designing feeding systems for investment castings.

by:Max Apparel     2020-09-17
Keeping a close eye on these 17 steps can simplify the mystery of designing a feed system for this precision casting method.
In any casting method, when the alloy is poured into the mold, it begins to shrink or shrink the volume when it cools and subsequently sets.
The foundry compensates for both volume shrinkage by providing the reservoir-feeders--
As part of mold cavity design.
The solution for the design of the complete feeding system includes the dimensions, shape, position and connection method of the feeding device with the castings and the materials used.
A method similar to sand casting can also be applied to investment casting.
The design of the feeding system for investment casting parts has changed because the melting, molding and pouring methods used by the Foundry are different.
However, some general guidelines in the feeding system design procedure can be followed.
A method is proposed to combine the concept of feeder size based on o Chvorinov rule with experimental, theoretical and practical data for the feeding system for investment casting.
Through this procedure, the digital-analog of direct and reusable feed systems of the appropriate size are calculated-Based on technology.
Modulus is the ratio of the volume of the casting to the cooling surface area (
Or part of the casting)or the feeder.
To show how the program can be used in practical applications, an example of investing in a cast clamping arm is included.
Casting Design 1.
Design modification--
Check the casting geometry to see if the freezing provides a directional cooling gradient towards the feeder.
Work with customers to make design modifications if needed to improve the temperature gradient of directional setting, the purpose of connecting feeder and quality control. 2.
Alloy Selection--
Designers usually select alloys from standard specifications and alloy manuals.
In order to meet the process requirements, designers and foundry workers must work together.
Numerical analysis is performed if several alloys are feasible. 3. Feeding system--
The modulus method is used to identify the quantity and position of the feeder from the casting design.
Select the appropriate gate and feed system.
The mesh consists of vertical and horizontal component frames that are attached to the pot and pattern.
Standard grids, improved grids, or feeder systems for rural networks can be designed.
I later made a detailed adjustment to the feeder position. 4.
Cut off and clean-
Check the casting design and the proposed feed system to ensure access to the feed during subsequent cut-off operations.
The attached ceramics and cores must be removed by proper cleaning.
Alloy properties 5.
Feeding properties--
Cooperate with the designer to make any necessary adjustments to the composition of the alloy (
Addition or dilution of alloy elements)
Improve feeding properties such as freezing range, co-crystal area and casting fluidity. 6.
Melting treatment--
Feeding behavior can be enhanced by affecting the freezing nucleus and growth behavior.
Prescribed test procedures for checking alloy melting quality control: Incubation, gas and inclusion control, alloy overheating and pouring temperature, and test rods for obtaining mechanical performance tests. 7.
Product quality--
Due to the mold material, the final casting quality is affected by the mold phenomenon, such as mold atmosphere, metal flow, cooling direction and speed.
The production of pores-
Free casting depends on the success of the entire feeding system.
Check the specified product quality control test (
Types of non-destructive or destructive testing procedures related to casting design, alloy and product applications used).
Mold Structure 8.
Plate making and assembly--
Check how the gate and feeding system affect mold and mold assembly.
Explore alternative methods for clustering patterns on the grid (
Location, direction)
Or create a favorable feed temperature gradient during mold preheating and allo pouring, while ensuring adequate cluster rigidity.
Keep in mind that while each casting is frozen separately, the entire grid acts as a cooling system. 9. Gating--
The gate system is selected to optimize the flow that benefits the feed temperature gradient, which will minimize the flow turbulence and maximize the feed pressure.
Explore the feasibility of horizontal, vertical and bottom gates.
While optimizing the gate system functionality, review the feed requirements associated with pattern assembly.
Design the gate and feed system by considering the flow and feed requirements together.
For grid systems, identify the grid part that acts as both feed and gate elements. 10. Mold materials--
Check if the standard mold, feeder wall material, mold manufacturing and preheating technology should be changed-
Using insulation and cooling technology-
Increase the feed temperature gradient. 11.
Feeding pressure--
When the flow channel becomes fine, the total feed pressure of the feed liquid flow is the vita of the final stage of the feed.
With the appropriate mesh design, the maximum benefits of atmospheric and metal static pressures of the incoming liquid can be obtained to eliminate the air holes.
Feed element size 12.
Number of feeders--
Using the knowledge in steps 2, 3, 6, 8, 9, 10, and 11, determine whether directional feed for the entire casting can be obtained from a single feeder.
Calculate the freezing modulus of the part that must be fed separately.
Excluding the calculation of all \"parasites\" sections (
Thinner casting parts, such as the boss, provided by thicker adjacent parts)
Attached to the feed parts.
Excluding non-cooling surfaces (
In the modulus calculation, the casting surface is not facing the mold.
For complex parts, the principle of shape replacement is applied. 13.
Shape and position of feeder-
Select the feeder shape and position from steps 2, 4, 8, 9, 10, 11, and 12.
For grid systems, verifying in Step 14 that the gate system elements involved in the feed flow will also comply with the freeze modulus rule. 14.
Standard feeder volume from freezing time--
Calculate feeder volume from: [M. sub. f]= k [center dot][M. sub. c].
Freezing modulus of castings ([M. sub. c])
, Obtained from Step 12, while the \"k\" value (
Modulus ratio)
Select from steps 1, 8, 10, and 11, and select the feeder shape from 13. 15.
Volume standard feeder volume--
Compare the feeder volume obtained from Step 14 with the feeder volume obtained from [V. sub. f]= [V. sub. c][center dot]([Beta]/[Eta]-[Beta]). [V. sub. c]
Is the total volume of all parts fed from a single feeder (including the parasite part; [Beta]is total (
Liquid and frozen)
Percentage of contraction; and [Eta]
Is the available feed liquid factor, such as the percentage of feed volume delivery generated under conditions 8 and 13. 16. Feeder neck--
Calculate the neck size of the feeder from [M. sub. n]= [k. sub. n][center dot][M. sub. c]. The value of [k. sub. n]
Select the neck shape from points 1, 3, 4, 6, 8 and 9. 17.
Feeding distance--
Verify from 3, 8, 10, 11 and 12 whether the required temperature gradient will be obtained to meet the required feed distance.
Practical guidelines for explaining these guidelines, fig.
1 shows the basic dimensions of the investment casting clamping arm.
Bronze alloy specified by customer with composition Cu 88%, Sn 8%, Zn 4%.
The shrinkage of the alloy is estimated at 6%.
At 18% of the bulk feed, the volume ratio (
Calculated by feeder volume/casting volume)is 0. 50.
This standard sets a minimum value for the feed size required to ensure sufficient volume in the feed liquid supply.
After dividing the casting into four parts and calculating the modulus, I see the arm and ribs set in front of the smaller, larger cylinder.
The feeder is needed to feed the large cylinder, which can feed the arms and ribs.
A separate feeder is needed to feed into the small cylinder because the thinner parts s2 and 3 cut off the feeder 1 pair of its feed.
To take advantage of the substantial taper in the arm and ribs, the component can be cast vertically.
In this direction, gravity provides the required pressure for feeder 1 (
And cylinder 1)
Feeding long arms (2)an the rib (3).
Feeder 1 is designed to feed three sections--
Large cylinders, arms and ribs.
Freezing is 1 than k. 2 and [M. sub. c]
The highest modulus in the Fed section is the first part ,[M. sub. f]= 14. 2.
D modulus of side bar feeder ,[M. sub. f]
= D/4, when the feeder is considered to be part of the grid, the two sides are not cooled.
So the side of feeder 1 or 8-
The charging weight of the alloy is 70 lbs (32 kg)
The yield of castings is 51. 4%.
Other alternative designs such as six
The block cluster is possible, and the optimal size of the feeder is installed again.
Can be based on the available casting equipment (such as the shell-
To melt.
For example, 8-
The workpiece cluster mold needs robot immersion to make the shell, and manual immersion is enough to make the fourpiece cluster.
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