Aluminum Shearing Operation

Your description is very general so all I can give is a general answer.

1) 10% clearance per side works well for most aluminum applications, perhaps slightly less for very soft aluminum.

2) Choice of tool steel and lubricant depends on the alloy content primarily, since the abrasivness of aluminum is greatly influenced by certain alloying elements. If the aluminum is fairly pure, such as 1100 alloy, it is feasible to use a lower grade steel such as A2 and light weight lubricants, even of the "vanishing" or evaporative type.

Question is very vague. You need to specify 1) Material thickness 2) Aluminum specification. 3) Production quantity. 4) Generally no lubrication is used for punching sheets or is it for lubricating the blanking tool? Or 5) is it a very expensive fine blanking where the need for post burr removal is unnecessary? If the variables are known any standard tool design manual will specify the clearance or for simple application there are hundreds of references available in Google search.

Krishnan,

I did not understand the scope of this question, and I didn't understand your addressing this problem. CAn you please explain what blanking is? Would you also clarify lubrication of blanking tool? Also fine blanking, burr use are also not understood.

The reason I ask, is because I was interested in punched aluminum sheets, and I didn't know where I could find the companies that would do it. Similar to the aluminum containers of candles... These questions may be stupid to you, but I am unable to ask for what I want, and I would really like to learn the jargon.

Would you help me understand? Would you also bare with me to first learn how to ask, and then ask you for what I need. Thank you in advance.

Sean Rashti

Dear Sean Rashti, There numerous several methods through which sheet components can be made. It all depends on various factors like material specification, end use, cost, quantity required, facilities available etc. 1. Limited quantities of extremely tough and hard conducting materials can be intricately profiled to extremely precise dimensions by NC-EDM Wire cutting or water jet cutting. The process uses fine copper wire for spark eroding NC controlled profile. This is followed only for very limited quantities. 2. Fine blanking is resorted to for tight dimensional controlled components like delicate components used in precision instruments like watch etc. Fine blanking tools are very expensive. Since the cutting edges are very finely controlled dimensionally the ends products highly refined edges requiring no post cutting processing of edges. 3. Water jet cutting is used extensively now a day for cutting or profiling of hardest of materials like granite, advanced composites etc. The cutting is done using the extreme concentrated forces of jet of water NC controlled. 4. Lower end of manufacturing spectrum there are millions of small scale manufacturers resorting to banking and piecing, forming of sheets to deep drawn shapes using their ingenuity. Every one of the above processes are unique and should chosen after careful consideration cost factor and technical parameters. A Google search will be very illuminating.

The specifications are as follows:

material grade - Aluminum 6101 (Al-97.6%)

Thickness - 10 mm

qty - 10,000 nos

operations - blanking followed by fine blanking

There is nothing like "blanking and fine blanking". Please refer http://www.fineblanking.org/ for further technical details of fine blanking. It is impossible to advice with out knowing component profile, tolerances, end use, temper designation of the sheet etc.

This is in reply to your comment and Sean_rashti's comment

The components that i'm talking about are aesthetic part of the watch also called as the case center inside which the movement, dial, hands are placed. We manufacture the the Watch case center in SS & Brass materials. However as a new initiative, we wanted to explore Aluminum Case Centers.

In Brass we do Piercing, Blanking, Fine Blanking (Shaving) Followed by forming & trimming. To differentiate between blanking & fine blanking as per my understanding let us take up manufacturing a rectangular component. In blanking, I would consider 5% clearance between punch & die of the RM thickness & cut the required cmpt from the Raw material. The Side wall of the component thus obtained will have heavy scoring marks, pluck off etc. In order to remove this I will remove 0.5 mm per side again by shearing operation called shaving or fine blanking. The tool clearance for this operation would be 1% of RM thickness. This operation would cut all undesired side wall surface finish and give a clean surface which is suitable for further operation.

Similarly I want to do in aluminum and hence the clarifications.

"The Side wall of the component thus obtained will have heavy scoring marks, pluck off etc." It my opinion a professionally designed tool with calibrated clearance the scoring marks etc can be totally over come. The crux of the issue is to approach organizations specialized in such tool design and fabrication. One such eminent place is NTTF Katpadi. Tamil Nadu, India, who excel in these kind of tooling. http://www.nttfonline.com/home.html refers.

ALUMINUM 10% OF MATERIAL THICKNESS

STEEL 15% OF MATERIAL THICKNESS

STAINLESS 20% OF MATERIAL THICKNESS

I strongly dissagree with your clearance percentages of stock thickness.

The base-line, most commonly used for CRS and HSLA would be 10%.

Softer material uses tighter tolerances, such as 5% for CDA110 (brass).

Stainless is generally still within the 10% range, and only extreemly hard material such as blue-tempered spring steel would approach 20%.

30 years experience

WOW,

my head is spinning from all the comments going in different directions.

First off I have a question - 10 mm thick watch inserts? - Did I miss something here? or is it 1.0mm?

Please all who commented, including people with 30 years experience(!) realize that the material thickness, and material type has a profound effect on the tool life as well as the edge quality - namely the "shear" zone and the "break" zone. What seems to be desired here is a near full shear zone hence a near 100 % square smooth edge. When dealing with material such as this Aluminum it is imperative that there is ample lubrication on the upper knife, which essentially will be rubbing to create the "shear zone" on the side of the material.

It is likely possible to manufacture 10000 pieces with a very minimal cutting clearance (2% of material thickness or less) and using A2 tool steel. This min. clearance will result in rapid tool wear, and a higher applied force requirement, as well as a slow or preferably hydraulic pressing operation, which in the case of only 10000 pcs is somewhat irrelevant.

When reducing the cutting clearance this dramatically from the norm it likely will result in having to sharpen the upper and lower tool steels throughout the process. The pressure on the tool steels will be immense and rubbing on the cutting faces will be also extreme, maximum lubrication will be key and should be applied (spray) from below on the "die opening" as well as the punch.

I assume this component is round, and the edge you are after in the "good" part of the stamping process will actually be the edge of the "slug" or round piercing which will be a reflection of the lower die section or insert. This would most certainly be my first attempt, as the cutting clearance can be increased if needed but not easily reduced by using the same punches.

If flatness of the component is an issue then a Standfast or Dadco Nitrogen self contained gas spring can supply the pressure required to hold the part flat during piercing.

Please be aware that the sizing will be on the slug side and is a reflection of the lower hole, in your case with aluminum at min cutting clearance an expansion of up to .03 mm can be expected after slug ejection.

A True Fine blanking process will not likely be practical due to the high tool and press operating costs, although if it were not for the small quantity may be the right process, although much slower than stamping and shaving. A shaving process will require an additional tool or tool insert, hence it is back to using one operation, near zero clearance hydraulic conventional stamping.

Please realize that my advise is based on many years of stamping experience, but your application proposes a unique challenge, and there may be other ways to manufacture your part, as described by others, water jet may be an good option, depending upon tolerances.

It would be interesting to know what your actual processes and results were, share them if you can.

All the Best, Mirco Graenert Consulting Inc.

This advice was free, and has been given without any sort of testing, hence I will not be liable and I cannot guarantee positive results, there are too many factors, but I do feel very positive about my answer.