Guide

Metal forming is one of the most important manufacturing processes available for the production of an expansive array of parts and products. Inside the overarching category of metal formation and fabrication, deep drawn methodology is one that offers the most value, in relation to cost effectiveness, production efficiency and time efficiency – one of the driving reasons why deep drawn manufacturing has gained wide adoption. Importantly, when engaging in the process, there are five key elements to keep in mind, as each of these concepts have an effect on your end design. These elements include material type, material thickness, stress distribution, part geometry, and draw ratio, in no specific order.

1. Effective Determination

Each of the these five elements have an effect on the manufacturing process and ultimately, the end product. Most, if not all, should be addressed in the initial design brief and this will continually be updated as the process continues. Both material type and material thickness play a role in determining the other three aspects or elements, although these are not solely dependent on the material thickness as much as type, depending on the desired result. When combined, all these elements determine the effectiveness of the processing to produce an acceptable, quality end result.

2. Material Type

While the material type does not change throughout the process, it will determine how efficient the process is and how many passes are required to produce the part. Each material has its own qualities and these will in turn affect how well the material responds to the manufacturing process and how readily it will accept defects.

3. Material Thickness

The amount of material contained in the originating blank must correspond to the amount of material for the finished part. This includes the necessary thickness required by the end part. Often, material can be purchased in a range of thickness but this increase or decrease in the amount and quality of the material will directly affect the thickness of the part as well.

4. Stress Distribution

Stress applies to a range of situations throughout the manufacturing process. From the stress capability of the material itself, stresses applied during processing and the stress capabilities of the final construct. The material and material thickness must be able to undergo the various stress brought about by the process but also by maintaining the final shape.

5. Part Geometry

While it is true that almost any part shape is available, some part shapes are easier to produce, require less processing and have different stress characteristics. Additionally, the material type can have an effect on the part geometry, in some situations, the material can require a different geometry than what is planned. At which point either an alternate geometry is required or an alternate material used.

6. Draw Ratio

Draw ratio can correspond to a variety of different things, but in this context, it refers to the amount of material necessary, with minimal waste by-product. Some materials can be drawn farther than others and the draw ratio is the amount of material used versus any required to maintain the blank. Blank holding material is sometimes wasted material that has to be removed.

Other elements exist concerning Deep Drawn manufacturing and the process and different elements are used when the various deep drawn processes are used, i.e. hydroforming. It is important to understand these elements as your order is processed and ultimately delivered. This is so you can properly design, respond to any concerns, and work with your manufacturer to deliver the best part possible for your needs.

The manufacture of equipment, machinery and consumer goods involves numerous steps that culminate in final assembly. Some operations are performed in-line and others off-line, the choice depending upon the manufacturing process used, production rates and logistics.

In general, the more operations that can be performed in-line, the greater the efficiency and the lower the amounts of work in progress (WIP). However, as production lines become longer, their vulnerability to holdups increases and throughput is determined by the slowest process. In such situations, it makes sense to streamline a lengthy process by producing items off-line or to consider alternative manufacturing methods that are faster and more efficient.

In-line Vs. Off-line

There are several reasons why it makes sense to have a combination of in-line and off-line manufacturing. Firstly, some processes take too long and would hold up the line; a good example is powder coating, which requires a certain amount of time for the coating to cure. Secondly, it may be possible to manufacture items at a higher production rates than the production line.??? Examples include metal stamping and deep drawing processes. In both situations, offline manufacture makes sense because facilities can be used for other processes as well.

Identifying Bottlenecks

The first step in assessing what processes should be taken off-line is to identify production bottlenecks. To do this, an analysis of each operation should be made to identify its true duration. Because manufacturing processes often include sub-processes that feed into the production line, these must also be considered.

Production lines generally operate on a pull basis, which means that operations toward the end of the line are slightly faster than earlier ones; this prevents items from piling up. However, when a process is too slow, a bottleneck exists and the output of the production line is limited by the slowest process.

Change the Manufacturing Method

In many instances, the way around a bottleneck is to change the manufacturing process. This is often the case with operations that require a significant amount of machining or a number of fabrication operations. One way around labor-intensive processes is to evaluate the possibility of manufacturing the part on a stamping press. This particularly applies to parts that were not historically considered suitable for pressing but which now can be contemplated as a result of technological development. Examples of this include hydroforming and deep drawing.

Benefits of Deep Drawing

Modern deep drawing processes and increasingly innovative support can achieve higher draw ratios and produce parts that previously could not be drawn. The process is fast and repeatable, and the primary benefits include:

• High draw ratios: Deep drawn parts can be readily produced with a draw ratio that exceeds 10. This means that the length of the drawn part can be 10 times the largest outside diameter, and this facilitates the manufacture of long, thin cylindrical components.
• Low cost: The cost of deep drawn parts is generally lower than other forms of manufacture, even when the cost of tooling is factored in.
• High volume: Production volumes are determined by press stroke rates and are significantly higher than machining or other fabrication processes.
• Fast setup: Tool changes on a well equipped deep draw press are fast and require minimal setup time.
• Product quality: Off-press quality is high, and in many cases parts can be assembled without the need for further processing, usually only cleaning.
• Added operations: Additional operations can be incorporated into the tooling, such as notching, slotting, thread forming and name stamping.

If assembly line volumes are limited because of lengthy manufacturing processes, it may be time to re-evaluate deep drawn stamping as a way of increasing throughput and plant utilization.

The traditional approach to the manufacturing and assembling of small components and products is a combination of fabrication and machining processes. This is especially the case for the low-volume production of delicate parts where manufacturing tolerances are critical.

However, a viable alternative is to manufacture these parts by using deep drawing pressing operations. Deep drawn parts can be made to exacting tolerances, and often at a lower cost than is achievable by alternative methods. Deep drawing is feasible for small symmetrical parts that have a tubular or cylindrical shape. It is possible to stamp a wide range of materials, including carbon steel, stainless steel, copper, brass, silver and gold, to meet varying manufacturing needs.

Manufacturing Process Limitations

Although CNC machining centers are capable of producing parts of complex shapes to high tolerances, two major constraints exist. Firstly, the process is relatively slow as parts have to be machined from solid blanks that are larger than the final part, and, secondly, there needs to be sufficient material available to allow the part to be securely clamped. Another limitation is that the minimum wall thickness that is achievable is constrained by a combination of physical constraints and material properties.

A typical example of this problem is the cylindrical barrel of a pen or the inner and outer housing of tubular devices. An alternative way to manufacture such parts is to use specially drawn tubing of the right diameter and wall thickness, and to fabricate end pieces.

Both methods work, and an acceptable surface finish is attainable. However, these processes are slow, and costs are relatively high due to increased labor requirements. Additionally, once equipment is fully utilized, the ability to ramp up manufacturing volumes is constrained by the need to purchase additional machinery.

The Deep Drawn Alternative

In many instances, it’s possible to manufacture these same parts using deep drawn stamping processes. Current technology is capable of producing thin walled parts with a length to diameter ratio that exceeds 10:1, depending upon the material used. The wall thickness of the parts can be as low as seven-thousandths of an inch and critical dimensional tolerances as tight as one-thousandths of an inch are possible. These are almost impossible to achieve by other manufacturing processes.

Although deceptively simple, the design of deep drawn tooling is complex, requiring insight into material properties and deep drawing techniques. Typically, several stages of drawing are required to transform a flat, round blank into a hollow cylindrical shape. This is achieved by using multistage tooling with automated transfer systems so that one part is completed and ejected for each stroke of the specially adapted deep drawing press.

During the drawing process, parts are naturally work hardened and require no further heat treatment before use. In addition, deep drawn tooling produces an excellent surface finish that in many instances requires no further processing, especially if rust-resistant materials are used. Alternatively, parts can be coated in semi-automated processing machines or highly polished.

Increase Throughput and Lower Costs

Depending upon the size of the part, a deep drawn press can produce several thousand parts per hour. This is way above the output of comparable processes, and as a single stage operation, deep drawing greatly simplifies the assembly line.

The production cost of deep drawn parts is low, and although it is necessary to amortize tooling costs over the life of the part, the overall cost per part is almost always lower than parts produced by machining and fabrication processes. Apart from this, less material is used, tighter tolerances are possible and the final appearance of the part is usually better.

Deep Drawing manufacturing processes offers significant cost efficiency over other manufacturing methodologies. This is particularly true in cases where specific parts have complex geometries or require a high degree of precision and accuracy. Of course, even more cost savings can be achieved with the Deep Drawn process when simple geometries are necessary or parts are required to be seamless. When coupled with the fact that the deep drawing process can reliably be undertaken with a wide range of materials, the potential for cost saving on a per unit basis becomes apparent.

Effective Efficiency

In simplistic terms, deep drawing is a manufacturing process in which a material is drawn into the shape and configuration required. There are different dies and specific processes used by a variety of manufacturers but the process itself is efficient and more effective than traditional stamping techniques. One of the advantages and cost saving aspects is the deep draw process offers minimal material waste as opposed to extrusion or machining processes. Thus there is less excess material and little, if any, waste. When you consider the material cost effect, less waste means more material is going to the product thereby maximizing the efficiency of the material used.

Direct Effects On Costs

The direct effects on costs are numerous, in the ways of producing a low cost, highly efficient alternative to traditional part production. These include;

• Better Material Handling; Meaning less material required to generate a part over traditional manufacturing techniques.
• Higher Volumes lower the per unit cost
• Accurate and Precise Part Production; Less secondaries required, thereby lowering labor costs

While not specifically bearing on the cost analysis of Deep Drawn manufacturing, Deep Drawing has the advantage of producing parts that are tight tolerance, and require significant strength while having minimal weight characteristics.

Combined, all of the above create an opportunity for lower per unit costs as well as cost savings for a project, which becomes apparent in multiple part end products. Thus providing the opportunity to put a cost effective and efficient process at your disposal.