SCHEDULES (Aug93)       furnace

NAME

schedules --- oven schedule description and editing procedure

DESCRIPTION

Once a minute, a power level for each heater element is calculated from a weighted average of its neighboring thermocouple temperatures, and the temperature called for at the current point in the schedule of temperature versus time. There are separate temperature versus time schedules for each of several zones of heater elements as well as the rotation speed. These schedules can be interlocked so as to synchronize their progress according to real temperature data.

Oven schedules consist of nodes which are composed of a GOALTIME and a GOALTEMP. The node also has a LABEL and some wait conditions which allow the schedules of various zones to be syncronized. The parameters and data for the current node of each active zone schedule are shown in the 'Oven Overview' menu. Additional details for the current node are shown in each of the 'Zone' menus. The full schedule for a particular zone is shown in the 'Zone Schedule' menu.

WARNING

Changing the schedule on the fly is very dangerous. Do not attempt it unless you are very sure that you know what you are doing.

SCHEDULE EDITING

Temperature schedules may be editted by the oven task in the 'Configuration and Status Menu'. Move to the 'Zone' menu, the press GOTO at the 'Zone ID' to get to the 'Zone Schedule' menu. To edit a node, use the UP or DOWN keys to point the cursor at the node you wish to edit. Then use 'P' to cache the parameters. To change the GOALTEMP, press the 'e' key and enter a temperature at the prompt followed by return. To delete the node, enter 'del' at the prompt. To insert a node above the one you are pointed at, enter 'ins' at the prompt. To append a node, point the cursor at the first blank line beyond the end of the schedule, and use the insert function.

To edit other node items use the GOTO key to the 'Node' menu page for the node you are editing. Use the UP or DOWN keys to move to the value that you wish to edit; press 'e', type the new value, and press return to change the value. When you change a parameter, other related parameters are automatically updated to reflect your change i.e. change GOALTEMP and RATE, GOAL CLOCK TIME, DELTA TEMP, and DELTA CLOCK TIME are all updated immediately. When you are done changing values, use the 'W' key to write the changes to the oven or discard them (press GOTO at the option you choose). All affected nodes will THEN be updated and NOT before. Schedule changes should be saved between 30 and 45 seconds after the minute to avoid disrupting the schedule computation.

These instructions apply to all the schedule parameters except the biparameters for clock time and clock status. See help clocks for instructions on how to change the clocks. The clocks tend to get out of sync when the schedule is edited, so we need to check them after changes are made. If you edit the current node, the schedule editor will display the appropriate time to set the clocks to at the top of the screen. (This applies to editing, not to copying schedules.)

SCHEDULE COPYING

While pointing at the schedule labels, 
"Lab  Rate  Dev  GTemp  Gtime  DTemp  Dtime  Wait"
you may copy over a schedule from another zone, OVERWRITING the current schedule in this zone. To do this, type 'e', type the zone address, and press return again. Remember that zone addresses are: 
Z0 Z1 Z2 Z3 Z4 Z5 Z6 Z7 Z8 Z9 Z10 ......... R

Be careful not to confuse zone R with node label 'r'. Node labels are optional for all nodes not involved with wait states. Labels are highly recommended for clarity. In the rotation zone, the parameters have special meanings: 

                Sch Temp = scheduled rotation speed (RPM)
                Avg Temp = measured rotation speed (RPM)
                Error    = Error (scheduled-measured)
                Rate     = rate (RPM/hr)

SCHEDULE PARAMETERS

Node Label
A lowercase or uppercase letter to identify each node in the schedule. For example 'b' or 'B'. A '*' appearing next to the label indicates that this is the active node. Note that labels need not be sequential. You may edit them to appear in any order.

Rate (C/hr)
The rate of change of scheduled temperature for this node. Note that the units are (degrees per hour) not (degrees per minute). The scheduled temperature changes at this rate until reaching the goal temperature for the current node.

Deviation (degrees C)
This is the permissible difference between the scheduled temperature and the computed heater temperature or zone average temperature. Deviation is also used as a parameter for one of the wait states.

Tdeviation (degrees C)
This is the new deviation parameter used to identify discrepant thermocouples in reference to their neighbors.

Goal Temperature (degrees C)
Goal temperature is where the schedule should be when it finishes a particular node.

Goal Clock Time (dd:hh:mm)
Zone clock time at the end of the node.

Delta Temperature (degrees C)
Amount the temperature changes during this node. This is redundant with Goal Temperature, Goal Time and Rate so the schedule editor calculates the other parameters hierarchically when you specify one of them.

Delta Clock Time (dd:hh:mm)
Amount the zone clock time changes during this node, or the length of the node not including wait states.

Wait on Tolerance (Yes/No)
Should the schedule wait until the average temperature of the zone is within 1 degree of the scheduled temperature?

Wait on Deviation (Yes/No)
Should the schedule wait until the scatter in the zone is less than the scheduled deviation?

Wait on Zone/Node (Yes/No)
Should the schedule wait until some other zone has reached a specified point?

Wait on Zone ID (ID) (Z0-Z18,R,A)
The name of the zone to wait on. (A to wait on all zones)

Wait on Node Label (label) (a-z,A-Z)
The label of the node to wait on. Labels are not automatically assigned. The pilot is responsible for keeeping them aligned in the schedule.

Proportional Coef. (power units per degree)
If the heater temperature is less than the scheduled temperature by one degree, apply this many power units to the heater for the next minute.

Integral Coef. (power units per degree)
If the integrated heater temperature error is one degree, apply this many power units to the heater for the next minute.

Derivative Coef. (power units per degree)
If the heater temperature error (compared to the previous minute) increases by one degree, apply this many power units to the heater for the next minute.

Integral Depth (minutes)
Depth of the leaky memory to integrate the heater temperature error.

Power Limit (power units) (0-240)
Maximum number of power units to apply to a heater in the next minute. 180 units gives a 75% duty cycle to the heater.

EXAMPLE --- Zone Schedule Menu

Zone Z0             7.6 00:01:12 S
Lab  Rate    Dev  GTemp    Gtime   DTemp    Dtime Wait
a     0.0   50.0    0.0 00:00:00     0.0 00:00:00
b*    6.3   50.0   20.0 00:03:10    20.0 00:03:10
c    25.0   50.0   95.0 00:06:10    75.0 00:03:00
d    30.0   50.0 1190.0 01:18:40  1095.0 01:12:30
e     0.0   50.0 1190.0 02:00:40     0.0 00:06:00
f   -16.7   50.0  540.0 03:15:40  -650.0 01:15:00
g   -10.0   50.0   20.0 05:19:40  -520.0 02:04:00


Lab Proportional   Integral       Derivative     depth  Plim
a   2.000000e+00   5.000000e+00   1.000000e+00       8    60
b*  2.000000e+00   5.000000e+00   1.000000e+00       8    90
c   1.000000e+00   5.000000e+00   1.000000e+00       4    90
d   4.000000e+00   1.000000e+01   3.000000e+00       8   120
e   4.000000e+00   4.000000e+00   3.000000e+00       8   120
f   5.000000e+00   1.000000e+01   3.000000e+00      12   180
g   5.000000e+00   1.000000e+01   3.000000e+00      12   180

EXAMPLE --- Node Menu

Zone Z0             7.6 00:01:12 S
Node Label          b*
Rate (C/hr)             6.3
Deviation              50.0
Goal  Temperature      20.0
Goal  Clock Time    00:03:10
Delta Temperature      20.0
Delta Clock Time    00:03:10
Wait on Tolerance   No
Wait on Deviation   No
Wait on Zone/Node   No
Wait on Zone ID
Wait on Node Label
Proportional Coef.   2.000000e+00
Integral     Coef.   5.000000e+00
Derivative   Coef.   1.000000e+00
Integral Depth        8
Power Limit          90

SYNCHRONIZATION

This is an example of how the heated oven zones wait for the mold to reach a specified temperature and then resynchronize the clocks. First the mold zone stops and waits for tolerance (T, 1 degree error) at node d with T=475. Meanwhile, the other zones continue ramping to T=500 where they stop and wait for zone 5 to finish node d. If the other zones had stopped to wait at node d, then it would take an arbitrarily long time for the mold to reach T=475 in an oven at T=475. After the mold reaches T=475 and starts node e, the other zones begin node f (in this case, a hold). Node f is made only 1 minute long so all zones wait there until zone 5 finishes node e and catches up to the same clock time. The synchronization hold must be only 1 minute long so all zones begin and end the node on the same minute. 

......mold zone 5 
c     2.0   40.0   40.0  104.0 00:15:15    12.0 00:06:00          
d     7.5   50.0   50.0  475.0 02:16:43   371.0 02:01:28 T        
e    12.0   50.0   50.0  500.0 02:18:48    25.0 00:02:05   W Z5  e
f     0.0   50.0   50.0  500.0 02:18:49     0.0 00:00:01   W A   f
g     0.0   30.0   30.0  500.0 03:18:49     0.0 01:00:00          


......all other zones
c     2.0   40.0   40.0  104.0 00:15:15    12.0 00:06:00          
d     7.5   50.0   50.0  475.0 02:16:43   371.0 02:01:28          
e    12.0   50.0   50.0  500.0 02:18:48    25.0 00:02:05   W Z5  e
f     0.0   50.0   50.0  500.0 02:18:49     0.0 00:00:01   W A   f
g     0.0   30.0   30.0  500.0 03:18:49     0.0 01:00:00

BUGS

The schedule displays only show the rate to 1 decimal place. Thus if the rate was entered as 0.125 degrees/hour, it shows as 0.1. The schedule runs correctly at 0.125 even when the display says 0.1.

RELATED MIRROR HELP TASKS

oven, clocks, wait_states, menus, ograph