A pneumatic orbital sander for composites uses around 300 to 400 l/min at 6.3 bar, and it runs continuously: it counts in full, with no reduction for the air receiver. Three sanders working together therefore need around 1.7 m³/min with the margins, which points to an 11 kW 4-in-1 screw compressor such as the K 110. The dust, meanwhile, must be extracted at source and kept well away from the compressor's air intake.
Why sand composites with compressed air?
Air sanders are light, compact and do not heat up in the hand. They stand up to hours of overhead work under a fuselage or a fairing. They have no electric motor in contact with the dust, which matters with carbon dust, since it conducts electricity. And many models have a built-in extraction port, for a central extraction system or a mobile extractor.
Composites are sanded at several stages:
- Preparation for bonding: abrading the surface so an adhesive or resin will key.
- Repair: removing damaged plies in steps or as a scarf before rebuilding the laminate.
- Finishing: flatting a primer, preparing for paint.
- Trimming and deburring of parts fresh from the mould, often with die grinders and belt sanders.
How much air does a composite sander use?
As a rough guide, at 6.3 bar:
| Tool | Indicative consumption |
|---|---|
| 150 mm orbital sander | around 300 to 400 l/min |
| 75 mm orbital sander or small angle sander | around 200 to 300 l/min |
| Belt sander, trimming die grinder | around 300 to 450 l/min |
| Dust-off blow gun | around 150 l/min |
Each tool's manual is the reference. One point to check: some sanders with built-in extraction use compressed air to create the suction themselves, by venturi effect. They then use more air than a sander connected to an electric extractor. Our article on orbital sanders in the body shop gives further reference points on these tools.
How do you work out the air flow for a composite sanding shop?
Take a composite parts repair shop: three operators sanding, with one shared blow gun for dusting off before bonding.
- Three sanders, continuous: 3 × 350 = 1,050 l/min, counted in full.
- One blow gun, in bursts: 150 l/min counted at half, so 75 l/min.
- Subtotal: 1,050 + 75 = 1,125 l/min.
- 25% safety margin for leaks and wear: 1,125 × 1.25 = 1,406 l/min.
- 20% expansion margin: 1,406 × 1.2 = 1,688 l/min, or 1.69 m³/min.
The K 110 delivers 1.7 m³/min at 8 bar: it covers this shop, but with no spare capacity. If the sanders use venturi extraction, or a fourth station is planned, choose the K 150 at 2.2 m³/min. For a single operator who sands now and then, the K 75 at 1.1 m³/min is more than enough. Our configurator does this calculation with your own tools.
Why a screw compressor rather than a piston compressor for sanding?
A piston compressor is designed for intermittent use. A sander running all day keeps it working without a break: it overheats, its efficiency falls and more oil passes into the air. A screw compressor, on the other hand, is built to run continuously. With the variable speed of the S and K series, it adjusts its speed when an operator stops to inspect the part. See piston or screw compressor.
How do you protect the compressor from composite dust?
Composite sanding dust is very fine. It stays in suspension and ends up settling everywhere, including on the compressor if it sits in the workshop. Three consequences:
- The intake filter clogs quickly. The compressor draws in less air, runs hotter and delivers less.
- The cooler gets fouled. Dust sticks to the oily fins, the temperature rises and the compressor can trip on a fault. See compressor overheating.
- Carbon dust is conductive. On terminal blocks and circuit boards, it can cause faults.
The solution: install the compressor in a separate room, with an air intake on the clean side of the building. If that is not possible, partition it off and check the air filter far more often than the standard interval. Our article on the compressor room gives the ventilation rules.
How do you organise dust extraction?
- Extract at source. Sanders with perforated pads connected to central extraction or a mobile extractor. This is the most effective measure, well ahead of general ventilation.
- Limit blow gun use. Blowing dust puts it back into suspension. To clean a part before bonding, vacuuming is preferable; the blow gun is for the final touch, with dry, filtered air.
- Clean the dust extractor filters. Bag or cartridge filters on dust extractors are often cleaned by pulses of compressed air. That flow adds to the workshop's demand. See our article on pulse cleaning of bag filters.
- Assess the explosion risk. Some resin or carbon dusts can be combustible. Assessing any ATEX risk, and choosing the equipment that follows from it, is done with your health and safety adviser and the dust extractor supplier.
What air for sanding before bonding?
For sanding itself, dry air is enough. But the blow gun that dusts off a surface before bonding or painting must leave neither water nor oil behind, or the adhesive will not take. Feed it from a point fitted with fine filters and an activated carbon filter, with no lubricator on the line. The 4-in-1 compressors in the K series dry and filter the air at the outlet; as our compressors are oil-lubricated, fine filtration at the point of use captures the remaining carried-over oil.
Find every use of air on our page on the compressor for aerospace, and send us the list of your sanders with a quote request.
For your trade: Compressor for aerospace, aircraft maintenance and subcontracting.