Tweco SC-3000 - Manual (Page 60)

SC-3000
OPERATION 4-20 Manual 0-5100
Control Delay
Often called AVC delay, this is time starting when torch is moved to cut height until THC starts control-
ling height to the sampled arc voltage.
a. Delay before system starts controlling height using arc voltage. Set in tenths of second (0-10.0
sec).
b. System finds surface of the metal then using an encoder for accuracy lifts the torch a measured
distance to Pierce Height. Following Pierce Delay torch is moved to Cut Height using information
from the encoder.
• Control Delay time starts. Torch remains at Cut Height during Control Delay. Near end of
Control Delay system samples arc voltage and saves it as a reference. At end of Control Delay
system start controlling height to maintain the actual arc voltage to equal the saved arc voltage
reference.
Hint: Set the delay long enough so cutting table is up to full cutting speed, torch has moved beyond
cutting slag and arc voltage has stabilized. But don’t set the delay so long that the distance to the metal
has changed from the initial cut height. To determine the correct setting, first determine how far you
want the torch to move before turning on arc voltage control. Then considering the cutting speed, figure
how long it takes the torch to move that far.
Retract Position
• Sets the height the torch is raised (retracted) following end of a cut. Select in increments of 0.04”
(0- 4.0”) or 1 mm (0-100mm.) For full retract to the top position select 10.2” or 255mm. It may
not actually rise up 10.2 or 255 mm but that selection causes it to rise to the top.
• At end of a cut, before moving to the next cut, torch is normally retracted to clear any obstructions
such a part that tips up. Time is saved if a full retract is not required.
Hint: If cutting small parts that may tip up or thin metal that is likely to spring up, set for higher retract
to make sure the torch clears the cut piece. Use lesser amounts for larger pieces.
Upper Threshold
• Sets voltage upper limit as percent (0-20%) of operating arc voltage.
• When crossing a kerf or hole or going off the edge of the plate, arc voltage rises very rapidly.
System will respond to the rise in voltage by lowering the torch trying to keep voltage constant.
Without Upper Limit torch will be driven into the plate. When voltage exceeds Upper Limit set-
ting, system stops trying to control height. Also refer to the Dynamic setting.
Hint: For thicker metal which tend to be fairly flat and using lower cutting speeds the arc voltage
doesn’t change very rapidly except when crossing kerfs & holes so using a lower % will respond
quicker, typically 5-10%. For higher speeds on thinner or warped metal where normal cutting voltage
changes more rapidly, use a higher number around 10-15% or even 20%.
Dynamic
• Sets gain (response) of system (0-100). Factory setting of 40 is usually OK.
• With thicker metal and lower cutting speeds where a faster response is not needed a lower Dynam-
ic setting in combination with a lower Upper Threshold %, can help prevent or limit torch diving
when crossing kerfs or holes or when the part or scrap drops out before finishing the cut.
• Very high speeds on very thin or highly warped metal may require increasing the Dynamic setting
to respond faster. Be careful to not go so high the torch overshoots and oscillates up and down.
Remember you will generally want to go back to 40 normal cutting.