Chapter 4
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 reaches the
target temperature, it can hold, or soak, the kiln at that tem-
perature for the length of time that you program.
The Sentry fires at a controlled heating rate. The rate is
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.
In summary, Ramp-Hold mode does three basic tasks:
1) It fires at a controlled heating rate, or speed, mea-
sured 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 fires in segments, or stages. A segment is a
controlled heating rate to a target temperature. A segment
can also have a hold. Shown in the chart below 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.
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 at a rate per hour,
see the Rate option, page 23.
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 below the shut-off tempera-
ture
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 has finished firing the last segment, it
will turn off the heating elements.
Storing “USER” Programs
To program the controller in Ramp-Hold,
[IDLE]
must
appear. From
[IDLE]
press
4
.
[USER]
will appear. The
controller is ready for you to choose a stored program or to
enter a new one. (See next page for programming instruc-
tions.)
The controller can hold 35 programs in memory. They
stay in memory even when the power is turned off. Stored
programs are numbered 1 - 35. Each program can have up
to 20 segments. You don’t have to use all the segments
available—use only the number needed. Sometimes one
segment is all you will need.
14
Cone-Fire / Ramp-Hold
Do not leave your kiln unattended during operation.
Here is a simple 3-segment program. Segments 1 and 2 each have a hold.
Segment 3 is a controlled cooling segment.
This segment will reach the target temperature of 1250° in 2 hours, then
hold that temperature for 1 hour.
