KDM Sheet Metal Deep Drawing
Deep drawing is the commonly used process to form sheet metal. The process occurs under compressive and tensile conditions. There are three types of deep drawing processes. It may include deep drawing with tools, active means, and active energy.
KDM specializes in sheet metal fabrication, performing deep drawing techniques. The process allows us to form any sheet metal into a box-like structure or cup. Through our deep drawing capabilities, we can produce pans and pots for cooking, automobile parts, sinks, containers, and many more.
Sheet metal deep drawing can eliminate assembly steps, produces complex geometries, and produces very strong parts. This capability ensures high speed, high accuracy, and seamless. Because of its seamless benefits, deep drawing can produce anything that requires to be gas or water-tight.
Sheet Metal Deep Drawing: The Ultimate Guide
I know you are probably wondering how sheet metal deep drawing works.
Well, this guide explores everything you need to know about sheet metal deep drawing.
Keep reading to learn more.
Deep drawing is a fabrication procedure that you can use to create seamless sheet metal parts.
The depth of the sheet metal part is greater than its diameter and is enclosed on one of its ends.
You can simply recognize a deep-drawn part by examining its depth and radius corners which are characteristically smooth.
Deep drawn sheet metal parts can achieve more complex contours and shapes beyond common squares and circles.
sheet metal deep drawing
At a basic level, you can employ a basic deep-drawing operation to create a multi-dimensional box or cup from a flat sheet formation.
However, you can also create more complex contours and shapes beyond common squares and circles from deep-drawn sheet metal parts.
You can use any ductile metal for sheet metal deep drawing.
Generally, any metal that can be cold-rolled should possess sufficient ductility ideal for sheet metal deep rolling.
However, you must also consider the material’s properties such as anisotropy or work hardening.
Some of the materials you can use for deep rolling include copper, copper alloys, brass, aluminum alloys, low carbon sheet, steel, brass, bronze, titanium, invar, silver, tungsten, Kovar, iron, nickel, molybdenum, and cold-rolled stainless steel.
You can shape components into the desired final product through the tooling method.
You can also convert sheet metals into deep-drawn cans and enclosures.
Key forms of tooling include hold-downs, punches, dies, and knockouts.
There are different types of tooling that you can use to model the desired enclosure through multiple press operations.
Selecting a tooling type is dependent on desired quantities of parts and budget.
This type of tooling uses multiple tools on the same press and changes tooling between each operation.
This is the most expensive tooling type in reference to cost per part but also offers the lowest overall tooling cost.
The high part-per cost results from the slow fabrication speed associated with the tooling type. All parts are cold-formed.
Under some circumstances, you will have to clean and anneal some parts between the forming operations.
The parts are heated in a furnace to increase malleability and facilitate further press operations in the course of the annealing process.
You will have to repeat the tooling and annealing process severally before the desired final product is achieved.
Progressive Die Tooling
This type of tooling is ideal for high throughput production that exceeds 50,000 per year.
Overall, they are more costly but in isolation, their price per piece is lower compared with stage tooling.
In progressive die tooling, a single die set is created from a compilation of all required tooling in a press.
A metal sheet is then supplied through the press.
It progresses through each toolset and facilitates the subjection of each component to every series operation.
The finished part is then cut from the metal sheet by the final die and ejected off the press.
Transfer Press Tooling
You can also use this type of tooling for your high-volume product.
Unlike progressive die tooling, the metal sheet and the part are separated during the first operation in transfer press tooling.
An automated transfer mechanism then moves the part through a series of various forming operations.
The simplest and most basic deep metal drawing procedure utilize a punch and die.
The punch corresponds to your desired base shape.
On the hand, the die cavity has to be a little wider than the punch to provide sufficient space for passage and clearance.
deep drawing for sheet metal
Basically, you place a blank piece of sheet metal into a die and apply force through the punch to push the metal into a die and produce the desired shape.
However, a number of steps that the sheet metal blank undergoes before it is transformed into a finished product. These include:
This is the most important stage as it lays the groundwork for the actual deep-drawing operation.
The design process should consider the desirable shape, thickness, and radius of the finished part according to the customer’s specifications.
You should also determine the blank holder’s force and plank force beforehand.
The punch force varies throughout the operation and maximizes at about one-third of the stroke.
On the other hand, the blank holder’s force varies between 30 to 40% of the punch force.
Sheet metal flow occurs when the plant is punched into the die cavity.
The progression of the metal sheet into the die cavity and the formation of a cylindrical object in the process constitute the metal flow.
First, the sheet metal blank is placed on top of the round die cavity and external force is applied through the punch to force the blank into the die cavity.
With increasing force, the blank progress inwards into the die cavity, leaving material not yet drawn into the die radius and cavity, normally known as the flange.
Forces Involved In Metal Deep Drawing And Wrinkling
As the sheet metal blank flows from the peripheral flange into the die cavity, the constricted space in the cavity exposes the material to compression and tensile forces.
The compression forces originate from the punching action and force the material into the desired shape.
When the thickness of your metal sheet blank is small, then the blank succumbs to wrinkles.
Sheet metal wrinkles commence in the flanges then progress into the die and end up in the wall of the parts.
You can avoid sheet metal wrinkling by using a blank holder and using a blank of an appropriate thickness.
Sheet Metal Thickness
As earlier mentioned, sheet metal thickness plays a vital role in determining the quality of the final product.
The geometry of a blank primarily depends on the sheet metal blank’s thickness to diameter ratio.
The ratio is generally expressed as a percentage. Holders are only effective for thickness ratios of 1% and over.
The effectiveness of holders for marginal ratios between 0.5 and 1% are chance dependent and almost nonexistent for ratios below 0.5%.
Size Of The Corner Radius
The radius of the die corner and punch corner critically influences the distribution of force and how the material flows during the deep drawing process.
The corner radius should be optimally spacious to enable the smooth metal flow. Metal tearing is a common defect for too small a corner radius.
Too large a radius can also cause wrinkling.
The part’s wall forms with cavity ingression of more sheet metal from the flange.
The tension present in the material forming the part wall creates a thinning effect and it is greatest near the part’s base.
Though it is impossible to avoid a certain level of thinning, you can mitigate against it by controlling the process parameters.
In conclusion, you should iron the finished part for evening the wall thickness.
You can use sheet metal deep drawing in a wide variety of applications and parts with greater depths compared to diameter.
Sheet metal deep drawing is relative an inexpensive process for producing simple design parts.
You can use sheet metal deep drawing to produce ideal shapes such as rectangular structures or axisymmetric structures such as hemispheres or cylinders.
However, you can also still produce complex shapes using this process but at an elevated production cost.
The following are the characteristics of applications that will suit sheet metal deep drawing:
- High volume parts that require longer runs.
- Applications that require gas- and watertight parts. The seamless production process makes the sheet metal deep drawing process the most ideal.
- Components and parts that require tight tolerance production conditions.
Sheet metal deep drawing has high accuracy and you can set its tolerance to as low as ±.0005 in.
- Parts with axisymmetric and complex shapes.
Sheet metal drawing offers fast and accurate options for the creation of these geometries compared to other machining processes.
- Parts that would not support welding, either for aesthetics or durability reasons.
Generally, you can produce a wide range of products using the sheet metal deep drawing technique. Some of the common products include; tanks, cylinders, panels, containers, kitchen pans and pots, automotive parts, sinks, etc.
Sheet metal deep drawing is a versatile metal forming technique that has been around for years and for good reasons too.
The following are some of the advantages associated with the sheet metal deep drawing technique:
High Volume Production
The sheet metal deep drawing technique is specifically ideal for operations that require high-volume production of metal parts.
It can efficiently and economically produce a significantly large number of parts once you set the die and tooling correctly.
It requires very little downtime and maintenance.
Production will proceed at high throughput as long as you maintain a stable supply of metal blanks into the system.
Sheet metal deep drawing is one of the most cost-friendly metal forming methods available at the moment.
This technique has proven its versatility over time and has been known for the high-volume production of metal parts at significantly lower costs compared to alternative techniques.
Significant return on cost draws from economies of scale associated with the high throughput production characteristic of this process.
However, the process can still even be multiple folds cheaper in applications producing only small quantities compared to other processes like progressive die stamping.
Versatility In Application
You can use deep drawing in sheet metals to produce a diverse assortment of shapes and products. Though cylindrical products are by far the most popular shapes and parts manufactured by this
deep drawing sheet metal parts
technique, you can efficiently utilize the process for other parts such as squares, rectangles, and more complex geometries.
Such geometries are usually unachievable with other techniques.
The sheet metal deep drawing technique is an exceptional procedure for producing cylindrical products.
You can draw a three-dimensional shaped cylindrical object with a metal blank in a single draw ratio.
At its best, you can efficiently produce parts or objects that demand considerable minimal weight and considerably high strength using this technique.
In addition, it also utilizes considerably less metal than other alternative methods.
Creation Of Seamless Parts
Deep drawing for metal sheets is perhaps best used for applications that require liquid- and airtight containers.
Since you will only be using a single sheet of metal in modeling such objects, your products will possess uniform shapes and lack weak points known for joined or welded objects.
You can use the sheet metal deep drawing technique to create identical components and products. The components that exit the forming press are highly repeatable.
However, for close conformity to the drawing, the tooling has to be correctly made.
The processes involved in the sheet metal deep drawing technique harden the metals during deformation.
Consequently, you end up with finished parts and products that are more stable and stronger than machined or alternatively formed metal parts.
Your finished components and products produced from deep drawing possess a very high level of consistency, initiated at the beginning of production till the end.
The seamless nature of the procedure also facilitates the creation of uniform products.
This is more so desirable if you intend to use your end products in a system that requires high hygiene standards.
The lack of crevices and cracks from welded parts delivers a product that can be easily cleaned and withstand some high pressure/high-temperature treatment procedures.
Reduced Technical Labor
You can easily automate the deep drawing process and significantly reduce production time and cost.
Faster Assembly Process
You can produce thousands if not millions of parts, components, and products using the deep drawing technique.
Since it produces parts and products with one closed-end, you won’t need any of the secondary processes like welding and fabrications.
Automation of the process also considerably set it above other semi-automated or manual techniques.
Recycling Of Waste Materials
The deep drawing process supports the recycling of waste products generated in the course of the deep drawn stamping process.
You can reuse the recycled materials for other parts later.
During the deep drawing process, circumferential compressive stress comes about as a result of pressure-forcing the blank into the die cavity and reducing its diameter.
The stress increase is inversely proportional to the reduction in blanks diameter and with higher stress also comes higher flow resistance.
Consequently, the section of the blank close to the punch’s nose will stretch or tear if the flow resistance exceeds, the tensile strength of the blank.
Consequently, you have to design the process to optimally reduce the diameter of the blank without exceeding its tolerance levels to avoid stretching and tear.
The following formulas offer quantitative methods of addressing the above-mentioned challenges.
The draw ratio is a computed figure that quantifies the quantity of drawing subjected on a sheet metal blank.
The drawing ratio can be computed by diving the diameter of the blank by the diameter of the punch.
You can use either the maximum diameter or surface areas in cases of non-circular shapes and objects.
The maximum draw ratio for a single operation depends on drawing depth, die and punch radius, sheet anisotropy, and the material used to construct the sheet. Under normal circumstances, the limit of a draw ratio should not exceed 2.
You can also express the drawing ratio as a reduction (r).
You can compute reduction using the formula; r=(Db-DP)/ Db, where Db is the blank diameter and DP is the punch diameter.
The corresponding product from the computation should not exceed 0.5.
You can also express reduction in terms of percentages.
In this regard, you will need to multiply the product computed from the above-outlined formula by 100%, in which case the percentage reduction should not exceed 50%.
Redrawing Sheet Metal
Redrawing sheet metal refers to subjecting an already deep-drawn blank to the subsequent deep drawing process.
This technique enables you to achieve a higher magnitude of deep drawing beyond the possibility of a single operation.
You can redraw a metal sheet if the desirable metal sheet’s percent reduction exceeds 50%.
The 50% reduction is rarely useful in industrial applications. Though still, this first reduction usually range between 35 to 45%.
Subsequent deep drawing techniques deliver different reductions on the sheet metal blank.
For instance, the first redrawing can deliver between 20 to 30% while the second redrawing can deliver between 13 to 16% reduction.
You should anneal the part after every two operations if you desire to perform a severe amount of deep drawing that requires several redraw operations.
Since every redrawing to be performed will require an intermediate part, the design of the deep draw process must accommodate the drawing of these intermediate part shapes.
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