Plotters for direct-to-textile inkjet printing are a technological solution that has only recently been launched on the market.
It came initially from the idea of using plotters previously made for printing a design onto paper (which was subsequently transferred onto fabric by means of calanders or flat presses ) using the new inks suitable for printing directly onto the fabric, combined with a source of heat (such as an oven/calander) to achieve sublimation without the need for additional steps.
An idea that became reality for some manufacturers during the 80’s.
However, in practical terms, working with fabrics is very different to handling paper.
Plotter manufacturers soon realised there were various phases to be managed during production:
- handling the fabric
- loading the fabric into the machine
- pulling it through
- initial drying
- adjusting the passage of the fabric in the oven
All well-known critical stages in traditional textile manufacturing but that were issues for the “new” digital printers.
At the beginning, plotter manufacturers were met with an unpleasant surprise: their know how in the design of machines for printing on paper, PVC and vinyl was basically insufficient.
They soon found out that the very nature of fabrics means they are in constant “motion”, unlike the supports they were familiar with, and so fabrics are difficult to control.
The first users and industrial textile printing firms were already encountering the associated problems, considered by the pioneers in the business challenging to the point that these machines were “unmanageable”.
As with any new technology, anything newly-launched on the market should be analysed calmly and with due caution before going ahead and buying it.
After getting off to a fast start and coming to a sudden stop, some plotter manufacturers decided it was best to study the machines in greater depth, adding the necessary adjustments.
Recent industry exhibitions have shown that the reliability and simplification of the plotters currently available today have improved significantly, rekindling interest among customers and generating cautious optimism among those directly involved in the sale of these products.
As far as technology is concerned, the equipment you need is: a plotter for direct-to-textile printing and an in line/separate oven or calander for fixing and developing the dyes.
Unlike transfer printing, the right-side of the design is printed onto the fabric, as there is no transferring of mirror-images.
The printing speed for plotters with an in-line oven has to be adjusted according to how long the fabric will stay inside the oven and not vice versa, in order to prevent the fabric from yellowing or shrinking excessively.
Just like printing on transfer paper, it is vital to prevent the heads from touching the support.
In direct-to-textile printing, one of the issues that presented a major challenge for engineers was finding the best applications and solutions so that all fabrics have the same tension preventing the printing heads from touching the support during scanning along the width of the fabric.
It is an issue that concerns every phase in production, which should not be underestimated but be monitored at all times.
As concerns materials, POLYESTER fibre is the best choice, but requires the application of a specific chemical.
This lets the ink droplets stop without expanding, guaranteeing excellent design definition. However, it means that fabrics treated in this way will generally be more expensive than those used for transfer printing, but the extra cost is offset by the savings for the paper cost .
Some special applications (such as flags) need the colour to pass through to the reverse side of the fabric; as it is not possible to adjust the temperature and speed like you can with a calander/press, it is necessary to source purpose-processed products or fabrics on the market.
A “cost” related aspect to consider is the threading of the fabric, i.e. the section of material needed for it to reach the starting point and the finishing point of the machine – also in case of printing faults –, where losses correspond to the cost of using fabric instead of paper, whose price is much lower.
Using plotters reduces the range of items that can be printed on directly, such as long pile fabrics like felts, rugs and carpet. Stretch items require the use of a permanent adhesive mat placed at the inlet mouth of the machine to hold the fabric still and so prevent shrinkage, which would make it impossible to achieve correct printing.
The rolls must be handled and stored with the utmost care.
The pieces of fabric must be stored horizontally, overlapping them by their full length and avoiding crossing them over.
Never straighten the rolls vertically. If this is unavoidable, never stand the rolls on their edges (especially rolls of lightweight fabrics) because this would cause the fabric’s selvedges to become “wavy” and raised up, which could hamper the proper passage of the printing heads.
Generally, plotters for direct-to-textile printing are preferable to printing with transfer paper in the following cases:
- there is a limited amount of material to be printed, so that the cost of switching the calander on and off is not covered (even60/70 minutes)
- a few items have to be made up rapidly (an oven takes 15/20 minutes to heat up).
In quality terms, dye-sublimation printing using a calander/press guarantees better fixing-quality for the ink. Using a plotter results in 15/20% better fastness to light, but these are values that are all conform for advertising and use in-house.
For apparel, home textile, footwear, and luggage, it is essential to complete all the reference tests for the relative parameters!