Chapter 3
Ramp-Hold
In this chapter you will learn to . . .
G
Program a Ramp-Hold firing
G
Store programs in memory
G
Turn a vent fan on or off throughout the firing
G
Control the cooling rates for down firing
Before using Ramp-Hold, read all of this
chapter with your controller in front of
you so you can press the keys as you read.
Theory of Ramp-Hold Operation
The temperature you are firing to in Ramp-Hold is
called the target temperature. After the Sentry Xpress
reaches the target temperature, it can hold, or soak, the kiln
at that temperature for the length of time that you program.
The Sentry Xpress fires at a controlled heating rate. The
rate is usually figured in degrees per hour. If you selected a
rate of 100° per hour, it would take 10 hours for the kiln to
reach 1000°. Rate is similar to miles per hour.
Ramp-Hold mode does three basic tasks:
1) It fires at a controlled heating rate, or speed, usually
measured in degrees of temperature change per hour.
2) It fires to a target temperature.
3) It can hold, or soak, the target temperature for a pe-
riod of time.
The Sentry Xpress fires in segments, or stages. A
segment is a controlled heating rate to a target tempera-
ture. A segment can also have a hold. Shown in the chart
above is a segment with a target temperature of 1250°, a
rate of 625°, and a hold of one hour.
A segment has two parts:
I
Ramp
: The temperature changes at a rate that you
select.
I
Hold
: The temperature remains the same.
The heating rate is figured in degrees per hour. The rec-
ommended heating rate for the material you are firing is
usually available from your supplier. The heating rate also
varies depending on the thickness of the material.
Note:
Some brands of controllers fire to a temper-
ature in a given length of time. If you would prefer
to program that way instead of in degrees per hour,
see the Rate option, pages 13-14.
A segment can have only one ramp and only one hold.
Therefore, if you need more than one hold, add more seg-
ments to the firing. Firing to a temperature at a single rate
would need only one segment. Reasons to add more seg-
ments:
I
To change the heating rate.
I
To add a hold somewhere in the firing.
I
To control the cooling rate.
The diagram below shows a 3 segment firing. Segments 1
and 2 were used on the way up in temperature. Segment 3
was added to control the cooling rate.
To figure how many hours a segment will take to fire,
subtract the current temperature from the target tempera-
ture and divide the result by the heating rate. In the diagram
in the left column, the firing time is 1250° - 80° (room tem-
perature) = 1170 ÷ 625 = 1.87 hours.
After the Sentry Xpress has finished firing the last seg-
ment, it will turn off the heating elements.
Note:
If you enter a rate of 0000 in segment 1, or if
the target temperature in segment 1 is lower than
the current temperature,
[BADP]
(Bad Program)
will appear in the display.
How to Store Programs
The controller can retain 25 Ramp-Hold programs that
can each fire up to 20 speeds and temperatures. (Each set of
speeds and temperatures is called a segment.) The pro-
Sentry Xpress 5 Cone-Fire / Ramp-Hold
12
Do not leave your kiln unattended during operation.
This segment will reach the target temperature of 1250° in 2 hours, then
hold that temperature for 1 hour.
Here is a simple 3-segment program. Segments 1 and 2 each have a hold.
Segment 3 is a controlled cooling segment.
