CNC Auto Drainage System: No Production Stop, Stable Vacuum

Puyan Machinery customized a vacuum system for a precision manufacturing company to enable uninterrupted intelligent drainage and continuous production. In the CNC precision machining industry, vacuum adsorption fixtures are key to achieving high-precision positioning in high-speed milling, drilling, and other processes. However, the problem of cutting fluid, coolant, and compressed air condensate entering the vacuum piping along with the airflow has long been a challenge for many manufacturing companies. Recently, Puyan Machinery successfully delivered a CNC negative pressure automatic drainage system to a precision manufacturing company. With the Puyan single-stage vacuum pump PV100 as the core, combined with a 100L buffer tank, a 50L liquid collection tank, and a Puyan control panel, the system completely resolved the customer's continuous production challenges under liquid-carrying conditions.

Project Background: Cutting Fluid Backflow Causing Frequent Vacuum System Shutdowns

The customer primarily engages in batch processing of aluminum alloy, stainless steel, and engineering plastic parts. The workshop houses dozens of vertical machining centers and CNC machine tools, all using vacuum adsorption for workpiece clamping. However, as production load continued to increase, the original vacuum system presented the following serious problems:

• Cutting fluid backflow and accumulation: During CNC machining, large amounts of cutting fluid splash, and some liquid is drawn back into the vacuum system through suction cups and piping. Long-term accumulation leads to pipe blockage, pump chamber corrosion, and continuous vacuum degradation.
• Manual drainage requiring production stops: The traditional approach required dedicated personnel to stop the system and drain fluid every 2–3 hours, with each stop lasting 15–20 minutes. This accumulated to over 1 hour of downtime per day per machine, severely constraining production capacity.
• Drainage process affecting adsorption: Drainage required depressurizing the entire vacuum system, causing workpieces to lose holding force instantly – resulting not only in workpiece displacement and scrap but also posing a risk of tool collision.
• Vacuum fluctuations affecting machining accuracy: Without a buffer tank for pressure stabilization, accumulated liquid reduced the effective pipeline volume, exacerbating vacuum fluctuations, compromising dimensional consistency, and increasing the scrap rate.
• High maintenance costs: Accumulated liquid caused emulsification and degradation of the vacuum pump lubricating oil, significantly shortening oil change intervals and increasing pump maintenance frequency.

Puyan Solution: PV100 Vacuum Pump + 100L Buffer Tank + 50L Liquid Collection Tank + Puyan Control Panel

After an on-site survey, the Puyan Machinery technical team proposed an innovative solution combining "high pumping speed oil rotary vane pump + dual-tank separate liquid storage + intelligent drainage control system." This ensures vacuum stability while enabling automatic drainage without stopping production. The specific configuration is as follows:

1. Core Vacuum Source – Puyan PV100 Single-Stage Rotary Vane Vacuum Pump. The pump offers a pumping speed of 100 m³/h, an ultimate vacuum of 0.1–0.5 mbar, and a motor power of 2.2 kW. Featuring a single-stage oil rotary vane design with precisely optimized rotor and end-face clearances, it is insensitive to dust and moisture. The built-in high-efficiency oil separator ensures stable and reliable operation, supporting 24/7 continuous running to match the high-intensity production rhythm of a CNC workshop.
2. Dual-Tank Separate Structure – Buffer Tank + Collection Tank with Segregated Functions. Unlike traditional single-tank systems, this design separates negative pressure energy storage from liquid collection and drainage:
   • 100L Carbon Steel Buffer Tank: Acts as a negative pressure "reservoir," continuously supplying stable negative pressure to CNC machining centers, ensuring consistent and stable holding force at each workstation.
   • 50L Stainless Steel Liquid Collection Tank: Independent from the buffer tank, dedicated to collecting cutting fluid, condensate, and other liquids that enter the system with the airflow. A solenoid valve between the collection tank and buffer tank controls the connection, automatically isolating the collection tank during drainage to ensure buffer tank pressure remains unaffected.
3. Puyan Intelligent Drainage Control System. The collection tank is equipped with three sets of high-reliability solenoid valves, coordinated by the Puyan control panel:
   • Connecting valve: Controls the connection between the buffer tank and the collection tank
   • Vent valve: Introduces atmospheric pressure into the collection tank before drainage to release negative pressure
   • Drain valve: Controls the opening and closing of the drain port at the bottom of the collection tank

Detailed control logic:

• Initial start-up phase: The connecting valve opens, while the vent valve and drain valve remain closed. The vacuum pump evacuates both the buffer tank and the collection tank simultaneously. Once the preset vacuum level is reached, the connecting valve automatically closes, and the buffer tank independently supplies vacuum to the CNC machines.
• Normal operation phase: CNC adsorption uses the negative pressure stored in the buffer tank. The connecting valve opens intermittently and automatically, allowing accumulated cutting fluid in the buffer tank to flow into the collection tank by gravity. The buffer tank pressure is automatically maintained by the vacuum pump (intelligent pressure-holding function).
• Timed drainage mode: Users can preset the drainage cycle based on operating conditions. When the set time is reached, the control system automatically executes the drainage sequence – close the connecting valve to isolate the collection tank → open the vent valve to release negative pressure → open the drain valve to discharge liquid → close the drain valve and vent valve → reopen the connecting valve to resume evacuation.
• Manual drainage mode: Operators can manually trigger the drainage sequence at any time via the control panel with a single button, following the same process as timed drainage.
• Throughout the entire drainage process, the buffer tank maintains negative pressure, and CNC adsorption is completely unaffected.

The Puyan control panel integrates a PLC control system with intelligent pressure-holding (pressure fluctuation controlled within ±0.5%), intelligent start-stop (automatic control based on air demand), phase sequence protection, overload protection, audible and visual alarms, fault logging, and drainage history recording.

Project Results

The customer's production manager commented: "Puyan's vacuum system with intelligent drainage is extremely practical. Previously, we had to stop production every two to three hours to drain liquids – during rush orders, it was a dilemma. Now with the timed drainage set up, we hardly need to worry about it. The holding force on the machining centers stays rock solid, and we no longer have to worry about workpieces flying off during drainage. The drainage and fault logging features are also very useful, making equipment management much more standardized."

Why Choose Puyan Machinery's CNC Negative Pressure Automatic Drainage System?

Puyan Machinery specializes in vacuum pumps and custom vacuum systems. Our core strengths lie in on-demand customization (providing non-standard designs based on air volume, vacuum level, media, control requirements, etc.), our own brand with reliable quality, and rapid response (providing solutions within 24 hours). This CNC negative pressure automatic drainage system uses a dual-tank separate structure combined with intelligent drainage control, ensuring that CNC adsorption remains unaffected throughout the drainage process – completely solving the continuous production challenge under liquid-carrying conditions. Besides CNC machining, this series of systems is also widely used in semiconductor, lithium battery vacuum drying, food and pharmaceutical packaging, electronic component handling, shipbuilding, and other industries. If your plant faces issues such as insufficient vacuum, system instability, or the need for a new system, please contact Puyan Machinery for a customized solution.