Need to know… • Sheet metal is two words • Mechanical Engineering uses • Four primary opera;ons • Fabrica;on Machines • Tools & Cu@ng Theory • Gages • Coa;ngs
Although Sheet Metal is commonly used in building construc;on such as framing and HVAC, that is an industry unto itself and does not have a lot of cross-‐ over with Mechanical Engineering
Mechanical Engineering more commonly uses sheet metal as an exoskeleton holding more important stuff inside while trying to s;ll look good (or at least not too ugly)
Basic Sheet Metal Opera;ons 1. Punching 2. Bending 3. Forming 4. Joining
Punching and Blanking
Blanking is shearing out a desired part from the sheet Punching is shearing out waste from a sheet Machines are known as Turret Punches. Two major manufacturers are Amada and Strippet
Bending
Sheet metal bending is a blend of science and art. There’s always a degree of outcome uncertainty!
Forming
Embossing-‐ LiYs and Sinks. Care must be used to keep sheet metal well-‐ clamped to minimize warp and wrinkle. Lancing-‐ A combina;on of shearing and embossing; e.g., guide features. Deep Drawing-‐ Severe stretching of sheet metal to create volumetric shapes. Spinning-‐ Rota;onal process in which round blank is held, spun, and rolled over a mandrel to create a turned shape like ligh;ng fixtures
Joining
Clekos (Clecos)-‐ Temporary joining device which both aligns ma;ng parts and holds them clamped together Rive;ng-‐ Rivets are pins used to align and permanently a`ach two or more pieces of sheet metal together
Pop Rivets Solid Rivets Blind Rivets Fast/Cheap Strong Threaded
Joining (cont.)
Tog-‐L-‐Loc-‐ Clinching two parts through a forming an swaging opera;on Spot Welding-‐ Intense heat is added via an upper and lower
Self Tapping Screws-‐ • Use only when parts must be occasionally separated aYer assembly • Use in conjunc;on with pierced and extruded holes to give more thread depth
Threaded Inserts (PEM nuts)-‐ • Use when parts must be frequently cycled on and off • Use with conven;onal machine screws
Gauges
• Sheet Metal fabrica;on generally falls in the thickness range of 1/32” (0.032”) to 3/16” (0.187”) • Thinner material falls into the stamping category • Thicker material (plate stock) gets machined • Sheet Metal “Gauge” is a unit of thickness. Note, however, it varies slightly depending on the material type
Coa;ngs
• Stainless requires none • Aluminum can be used with, or without post-‐opera;on coa;ngs (pla;ngs), but will oxidize and leave your fingers black Alodining – chemical (chromate) pre-‐paint prep cosme;c enhancement Anodizing – electroly;c passiva;on creates a “skin” black –cosme;c and wear resistances hard-‐ sliding surfaces; extremely wear resistant • Steel Preplated-‐ (electrogalv, mechanical galvaniza;on) Spangled finish Post-‐plated-‐ Zinc pla;ng with clear or yellow chromate conversion Cr6 now banned! Pain;ng