5. Replacing the laser tube
The laser tube is one of the main components of any laser engraver. The Speedy
uses for the 12, 25, 30 and 50W version Synrad tubes, and for the 100 W version a
Coherent tube. The 50 and 100W tubes are liquid cooled, all other tubes are air
cooled.
To make the tube fire it must be
- Connected to the power supply (48V for the 100W unit, for all other
machines 30V)
[On Synrad tubes this will be indicated with a green LED]
- Provided with a control signal (BNC connector, two for the 50W)
The control signal is a 5V TTL signal that comes from the main board.
[if there is a signal Synrad tubes will indicate this with an illuminated red
LED]
Additionally on the 100W machines the coolant velocity must be above 5.7 l/min.
All tubes have an integrated overtemperature protection. If the tube exceeds a
certain limit it is switched off to prevent a damage of the gas/electronics.
The following reasons might cause you to replace the tube:
• A too low laser power
• Fluctuations of laser power (typically jumps from 100% to 50% engraving
depth on a 25W unit, or from 100% to 75% on a 50W machine)
The frequency of these power fluctuations is low (e.g. every 5 minutes)
• Uncontrollable timing behaviour (high frequency effect).
This effect shows shifted start/end points of the pulses so that the image looks
frayed although the mechanics (of the motion system) and software
adjustment are OK.
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