Tweco SC-3000 - Manual (Page 58)

SC-3000
OPERATION 4-18 Manual 0-5100
4.11 SC 3000 Torch Height Control (THC) Modes of Operation
SC 3000 Torch Height Control (THC) Modes of Operation
Cutting Height Mode
Normal operating method is to use Cut Height Mode where desired cutting height is set directly in inch
or mm. This is somewhat different and easier to than most other height controls where you first have to
determine the desired arc voltage. Refer to section 4.12 for details of setting the cutting parameters.
Arc Voltage Mode
Arc Voltage Mode
In the Arc Voltage Mode in addition to the cutting parameters used for Cut Height Mode you must
specify the desired Arc Voltage. Instead of the SC 3000 determining the correct arc voltage by sampling
it will use the voltage you enter as the reference. This requires you know the correct voltage for the
desired cutting height.
With Arc Voltage control the system still starts at Pierce Height, moves to Elevation Height at transfer,
goes to Cut Height (you must still enter a Cut Height) then after Height Control Pierce Delay and after
Control Delay the SC 3000 starts regulating height to the arc voltage you entered.
Cut Height Mode vs. Arc Voltage Mode—Advantages and disadvantages.
Cut Height Mode advantages:
• It is really the distance from the end of the torch to the work, not the arc voltage, that you want to
maintain constant. As torch consumables wear the arc voltage for a given height changes. With
Arc Voltage mode a smart operator will adjust the arc voltage setting to compensate. Many do not.
With Cut Height mode which takes a new sample each cut voltage change from consumable wear
is automatically compensated.
• You do not have perform test cuts to determine the correct arc voltage setting or rely on cut chart
numbers which are an average and may not be exactly right for your application.
Cut Height Mode disadvantages/Arc Voltage Advantages:
• The cut height the torch is positioned to and thus the sampled voltage is relative to the Pierce
Height which is found during the Find Height sequence. If that is not accurate, for example,
height was found on a piece of slag, then the height for the entire piece is wrong.
• With Arc Voltage Mode even if Pierce Height is off, as soon as Control Delay is finished it goes to
the height set by the arc voltage you entered assuming you got it right.
• If your CNC doesn’t allow setting a Pierce Delay so you have use Height Control Pierce Delay
(Correct use of Pierce Delay and Motion Delay for SW2 switch setting) then using Arc Voltage
Mode you can set the Cut Height somewhat higher than you want to cut at so that when the Height
Control Pierce Delay ends and the torch moves to Cut Height it is still above the piercing slag. Set
Control Delay just long enough that the torch moves past the slag the when THC starts controlling
the arc voltage torch will move to the correct cutting height.
Arc Voltage Mode disadvantages:
• Doesn’t compensate for consumable wear.
• Requires knowing and entering the correct voltage setting.