Design Guide
This guide was prepared to give designers an overview for quick reference to the most commonly used metals and manufacturing methods.
For more information on specific processes, or to learn how we may help you with prototypes or finished product formulas, please contact us here.
Material: Aluminum, Iron, Steel
Process: Fluid metal poured into cavity or form of sand without external pressure
Complexity: Considerable - Many shapes and ribs possible
Size Range: 1" to huge
Wall Thickness: 0.250" min. preferred (0.090" possible)
Tolerance: 1/16" - 1/8" per foot, but greater for larger sizes
Draft Angle: 3° minimum
Radii: Generous, at least 1 rib thickness and constant wall section preferred
Surface Finish: 250-300 rms
Tool Cost: Low(0.25) Plastic injection molding = 1.00
Opt. Lot Size: Few pieces to large quantities
Dir. Labor Cost: High (labor intensive)
Finishing Costs: High (much finishing required)
Scrap Costs: Moderate (recyclable)
Design Features
- Basic Casting method of the industry
- Good for low volume parts
- Large, moderate to high strength parts possible
- Hollow shapes possible with cores
- Section transitions must be gentle
- Parts must generally be machined if mating with other parts. Machining material allowances required
- Closer tolerances (1/32" - 3/32" per ft.) with better surface finish (150-250 rms) may be produced using the Shell Molding process, but larger quantities would be required to offset increased tool cost.
Material: Aluminum, Brass, Magnesium, (some Iron)
Process: Fluid metal poured into metal molds and around metal cores without external pressure
Complexity: Moderate-Metal molds somewhat limit shapes
Size Range: Moderate
Wall Thickness: 0.100" minimum
Tolerance: 0.032" - 0.100" per foot
Draft Angle: 3°
Radii: 0.060" minimum
Surface Finish: 90-125 rms
Tool Cost: Medium(0.50-0.75) Plastic injection molding = 1.00
Opt. Lot Size: 1,000/run & up
Dir. Labor Cost: Moderate
Finishing Costs: Low to Moderate-less labor than sand casting
Scrap Costs: Low(recyclable)
Design Features
- Economic with substantial quantities
- Stronger than die castings
- Relatively close tolerances achievable
- Good surface finish
- Machining may be required
- Generally smaller radii and thinner sections are possible than with sand casting, and consequently smaller parts can be made
Material: Aluminum, Iron, (Steel possible with special handling)
Process: Fluid metal poured into a permeable shell which has been formed around an expanded styrofoam bead form made in a tool. When the metal is poured into the shell it vaporizes the foam form and takes its shape for the finished part
Complexity: Considerable (more shapes and thinner walls than sand castings)
Size Range: Moderate-Part size determined by manufacturers flask size
Wall Thickness: 0.060" minimum
Tolerance: 0.030"/in. (small holes to +/- .005")
Draft Angle: 2° minimum (less is possible)
Radii: 0.060" minimum
Surface Finish: 200-250 rms (depends on foam bead size)
Tool Cost: High (1.25) Plastic injection molding = 1.00
Opt. Lot Size: Moderate (small quantities expensive)
Dir. Labor Cost: High (much hand work)
Finishing Costs: Low to Moderate
Scrap Costs: Low (recycleable)
Design Features
- Used a lot to replace steel parts with iron
- Used to reduce cost of aluminum parts
- Hollow shapes possible
- Closer tolerance and thinner parts can be made than when using sand casting
Material: Aluminum, Zinc, ZA alloys, lead, Magnesium
Process: Fluid metal injected, under pressure, into precision molds mounted in special machines with special handling equipment
Complexity: Considerable (intricate shapes, thin walls possible)
Size Range: Moderate-Part size determined by mold and machine size
Wall Thickness: 0.025" minimum (some thinner possible)
Tolerance: +/- 0.003"/in. (0.001" possible with special handling)
Draft Angle: 1° minimum (no draft possible)
Radii: 1 wall thickness (near 0 possible)
Surface Finish: 60-125 rms
Tool Cost: High (1.25) Plastic injection molding = 1.00
Opt. Lot Size: Substantial quantities required (small lots not desireable)
Dir. Labor Cost: Low-Medium
Finishing Costs: Low (little finishing required)
Scrap Costs: Low (recyclable)
Design Features
- High volume parts most economical
- Molds capable of 100,000 - 300,000 parts
- Hollow shapes possible
- Net shapes and sizes from mold
- Materials have bearing properties
- Moderate to high strength parts
- EMI shielding obtained with part
- Finished parts can be used in pressure tight assemblies
- Parts may be inserted for threads, hubs, etc.
- May be painted, anodized, polished, plated
- Good surface finishes and decorative applications
- Trim dies may be required
- Limited to low melting temperature metals (non-ferrous)
- Materials must be selected to eliminate galvanic corrosion
- Prototyping can be done by the Plaster Mold Process - Low tool cost, good dim. and surface finish quality with higher piece part cost
Material: All Steels (including Stainless), Aluminum, Copper, Brass, Bronze, (some iron)
Process: Fluid metal without external pressure, poured into hollow shell molds which have been formed around wax forms and the wax subsequently melted out. Aluminum tools required for wax forms
Complexity: Greatest of any casting method
Size Range: Moderate-Part size determined by manufacturers flask size
Wall Thickness: 0.010" minimum
Tolerance: .003"/in. possible
Draft Angle: 1° - 3° (0° possible with special handling)
Radii: 0.02" - 0.03" (0 radius possible)
Surface Finish: 90-125rms
Tool Cost: Low-Moderate (0.25-0.75)
Opt. Lot Size: Wide range (depends on part size)
Dir. Labor Cost: High (Pouring by hand, much hand work with wax forms)
Finishing Costs: Low (Net parts possible, some secondary operations needed)
Scrap Costs: Low (recycleable)
Design Features
- Best for steels needed in complex shapes
- Good for accurate small parts
- Hollow parts with cores
- High strength parts
- Net shape parts
- Excellent tolerances and surface finish
- Very economical for small parts
- Large parts are possible, but limited by flask size
Material: Steel, Iron, Aluminum, Brass, Magnesium
Process: Broaching, Milling, Planing, Shaping, Grinding, Polishing, Machining Centers, Drilling Reaming, Threading and Gear Cutting Machines (most machine names indicate function performed)
Complexity: Great (there are tools or machines to produce most any intricate shape)
Size Range: Great-Limited only by machine capability
Sheet Thickness: N/A
Tolerance: +/- 0.001" and less
Draft Angle: N/A
Radii: square corners possible - practically and good design requires radii if possible
Surface Finish: 16 rms (better with grinding, reaming, burnishing)
Tool Cost: Ranges from Low to Medium (complicated parts may require more expensive fixturing, including dedicated systems; broaches can be expensive)
Opt. Lot Size: Any size, but larger lots more economical
Dir. Labor Cost: Medium (Complicated parts can be High)
Finishing Costs: Low (depends on material and ultimate use)
Scrap Costs: Low (recycleable)
Design Features
- Greatest variety of machinery of all metal working processes
- Nearly any shape can be made, but could be labor intensive
- Excellent tolerances and surface finishes obtained
- Required secondary process for most other processes
- Machinery and tools exist to work almost any metal or any other Engineering material
Material: Steel, Aluminum, Brass
Process: Lathe Tuning
Complexity: Limited to circular profiles
Size Range: Round stock, limited only by machine capability
Sheet Thickness: N/A
Tolerance: +/- 0.001" or less
Draft Angle: N/A
Radii: square corners can be made, but good design and part strength requires some radius
Surface Finish: 16 rms (better with secondary grinding)
Tool Cost: Lowest of all metal working methods
Opt. Lot Size: Any size, but larger lots more economical, especially with computerized turning equipment
Dir. Labor Cost: Medium (Low with automatic equipment)
Finishing Costs: Low
Scrap Costs: Low (recyclable)
Design Features
- Lowest cost tooling of any production method
- Sometimes poor material utilization
- Excellent tolerances and surface finishes obtained
- Complex round shapes can be made
Material: Steel, Aluminum, Copper, Alloys
Process: Blanking, Forming, Drawing sheet thickness parts. Formed shapes with progressive dies
Complexity: Very good to blank, form angles, punch holes, draw shapes and coin
Size Range: Great, but limited to sheet material
Sheet Thickness: Up to average .250"
Tolerance: +/- 0.003"-holes and edges; +/- 1°-formed angles
Draft Angle: N/A
Radii: Minimum 1" thickness, but near 0° with correct material
Surface Finish: 63-125 rms (mill finish) (smooth paintable or plating surface)
Tool Cost: Low (simple parts), Medium (complicated parts), High (drawn parts), Plastic injection molding = 1.00
Opt. Lot Size: 1 - 1,000,000's
Dir. Labor Cost: Medium
Finishing Costs: Low-Medium
Scrap Costs: Low (recycleable)
Design Features
- Best economy if simple stamping
- Utilization of material may not be very good
- Progressive dies raise tooling costs
- Drawn Parts require higher tooling costs
- Edges can be smoothed by secondary operations, if required
- Tooling cost is relative to the number of dies required and pieces needed
Material: Steel, Aluminum, Copper
Process: Precision stamped blanks in one operation without fractured edges. Eliminates secondary operations such as shaving, reaming, grinding by using a triple action hydraulic press
Complexity: Limited to blanking, punching, and some forming without burrs and sharp edges
Size Range: Good, but limited to sheet material
Sheet Thickness: Up to 0.500"
Tolerance: +/- 0.003"-holes and edges; +/- 0.001"-formed angles
Draft Angle: N/A
Radii: Minimum 1" thickness, but near 0° with correct material
Surface Finish: 63-125 rms (mill finish) (smooth paintable or plating surface)
Tool Cost: Medium (dies are more complicated than regular stamping)
Opt. Lot Size: 1-1,000's
Dir. Labor Cost: Low
Finishing Costs: Low (less finishing required than stamping)
Scrap Costs: Low (recycleable)
Design Features
- Best economy if all blanking done in one operation
- Does not leave fractured edges as in the stamping operation
- Progressive dies allow some forming
- Utilization of material requires attention
Material: Iron, Steel, Copper, Bronze, Aluminum, Molybdenum, Tungsten, Tungsten Carbide
Process: Pressing a measured amount of pre-produced metal powder into a cavity (die) using large tonnage presses. The amount of powder and press forces are controlled to obtain the desired density and cohesion of the part.
Complexity: Considerable (Uniform thickness and symmetrical sections desirable, but many unique shapes can be made by working with the manufacturer)
Size Range: Most parts are less than 5lbs.
Wall Thickness: 0.040" minimum - Less is possible with special handling
Tolerance: +/- .001" to +/- .003" depending on material
Draft Angle: Normally not required
Radii: Generous radii and fillets make for economical tooling and good tool life, but sharp edges are possible
Surface Finish: Difficult to determine accurately because parts are porous, but 63 rms equaled easily
Tool Cost: Relatively High-tooling is subjected to high stresses
Opt. Lot Size: Moderate to High Volume required. Some parts economical at 1,000 pieces
Dir. Labor Cost: Medium
Finishing Costs: Low (all common finishing methods may be used)
Scrap Costs: Low (recycleable)
Design Features
- Alternate for some Castings, Machined Parts
- Net shape parts with any shape holes, bosses, chamfers, keys, keyways, tapers, countersinks, counterbores, undercuts, flanges and irregular shapes can be made
- Two parts can be joined
- Porous filters can be formed. Magnetic parts also formed
- Bearing materials can be oil impregnated for lubricity. Parts can be infiltrated with other materials
- Minimizes machining and scrap losses
- Close tolerances and good surface finish
- Produces metal of controlled porosity and density
- Produces large numbers of small parts more cheaply than by other techniques
- High strength parts may be a problem with this method
- Dissimilar materials may be combined homogeneously
- Refractory or Reactive metals can be fabricated
Material: Steel, Aluminum
Process: Bending of round, square, rectangular tubing into functional shapes. Hole punching and coping possible
Complexity: Limited
Size Range: Limited only by bending equipment
Sheet Thickness: All standard tubing walls
Tolerance: Depends on tubing diameter, wall thickness, length and complexity
Draft Angle: N/A
Radii: Limited by tubing material, diameter, and wall thickness
Surface Finish: Mill finish of tubing
Tool Cost: Low (most fixturing simple and fits existing bending tool)
Opt. Lot Size: Any size
Dir. Labor Cost: High, unless automated
Finishing Costs: Low (smooth finished part for paining or plating)
Scrap Costs: Low (recyclable)
Design Features
- Many furniture applications
- Excellent for frames of parts made of other material
- Special attention to radii
- Out of the ordinary bends can be made using special techniques
Material: Steel, Aluminum, Copper
Process: Forming functional shapes from varying wire sizes and materials
Complexity: Very
Size Range: Limited by wire size, strength, and rigidity
Sheet Thickness: N/A
Tolerance: Depends on length, wire dimension and compatability
Draft Angle: N/A
Radii: Limited by material and design
Surface Finish: Mill finish of wire
Tool Cost: Low (most fixturing simple and fits existing tools)
Opt. Lot Size: Any size, but more economical with larger lots
Dir. Labor Cost: High, unless automated
Finishing Costs: Low (smooth finished part for painting or plating)
Scrap Costs: Low (recyclable)
Design Features
- Pre-plated wire may be used to reduce finishing costs
- Excellent for special shapes or uses
- Can be made to conform many odd shapes
Material: Carbon Steel, Stainless Steel, Copper, Brass, Phosphor Bronze, Monel, Aluminum, Plastic, Galvanized Steel
Process: Fabrication of previously woven, molded, perforated, stamped, or etched wire cloth or mesh into shapes or forms as desired for specialized screening and filtering applications
Complexity: Considerable-mainly achieved by joining of various parts into an assembly. Applications in Aerospace, Automotive, Agricultural, Chemical, Textile, Medical, Mining, Energy, Good Processing, Paper Processing, Petroleum, Refrigeration and A/C industries
Size Range: Limited only by designers imagination and the machinery to work the materials
Sheet Thickness: .002 - .003" thickness stainless steel available
Tolerance: Finished Parts-generally +/-0.030" to +/- 0.060"
Draft Angle: N/A
Radii: As desired
Surface Finish: Determined by materials used (generally rms 63 or better)
Tool Cost: Low (mostly custom work with forming or machining tools required)
Opt. Lot Size: Any size (cost is greatly dependent on part complexity)
Dir. Labor Cost: Medium-High, unless automated
Finishing Costs: Low (minimal finishing required because of materials used)
Scrap Costs: Medium (disposal of some parts with several different materials in them may be difficult)
Design Features
- Filters can be made with large to micron filtering ability
- Used for straining, filtering, screening, flame, arresting, electrical and magnetic shielding, parts protection and many more
- Can combine or bond dissimilar materials and may have several different materials in one assembly
- Parts may be joined by solder, silver brazing, resistance welding, epoxy glue, or ultrasonic welding
- Many different weaves or meshes are available. Example: A 400x2800 Dutch weave stainless steel that looks and feels like fine natural silk fabric
- Making of filters and screens not possible by any other method
Material: Steel, Aluminum
Process: Any of the many welding processes
Complexity: Intricate shapes possible
Size Range: Great (plates and sheets of any size can be assembled)
Sheet Thickness: Minimum determined by process-very thin sheet is difficult
Tolerance: +/- 0.125" as welded - secondary machining required for accuracy
Draft Angle: N/A
Radii: N/A
Surface Finish: 60-125 rms (mill finish) - care must be taken to eliminate splatter
Tool Cost: Low (most fixturing simple, but some complicated and some automatic tooling)
Opt. Lot Size: Any size
Dir. Labor Cost: High, unless automated
Finishing Costs: Medium-High (secondary machining and stress relieving usually required)
Scrap Costs: Low (recyclable)
Design Features
- Excellent for prototype or small quantity parts
- Must be fixtured for repeatability
- Very large assemblies can be constructed
- Good for "one of a kind" parts
Process: Several DFMA (Design For Manufacture and Assembly) design guides and electronic programs are available for purchase and use DFMA is merely common sense married to some knowledge of assembly method
Method:
- Manual Assembly
- High Speed Automatic Assembly
- Robot Assembly
- PC Board and Related Types of Assembly
It is desirable to choose the assembly method as early as possible in the design process. The assembly method chosen depends greatly on the anticipated production volume, but some general values will apply to most methods.
I. General
- The assembly with the fewest parts is desirable: Parts = $ Cost
- It is obvious from this, that "fewer parts = less cost", especially if fasteners or fastening process are considered "parts"
- Design to incorporate fastening methods into the basic parts of the assembly
Consider:
- How will the assembly be used?
- What will be the use of environment? (Abuse, Stress, Climate)
- Avoid stresses at fastening points
- Try to make fastening points serve a functional purpose as well as fastening
- Are there enough fasteners?
- Are they of sufficient size and strength?
- Are they located correctly?
II. Manual Assembly
Design should consider:
- Can detail part/parts be cut, punched, formed, welded incorrectly?
- Will part/parts fit into assembly in more than one place or orientation? (ie. backward, upside down, opposite hand)
- Are parts self-locating? Design to self-locate
- Are parts self adjusting? Design to eliminate adjustments
- Can hinges, latches, threads, studs, slots, tongs be incorporated into detail part/parts?
- Can "snap together" fits be used?
- Is assembly fixturing required?
- All sharp edges removed?
- Minimize Assembler operations
- Minimize Assembler decisions
III. Automated or Robot Assembly
Consider machinery to be used:
- Does machinery exist?
- Will machinery have to be designed and created? What type?
- How will part/parts fit into machinery?
- Interface with machinery is major design effort
- Incorporate fixture points and fastening into detail parts
Materials:
- All steels (except stainless steels which are generally rust resistant) and irons need a protective coating to prevent rust (oxides) from forming
- If the part being considered is decorative or an appearance part, then a coating which performs both functions may be desirable
- Aluminum, copper & copper based alloys, magnesium, and zinc will not rust, but oxides will form on their surfaces over time and polishing may be necessary to restore them to their original finish. Some additional coating may be considered to eliminate maintenance of the finish if the part is used in a decorative application.
Process
Chrome Plating: Bright on Satin finishes - Appearance and functional uses
Nickel Plating: Bright on Sating finishes - Appearance and functional uses
Zing Plating: Bright (blue) zinc - Appearance and functional uses
Cadmium Plating: Good protective finish, not available in USA any more, but still used in Europe and Asia
The following are mainly rust preventers, but can have some appearance qualities:
Black Oxide: Must be oiled to maintain rust proofing
Phosphating: Must be oiled to maintain rust proofing
Coloring:: Steel or Iron may be finished in Bluing, Blue-Black, Gun Metal, Coppering, Graying, Mottled, Browning, and Bronzing. Most must be oiled to preserve finish and rust proofing. Brass may be made from Yellow to Orange, Black, Silver, Green and White. Once finished, must be lacquered to preserve finish
Anodizing: Coloring and Hardening process for aluminum and magnesium. Colors may be Black, Blue, Green, and Gold with excellent appearance. Hard Anodizing is used for surface hardness
"E" coating: May be used on nearly all metals. Produces a bright, black, durable, rust-proof finish (ultra violet sensitive)
Painting: Several methods for nearly all metals with powder coating being the ultimate in protection and appearance
Polishing: Several methods for materials using different polishing medium and a complete range of luster
- Additionally, most metal parts may be impregnated with substances which will impart lubricity, pressure tightness, and rust protection
- Plasma spraying with other materials will add these some properties in addition to surface hardness and appearance improvements