True, insufficient protection from sunlight and glare will cause unstable readings. Whilst we have protective covers, severe conditions outdoors will limit laser use to a night operation. We would normally be able to machine high points during the day and precision machine at night only when this occurs. Note high temperatures during the day always limit outside machining due to thermal distortion.
We have machined up structures over 30metres in diameter (100ft), the most recent being a radio telescope base. We have had many projects where large volume of metal removal has been required (over 10 Ton). Our rim cutting technique enamors roughing to be carried out at over 1 ton per shift.
In some instances we can be machining a circular structures within 6 hours on arriving on sire. This can include Blast Furnace lip rings and slew ring surfaces. When lifting equipment is immediately available it is rare for SLM not to be able to start machining after 12 hours on site even on very large structures.
A scanning laser spins a fixed beam such that the beam in effect creates a flat plane. A target supported on a surface being surveyed must be placed such that it is looking at the laser source. The target, by means of a readout can then measure the differential in readings from various points on the surface being surveyed. Thus flatness information can be obtained for as many points as required. An absolute reading of distance from the surface to the laser plane is not obtained, but specialist laser equipment can allow this to be measured.
Typically at 15metres (45ft) distance 0.02mm (0.001") with a resolution of 0.01mm (0.0005") under good atmospheric conditions.
The refractive index of air changes with temperature. If air is subject to different temperature layers then the light beam will bend as it travels from one temperature layer to another. This effect is increased with increasing humidity. The solution is to mix the air up with fans and to have the readout average more readings before displaying. This effect also applies to optical instruments.
The client may witness an on site calibration check of the scanning laser. Also placing a shim under the laser target magnetic base will change the reading by the thickness of the shim. A very simple demonstration.
The machines will tolerate severe height changes with little effect on the final flatness. A second cut after weld removal will be perfectly flat.
The components are placed on trolleys in the container. On site extensions are placed on the ground allowing the trolleys to be tolled clear of the container giving both crane and forklift access.
With crane availability SLM can comfortably assemble within in the time stated in our proposals. Normally one shift to be assembled on your work piece.
For large circular machining projects, the component must be rigidly supported to a solid foundation. Vibration and movement relative to the foundation should be avoided. By supporting on say timber cribbing, the structure can defect under the weight of our machine causing errors. The support posts should be steel or other rigid materials.