ZPL Change Backfeed Sequence (~JS) and Inhibit Backfeed (^XB) Function Explained

Article ID: 78845977



Topic or Information

  • ZPL Command Backfeed Sequence ~JS  and Inhibit Backfeed ^XB Details
  • LCD Display Menu Item BACKFEED 
  • How do I control Backfeed?
  • How does backfeed function and what do the BACKFEED settings actually change.

Applies To

Zebra Printers that support ZPL

Excludes: 2824 Series, 2844 Series, S4M (E53 Firmware Version), 888 DD/TT Series, MZ Series, ZQ110, EM220, EM220II


Why backfeed?

The printer supports multiple PRINT MODES to support a variety of label presentations after labels are printed. For each label presentation (other than Rewind) a forward feed of the label occurs as decribed below resulting in a portion of the next label to be printed being forward of the printhead. To avoid a dead band at this leading edge, a backfeed is required to properly place the label under the printhead for the next print cycle.

Print Mode details are as follows:

Tear Off Mode– The inter-label gap is moved forward to the Tear Bar so a user can tear the printed labels cleanly at the gap. 

Peel Off Mode – After printing the label is fed forward to allow the edge of the printed label to hang from the peel bar until taken,

Cutter Mode – The label is fed forward to the cut line where the cutter cuts the printed label.

Rewind Mode – There is no backfeed associated with Rewind Mode  

Backfeed Control

Backfeed is controlled with the following settings or commands:

^XB Command Read More>>

The ^XB command inhibits backfeed when included with the label format. This prevents any forward feeding as described in the PRINT MODES above. Also, when in CUTTER MODE it prevents the labels from being cut.

LCD Display BACKFEED and ZPL Command ~JS

These settings control if backfeed occurs, when backfeed occurs and the amount of backfeed.

~JS Command Read More>>

Using the LCD Display or the ~JS command you can control the following:

Backfeed OFF (~JSO) -

The printer will not backfeed and a dead band will occur on the leading edge of the label. That amount will be based on the PRINT MODE selected. (i.e. CUTTER =1" dead band)

Backfeed AFTER (~JSA) -

In CUTTER MODE the printer will cut and then backfeed the label

In PEEL MODE the next label to be printed will immediately backfeed when the printed label is taken.

When in APPLICATOR MODE, we will backfeed each and every label. The reason for this is that when we are set to backfeed after, the printer/print engine does not know what the next label format is going to be, so it will backfeed every time to make sure it prints the entire label format.

Backfeed BEFORE (~JSB) 

In CUTTER MODE the printer will cut and hold the position until the next print cycle. This is often used to avoid media curl and cutter jamming as the leading edge of the label is prevented from resting on the platen for any length of time.

In PEEL MODE the printer will hold the position after the label is taken until the next print cycle begins.

When in TEAR OFF MODE, we will backfeed the very first label, and only the first label. We will then print the balance of the batch with no backfeed.

When in REWIND MODE, we do not backfeed. This is similar to the tear off position. This is not adjustable in rewind mode. If a PAX user is using rewind there is a reason for this. One of them could be that they are trying to increase their application speed, and do not want to backfeed, as this takes time.

When in APPLICATOR MODE, we will backfeed only if we are required to print on the leading edge of the label. The reason for this is that when we are set to backfeed before, the printer/print engine knows what the next label format is going to be, so it will backfeed if it is required to do so. This is where our smart backfeed comes into play. If we do not need to backfeed, we will not. To test this, have the customer modify their top position in the front panel to move the printed image to the leading edge of the label. They should now see it backfeed. Remember, our printhead elements on the printhead are located roughly a quarter inch back from our peel bar. This is the area that is affected. If we are required to print in this area, we will backfeed. If we are not, then no backfeed is necessary.

10%-90% (~JS10 - ~JS90) - The value you select will be the amount of backfeed the label retracts acting as if set to AFTER. The remaining percentage is the BEFORE amount. (i.e. 10% will result in 10% of the label being retracted after cutting, then 90% when the next label is ready to print)

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