The manufacturing process for a casual T-shirt with a blazer can vary depending on the specific materials, design, and production methods used. However, here is a general overview of the typical steps involved:

1. Design: The first step is to create a design for the T-shirt and blazer. This can be done by a fashion designer or a team of designers.
2. Material selection: The materials used for a casual T-shirt with a blazer can vary widely, but are often made from cotton, polyester, or a blend of these materials. The specific materials chosen will depend on the desired look and feel of the garments, as well as their performance characteristics such as breathability, stretch, and durability.
3. Cutting: The fabric is cut into the desired pattern pieces using a cutting machine or by hand. For a T-shirt, the pattern pieces may include the front and back panels, as well as any necessary details like sleeves or a collar. For a blazer, the pattern pieces may include the front and back panels, as well as the sleeves, lapels, and pockets.
4. Sewing: The pattern pieces are then sewn together using a sewing machine. This includes stitching the seams, hemming the edges, and adding any necessary details like buttons, zippers, or pockets.
5. Finishing: After the garments are sewn together, they undergo a finishing process to smooth out any rough edges and ensure that all seams are securely attached. This can include pressing with a steam iron to remove any wrinkles and give the garments a polished look.
6. Quality control: Once the T-shirt and blazer are finished, they undergo a quality control process to ensure that they meet the desired standards for fit, construction, and overall quality.
7. Labeling and packaging: The final step is to label the garments with any necessary information, such as size and care instructions, and then package them for shipment to retailers or customers.

Overall, the manufacturing process for a casual T-shirt with a blazer can be complex and involve multiple steps, but attention to detail and quality control are essential to ensuring that the finished products are comfortable, stylish, and of the highest quality.