Hypertherm HPR800XD Auto Gas Rev.2 - Manual (Page 131)

OperatiOn
HPR800XD Auto Gas – 806500 4-25
Additional improvements Additional improvements
Some of these improvements involve trade-offs, as described.
Piercing
The pierce delay should allow sufficient time to penetrate the full thickness of the material, but not so long that it allows
the arc to “wander” while trying to find the edge of a large pierce hole. As consumables wear, this delay time may need
to be increased. Pierce delay times given in the cut charts are based on average delay times throughout the life of the
consumables.
Using the “pierce complete” signal during piercing maintains the shield-gas pressure at the higher preflow pressure,
which provides additional protection for the consumables (for example: 30 amp O
2
/O
2
and 50 amp O
2
/O
2
processes).
The pierce complete signal must be turned off for processes with shield gas preflow pressures that are lower than the
cutflow pressures (for example: 600 amp and 800 amp processes).
When piercing materials close to the maximum thickness for a specific process, there are several important factors to
consider:
• Allow a lead-in distance that is about the same as the thickness of the material being pierced. 50 mm (2 in)
material requires a 50 mm lead-in.
• To avoid damage to the shield from the build up of molten material created by the pierce, do not allow the torch
to descend to cut height until it has cleared the puddle of molten material.
• When pre-piercing with the 400 amp O
2
/air process, the arc should be on for a minimum of 4 seconds or the
electrode may experience rapid wear. This 4 seconds allows the current to properly ramp-up and ramp-down
which is required for the long life process. A small torch movement may be necessary if the peirce time is less
than 4 seconds to keep the arc transferred to the plate.
• Different material chemistries can have an adverse effect on the pierce capability of the system. In particular,
high-strength steel and steel with a high manganese or silicon content can reduce the maximum pierce
capability. Hypertherm calculates mild steel pierce parameters with certified A-36 plate.
• If the system has difficulty piercing a specific material or thickness, increasing the shield preflow pressure can
help in some cases.
Trade-off: This may reduce starting reliability.
• Using a “moving pierce” or “flying pierce” (starting torch motion immediately after transfer and during the pierce
process) can extend the piercing capability of the system in some cases. Because this can be a complex
process that can damage the torch, lifter, or other components, an edge start is recommended unless the
operator is experienced with this technique.
How to increase cutting speed
• Decrease the torch-to-work distance.
Trade-off: This will increase the negative cut angle.
Note: The torch must not touch the workpiece while piercing or cutting.