Today I will be writing about the project that me and 3 of my friends made in the final year of my diploma in Mechanical Engineering back in 2013!
So, have you heard about casting? Well, its a process that involves rapid cooling of molten metal into whatever object you want. The casting process involves 3 major steps : Melting the metal/alloy in a furnace, Pouring it into a specially crafted mold of sand and finally allowing it to cool and thus, solidify gradually. Our project dealt majorly with the second step i.e. Creating the mold.
Creating the mold in actual life requires making a “Pattern” or an exact copy of the object you desire to create. This is generally made of either wood, plastic or metal. This has to be placed into a “Mold box” filled with sand, to make a negative impression of the object. Finally, the liquid metal will be poured into this cavity and allowed to solidify as explained above.
Now, what we made was a semi-automatic machine to make this mold. The sand inside the mold has to be hardened so that when you pour the molten metal into the cavity inside it, it does not get warped or misshaped.
A Jolt-Squeezer machine is the machine used in the casting industry to manufacture the molds for casting. The machine generally uses high pressure hydraulics to achieve the necessary forces required to compact the sand within the mold box.
Our machine utilised two basic processes, Jolting and Squeezing to accomplish this. Jolting is the process of rapid to and fro movement of the sand filled mold box. Squeezing is the process of high pressure compacting of the sand in a single stroke to harden the sand and ultimately prepare the mold. Keep in mind that both these processes are performed with a pattern enveloped within a sand-filled mold box.
So, this is how our machine looked like.
The main Structural parts of the machine were
- Squeeze Plate Assembly : This assembly compacts the sand during squeezing.
- Movable Arm : The upper arm which can be moved about the column to facilitate easy loading and unloading of the mold box
- Column : This massive column holds the movable arm and the squeeze plate assembly in place.
- Grab Bolt : This bolt joins the movable arm and the column while allowing free movement of the arm.
- Base: This is the component at the bottom which holds the column and the cylinders in place.
The main Functional parts of the machine were :
- Main Cylinder: This is the cylinder providing the squeezing movement
- Squeeze Piston: This reciprocates in the main cylinder
- Bottom Plate : This has multiple ports machined within to act as air passages
- Jolt Piston : This is the piston which reciprocates to provide the jolting movement
- Jolting Table : This holds the pattern and mold box in alignment
- Guide Posts : The guide the reciprocating jolt piston and prevent rotation of the jolt plate
- Jolt Plate : This is the plate on which the pattern is attached
- Pattern : This is the negative imprint of the cavity required.
The Jolt Piston
The Squeeze Plate assembly
The Jolting movement was carried out by the rapid traversing of the jolt piston and the jolt plate. The rapid movement was achieved by controlling the airflow through machined ports within the piston and the surrounding cylinders. The piston tended to rotate within the cylinder which we constrained using two guide posts, housed within the main cylinder.
The main purpose of carrying out Jolting is to cause the sand to spread evenly within the mold box such that it completely envelopes the pattern.
The Squeezing motion was achieved by lifting the entire mold box with the pattern inside it using a bigger piston and cylinder arrangement in one powerful stroke.
Squeezing completes the hardening procedure of the sand. The addition of a hardening agent in the sand initiates the hardening procedure when jolting is done. The hardening process is in reality an intricate chemical reaction which involves combination of the hardening agent with water and sand. The squeezing motion causes forced compacting of the sand, forming the required pattern cavity in the process.
Here’s a video of our machine in action!
Here’s the cavity that we obtained, using our machine.
To obtain the required flow of air, we used precisely machined ports which ran through the concentric pneumatic cylinders. We used a reciprocating air compressor to get the adequate pressure that was required to lift the weight of the pattern and the mold box. The controlling of air flow called for a pneumatic circuit which we designed and made using manually operated direction control valves, a pressure gauge and pneumatic hoses.
- Jolting Load : 42.67 kg
- Squeezing Pressure : 29.4 Pa
- Jolt Plate size : 402 mm x 242 mm
- Squeeze Stroke : 90 mm
- Net weight : 246.52 kg
This project was a great way for us to learn about manufacturing processes and pneumatic circuitry. We got ourselves really great grades for this and we learnt a lot!
I would really like to thank my group members, Parth Gandhi, Dinesh Rawal and Kunal Mehta for their great contributions in this project. It was an honour to work with you guys on this!
Also, I would like to thank Mr. John and his colleagues from L.S. Engineering Corporation for their valuable insights on this project. They are the leading manufacturers and retailers of the actual machine here in Mumbai. This project wouldn’t have been possible without them.
Hope this post was interesting! Check out some of the links below to learn more about this wonderful machine.
References and links:
- Casting :
2. Jolt Squeezers :
- L.S. Engineering website : http://www.foundrymachineindia.com/
- L.S. Engineers’ actual working machine https://www.youtube.com/watch?v=BW7NupDyyKE