SHEET METAL FABRICATION PROCESSES EXPLAINED

When considering a Contract Manufacturer for a Sheet Metal Fabrication Process for a part to be fabricated out of sheet metal you need to know the processes available to understand how you will design your sheet metal fabricated part  to be the most economic manufactured. Each process has its positives and negatives. Many fabricators will force feed you what is easier for them not necessarily what is the best for your product in quality and cost.  Let us summarize the major process; Laser Cutting, CNC Turret Punching and Traditional Stamping using a mold, pointing out the positives and negatives of the processes together.

Laser Sheet Metal cutting machine Contact manufacturing

Laser Cutting

Laser cutting is a simple process using a laser to cut a pattern out of a sheet metal sheet/plate. A sheet metal plate is put on a table and either the laser is programed to move or the table is programed to move to cut the shape required.  This is the go-to for many products because it can be quickly and easily programed from a 2D drawing to cut any simple to very complex shapes.

Positives:

  1. Sheet metal fabricated cuts are smooth, clean and precise, no or little cleanup after cutting is usually needed.
  2. No tooling is required.
  3. Many lasers can cut from very thin to very thick, 3/8”, materials.
  4. Lasers can cut Stainless Steel from 1/32” – ¼” depending on the Laser cutting equipment’s capabilities.
  5. Depending on the fabricators and part fabricators will cut from quantities as small as 10 to 1000. however, the sweet spot for most parts is 10-250 regarding to cost.
  6. Product design changes are easy.

Negatives:

  1. For Carbon steel and aluminum depending on the complexity and the quantity of the part, this can be the most expensive process especially for quantities of 100 and greater.
  2. The actual cutting time is longer than other processes.
  3. Must use a secondary process to bend the parts, a break.

Summery, if you have a low quantity, very complex shape sheet metal fabricated parts, stainless steel material or thick material this is a very good option.  However, laser cutting is easy to set up for the fabricator also so be aware they might force feed you this process if they are not equipped or specialized in other processes.

CNC Punch Press

The CNC Turret Punch Press process that uses a turret that will quickly change tools to cut the desired shape while normally the table is programed to move to accept the punch tool. The tool rapidly goes up and down and nibble’s the cutout. Think of a 2” square hole, you would use a ½” cutter to nibble the cutout along the cut line until the cutout is complete.

Positives:

  1. If special tooling is required for clean cut holes or cutouts the cost is minimal.
  2. Extremely quick cutting process.
  3. Design changes are easy to incorporate.
  4. Great for carbon steel and aluminum up to 3/16” thick depending on the complexity of the cut.
  5. Depending on the size and thickness of material this process is good for 50-1000 parts but ideal for larger parts, 12” + square, at volumes of 100-1000.
  6. Quick and easy to program from a 2D.
  7. The ability to easily change the design makes this process great for smaller trial production runs to test a product’s viability.

Negatives:

  1. Not efficient when cutting any thickness of stainless steel or Carbon Steel and aluminum over 3/16” thick.
  2. Most processes  will leave some cut / “nibble” marks, see the  picture to the right. However Ionthis uses special tools and clean up processes to eliminate such marks if required much of this can be removed by process control and hand clean up. Make sure you are aware that most CNC manufactures will not clean up these marks.
  3. Must use a secondary process to bend the parts like a break press.

Summery, if you are looking at a routine production parts in Carbon Steel or Aluminum between the production quantities of 100-1000 or be able to do design changes on the fly, this is an excellent process to use.

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CNC Punch Press
CNC Punch Press Sheet Metal Cut Marks
CNC Turret Press Cut Marks
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CNC Punch Press and Maol Punch Press
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Traditional Sheet Metal Mold Stamping

Traditional mold stamping is a process that requires a mold to be made to replicate the parts. Depending on the exact punch process you can punch martial of copper, nickel, aluminum, steel and stainless steel to great thicknesses. For small simple parts a single mold can be used to cut and bend the sheet metal. The larger and more complex the part becomes 2+ molds are used. To increase efficiency over multiple molds a “progressive die” mold can be used. This is a single mold were a long strip of material from a coil is feed into one end and as it goes through the mold from one end the material is punched in steps as it is pushed through the mold at the far end/exit the final step cuts the material off and a finished part is dropped off.

Positives:

  1. A multitude of materials and thicknesses.
  2. Fastest quick production.
  3. Does not need a secondary bending process, a break.
  4. Part edges are cosmetically clean, no extra finishing normally require.
  5. Smaller parts, say 2” square, molds are economical.
  6. Most cost effective with high volumes when you can amortize the cost of the mold over the large volume.

Negatives:

  1. Mold cost could cost from $1000-500K++ especially costly for 12” square and above
  2. Hard to change the mold if the design changes.

Summery, if you have a high production quantity sheet metal fabrication with a long-life cycle that allows you to amortize the mold cost, this is the process of choice.

Additional Considerations

Other areas you should consider when at your design stage but not limited to are:

  • Deep Draw, this is where a LARGE press and mold is used to “draw” the metal. This means shape type metal.  Think of it as making a flat sheet into a bowl. This is usually costly but if it is a must have shape it is unavoidable but must be in high quantities to justify.
  • PEM and Fastener installation. This needs to be thought through carefully, when it is a must in your design, consider the cost and minimize the numbers much as possible.
  • Welding/Joining. There are a multitude of different process to weld and join two materials together. These include from simple rivets, spot/resistant welding, friction welding, MIG, TIG and stick welding. They will all will impact cost differently so consider them wisely.
Contract Manufacturing Sheet Metal Deep Draw
Sheet Metal Deep Draw
PEM Fastener Installation in Sheet Matal
PEM Fastener Installation
Sheet Metal welding Considerations
Sheet Metal welding Considerations

Conclusion /Sheet Metal Fabrication Processes

For sheet metal fabrication it all comes down to cost depending on your product and quantity. To understand more clearly think of a 2” x2” x2” open ended box out of 16 Gauge aluminum .A Laser cut and Brake bend would take less than 2 minutes to produce. On the other hand, a CNC Punch and Brake Bend would take less than 1 minute to produce. Last a standard punch press would take less than seconds to produce.

 

The last two items you must consider are a “Cradle to Grave” and a FULL-SERVICE COMPONENT CONTRACT MANUFACTURER.

 

FULL-SERVICE means the contract manufacturer can provide you with a finished part including machining, PEM/Fastener installation, Powder Coating, Plating (anodizing, Chromate, Alodine and so on) &silk screening/engraving, a “one stop shop” This eliminates having to resend out your part for a secondary process to a separate multiple vendors. The significant advantage to this is you now only have one source responsible for your quality and on time delivery needs..

 

“Cradle to Grave” means as your product matures, we will continually give you suggestions, (process changes, material changes, sub-assemblies) to reduce your cost giving you an improved sales advantage.  Ionthis can do both!

 

For a DFM/Analysis of your Sheet Metal Fabricated component or assembly, feel free to contact Ionthis at engr@ionthis.com

 
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MFG PROCESSES EXPLAINED