Deep Drawing 101

Why Deep Drawing?

One of the main reasons we choose deep drawing over other manufacturing processes is to keep a one-piece construction, rather than turning to welding, or a multi-piece assembly involving multiple step processes. It is more timely, cost-effective, and efficient to utilize our deep draw presses. 

To classify a part as deep-drawn depends on its height to depth ratio, or H/D ratio. When these ratios are large enough to classify as a deep draw is when other processes would not be able to achieve the final product in one step. If another process would be used, the design would need to be separated into a multi-stage construction. This is because the material would be pushed beyond its mechanical limits. Deep Drawing is one of the few metal forming processes where extreme H/D ratios can be achieved with a single parent blank.  

 Deep Drawing VS Metal Spinning

We compare deep drawing to metal spinning at TMS, because consistent wall thicknesses are easier to estimate and achieve with deep draw forming, rather than metal spinning. Deep drawn parts are cold-formed, which means that the amount of stress in the part is far less than in a spun part. Deep drawing allows for a larger batch of products to be finished, much quicker than if we were to spin them. 

How Accurate is Deep Drawing?   

The accuracy of a deep drawn part depends on a few different variables including our laser cut blank tolerance, inner diameter, outside diameter, wall length, and material type. These all affect the tolerance of the final deep drawn product.  

If the incoming material, the laser cut blank, from run to run is consistent, the press tool is capable of holding that +/-.010” from run to run. Consistency is one benefit to our deep drawing capabilities. In terms of final product tolerance, we meet or exceed our +/- 0.030” tolerance with all of our deep drawn parts. However, there are certain parts where the overall form is consistent within 0.010”. 

Below, we have a drawing of our popular deep drawn cup, TMS141214, to help us to understand specific measurements with deep drawing. Each part will have what we call ‘tool-controlled’ features, meaning that the deep draw tool feature forming that detail will be extremely accurate every time. Examples of tool-Controlled features would be these radii on this cup (R.50 and R.20 in the drawing below). Those features will be exactly that value, every single time. The ID and OAH features may vary but can be dialed in to be the +/- 0.010”. The wall thickness on the cup can also vary but much less – about +/- 0.005”