to give print job directly to printer angular 6

As already mentioned by others, there's no easy, one-fits-all, solution to this.

The options I could find fall in the following 3 categories:

1. Browser specific settings

   For some browsers (firefox, chrome) specific settings can be switched on/off or added for silent and/or kiosk mode printing. As these settings are so diverse and sometimes dependent on the version of browser, I'm not going to try to list them here. you can find the methods online for the browser you use under silent printing.

2. Browser specific plug-ins

   Some plugins can be found too, but they might just do the same things as toggling the settings in the background as number 1

3. Custom

   One very specific/involved/"hands-on" option that I have found is to work through a service whith custom designed url/file type handlers. you can find the video here: https://www.youtube.com/watch?v=MQMD4Pb7jzY

As you already mentioned. choices are not optimal, but maybe there's something you could work out from these.