Are you unsure how to approach your sheet metal fabrication project? If you fail, your entire project could be blown. Mistakes made during the fabrication process are often impossible to rectify.
If you want to avoid the pitfalls most novices face, learn from the experts before you begin. In the sections below, you will find 6 tips from master fabricators. If you want to ensure your project goes off without a hitch, read on.
1. Pick the Right Material
Your material costs and labor costs are the most significant costs in sheet metal fabrication. Plan to use stock sizes for your metal. If you are purchasing sheet metal in the USA sheet metal, you will purchase the thickness in a sheet metal gauge. Overseas you would purchase material in a metric thickness. It will save you up to 20% on metal costs when purchasing stock sizes.
Note that Sheet metal thickness gauges are based on the weight in pounds per square foot per inch of thickness. This means that to the novice, the interpolated thickness of the material will look funny. Also, note when considering a sheet metal fabrication project, the sheet metal thickness gauges for steel are based on a weight of 41.82 pounds per square foot per inch of thickness that the gauge thickness of aluminum and steel are different.
You also must choose your metals carefully. Assuming size and thickness are comparable, as far as the raw material cost, Carbon Steel is your least expensive type of sheet metal, followed by Aluminum, then Stainless Steel. More expensive choices include Brass & Copper.
Aluminum is the lowest in manufacturing cost, followed closely by Carbon Steel and Stainless Steel is the most expensive. This is because aluminum and steel basically up to 1/4″ can use a CNC sheet metal turret press and press break were on stainless steel anything above 1/16″ you must laser cut it the use a press brake which the laser cutting is a slower and more expensive process. As for the traditional sheet metal punch press, stainless steel must have a more robust expensive mold and higher ton capacity traditional sheet metal punch press.
If you have your heart set on a certain type of metal, ask yourself why. Is it a functional choice or a stylistic choice? If it’s stylistic, can you achieve the same results with powder coat, platings, anodizing or zinc-rich coating of industrial paint sheet metal fabrication needs?
If that’s the case, calculate the price difference. It might just save you a significant cost.
2. Limit Your Use of Tight Tolerances for Sheet Metal Manufacturing Designs
More than a few surfaces of your design will rarely be critical to your sheet metal fabrication product’s function. Unfortunately, most inexperienced engineers build their prototypes using unnecessary tight tolerance call-outs on every dimension, such as:
- Hole diameters
Unfortunately, the tighter call-outs you include in your design will cost the more expensive the finished product. Instead of falling into this trap, only include features and surfaces critical to your project’s function.
Just think of it this way: if you want to fabricate a piece of sheet metal, a flat, unadorned sheet would be the least expensive. Each bend, countersink, hem, and the hole will increase the price. The more work you make for your manufacturer:
- More complicated traditional sheet metal punch press mold.
- More work the CNC turret Punch press must perform
- More complicated and time-consuming bends on the sheet metal press brake
- having to utilize the more expensive laser cutting over CNC turret punch press
- longer programming and set up a time/cost
- Higher scrap rate!!!!
The more you will have to PAY for your sheet metal fabrication.
Get back to the basics. Strip your design down to the bare minimum For your sheet metal manufacturing project.
3. Use a Stock Gauge for Sheet Metal Fabrication Manufacturing
Once again, using a standard option will save you big bucks in the long run. Every sheet metal fabricator offers slightly different options. The most common sheet metal gauge for the USA or standard millimeter thickness overseas for manufacturers runs up to one-quarter inch (6.35mm) thick. The thickness of the wall all depends on the project and the geometry of the part.
Thicker metals limit the angle of the bend you can achieve on a press brake. If the bend is too sharp, not only is it difficult to achieve on a press brake or even a traditional sheet metal punch press, it creates microscopic cracks in the metal. The cracks leave the metal brittle and easy to break.
You can also outright tear the metal. Many press brakes or traditional sheet metal mold punch press cannot be set up to make such bends. You run the risk of expensive setups and long production times.
If you want any complicated fabrication, just stay away from thick stock. Choose the thinner, more pliable metal.
4. Keep a Uniform Orientation to Your Bends
Fabrication machines, press brake, and traditional sheet metal punch press have their limits. One of these is their inability to bend an object in a different direction without reorienting it first. Each time your manufacturer needs to adjust your sheet metal physically, it will cost you.
Instead, make sure all your bends located on the same plane bend in the same direction. If you keep those bends in the same radius, it will save you even more money. You might be surprised just how much the extra step in your bending and reliefs will cost you
5. Simplify Your Folds
In general terms, the more complicated your design, the more it will cost you. To save your pocketbook, simplify the angles you use in your bends. A good rule of thumb for best sheet metal folds is to choose a radius equal to or greater than the thickness of the metal you use.
Small bends on thick parts are less accurate than on thin parts. Avoid the small bends if you’re using thick parts unless they’re absolutely necessary. If they aren’t, head back to the design of your sheet metal fabrication process and see if you can work around them.
6. Other Quick and Dirty Rules to Sheet Metal Fabrication
Below you will find the most common specifications that novice fabricators mess up. Follow this quick and dirty chart, and it will save you both money and hassle.
Minimum Clearance Between a Hole and Bend or Hem: Place holes at a distance at least equal to the radius of the Bend or Hem plus the thickness plus 2.5X the material thickness. Bend radii should be equal to, or greater than, the radius of the curl plus 6 times the thickness of the metal.
Keep the outside radius of your Rolled Hems (Curls) to at least twice the thickness of the metal.
Sheet Metal Fabrication Hem Styles
Hole Size: To prevent breakage of the punch the hole size must be equal or larger than the thickness of the material,
ideally 2-1/2 x the size of the hole
Flange Width: Should not be smaller than 4 times the thickness of the material
Bend Radius: This depends greatly on the material and the equipment; however, the radius must be at least the thickness of the material.
Bend Relief: In sheet metal fabrication, when bending a flange on the inside of the sheet metal edge, a relief must be used so as not to distort or tare the metal. The relief should be the length of the radius or greater, and the width should be as this as the material or longer.
Countersinks: Separate each countersink from other countersinks by a distance equal to, or greater than, 8 times the metal’s thickness. They should also be separated from the corners by at least 4 times the thickness of the metal. They should be separated from a bend by at least 3 times the thickness of the metal or from an edge by 4 times the sheet metal thickness.
The depth of your countersinks should be no more than 3.5 times the thickness of your metal.
Tabs and Notches: In sheet metal Fabrication, keep your notches at least one-eighth of an inch away from each other. If you bend the notches, they need to be at least 3 times the thickness of the metal plus the bend radius. Tabs need to be 0.04 inches away from each other or more.
As you can see, sheet metal fabrication can make for a tricky project. The key is to map out your needs, step by step. Start with the final product design and work backward, determining each step you need to accomplish that goal and discuss you concept with a contract manufacturer.
If you have more questions or you would like to discuss your sheet metal fabrication with an expert, reach out to us today with any questions you might have or a DFM analysis on your concept.
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