A vacuum table can speed up workholding on a CNC milling machine considerably, or it can turn out to be an expensive mistake. When is the purchase really worthwhile? This guide helps you decide.
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How does a vacuum table work?
The principle is simple: a vacuum pump creates negative pressure under the workpiece. The air pressure (approx. 1 bar) presses the part onto the table surface from above.
The Components
- Vacuum panel: Perforated or studded clamping surface
- Vacuum pump: Creates the negative pressure
- Seals: Limit the vacuum area to the workpiece
- Valves/controller: Switch the vacuum on and off
The Physics Behind It
At 0.8 bar of negative pressure and an area of 1000 cm², the holding force is about 800 kg. That is more than enough for most machining operations.
Advantages of the Vacuum Table
Fast Clamping
The biggest advantage: place the workpiece, switch on the vacuum, done. In series production, this saves an enormous amount of time.
Full Accessibility
No clamping devices in the way. You can machine the entire workpiece, including cut-outs (with a spoilboard).
Even Pressure
Unlike with screw clamps or strap clamps, the pressure is distributed evenly. Ideal for thin materials that would otherwise deform.
No Clamping Marks
No pressure marks, no damage from clamping devices, which matters for visible surfaces.
Limits and Disadvantages
Not for Every Material
- Porous material: Wood, untreated MDF: air flows through and the vacuum collapses
- Small parts: A minimum area is needed for sufficient holding force
- Uneven undersides: The seal does not work
Investment Costs
A good vacuum system costs €500–2,500 depending on size and equipment. Consumables (sealing rubber) come on top.
Cutting Through Requires a Spoilboard
If you mill all the way through, you cut into the vacuum. Solution: an MDF spoilboard between the workpiece and the vacuum table.
When is a vacuum table worth it?
Yes, if:
- Series production: Many identical parts from sheet material
- Sheet processing: Mainly plastic, coated boards, composites
- Time-critical work: Fast changeover times matter more than investment costs
- Delicate materials: No clamping marks acceptable
No, if:
- Mainly wood: Solid wood in particular is too porous
- 3D parts: Complex shapes cannot be clamped flat
- Small parts: Problematic below about 100 cm²
- Rare use: For occasional work, the investment does not pay off
Vacuum Systems Compared
| System | Advantages | Disadvantages | Price |
|---|---|---|---|
| Plug-on vacuum module | Flexible, can be retrofitted | Limited size | €500–1,000 |
| Integrated vacuum table | Large area, stable | Permanently installed | €1,000–2,500 |
| Grid plate with suction cups | Very flexible | Less holding force | €300–800 |
Which pump for the vacuum table?
For CNC vacuum tables, side channel blowers have become the usual solution: they run dry and oil-free, and the impeller works without contact and with little wear, so they are designed for continuous operation on the milling machine. Typical models cover 0.2–7.5 kW and reach up to −440 mbar of negative pressure; their strength is the high volume flow (50–700 m³/h). You will find an overview in our side channel blowers category.
Sizing: How much pump power does the table need?
As a guideline, allow 0.5–1 kW per m² of table surface. For small tables, 0.25–0.7 kW is often enough; for around 1 m² of clamping area, models with 1.1–1.5 kW are common. If you want to clamp porous materials such as raw MDF or wood, plan for 2.2 kW or more, because leakage air constantly flows in through the material.
Dust Load: The Underestimated Factor
On a CNC milling machine, the pump inevitably draws in air containing milling dust, especially when cutting through or over uncovered suction zones. Fine dust clogs the impeller and valves. That is why a fine filter or a cyclone separator belongs in front of the intake: the cyclone removes most of the chips and dust before the air reaches the pump, which relieves the pump and the filter.
And what about rotary vane pumps?
Rotary vane pumps reach a higher ultimate vacuum, but they are oil-lubricated and need more maintenance in a dusty milling environment (oil changes, filter care). For vacuum tables on gantry mills, where a high volume flow matters more than the maximum ultimate vacuum, the dry-running side channel blower is therefore usually the more practical choice.
Material Suitability at a Glance
| Material | Vacuum suitability | Notes |
|---|---|---|
| Plastic sheets (PMMA, POM, etc.) | Excellent | Ideal application |
| Coated chipboard | Very good | The coating seals |
| HPL/laminate | Very good | Ideal application |
| Aluminium sheets | Very good | Smooth underside required |
| MDF (lacquered/coated) | Good | Only with a sealed underside |
| MDF (raw) | Poor | Too porous |
| Solid wood | Poor | Air flows through the fibres |
| Plywood | Moderate | Depends on quality |
Tips for Use
Use a Spoilboard
Place a thin MDF or HDF board between the workpiece and the vacuum table. You can then cut all the way through without damaging the vacuum table.
Optimise the Seal
- For smaller workpieces: place sealing rubber around the part
- For porous materials: seal the underside with tape or film
- Check the sealing rubber regularly for wear
Monitor the Vacuum
A vacuum gauge shows whether the vacuum is holding. If it collapses, something is wrong with the seal.
Allow a Safety Margin
Do not mill too close to the edge, because the holding force is weakest there.
Alternatives to the Vacuum Table
If vacuum does not suit your application, there are alternatives:
- T-slots with strap clamps: Flexible, for all materials
- Screws through a spoilboard: Simple, inexpensive, secure
- Double-sided tape: For light machining
- Hold-down system: Springs press down from above
The guide CNC Clamping Fixtures: Clamping Workpieces Correctly gives a systematic overview of which clamping device suits which workpiece, from the vice to the 4th axis.
FAQ: Frequently Asked Questions
Which vacuum pump do I need?
A dry-running side channel blower is the usual choice. As a guideline, allow 0.5–1 kW per m² of table surface; for around 1 m² of clamping area, 1.1–1.5 kW is common. Large tables need more power or several pumps. Details are in the section “Which pump for the vacuum table?”.
Which pump is suitable for high dust loads?
A dry-running, oil-free side channel blower with an upstream fine filter or cyclone separator. The cyclone removes chips and dust before they reach the pump. Oil-lubricated rotary vane pumps need more maintenance in a dusty milling environment.
How much vacuum is needed?
For workpieces that seal tightly, 0.6–0.8 bar of negative pressure is typical; more than 0.85 bar is technically difficult to achieve and usually not necessary. When clamping over a large area on a vacuum table with a side channel blower, a lower ultimate vacuum is enough (up to −440 mbar, i.e. approx. 0.44 bar), because the high volume flow compensates for leakage air through porous areas and uncovered zones.
Can I retrofit vacuum?
Yes, with a plug-on vacuum module. It is placed on the existing table and connected to a pump.
How large does the workpiece have to be at a minimum?
Rule of thumb: at least 100 cm² for a secure holding force in normal machining. More for heavy cutting.
BZT Vacuum Solutions
We offer various vacuum options for our gantry mills:
- Vacuum table modules: Can be retrofitted to existing machines
- Integrated solutions: Can be configured directly when buying a new machine
- Accessories: Pumps, sealing rubber, hoses
Conclusion: A Question of Application
A vacuum table is a worthwhile investment if the application suits it. With regular sheet processing of suitable materials, the investment quickly pays for itself through time savings.
Related Accessory Guides
Not sure whether vacuum makes sense for you? Describe your typical workpieces and we will check whether vacuum clamping suits your application.
Vacuum Technology at BZT
Our range of vacuum technology for CNC gantry mills at a glance:
- Vacuum tables: Various sizes for your machine
- Side channel blowers: dry-running vacuum pumps, 0.2–7.5 kW
- Entire vacuum range: Filters, hoses and accessories
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