Chemically Bonded Sand Questionnaire_S22 - Dean Berger
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California Polytechnic State University, San Luis Obispo *
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Course
141
Subject
Mechanical_engineering
Date
May 4, 2024
Type
Pages
4
Uploaded by AgentField11890
IME 141 –
Chemically Bonded Sand Questionnaire_S22 1 Module 2. Chemically Bonded Sand Mold Casting Study Guide Questionnaire Transmission case casting
Objectives: 1.
Describe three types of chemically bonded sand binder systems and how they work. 2.
Choose an appropriate alloy given mechanical design requirements and alloy mechanical properties. 3.
Describe how three rigging methods help minimize defects in a casting. 4.
Describe the optimum part orientation relative to the mold given the locations of key part features in a large casting. Introduction Chemically bonded sand systems are those which do contain water as a principal component of the binder. These types of binders are distinguishable in several ways, but primarily they can be characterized as having long shelve lives and producing relatively little gaseous products when contacted with molten metal. Compared with water-containing binder systems such as green sand, benefits include greater flexibility in manufacturing, improved surface finish, and they can be used as cores to create internal features in the castings. A key tradeoff is that the sand is not as easily re-usable as green sand. Typically, to reuse chemically bonded sand after molding, a thermal reclamation process must be employed to oxidize and remove the binder. Frequently, chemically bonded sand is employed for cores and green sand used as the outer mold material. Chemically Bonded Binder System Types There are three primary categories of chemically bonded sand binders: 1.
Ambient Temperature curing types (also known as Air Set, Self-Setting, or Warm Box process) –
The sand is coated with 2- or 3-part binder system that cures in a known time period (e.g., 10-minute epoxy resin). The curing reactions are typically slightly exothermic, henceforth the name Warm Box.
IME 141 –
Chemically Bonded Sand Questionnaire_S22 2 2.
Gas or Vapor curing types (also known as Cold Box process) –
The sand is coated with a resin that cures by activation with a gas or vapor. As the gas expands upon release from a compressed gas cylinder, it absorbs heat and cools the surroundings, henceforth the name Cold Box. 3.
Thermally curing types (also known as Hot Box or Shell Sand process) –
The sand is coated with a heat-
activated resin that cures only with elevated temperature (~500F). Core Blower method
: resin-coated sand is forced upward in an airstream through a hole in the bottom against the heated core box pattern for a period. Shell Sand method
: the pre-heated pattern is placed over resin-coated sand in a hopper. The assembly is then inverted allowing sand to fall onto the pattern and rest for a period. In both methods, as heat transfers through the sand mass, the resin is cured to desired thickness forming a bonded sand shell. Once the shell is formed, the airstream is halted or the assembly inverted again, and the uncured sand returns to a hopper. Hollow cores can be made this way, reducing their cost compared to solid cores. Resources The following is a table of resources and links to assist with this learning module and for answering the study questions below. Resource Description Link Canvas page in Module 2 Intro to sand and binder systems Intro to Sand and Binder Systems Case Study: Transmission Case for the Amphibious Vehicle Interactive Case Study (Link to American Foundry Society) Case Study: Transmission Case for the Amphibious Vehicle Video: Shell Sand Process Animated Video (1.5 min) Video: Shell Sand Process Study Questions The questions below are for practicing concepts around chemically bonded sand systems and its application in a relatively large industrial metal casting example presented in the case study: Transmission Case for the Amphibious Vehicle
. You may write or type answers directly in this document, but you must save as a .pdf before uploading to submit to Canvas. The due date for this assignment is Saturday of week 4 at 11:59pm.
We will build upon these concepts throughout the term with in-class discussions, discussion board posts and lab projects. It is important to practice articulating your ideas using relevant terms and concepts. The quality of your responses is assessed based on your clearly answering all parts of the questions using appropriate casting terminology. Please use the rubric below as a guide.
IME 141 –
Chemically Bonded Sand Questionnaire_S22 3 Study Guide Questionnaire Rubric Criteria Rating Pts Answers all parts of the five questions. 5 pts Meets Requirements 3 pts Needs Improvement 0 pts Not applied 5 pts per question Answers five questions clearly using casting terminology. 5 pts Meets Requirements 3 pts Needs Improvement 0 pts Not applied 5 pts per question Total Points: 50 Please answer questions clearly and consider including examples that support your ideas. 1.
List three chemically bonded sand binder systems and briefly describe how they function. Identify the binder system employed in the transmission case study and discuss why it was chosen. The three chemically bonded sand binder systems are Ambient Temperature curing types, gas or vapor curing types, and thermal curing types. Ambient Temperature curing function is that sand is coated by a 2 or 3 part binder system which then the reaction creates the type of curing. Gas or vapor curing is the use of gas which is heated and cooled to produces the process of a Cold Box. Thermal curing is just like a hot box in which temperatures are well around 500 C. The transmission case study chose the binder system of “
no-bake
”
in which the company chose this type of binder system to be able to make an exact design that would also fit the budget to make the cast which is called “
mold design
”
. Also, it is similar to green-sand which is a process that is very good at making exact replicas after one cast called gating systems. 2.
In the case study, three alloys were compared against the mechanical property requirements for the transmission case. Identify the alloy chosen and discuss why you think it was selected for the application. In the case study it was chosen to use aluminum as the chosen alloy. They selected aluminum is that it is reinforced with Silicon Carbide particulate has superior elastic modulus, strength, and wear resistance compared. Now that the aluminum has a wall of thickness and lots of resistance to heat the company made the choice of an alloy that meets all check marks. 3.
In the case study, three mold designs with differing parting line placement and part orientation were discussed. a. Describe one or more factors considered in choosing the parting line
location a large casting. The factors of considering the parting line of a large cast like in the case study is to make sure no parts get caught or stuck in the mold. One factor that should always be taken into account is to make sure the parting line is the largest circumference of the object to not cause damage. b. Describe two considerations made in deciding the optimum part orientation
in the mold. The two considerations made in deciding the optimum part orientation is the surface finish and the consideration of the flow which is involved with cooling.
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IME 141 –
Chemically Bonded Sand Questionnaire_S22 4 4.
In the case study, rigging design was shown to help ensure clean metal enters the mold cavity in a smooth, non-turbulent fashion. List three rigging system features employed in the case study and briefly describe how each function to improve casting quality. One of the rigging designs didn
’
t allow the transmission to be produced by welding, but by casting due to the complexity and precise measurements that are need in the engine. The “
no bake
”
casting method is very closely related to green-sand which makes exact molds that can used many times which improves productivity. The last system was the machining process being cost-effective which was the use of alloy like aluminum being cheap and the material the company is looking for. 5.
In the case study, gating system design considered two options for in-gates. Which option was chosen and why? The two options for in-gates were five in-gates on the side or three in-gates. The option that was chosen by the company was the five in-gates due to there being more in-gates to make the process smoother. Plus, the walls are thin which makes the three in-gates option might cause misruns and waste much more time then the five in-gates.