Limits and Delays

Overview

Every limit and delay programmed for an operation is stored in the job. Limits and delays can be edited at any time. The available limits for an operation depend on the channel class being monitored and if adaptive control is enabled.

Note: The limits and delays described in this chapter are not applicable to Millivolt operations.  

Limits and Delays Per Channel Class

Work (HP/s, kW/s) Limits

TMAC has the capability of using a work value for undercut and wear limits. Work limits (also known as "area under the curve") use signal value over time instead of peak values learned during an operation. Spikes in signal can satisfy undercut limits or trigger wear alarms unnecessarily. This can be prevented by using work limits.

For example: If a power spike reaches a value over the undercut limit but immediately comes back down under the limit, the undercut limit is satisfied, and the process continues. If the power stays below the undercut limit after the spike, the desired output is an alarm condition.

Work limits can only be applied to primary channel operations.

Extreme Limit

The Extreme Limit signals a catastrophic event (e.g., a severely worn or broken tool). When the signal value exceeds the extreme alarm for the amount of time specified in the Extreme Alarm Delay, TMAC halts monitoring and triggers an Extreme Alarm. The extreme limit is set at a percentage above the learned value for a given operation.

Setting the Extreme Limit

To set an Extreme Limit use the following steps:

1. Specify the operation by selecting the tool, section, and channel from the lists on the left side of the Job Editor. The selected operation is displayed at the top of the Job Editor.
2. In the Limits section of the Job Editor, click the Extreme Limit % field
3. Enter the percentage above the learned value that will trigger an extreme alarm condition.
   1. Allowable values range from 1% to 999%
   2. Entering a value of 0 disables the Extreme Limit
4. Click SAVE

Note: Although the above step list specifies entering a percentage for the limit, a direct value may be entered in the other field outlined in step 3 in the figure above. When a limit is set in either field, the other field is automatically populated.

Extreme Alarm Delay

The extreme alarm delay specifies a time period during which the signal value exceeds the extreme limit without triggering an alarm. This allows for brief spikes without unnecessary alarms.

Setting an Extreme Alarm Delay

In the Job Editor:

1. Specify the operation by selecting the tool, section, and channel from the lists on the left side of the Job Editor. The selected operation is displayed at the top of the Job Editor.
2. In the Extreme Limit section of the Job Editor, click the Delay field
3. Enter the duration of the extreme delay
   1. Allowable values range from 0.1 to 320 seconds in 0.1 second increments
   2. Entering a value of 0 disables the Extreme alarm delay
4. Click SAVE

Wear Limit

The Wear Limit alerts the operator that a tool has reached its optimum wear point and should be changed. An alarm activates immediately when signal value exceeds the Wear Limit, unless a Wear Alarm Delay is set. The Wear Limit is a percentage value above the learned value for an operation.

The user may need to experiment with different tools and parts to arrive at the best Wear Limit for a given set of conditions. Once appropriate limits are determined for all the machining processes, a direct and repeatable relationship to tool condition will be noticeable.

Setting the Wear Limit

To set a Wear Limit:

1. Specify the operation by selecting the tool, section, and channel from the lists on the left side of the Job Editor. The selected operation is displayed at the top of the Job Editor.
2. In the Limits section of the Job Editor, click the Wear Limit % field
3. Enter the percentage above the learned value that will trigger a wear alarm condition.
   1. Allowable values range from 1% to 999%
   2. Entering a value of 0 disables the Wear Limit
4. Click SAVE

Note: Although the above step list specifies entering a percentage for the limit, a direct value may be entered in the other field outlined in step 3 in the figure above. When a limit is set in either field, the other field is automatically populated.

Wear Alarm Delay

The Wear Alarm Delay specifies a time period during which the signal value for an operation may exceed the wear limit without triggering an alarm. This allows for brief signal spikes without unnecessary alarms.

Setting a Wear Alarm Delay

In the Job Editor:

1. Specify the operation by selecting the tool, section, and channel from the lists on the left side of the Job Editor. The selected operation is displayed at the top of the Job Editor.
2. In the Wear Limit section of the Job Editor, click the Delay field
3. Enter the duration of the wear delay
   1. Allowable values range from 0.1 to 320 seconds in 0.1 second increments
   2. Entering a value of 0 disables the Wear Alarm Delay
4. Click SAVE

Setting a Work Wear Limit

To set a work wear limit use the following steps:

1. Specify the operation by selecting the tool, section, and channel from the lists on the left side of the Job Editor. The selected operation is displayed at the top of the Job Editor.
2. In the Limits section of the Job Editor, click the Work toggle switch
3. Enter the percentage above the Learned Work value that will trigger an alarm.
   1. Allowable values range from 1% to 999%
   2. Entering a value of 0 disables the Wear Limit
4. Click SAVE

Undercut Limit

The Undercut Limit alerts the user to an incomplete machining process (e.g., a broken or missing tool).

The Undercut Limit is programmed as a percentage below the learned value for an operation. If the signal value fails to exceed the undercut limit for the amount of time specified in the Time Above Undercut field, TMAC generates an under-cut alarm when it receives a stop command.

Note: If using time increments, the undercut alarm is generated at the end of the time increment instead of the next stop monitor command.

Setting the Undercut Limit

To set an Undercut Limit:

1. Specify the operation by selecting the tool, section, and channel from the lists on the left side of the Job Editor. The selected operation is displayed at the top of the Job Editor.
2. In the Limits section of the Job Editor, click the undercut Limit % field
3. Enter the percentage below the learned value that will trigger an undercut alarm condition.
   1. Allowable values range from 1% to 99%
   2. Entering a value of 0 disables the Undercut Limit
4. Click SAVE

Note: Although the above step list specifies entering a percentage for the limit, a direct value may be entered in the other field outlined in step 3 in the figure above. When a limit is set in either field, the other field is automatically populated.

Time Above Undercut

The Time Above Undercut feature is a timer that adds an additional requirement to trigger an undercut alarm. When using Time Above Undercut, an undercut alarm is triggered when the signal value fails to exceed the undercut limit for a specified duration. The Time Above Undercut limit is cumulative. TMAC accumulates the time while the signal value exceeds the undercut limit.

If the time is equal to or greater than the limit, no alarm is triggered. An alarm is generated only when the total time the signal value exceeds the undercut limit is less than the programmed time above undercut. The best way to arrive at an undercut time is to use the Data Viewer and measure the duration that the signal value exceeds the undercut limit.

Setting a Time Above Undercut

In the Job Editor

1. Specify the operation by selecting the tool, section, and channel from the lists on the left side of the Job Editor. The selected operation is displayed at the top of the Job Editor.
2. In the Undercut Limit section of the Job Editor, click the Time Above Undercut field
3. Enter the desired Time Above Undercut time
   1. Allowable values range from 0.1 to 320 seconds in 0.1 second increments
   2. Entering a value of 0 disables the Time Above Undercut Feature
4. Click SAVE

Setting a Work Undercut Limit

To set a work undercut limit use the following steps:

1. Specify the operation by selecting the tool, section, and channel from the lists on the left side of the Job Editor. The selected operation is displayed at the top of the Job Editor.
2. In the Limits section of the Job Editor, click the Work toggle switch
3. Enter the percentage below the learned work value that will trigger an alarm.
   1. Allowable values range from 1% to 99%
      1. Entering a value of 0 disables the Undercut Limit
4. Click Save

Spindle Speed Limits

Coolant Limits

Extreme Feedrate Limit

Wear Feedrate Limit

Slope Limit

Signature Limits