An HMI panel has no printer driver, so a USB printer attached to it prints nothing. Let the panel save the screen capture as a JPG to a USB drive through its event manager, then print the file from a computer. This page plans the file names and the print size, and keeps capture failures and printer failures apart.
A screen capture on an HMI panel is easy to make and awkward to print. The panel is not a PC: it carries no printer driver and no print queue, so a printer plugged into its USB port receives nothing. The documented path is to split the job. The panel saves the capture as a JPG file to a USB drive through its event manager, and a computer prints the file. This page sets that path up, plans file names that survive a year of captures, and sizes the print so the capture reads on paper.
The answer: the panel writes a file, the computer runs the printer
Keep the two jobs apart and the troubleshooting stays simple. The panel's job ends when the JPG is on the drive. The computer's job starts when the drive is plugged in: it opens the image and drives the printer with the settings you would use for any photo. A panel of this class usually has no print action in its event list; the manual for your installed software version is the authority, and if it lists one, follow its steps. Where no print action exists, time spent testing printer compatibility at the panel is time lost. The capture-to-file path works with any printer the computer can reach.
What you need
- The USB flash drive in the type and format the panel's manual calls for.
- A computer with the printer already working and any image viewer on it.
- The panel's programming software and the project file, plus your site's change procedure for project transfers.
- A trigger you already have, such as a pushbutton bit or an alarm bit.
Set up the capture-to-USB event
- Open the panel's project in its programming software on a PC.
- Find the event list the manual calls the event manager: the table where a condition drives an action, usually indexed under events or screen captures.
- Add an event. Set the condition to the trigger you already use, a pushbutton bit or an alarm bit.
- Set the action to save a screen capture, choose JPG as the format, and choose the USB drive as the destination.
- If the software offers a file-name pattern, build it from date and time so no two captures share a name.
- Transfer the project to the panel under your site's change procedure, then trigger the event once.
The check is a file: a new JPG on the drive, usually inside a folder the panel created. One common panel family names that folder HMIScreenshot; your manual names yours. Give the panel a moment to finish writing before you pull the drive. A file cut off mid-write arrives corrupt and sends the check down the wrong branch.
Give each capture a name that survives a year
A capture fired once per shift on a three-shift schedule is 3 files a day, and 3 x 365 = 1,095 files a year. Two things break on that schedule: names and space.
Names break first. If the event action can write only one fixed name, each capture replaces the last, and the fix is the same one as in saving HMI trend screen captures without overwriting files: unique, time-stamped names, set before the first real capture.
Space breaks slowly. At 1,095 captures a year the drive fills on a predictable date, and a drive that filled yesterday saves nothing today. Confirm the oldest-file behavior before that date; the checks in confirming oldest-file rollover before the USB log drive fills apply unchanged to a folder of captures.
Print the file from the computer
- Move the drive to the computer, or copy the capture folder over the network if the panel shares it.
- Open the newest JPG and confirm it shows the screen state you needed to keep, before anything prints.
- In the viewer's print dialog, set the scale from the image's pixel size. The worked example below gives the numbers.
- Print, then read the sheet: alarm text and setpoint values legible at reading distance.
If the capture is headed into a procedure manual instead of onto paper, the steps in capturing HMI screens for operator manuals in Word continue from the same file. The end-to-end check for this workflow is the paper: trigger the event, pull the drive, print, and read the capitals at arm's length.
Worked example: an 800 x 480 capture printed on a letter sheet
The inputs: the capture is 800 x 480 pixels, the full-screen size many 7 in HMI panels save, and this is the one input you take from your own panel if it differs. The sheet is US Letter at 8.5 x 11 in, printed portrait with 0.5 in margins on every side, so the printable area is 7.5 x 10 in; example input. The print target is 150 DPI; example input.
The rule in words: printed size in inches equals the pixel count divided by the print resolution, so inches = pixels / DPI.
The arithmetic: 800 / 150 = 5.33 in wide, and 480 / 150 = 3.2 in tall. The notes space left under the image is 10 - 3.2 = 6.8 in of sheet height.
The result: at 150 DPI this capture prints 5.33 x 3.2 in and still leaves 6.8 in of the letter sheet for handwritten notes.
The decision: print at 150 DPI when the sheet carries notes under the image. Fill the full 7.5 in width when the sheet is pinned up to be read from a step away: 800 / 7.5 = 107 DPI, bigger picture, softer edges. Do not force 300 DPI on this file: 800 / 300 = 2.67 in and 480 / 300 = 1.6 in, a print too small to read standing up. 300 DPI belongs to files captured at more pixels, not to a 480-pixel-tall screen copy.
When no file appears, stop before the printer
The stage that failed decides where you work. A missing file is a capture problem and stays at the panel. A file that opens but prints wrong is a computer problem and stays at the desk. Printer settings never recover a capture the panel never wrote.
| What you see | What it points to | Next check |
|---|---|---|
| No new JPG on the drive | The event never fired, or the write failed | Re-check the event's condition and action against the manual, confirm the drive meets the panel's stated requirements, trigger once more |
| JPG present but corrupt or will not open | The write was interrupted | Trigger a fresh capture and check that new file before touching anything else |
| JPG opens on the computer but the print is wrong | The print stage | Check the viewer's scale and paper settings, then the printer itself |
Work the table from the top at the panel side, and leave the printer alone until a healthy JPG exists on the drive.
Recommendation
Recommendation: give the panel the capture and give the computer the print. Configure one event in the event manager that saves a JPG to the USB drive on a trigger you already use, timestamp the file names, and print at 150 DPI from a computer, or fill the 7.5 in letter-sheet width at about 107 DPI when the sheet is posted for the floor. If your panel's manual documents a print action for the installed software version, follow that documentation first and keep the capture-to-file path as the fallback. When no JPG appears on the drive, work the table above at the panel and leave the printer until a file exists.
Questions
Why does a printer plugged into the panel's USB port do nothing?
A USB printer needs a printer driver on the device it is attached to, and an HMI panel ships with none, so the printer receives no data and raises no error. The silence is easy to misread as a faulty printer. The capture has to leave the panel as a file first; the computer, which has the driver, does the printing.
Should the capture be saved as JPG or PNG?
JPG is the format this workflow uses and the one most event actions offer. Some panel families write PNG captures instead, into a fixed folder on the drive. Both open and print identically on the computer, so take the format your event action provides and set the print scale from the image's pixel size, not from its file format.
Can the capture fire from an alarm condition instead of a button?
Yes, wherever the event manager accepts project conditions: the same bit or threshold that raises the alarm can drive the capture action, so the panel files an image of exactly what the operator saw. Timestamp the file names first. Alarm-driven captures arrive in bursts, and a repeated name overwrites the previous capture before anyone has printed it.
Do you have to walk the USB drive to the computer every time?
Only if the panel offers no other way off. Some panels can share the drive or its capture folder over the network, so a computer can collect the files without pulling the drive; the manual for the panel tells you whether yours can. The printing steps stay the same either way, because they start from the JPG, not from how it arrived.
Planning information, not legal or engineering advice. Rules differ by place: check codes and permits with your local authority and your licensed trades.