Raw material calculation of Complex Deep drawn Geometry :

The complex automotive parts such as chassis cross members have complicated shapes that are not easy to handle for process engineers. Certain things to be considered while calculating their raw material size, which is a major factor and value addition to the cost estimation and cost accounting.

Why accurate raw material cost is the Key factor to control cost

The raw material contributes a 70% cost of the product cost and 30% are the processing, finishing and packaging, which therefore makes it most critical part of the final product costing. The process engineers should be trained enough to calculate the optimum material cost, wherever possible to combine/manipulate the process layout to save the material.

Why Right process selection is important :

The correct sequence of process is the key factor, since the raw material input would be the different based on the process selection. For instance, let's take example of the following Geometry with trimming Margin.

Extra raw material taken for trimming, that is to control the outer shape and could be avoided in case it's has no significance or not fouling with surrounding parts in the assembly.

Use of CAE to select first time right process :

The Computer aided engineering help to create the right process, since the manual calculations have high chances of errors, even with experienced engineers have mistakes which proves costly for the project deadlines.

The CAE helps in creating accurate process mapping with least errors along with optimum process and material input.

Blank calculation process through conventional method :

The one of the method to exact blank size is to cut out sections at various points and calculate the length to obtain the final blank shape, however there are high chances of errors if not done by professional. Eventually the final results are not that much accurate, nearly 60% accuracy obtained, even for expert cad users. Refer the article Blank size calculation of a sheet metal for calculating the length along sections.

Blank calculation process through CAE method :

CAE help the engineers to calculate the 90% accurate blanks with a blink of an eye, however the expertise of engineers is quite important. Since the output is directly proportional to the input such as mesh quality, material database, process inputs like press speed, pressure, tonnage etc.

Blank (Material) size Calculation of Cup Draw :

CUP DRAW

The best and accurate method to calculate the blank size of Cup/Hat shaped draw is by Volume method, however there are 5~7% error due to process thinning at radius point. Let's learn to calculate the blank size, Since we know the volume of blank should be equal to the volume of drawn part :

Volume of Blank = Volume of Cup (Calculate from the CAD geometry)

𝚷 X R X R X Thickness = 336009 ⇏ 3.14X R X R X 4 = 336009

R X R = 336009 / (3.14X4) ⇏ R = SQ RT (26752.3)

R = 163.5 and correspondingly Diameter = 327mm

This cup has to be drawn in to three stages, Draw-1, Draw-2 and Final Draw.

To make sure the final flange to be straight and dimensionally controlled, the part has to be trimmed before final Draw, therefore optimum Trimming margin has to be added and the final material size to be taken as circle of Diameter - 340mm

If you want to learn the Metal forming simulation, read the book "Practical guide to forming simulation"