To achieve optimal laser engraving results on slate, several key settings should be considered:

• Laser Power: For slate, a power setting between 30% to 50% is often effective. Higher power settings can cause excessive charring.
• Speed: Slower engraving speeds (around 200-300 mm/s) allow for better detail and more profound marking. Adjusting speed can help in controlling the depth of the engraving.
• Frequency: A frequency setting of 500-1000 Hz works well for slate, ensuring a smooth cut without excessive heat buildup.
• Focus: Proper focus is critical; ensure the laser is precisely focused on the slate surface to achieve clear and sharp engravings.
• Engraving Depth: Adjust your settings for your specific design; multiple passes may be necessary for deeper engravings, but be cautious about overburning.
• Cooling: Consider a cooling mechanism to prevent overheating, which can lead to undesirable results.

Remember to perform test engravings on scrap slate to fine-tune these settings for your specific machine and design requirements.