Precision Metal Stamping and Deep Drawing
Precision. Reliability. Performance. For more than 95 years, Toledo Metal Spinning Company (TMS) has played a vital role in American manufacturing. Recognized as an award-winning industry leader, our team combines time-honored craftsmanship with advanced forming and metal fabrication technology within the manufacturing industry.
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 minimizes 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.
Advanced Sheet Metal Stamping and Deep Draw Capabilities
We utilize hydraulic presses, mechanical presses, and hydro-mechanical deep drawing to provide exceptional flexibility. Whether it’s one-off prototypes or high-volume production runs, we deliver consistent, repeatable, and high-quality results every time.
- Hydroforming: Utilized to produce specialized components ideal for intricate, complex, or unconventional geometries with a demanding surface finish.
- Metal Stamping: Mechanical presses are utilized for piercing holes, extruding, trimming, marking, ribbing, and a variety of other common stamped features to enhance your customizations.
- In-House Tooling: TMS machinists design and manufacture custom tooling on-site, significantly shortening lead times while allowing quick design modifications when needed.
Types of Deep Drawing & Metal Stamping
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.
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.