Set Adjusting Additive and Admixture
For cement based or gypsum based product like mortar or concrete, set adjustment is so necessary, which is important for ensure the application time and early strength development. There are many types of product to change the initial and final setting time. In some case, Set Retarder is adopted to extend the setting for cement or gypsum including tartaric acid, citric acid, sodium gluconate etc. In other case, Set Accelerator is also critical to shorten the setting time and improve the early strength, such as lithium carbonate, lithium sulphate and calcium formate etc. CSA Cement, as fast setting cement, works as fast-setting admixture, which give excellent instant setting effect when used alone or combined with ordinary portland cement. Furthermore, in some fast-setting binder system, retarder and accelerator have to be added together to fine tune the hydration process.
Set retarder,cement retarder,gypsum retarder,set accelerator,early strength agent,tartaric acid,set adjusting admixture Shanghai Na Long Tech Co., Ltd , https://www.na-long.comSome Exploration and Testing of Hydrostatic Bearings in Grinding Machine Repairs
Hydrostatic bearings are widely used in various grinding machines such as the M210, M131W, 3160A, 2A710, and FYT10 diamond boring heads. These bearings are favored for their high precision, excellent rigidity, strong load capacity, and long service life without wear. With the development of CNC technology, hydrostatic bearings have also become essential in the spindle machining of CNC machine tools. Many static pressure grinders and diamond boring heads are in use, and during repair processes, several practical experiences and tests were conducted.
1. **Hole Saver Adjustments**
- **External Pressure Gauge Installation**: Replacing internal savers with external ones allows real-time monitoring of upper and lower chamber pressures, making maintenance more efficient. This setup enables regular cleaning and ensures better control compared to internal systems.
- **Optimal Savings Ratio (β)**: The theoretical value of β is typically between 1.2 and 1.5, with 1.25 being ideal based on experience. Precise adjustments are required for the spindle, front and rear bearing pads, including strict control over concentricity, roundness, and taper. The e-value (misalignment between the main shaft and bearing bush) is determined by the machine tool’s load to achieve the optimal β value.
- **Oil Chamber Flow Adjustment**: When the main shaft is not installed, the oil columns from each oil outlet should be observed and adjusted if necessary. For example, in a four-chamber system, the oil column height for the lower, left, and right chambers usually ranges between 20–25 mm, with small hole diameters between 0.25–0.4 mm.
2. **Film Reaction Issues**
- Hydrostatic bearings exhibit high stiffness, but some machine tools may show issues like "tiling," "pulling," or "pressure drop" during operation. These problems are often linked to the film layer. Common causes include plastic deformation of the film, slow response to load changes, and fatigue due to prolonged use.
- To address this, increasing the film thickness and using fatigue-resistant materials can significantly improve performance. A typical solution involves replacing a 1.4mm rigid film with a 4mm thick one, adding a 0.05mm tin foil paper to the cavity pad, and adjusting the spindle to be 0.05mm higher than the reference point. This ensures the spindle returns to its central position under cutting forces.
3. **Improving the Oil Supply System**
- In addition to coarse and fine filtration, other components of the oil supply system play a crucial role in maintaining hydrostatic bearing performance. Upgrades to the original system have been made to enhance reliability.
- **Pressure Monitoring**: Installing a pressure relay and gauge after the saver plate allows operators to monitor both chamber and inlet pressures. If the pressure difference exceeds a certain threshold, the system automatically stops to prevent locking. For example, if the inlet pressure is 2 MPa, the outlet pressure should remain between 1.2–1.6 MPa; if it drops below 1.2 MPa, the system halts immediately.
- **Digital Gap Measurement**: A gap of 0.04–0.05 mm exists between the main shaft and the bearing bush. By measuring the resistance in the oil, the gap size can be detected. One pole is connected to the main shaft, and the other to the bearing bush. This signal is sent to an alarm system and control amplifier, allowing the spindle motor to start or stop accordingly, preventing potential damage.
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Source: China Bearing Network | Date: April 6, 2014