Topics: DTG/DTF 101

Intro

The purpose of the white underbase is to neutralize the color of the garment when we DTG print onto or apply a DTF transfer to it. Think of the white underbase as a primer coat of paint on a wall to cover the old paint color before painting a new color.

The rip software automatically generates a pure white version of the image being processed as the underbase, as depicted below (with a black background for viewing on a white page).

Example of CMYK & full white underbase layers

There are sometimes misunderstandings about how the white underbase is applied, particularly the white underbase choke. There are a few underbase types, which we’ll detail below. The white underbase choke, on the other hand, has a singular definition regardless of the underbase type.

Choking the White Underbase

What do we mean by “choke”? Let’s be clear that no underbase was harmed during the making of this article. 😉 It might be helpful to think of creating the white underbase choke as slightly shrinking the white underbase by some number of pixels (usually 2) since that’s exactly what is happening.

Why would we want to shrink the underbase? Simple. It’s to provide a tiny margin of error to ensure that we don’t see a slight outline of white ink around the edges of our designs when they’re printed. This white outline can occur even with perfectly aligned printheads, so we proactively make the underbase 2 pixels smaller than the color layer at all image edges.

Here’s a representation of what the above design might look like when printed on a black shirt if the underbase is not choked.

White Underbase Types

“Diff’rent strokes for diff’rent folks.” -Sly Stone

Different designs and materials may all get optimal results from using the same type of white underbase. OmniPrint provides a variety of presets, called Environments with our rip software to deliver different types of white underbases (along with other parameters) for various printing conditions and preferences.

Full Underbase: The full underbase prints a solid white layer of the complete design. This provides the most thorough neutralizing of the garment color, using the heaviest layer of white ink in the underbase. When used for DTF printing on DTG printers without a heated platen, this may be too much ink for dense designs and result in bleeding. In DTG printing, the FreeJet 330TX “Color Media” Environment options provide a full underbase.

Standard Grayscale Underbase: In DTF printing, Environments not labeled or named with a specific type of underbase will produce a grayscale underbase. Such an underbase will use more white ink for the underbase of the highest intensity or brightest colors in a given design and less for the underbase of the darkest shaded colors. In DTG printing, the OmniPrint i2 and FreeJet 330TX-series “Dark” Environment options provide a grayscale underbase with no white underbase where a design is pure black (RGB = 0,0,0).

Black or Black Garment Underbase: Selecting a Black Environment type results in printing no underbase and no black ink where a design is pure black. The intention is to reduce black & white ink use when the print is produced on or for a black shirt by letting the black shirt’s color provide the black content of the design. Note: DTF printing with a Black Environment calls for special care to ensure that film prints created this way are only transferred to black shirts.

Light Garment: In DTF printing, the Light Garment Environment types use less white ink in the underbase since lighter-colored garments need less ink to cover the garment color.

White Environments (no underbase)

The White Environment types for the OmniPrint i2 and FreeJet DTG printers are intended for printing only onto white garments. They produce no white underbase and print no white ink in the parts of a design that are pure white (RGB = 255,255,255), instead allowing the shirt color to provide the white content.

White Outline on Single Edge

On a printer with multiple printheads, if you consistently see a white outline on either the left or right edges of a design’s print (but not both or all edges) it’s recommended to adjust the horizontal printhead alignment.

If there’s a consistent white outline on either the top or bottom edges of a design’s print (but not both or all edges) it’s recommended to adjust the vertical printhead alignment.

Increasing the white underbase choke beyond the normal 2 pixels may be an effective workaround to eliminate white “shadows” on single horizontal or vertical edges when a deadline requires ongoing high production levels. Remember to correct any alignment issues as soon as the urgent work is completed.

Pressure / Hover Settings for each Timer

The Stahl’s Hotronix Hover Press has two timers built in, and each of the timers can be configured to apply pressure (with the amount of pressure defined by manually adjusting a knob) or to hover slightly above the platen when latched down.

Given those two options (pressure or hover) on each of two timers, there is a total of four possible configurations that you can set up, as follows.

As shown above, timers 1 & 2 can be set to both use pressure (setting #001), to both use hover mode (setting #003), or to use a combination of pressure and hover (settings 002 and 004).

The only difference between 002 & 004 is which of the two timers gets pressure and which hovers — the 1st or 2nd timer. Either way, in those two settings the unit will alternate between pressure and hovering.

How to Change Setting Numbers

Changing the pressure/hover setting for either or both of the timers requires that we first turn the heat press off, then follow specific steps using the control pad to select the setting number for the pressure/hover setting we want for each timer using the following steps.

1. Turn off the heat press.
2. Press and hold both the ‘-‘ (decrease) and ‘+’ (increase) buttons on the control pad.
3. Turn on the heat press while holding the ‘-‘ and ‘+’ buttons for 3-5 seconds longer.
4. Press the ‘Mode’ button. Confirm that the number 555 appears on the display.
   • If ‘555’ doesn’t appear, go back to step 1 after confirming that you have a Hotronix Hover Press, not an Auto Open Clam or other model or brand.
5. After ‘555’ appears on the display, press the ‘Mode’ button again.
6. Press the ‘-‘ or ‘+’ button to cycle through the pressure/hover mode number (001 – 004), as shown above, selecting the number for the pressure/hover combination that you want.
7. Once you’ve selected the desired pressure/hover mode for the two timers, press the ‘Mode’ button two time to exit the pressure/hover selection mode.

You will now be in the regular temperature selection mode, where you can change the temperature setting and use the ‘Mode’ button to cycle through the timer settings and back out to operating mode.

OmniPrint offers a variety of inks for use in our DTF & DTG printers, but it’s important to note that each printer has only one specific ink type that should be used in it.

Ink Compatibility by Printer Model

Please see the following table to confirm the type of ink to be used with your printer.

Ink Shelf-Life

The shelf-life of our inks is 1-year. Any ink older than that should be disposed of and replaced.

All printers have a maximum printable area, at least for the width, related to the dimensions of the carriage mechanism which moves the printhead back and forth while printing.

DTG printers will also have a maximum platen size defining the biggest printable width and length. This maximum size will apply whether the operator is operating in DTG mode or printing onto a sheet of film.

DTF printers will also have a maximum width, while those which load film from a roll (such as the OmniDTF) can have a virtually unlimited print job length.

The following table shows the maximum printable area for all of OmniPrint’s DTG and DTF printers.

Dampers are deceptively simple-looking but critical components in the ink flow of DTG & DTF printers.

Dampers perform 4 functions.

1. Provide a consistent ink supply reservoir for the printhead.
2. Screen out any foreign material in the ink before it reaches the printhead.
3. Act as a “pump”. There is round diaphragm behind the clear film side which has a spring behind it. As the printhead uses ink and the damper empties, the diaphragm gets pulled inward and starts compressing the spring mechanism. When the spring mechanism is pulled inward far enough, it eventually pushes back out, pulling ink in from the ink line and bottles.
4. Dampen and regulate pressure changes in the ink line at the printhead as the printhead carriage rapidly stops and reverses direction while printing. When the carriage motion in one direction stops, the pressure momentarily increases and when it starts going back in the other direction, the pressure momentarily decreases, due to inertia. This is why the ink lines are not connected directly to the printheads. The dampers absorb these minor pressure deviations.

Damper failures can be caused by a number of things. The spring can start getting weak, so it doesn’t “pump” correctly. The O-ring that seals the connection to the ink line can start leaking air, resulting in banding or ink dripping from the bottom of the head. One of the clues you have a damper is failing is when the missing nozzles on your nozzle check prints keep moving around between head cleanings.