Design & Process Guidelines

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When designing a casting, active participation should take place between the Design Engineer, the casting producer and the machining source. Meloon Foundries LLC does this through direct contact with the casting buyer.

Aluminum Alloys | Copper Base Alloys | Casting Designs | Process Guidelines | Rapid Prototyping

Tolerances and Wall Section Considerations

The chart establishes general guidelines, the type of metal and other variables that will affect the casting cost directly linked to the process.

Our Processes

Other Processes

Green Sand Molding

No Bake Molding
(Chemically Bonded Sand)

Permanent Mold Cast Die Casting Ceramic & Investment Casting
Tolerances, inches +/- .030 in. +/- .030 in. +/- .050 in. +/- .015 in. +/- .020 in.
Relative Cost in Quantity Low Medium High Low Lowest Highest
Relative Cost for Small Number Lowest Medium High High Highest Medium
Permissible Weight of Casting Oz – 1500 lbs 5 – 2000 lbs. 100 lbs 75 lbs. Oz – 100 lbs.
Thinnest Section Castable, Inches 1/10 in. 7/32 in. 1/8 in. 1/32 in. 1/16 in.
Relative Surface Finish Fair to Good Fair to Good Good Best Very Good
Relative Ease of Casting Complex Design Fair to Good Good Fair Good Best
Relative ease of Changing Design in Production Best Good Poor Poorest Fair
Range of Alloys that can be Cast Unlimited Unlimited Aluminum-base and Copper-base preferable Aluminum-base preferable Unlimited

Pattern or Tooling

A significant variable in the construction of a pattern is the determination of the shrink factor. The shrink factors vary for different metals and also the configuration of the part. The number of impressions, the gating system, the process or methodology will affect the casting cost. This is better left to the foundry and pattern maker to determine.

Aluminum Alloys

The chart provides typical mechanical properties for aluminum alloys and copper base alloys commonly cast by Meloon Foundries.

Alloy Temper Tensile Strength (ksi) Elongation Typical Brinell Hardness
Ultimate Yield0.2% offset
319 F 27 18 2 70
SR319 F 31 27 1 70-80
355 F 23 12 3 65
355 T-6 35 25 3 80
355 T-51 28 23 1.5 65
356 F 24 18 6 40-70
356 T-6 33 24 3.5 70
356 T-51 25 20 2 60
443 F 19 8 8 40
535 F 35 18 9 60-90
713 F 32 22 3 60-90
ZA12 F 43 30 2 95-113
  1. Mechanical properties are dependent on the casting process
  2. Other and special alloys are available on request

Copper Base Alloys

Alloy (UNS No.)Tensile Strength (ksi)Yield Strength with
0.5% Extension (ksi)
Elongation in 2 in. (%)Hardness (BHN)
C8983337173050-65
C863001198318225
C86500712830130
C8720055253085
C87500673021120
C9030045213060-75
C9050045222575
C9070044222080
C9220040203060-72
C9270042212077
C95400853518140
C95800953825150
C9760040242075-90

  1. Mechanical properties are dependent on casting process
  2. Other and special alloys are available on request
  3. Bismuth is substituted for lead in above alloys – Alloys are lead free.

Additional information may be obtained by contacting Meloon Foundries or The Non-Ferrous Founders Society.

Casting Design

casting_design_big

A Between two points in same part of mold not affected by parting plane or core

Specified Dimension, in. Tolerances, in
Up through 6 +/- 0.030
Over 6 0.0300 +/- 0.003 in/in. over 6 in.

B Across parting plane. A-type dimension plus following:

Projected area of casting A1xA3 sq in. Additional tolerance for parting plane, in.
Up through 10 +/- 0.020
Over 10 to 49 +/- 0.035
Over 50 to 99 +/- 0.045
Over 100 to 249 +/- 0.060
Over 250 to 500 +/- 0.090

 

C Affected by core. A-type dimension plus following:

Projected area of casting affected by core,A3 x G sq in Additional tolerance for core, in.
Up through 10 +/- 0.020
Over 10 to 49 +/- 0.035
Over 50 to 99 +/- 0.045
Over 100 to 499 +/- 0.060
Over 500 to 1000 +/- 0.090
Over 1,000 consult foundry

 

D Dimension: Draft

Normally, a drawing does not show draft. Standard foundry practice is to “add” draft to the part. For the amount of draft required depends on design and type pattern.

E Allowance for finish

Maximum dimension, in. Nominal allowance, in.
Up through 6 0.060
Over 6 to 12 0.090
Over 12 to 18 0.120
Over 18 to 24 0.150
Over 24 consult foundry

 

Process Guidelines

It is important that the foundry and the casting purchaser work closely together in order for the casting producer to make an acceptable cost effective part. Producing a casting for the first time entails a certain amount of trial and error.

It is an experienced-based development process. The expertise and past experience with similar casting configurations provide a guideline for the initial production. Usually the more intricate the casting design and the more drastic the change in section thickness the less predictable the casting soundness.

This is why it is important to consider location of isolated heavy sections, uniform wall thicknesses and correct placement or ribs and junction design. Visual casting soundness many times is not sufficient to verify acceptability and machining the sample casting prior to production release is important.

Specifications

Over specifying can increase the cost of a casting appreciable. Proper alloy selection, welding permissibility, correct choice of temper, and final inspection criteria all figure into casting cost.

Under specifying leads in many cases to misunderstanding between the casting producer and the casting supplier. Castings that are designed for critical applications require specific quality criteria. Selection of material that does not meet environmental or mechanical properties frequently leads to poor casting performance.

New Jobs

What are the requirements of first run or sample castings?

  1. Is 100% casting layout required?
  2. What inspection standards are required: x-ray or liquid particle inspection?
  3. Tolerances and dimensions must be clearly legible on the raw casting and machined casting drawings?
  4. What received casting condition is specified? Is shot blasting,
  5. Is written sample approval requested?
  6. Surface finish, packaging or shipping requirements specified?
  7. Price, delivery and production quantities should be clearly defined.
  8. Casting certification critical to casting performance must be agreed to in the quotation. Mechanical and physical test must be specified.

Rapid Prototyping

Rapid Prototyping is the developing of a temporary pattern or tooling from a 3-D computer design. This temporary tooling reduces casting time from months to days. The computer model is used as the blue-print and its dimensions to produce a model. Any rapid prototype pattern that is durable enough to withstand green sand or no bake molding can be used. There are several rapid prototyping processes and the selection depends on the application.