Deep Draw forming with conventional tool and die technology is the stretching of sheet metal stock, commonly referred to as a blank, around a plug in either a hydraulic or mechanical press. The edges of the blank are restrained yet allowed to slide by a precise pressure between two tool surfaces; normally in a ring shape. One ring is the blank holder and the other is the forming die. The plug passes through the blank holder ring into the cavity of the die ring at the desired depth to achieve the end shape. The dimensions on the part are set based on the shape of the plug, the shape of the die, and how deep the part is drawn. For fatigue strength and applications where uniform metal thickness is critical, drawing and hydroforming are preferred over metal spinning. Like hydroforming, conventional draw forming applications are typically enclosures, cans, cups, canisters, containers, covers, motor shrouds, tanks, vessels, chambers, enclosures, domes etc.
Deep drawing and press forming are two essential processes used in the manufacturing industry to produce complex shapes and designs from sheet metal. Press forming involves compressing a sheet of metal into a specific shape using hydraulic or mechanical power. Deep drawing, involves creating a three-dimensional shape, such as a vessel, chamber or dome, from a flat sheet of metal by pulling it into a forming die with a punch. It is commonly used to produce pharmaceutical containers, automobile parts, Food Processing Equipment, Lighting, Bulk handling Equipment and more. Deep Drawn and Press formed parts can be made from a range of materials such as aluminum, stainless steel, copper and brass.
Both Deep Drawing and Press Forming require precision and experience to achieve the desired result, and Toledo Metal Spinning has over 90 years of expertise.
In summary, while both deep drawing and press forming are distinct techniques, they are critical processes that allow for the mass production of intricate and intricate designs using sheet metal.
Our presses also offer another unique service as we can use them to create “Pre-forms” or preliminary part formings that will be used to ease the metal spinning process and allow us to achieve more complicated forms with metal spinning and ensure the highest quality part using this process. This helps us minimize the material strain in the metal by utilizing the best aspects of each process. At TMS, we combine deep drawing and metal spinning to produce parts that deep drawing alone or spinning alone might not be able to do.
Parts can be created utilizing sheet or tube forms of aluminum 1100-O, 3003-O, and 6061-O, carbon steels 1008-1020, CDA 655 copper, 655 and 718 inconel, and stainless steel series 304, 304 DDQ, 316, 410, and 430. Our state of the art equipment utilizes a punch force of up to 368 t and a pressure of 10 ksi to create custom parts, achieving tolerances of +/-.020 in and +/-.030 in., with +/-.010 in., in special cases. The maximum punch diameter is 12 in, blank diameters can reach 15 in, and flange diameters are also up to 15 in. Hydroform drawn parts are possible in sizes of up to 7 in. in height.
Once the part is drawn, if it needs a hole, a stamped feature, welded fitting, or a metal polish specification you can also increase the value of your TMS drawn part while saving time and money by taking advantage of our secondary stamping, spin forming, machining, welding, and metal finishing operations.
Frequently Asked Questions about Deep Drawing and Metal Stamping
Deep Draw forming with conventional tool and die technology is the stretching of sheet metal stock, commonly referred to as a blank, around a plug in either a hydraulic or mechanical press. The edges of the blank are restrained yet allowed to slide by a precise pressure between two tool surfaces; normally in a ring shape. One ring is the blank holder and the other is the forming die. The plug passes through the blank holder ring into the cavity of the die ring at the desired depth to achieve the end shape. The dimensions on the part are set based on the shape of the plug, the shape of the die, and how deep the part is drawn.
1. Calculate the blank size and optimize.
One of the most common hidden costs for drawing parts is the hidden cost from engineered scrap necessary to procure a blank. When the annual quantity for a particular part number is in the thousands or tens of thousands, custom coil sizes can sometimes be procured. If not, blank material will normally come from master coil sizes, like 36″, 48″, 60″ or 72″ wide that are cut to width and the “drop”, or material removed in the blank shearing process, still maintains more value. If quantities are very low, it is common to produce blanks from standard sheet sizes of 8, 10, or 12 foot in length from the various coil widths. Optimizing a blank diameter and square size to eliminate excessive amounts of engineered scrap or planned drops can dramatically impact final part cost. Blank size also includes adequate amounts of material for trimming and work holding to make the part shape.
2. Design to minimize the material needed for trimming & work holding.
The blank size for the finished part is normally different from the actual blank that is used. This is due to the method necessary to hold and process the part from start to finish. Aside from the dimensional requirements, the required surface finish and tolerance of dimensions may require additional material to accommodate secondary processes or to eliminate features that could be permitted, yet are not specified on the drawing.
3. Plan for thin out in the design phase.
The material formed in the drawing or deep drawing processes experience a lot of surface tension and stretching throughout the cycle of the forming process. This means that typically, a section of the material will thin out in one or more locations, normally towards the closed end of the shape or the first contact surface on the plug. Other sections will normally thicken towards the open end of the shape, or the flange. Allowing for this in the part design will help scrap remain low and the design to work well in the application.
4. Allow for a taper.
Inherent to the process, due to the punch and die needing adequate clearance, and to accommodate mill tolerance on metal thickness there is a taper in straight walls of parts. The taper depends on the metal thickness, the total depth of the part, the grade of material, and the clearance between the punch and die. Typical taper is between 0.005 to 0.010 of an inch per inch of depth. In order to minimize taper; minimize part depth, use tooling designed specifically for the application, select materials with better formability that thin less, and accommodate material flow with larger draw radius. If tapers are not acceptable, secondary forming processes can reduce and sometimes eliminate the taper, however it tends to drive cost.
5. Select material that has better ability to form.
Selecting the most formable material and/or temper for the draw process may minimize or even eliminate scrap generated during the drawing process. This sometimes may be difficult if the application requires a certain amount of stiffness and or strength. Some materials like stainless strain harden when formed and others like aluminum can be tempered to improve mechanical properties. Sometimes selecting a superior material for the design that well exceeds the properties required by the design may be more cost effective in the long run because the processing costs may be significantly lower, such as drawing 304 stainless steel compared to 410 stainless steel.
6. Look to use existing tooling.
Many press and drawing companies such as TMS, may have a lot of tooling available for customer use. Like TMS, a company that invests heavily in its own tooling can produce shapes that are very close to the designed dimensions. Sometimes, the design can be altered slightly to avoid an engineering charge. Alternatively, a re-cut charge can be offered when the tool is no longer active and can be repurposed.
7. Hydro-mechanical drawing (hydroforming) requires less tooling costs.
Hydro-mechanical deep drawing, or hydroforming uses hydraulic fluid as either a punch that pushes metal into a cavity or a die to push metal over a punch. In hydroforming, a rubber bladder acts as a die with 1,000’s of PSI behind it. Compared to conventional draw forming, the rubber bladder PUSHES the blank around the plug, instead of pinching and STRETCHING the material thus, putting less stress on the metal and allowing for greater reduction ratios and more elaborate part geometries.
8. Uniform metal thickness is achieved by hydro-mechanical deep drawing (hydroforming).
Due to the lower forces applied onto the metal during the hydro-mechanical drawing process, the material is not stretched as much, allowing for a more uniform metal thickness to be maintained. This is especially helpful on difficult to draw shapes that are irregular and asymmetrical, where a metal die would not permit simple metal flow or dynamically change to be forgiving of the metal’s needs.
9. Optimize for a minimum number of draws.
Each time a part is drawn, it is reduced in size with respect to the diameter of the part or the length and width. Depending on the percent elongation, some metals can be drawn more than others. To achieve the maximum amount of reduction a metal is able to be reduced, it is often necessary to go through a series of steps or reductions. 14 gauge stainless steel 304 for example, normally can be reduced 45% the first reduction, and then up to 30% the second. To further reduce it, SS 304 typically requires an annealing operation and then can be reduced another 15%. So, if the original blank is 10 inches, the final diameter would be (1-.45)(1-.30)(1-.15) x 10 inches = 3.27 inch diameter of the part.
10. Add features that leverage the benefit of in-house secondary operations.
Whenever there is forming, usually there is cutting, finishing, secondary forming, and sometimes joining processes that are needed to complete the part so it is useful. A deep drawing house usually offers a variety of processes that can improve the usability of your part and with minimal cost depending on part design. Once an order is placed during the prototyping phase of a project or product life cycle, a reputable manufacturing firm will normally provide a design for manufacturing and assembly (DFMA) review to help identify cost saving opportunities and features that can assist in overcoming design, and or cost barriers.
When it comes to tool design, the most important formula is The Draw Ratio, also known as Limiting Draw Ratio (LDR).
The formula is: LDR = D / d
D = blank diameter
d = cup ID or punch diameter
This ratio shows how large of a blank can be drawn with that particular punch size (which would be the Cup ID size). This is why it is considered a limiting ratio.
Usually in this process of determining how many draws, and what size on each draw is required, we start with the blank size (calculated from the final product volume) and work backwards using this LDR formula for each draw/set of tooling. This generally indicates how many draws are required and roughly what diameter each step should be. At this point, this will be refined by using % reduction formulas. In summary, the LDR will yield a ROUGH drawing process, which is refined even further during the next step of the design process, with the % reduction calculations.
The Draw Ratio is the ratio the width of the part vs its height. If the width of a part you are Deep Drawing is equal to its height, the ratio will be 1:1. Once you start drawing a part that is deeper than it is wide, you will exceed the 1:1 ratio. This is when you encounter problems.
When the part you are drawing exceeds this ratio, for example, 1.5:1 or 2:1, then the part will need to be drawn in multiple progressive steps. Each step will require its own dedicated draw tooling. If you can keep your parts below the 1:1 ratio, then a single set of tooling will typically be enough. This reduces development and production time. Understanding the Draw Ratio is of great benefit to a customer, when we are in the design process.
This ratio helps to classify a drawn cup as a deep draw or not. Any shape exceeding a 1:1 ratio will be considered a deep drawn cup/form.
Blank Size, Thickness, Shape, and Part Geometry
Determining the blank size is a very crucial step for a successful draw. The amount of material needed for the final product must be included within the blank. When there are multiple draws for a single product, it can be tricky to determine how much material is needed. Since the draw process causes thinning and thickening of the metals, this is an important first step to a successful draw.
Draw Radii
It is important to note the size, accuracy, and finish of the die entry radius. If the die radius is too small, the material will not easily flow. This results in stretching and fracturing of the drawn product. If the die radius is too large, the material will wrinkle after leaving the pinch point between the draw ring surface and binder. If the wrinkling is extreme, the material flow may be restricted when pulled through the die entry.
Draw Ratio
The draw ratio is one of the most important elements of maintaining successful deep draws. The draw ratio is the relationship between the size of the draw post and size of the blank. During the forming process, the blank is pressed into a circumferential compression which creates a resistance of metal flow. If there is too much resistance, the metal will fracture. If the draw post is not big enough, the metal will stretch, becoming thinner until it cannot be formed. If the draw post is the appropriate distance from the edge of the blank, the metal will be able to flow, while becoming thicker as it enters into the die cavity.
The formula for the draw ratio is: D/d ≤ 2 for a successful draw.
D = the blank diameter
d = plug (or post) diameter
If this ratio is greater than 2, re-draws (or break downs) are required. In our industry, this is a general rule of thumb. Certain materials may have more accurate, material-specific rule of thumb ratios. For example, Aluminum is 1.8.
Lubricants and Die Surface Finish
Adding lubricants and a polish to the die surface helps with friction and reduces the chance of galling. Galling is when two metallic surfaces slide against each other, creating friction. This can harm the product and the tooling. Applying lubricant to the blank is a very important step in the deep drawing process, to create the highest quality product, while protecting the draw post tooling. Avoiding galling enables the blank to slide easier, allowing for free flowing of the metal.
Die Temperature
The die temperature can cause the lubricant to thicken or thin, depending on how hot the die is. When lubricants heat up, their viscosity drops and they thin out. As they get cold, their viscosity increases. Understanding this relationship is key to creating the best quality drawn part, while maintaining the quality of the die.
It is critical to select the correct lubricant for each deep drawing process. Each lubrication brand, type, and formulation performs differently at different temperatures, depending on their intended use. Certain lubrications need to increase to a certain “working temperature” before they will exhibit any friction-fighting properties at all. In contrast, other lubricants only work in a cold or room-temperature environment. When determining the correct lubrication, the tool temperature, (mid-run and at rest) blank material, and draw severity are all taken into account.
Binder Pressure
At Toledo Metal Spinning, we use pinch and pressure to control the material flow. Binder Pressure is a machine setting that controls the upwards force and/or pressure in the press that will be applied through the draw ring/binder, which sits on top of the cushion pins. The draw ring pressure rises, while the die pressure and slide force is in a downward motion, this is how the blank is “pinched.”
N and R Values
The N value is known as the Work Hardening Exponent, or the Strain Hardening Exponent. This describes steel’s ability to stretch. The larger the material’s N Value is, the more the material is able to elongate without necking, or deforming.
The R Value, also known as the Lankford Coefficient or Plastic Strain Ratio, describes the ability of a material to flow or draw. The blank size affects the ability of metal to flow because the press’ speed need to allow for time for the material to flow through. For a more technical explanation, it is a measure of how resistant a metal alloy is to thinning. Mathematically, it is the ratio of the true width strain to the true thickness strain at a specific value of longitudinal strain, up to the point of uniform elongation.
Common materials in deep drawing include Stainless Steel, Copper, Aluminum and Cold Rolled Steel.
Deep Drawing and Stamping are similar manufacturing processes that are often confused with each other. Each process produces strong and durable parts with high accuracy and tolerances.
Deep Drawing and Stamping each require a design process, with considerations of how the materials will affect the manufacturing process, production costs, and the ease of manufacture. Material thickness, the type of bending or formability involved are also characteristics that will be different for each process, depending on the shapes being formed, and the shape of the end product. While there are many similarities between these two processes, there are not as many differences.
What is Metal Stamping?
Stamping is a manufacturing process when coils or flat sheets of material are formed into specific shapes. The Stamping process is used to make small changes to parts, such as bends, tabs, or embossments. These features tend to be much shallower in depth than a deep drawn part. Stamped parts start flat and go through a sequence of stamps from a press, where new features such as small tabs, are folded in, or holes are punched out. These features are very sharp, detailed, and precise. Stamping is a broad term that includes many specific forming techniques such as embossing, blanking, punching, bending, flanging, and the list goes on. Each of these methods involve short, quick, and abrupt hits or press movements.
At Toledo Metal Spinning, our stamping capabilities lie with our Komatsu Mechanical Press, where we intertwine our deep drawing abilities with stamping and are able to pierce holes, or form small tabs or flanges. Before the integration of our laser cutting technology, we used to cut blanks with this press.
How is Stamping different from Deep Drawing?
Deep Drawing is used to make larger features such as as cups, pans, or domes. We draw parts from our two hydraulic AP&T presses. Drawing a cup requires exerting a significant amount of pressure on a flat sheet, and gradually drawing it over a die to sculpt it into the cup shape. Forming these shapes requires much more pressure over a longer period of time than a quick stamp. If the pressure is not controlled properly or is performed too fast, the metal will fracture or break, and will not be usable.
The shape of the part is the main difference between a stamped or deep drawn product. Drawn parts will have more pronounced curves in the shapes, and will be larger than a stamped part. Below is an example of one of our deep drawn cups. Take note of the defined edges and curves, while its strength and durability is present.
Hydroforming is a specialized Deep Drawing process also known as Sheet Hydroforming. Sheet hydroforming allows various materials to become complex and structurally sound parts. It allows for asymmetrical or irregular shaped geometries, while conventional Deep Drawn parts are symmetrical and uniform throughout the entire shape. Another big difference is the depth of the parts produced by each. The Hydroform Press cannot produce shapes with sharp edges or angles, and the shapes are not as deep as Deep Drawn parts.
The Hydroforming process begins by placing a laser-cut blank over a die (typically made from rubber). High pressurized water forces the blank down over the mold, forcing the blank into its new shape. Both Hydroforming and Deep Drawing are both excellent, seamless manufacturing processes that do not require any welding.
The Deep Drawing process is better suited for larger production runs, or smaller runs for applications or components that will have long-term usage. The Hydroforming process is a popular choice when we are producing complicated parts, which irregular shapes.
At Toledo Metal Spinning Company, we use a combination of stamping, hydroforming, and conventional deep drawing for a variety of applications. One application is to utilize our press capabilities for preforming a spinning operation. One advantage for using a press preform includes the benefit of flowing the metal towards the flange of the part, giving more material in this area verses a thickness reduction from our spinning process.
Deep drawing is an incredibly useful process that facilitates the creation of parts whose height exceeds their diameter or cross-sectional area. This type of component is highly valued across a range of industries and applications, but requires a particular set of manufacturing techniques to produce effectively. Deep drawing is typically measured as a ratio between the part’s depth and diameter, and the process can be tailored according to the type of material being used, as well as the desired form. Toledo Metal Spinning Company specializes in, but is not limited to, the deep drawing of stainless steel. In particular, grades 304 and 316, which are highly corrosion-resistant and offer excellent formability. The deep drawing process is incredibly versatile and offers numerous benefits over alternatives such as metal spinning. With deep drawing, it is possible to create much deeper, more complex forms at larger volumes and with minimal labor costs. Additionally, since deep drawing eliminates the need for welding or joining multiple pieces, it reduces the risk of complications related to corrosion.
Toledo Metal Spinning has state-of-the-art capabilities in deep drawing and press forming. Our triple action hydraulic presses are designed to tackle the production of deep drawn parts requiring more than one operation in a single press cycle. Our presses are available in a range of sizes and capacities, including presses up to 400 metric tons and a bed size of 48″ x 48″. We’re confident we can take on any project, so if you’re unsure if your needs fit within our capabilities, please don’t hesitate to get in touch immediately. Our in-house machine shop can design custom tooling for your part if we don’t have what you need. We’ve got you covered from prototype to production runs.We offer turnkey in-house tool & die services for custom tooling & DFMA support. Toledo Metal Spinning can help you streamline your assembly and reduce costs, assembly time, and inventory. Place an order for an assembly with us and we’ll work with your design team to perform design for manufacturing and assembly (DFMA) reviews. Let’s say you’re not quite sure if your prototype is going to work for you yet. No problem! With TMS prototyping, you can use lower cost metal forming options to ensure the reliability of your product. Our engineers and sales team are excited to work with you to take your press formed part from prototype to production. So call us today!
Ensuring that the drawing process proceeds smoothly requires an understanding of the impact that material properties can have on the overall outcome. This is because certain types of materials, especially those that are brittle or non-ductile, can pose significant challenges when attempting to draw them at ambient temperatures. Unfortunately, even materials that are otherwise strong and durable, such as tempered or strain-hardened steels and aluminum, often fail when subjected to the stresses of the forming process. To mitigate these issues, experts have identified Draw Quality (DQ) and Deep Draw Quality (DDQ) steels, stainless steels, and ‘O’ condition Aluminums as the most suitable materials for drawing. These materials possess a more stable structure, smoother grain, and higher elasticity, allowing them to be more easily formed while also reducing the wear and maintenance requirements over time. Therefore, it is of utmost importance to use formable tempers and Draw Quality materials to ensure optimal performance and a positive end result in the drawing process.
At Toledo Metal Spinning Company, we take pride in using only the highest quality standard materials for deep drawing. To ensure that we meet the unique needs of our clients. If you have another material in mind please don’t hesitate to let us know. We would be more than happy to work with you and put together a customized quote that meets your needs. Our experienced sales estimators have a deep understanding of the industry and are confident that we can provide the exact product you are looking for. So, whether you have a specific material in mind or simply want to explore your options, we invite you to reach out to us today and let us help you achieve your goals!
Mechanical Properties and Formability of Deep Drawing Stainless Steel
Good – Lowest cost of high quality deep drawing stainless steel material. The high nickel content allows for good deep draw working. Elong = 60%, Yield 34/30 KSI, Tensile 85/75 KSI
Good – More corrosion resistant than 304 grade due to the addition of molybdenum with the same higher levels of nickel, thus allowing for it to be an excellent deep drawing stainless steel. Elong = 60%, Yield 30 KSI, Tensile 75 KSI
Low – 400 series, generally lower cost stainless steel than 300 series since there is typically very little or no nickel, is not ideal for extremely deep parts since the lack of nickel reduces stainless steels deep draw ability. Elong = 30%, Yield 65 KSI, Tensile 95 KSI
Low – 430 is similar to 410 with little less strength. Like 410, material is readily available and is less expensive than 300 series stainless steel. Elong = 30%, Yield 45 KSI, Tensile 75 KSI
Low – 444 stainless steel is similar in its ability to form compared to 400 series stainless grades. Uncommon to 400 series, this specialty stainless grade has Molybdenum added with Titanium and Niobium added to stabilize the microstructure. This allows the material to be similarly corrosion resistant to 316, without the cost of 316 due to the lack of Nickel. The low Nickel also allows for excellent resistance due to corrosion cracking to chloride induced stress, which is why SS 444 is frequently used for parts in contact with tap water. Elong = 20%, Yield 40 KSI, Tensile 60 KSI
Are you in dire need of deep drawn parts? Look no further! With TMS flanged cups, you can be assured of a seamless stainless steel part, ideal for a range of applications such as motor shrouds, enclosures, lids, storage containers, and more. Unlike welded containers, our draw-formed cups lack seam welds, thereby reducing the occurrence of leakages and corrosion. TMS can also customize your deep drawn cup in-house or work harmoniously with your fabricator of choice. Our line of deep drawing products and expertise has been put to reliable use in the food manufacturing, hospitality, architecture, and automotive industries. Moreover, we have designed and developed a range of tooling with unique one-piece flow manufacturing processes to produce metal domes with minimal throughput time and exceptional quality. With secondary forming options such as edge rolling and stamping, TMS can offer a comprehensive fabrication process for your entire design. So why wait? Contact us now for quick delivery times and unbeatable prices!