamping processes include:
Sheet Metal Drawing (Deep Drawing)
Deep drawn metal parts usually have more profound depths and are cup-shaped. A similar and alternate version of this process is shallow stamping, where the metal only caves in, forming a cup-shaped part with tinier depths. Deep drawing is typical for producing metal parts used in virtually every day application, including in making kitchen appliances such as electric kettles.
Wide, Bar, and Tube Drawing
Wide, bar, and tube drawing processes create various electronics and appliance components as well as different metal parts for large-scale manufacturing. With wire drawing, steel rods pull through conical dies with a hole in the center, undergoing stretching and reduction in diameter. Also, the length increases quite proportionally. With wire drawing, more robust dies made of alloy steel, diamond, and tungsten carbide are used since the constant rubbing tends to wear them. A similar principle is also in use for tube and bar drawing.
Stretching stamping is somewhat varied from drawing stamping in that it doesn’t create a final hollowed part despite administering a punch to a metal blank. Instead, the movement is mainly lateral, more or less like during embossing. The blank stretches and thins in the process and forms contoured parts as it stretches, thanks to a punching force from above. To cut to the chase, stretching stamping involves stretching a metal while creating shapes on its surface.
The Stretching Stamping Process
Like drawing stamping, stretching stamping is quite a process, although the metal parts are relatively varied. The method uses hydraulic pressure to shape metal blanks, but the movement usually occurs horizontally rather than vertically. Here’s the general stretching stamping process in metalwork.
- Securing metal blank on a stretch press – The entire metal forming process happens on a stretch press. Here, a stamping operator ensures that the system grips the metal sheet on its edges with no potential to slip or slide. These gripping jaws are usually attached to a carriage pulled by a hydraulic or pneumatic force, stretching the sheet to its limit.
- Stretching the sheet blank – While the grips firmly hold the blank at its edges, stretching them horizontally, a ramming force from the form die (a solid and contoured block) shapes it.
- Retracting and assessment – Once the pressures and forces have done their part, an operator retrieves the metal part resulting from the entire and assesses it to ensure that it meets the needed quality. If not, perhaps further stretching may be necessary for most manufacturers. It wouldn’t be worth it. Such metal parts are defective and should be discarded, prompting a procedure repeat. However, given these machines’ high accuracies, it’s often rare to encounter such glitches.
What’s the Difference Between Drawing Stamping and Stretching Stamping?
The difference between drawing stamping and stretching stamping can be unnoticeable to most people, but it exists in its metal parts. The formation processes can appear similar since both use hydraulic or pneumatic forces to shape metal blanks. Here are the main differences between drawing stamping and stretching stamping.
The Metal Flow – usually, the metal flow determines the formation, especially in the drawing and deep drawing process. And while the metal flow is crucial in most metal forming processes, it appears not necessary with stretching stamping. With metal drawing stamping, the blank holders minimally grip the blank to minimize movement, encourage metal flow, and improve accuracy. Conversely, stretching stamping is quite varied since the grip is usually firm to minimize imminent wagging while restricting metal flow.
Punching and Formation – Drawing stamping utilizes specific tooling, precisely engineered to administer measured punch forces and grips. And while the stretching stamping forces exert measured punching pressures, the blank material hardly flows into the die’s hollow. Instead, the material moves horizontally, stretching in either direction.
Equipment Used – stretching drawing uses the stretch press to shape metals instead of regular dies. The tooling is quite sophisticated and includes a form die with premade contours to create the intended shapes. On the other hand, drawing stamping uses dies to shape metal blanks. Their tooling design is quite simple and relatively easy to assemble.
Blank Thinning – Usually, stretching stamping thins metal blanks in response to the tensile strength by the hydraulic and pneumatic forces applied. And although that may be a case in drawing stamping processes, the blank minimally thins towards the center, maintaining a reasonably similar thickness uniformity.
Costs – The production cost of drawing stamping is usually lower than stretching stamping. The process requires minimal supervision since machinery does the whole work creating cylindrical components and parts. However, the latter is generally costly and requires more management, requiring much labor to operate the stretch press.
Production Volume Rate – since the production in the metal drawing is machine-driven, it hardly takes time to produce metal parts in a short while. It’s a suitable process for high-volume run-ins and takes a reasonably short time with high production rates. On the other hand, the production volume and speed in stretching stamping are relatively lower since the stretching takes quite a while.
Market and Demand for Metal Parts Between Drawing Stamping and Stretching Stamping
Metal stamping parts have become a staple in metalwork and manufacturing across Eurasia and North America. The demand for the products of virtually every metal forming sector is high and cross-cutting across drawing stamping and stretching stamping. Comparing Drawing stamping and stretching stamping market demand is a close call since both metals forming processes are valuable in their capacities. For the most part, products from both metal forming processes serve the industrial manufacturing sector, including the automotive, aerospace, and civil works.
Common Defects in Drawing Stamping And Stretching Stamping
Metal stamping is never short of defects, as are these two metal forming processes. Given the correct metrics and proficient software simulations utilized, it’s often not understandable when such shortcomings occur. However, the tensile forces can be way over the edge, or the material may not simply cut it, so it’s only naïve to rule out that possibility. The possible defects in both processes include:
Fractures – fractures in both metal forming processes are possible since the forces stretching the material can sometimes be robust for them to handle. Regardless, it’s only a mere possibility if operators determine the correct forces to use beforehand. In drawing stamping, fractures occur towards the clearance between the die and the punch. On the other hand, fractures will likely appear on the edges of stretching stamping parts where tensile forces have the most impact.
Excessive Thickening and Thinning of The Metal – while stretching thins the material, it is likely to drag it further beyond its threshold, leading to a more defective part. Excessive thinning makes most metal parts unreliable and non-useable, which is more apparent in both drawing stamping and stretching stamping.
Splits and Wrinkles – Like fractures, breaks and wrinkles are also associated with tensile forces and are a possible defect in stretching and drawing stamping. These defects can only be minor, unnoticeable, or prominent to make a metal part useless. However, manufacturers may eliminate the possibility of this defect using a variety of ways like using the right metrics, materials, or annealing blanks to make them less subjective to the tensile forces.
Can the Metal Parts From Both Processes be Used Interchangeably?
Drawing stamping and stretching stamping may use similar modeling and forming processes, but the results are usually different. Most metal parts from drawing stamping are somewhat hollow with profound depths compared to metal parts from stretching stamping. Products from the latter are usually more elongated than deep since the tensile forces in the process stretch them just shy of their thresholds. However, more sophisticated procedures in stretching stamping can yield parts that appear almost similar to the drawing stamping. But, that doesn’t still imply that manufacturers can use them interchangeably.
Stamping stretching and drawing stretching are essential processes in the metalwork industry, yielding a vast array of metal parts useful in numerous sectors. Companies in the automobile and aerospace find an immense use for metal parts from stretching stamping as it helps create more complicated parts to suit their needs. Likewise, the home appliance and electronics sectors utilize parts from drawing stamping. Both processes are helpful, and their products have improved the metalwork industry. Hopefull, this article will help you understand the variations and similarities between Drawing stamping and stretching stamping and the best places to use their products in the metalwork industry.