A one-head big size embroidery machine with an open frame refers to a single-head embroidery machine that is designed with a large working area and an open frame construction. Here are some common characteristics of such a machine:

1. Large Working Area: The embroidery machine is equipped with a spacious working area that allows for stitching designs on larger fabrics or garments. The size of the working area may vary depending on the specific model, but it is designed to accommodate larger embroidery projects.

2. Single Head: The machine features a single embroidery head, which means it can stitch one design at a time. This configuration is suitable for smaller-scale or custom embroidery production.

3. Open Frame Construction: The machine has an open frame design, which refers to the absence of a traditional closed enclosure around the embroidery head. This allows for easier access to the working area, simplifies material handling, and provides more flexibility in maneuvering larger items.

4. Embroidery Digitizing and Control: The machine is typically equipped with software and controls that enable embroidery digitizing and design management. This allows users to import, edit, and adjust embroidery designs to suit their specific requirements.

5. Multi-Color Stitching: The machine is capable of stitching designs with multiple colors. It can automatically change the thread colors during the embroidery process, allowing for intricate and colorful designs.
   

6. Thread Tension Control: The machine features thread tension control mechanisms that ensure even and consistent stitching quality. Proper thread tension is crucial for achieving clean and professional embroidery results.

7. Automatic Thread Trimming: The machine may have an automatic thread trimming feature, which cuts the threads automatically at the end of each stitching sequence. This helps save time and improves overall efficiency.

8. User-Friendly Interface: The machine is designed with a user-friendly interface, often featuring a touchscreen or control panel. This allows operators to easily navigate through various settings, select designs, adjust parameters, and monitor the embroidery process.

9. Compatibility and Connectivity: The machine may offer compatibility with various embroidery file formats, allowing for easy importing and exporting of designs. It may also have connectivity options such as USB ports or network connectivity for seamless transfer of embroidery designs.

10. Precision and Durability: The machine is engineered to deliver precise and high-quality embroidery results. It is built with durable components and materials to ensure long-term reliability and performance.