HOW HAS THIS TECHNOLOGY EVOLVED AND AT WHAT COST? — TEXINTEL

19 Oct.,2022

 

Braided Rugs

Guest article written by Bob Balings, Owner at Bob Mats B.V.

Carpet printing technology compared

Printing designs on carpet and mats has been done for many years and technology has evolved. When looking closer at the technology, progress has been made but it comes at a cost that most companies are not aware of. Hence that is a general lack of knowledge and carpet companies rely to much on what a machine supplier tells them.

In this article we would like to give you some background information on the different carpet printing technologies and the evolution and problems.

This article focuses on printing on nylon carpet as this is the most used carpet in Europe.

For B2B contract use nylon is still the number one choice for long lasting quality.

When printing a carpet or floor mat the base color is always white. Dye is injected into the carpet pile and B2B customers expect that the printed color penetrates the white yarn as deep as possible. Ideally no or almost no white is visible when you open the pile. Besides good penetration for B2B contract use a good lightfastness is needed as carpets could be placed behind windows in full or part full sun. Preferably lightfastness is 6-7. For mats that are being washed and placed indoor wash/wet fastness will be more important.

There are also a limited number of so called millitron printers world wide. This is a technology patented and licensed by Milliken and only ideal for very large runs. The price of this machine and license model has never made is popular. For this reason we are not discussing this technology.

The first generation of carpet printers are the spot color printers. Typically for printing b2b carpet these printers have anywhere from 8 to 16 colors. For printing logo mats (small numbers) 16 to 48 colors to minimize changing colors. The most popular machine is build by Austria Zimmer and is called the Chromojet 200 or 400. Recently there has also been another manufacturer from China, Atexco who have build similar machines based on improved jet technology.

The difference between the 200 and 400 is the resolution and jets. The Chromojet 200 has bigger jets and prints at a resolution of 6 x 6 pixels per cm. This is roughly 15.24 dpi. The newer 400 prints at a resolution of 10x10 pixels per cm of 25.4 dpi

Owners of these machines mix the dye themselves using a thickener, mixing the powder based dye into it and set the correct viscosity and ph for printing. As colors are mixed over and over there will always be slight differences in color for batch to batch. The advantage of this printer is that a wide range of dyes can be used. For nylon this is typically acid, reactive or metal complex based dyes. Depending on the quality printed the dye type is chosen. For different production different dye types can easily be used.

The operator has different ways to influence the print result on the carpet.

  1. Jets are operated using air pressure. The pressure can be manually set. When setting a higher pressure more dye is injected at the same time. Lower pressure means les dye.

  2. Printhead speed can be changed. By changing the speeds the machine can print faster or slower.

  3. Viscosity of the dye. The lower the viscosity the more liquid the dye. When lowering the viscosity, keeping the pressure and speed the same, more dye will be injected into the pile.

The above might seem easy but it requires a balance depending on the carpet that is begin printed. High / low pile, open / dense, light/ heavyweight all this need to be fine tuned for best results. For example, if the dye is to liquid (low viscosity) penetration will be good but being to liquid, little dye will remain at the top causing the so called frosting effect.

Printing a heavier pile will require more dye to be injected. The easiest solution would be to increase the pressure but also a combination of higher pressure, a bit lower speed could be an option. When printing on a very dense high pile another option could be to lower the viscosity a bit. In order to get the best print results the operator has to use his/her experience and do trail and error when printing a new construction.

After printing the carpet is steamed, for typically 5-6 minutes to set the color > Washed to wash out non fixed dyes > Dried

The spot color jet printing technique is being used by many contract carpet and mat printers around the world and is a proven technology. The biggest technical issues are the reliability of the jets. For example, printing a checkerboard pattern where jets open and close, open and close for a long time was not possible on the 15.24 and 25.4 dpi machines. This would overheat the jets causing them to fail. When clogged for some reason it was also not possible to clean these jets. As technology evolves there are now version that you can clean yourself, have no issues to print checkerboard patterns and last longer. If you need more information on there type of jets please contact use. There are replacement jets for both 15.24 and 25.4 machine.

Designs for these machines have to be made manually. First step is to limited the number of colors in the design to the available number of machine colors. Next steps are to optimize the design for the print resolution. When doing this one has to also look at the resolution of the carpet. Printing a light color in 1 pixel (1mm) next to a dark color will result in an invisible line as colors will always blend a bit. In that case lines need to be at leas 2-4 pixels thick depending on color and color next to it.

Printing checkboard patterns is a way to blend some colors on some type or carpets. For example mid blue and dark blue will create a new blue on many carpet piles. Not all colors can be blended like this. This technique is used by us mainly on a 48 color machine. On this machine more than 100 extra colors are possible using this technique. Using the existing jets only small areas can be printed like this. The newer type of jets make it possible to print large areas. This can even be taken a step further using the 25.4 dpi jets and turn spot color printing into limited mixed color printing.

This jet printing technology is what we call the work horse or tractor in carpet printing.

Advantages:

  • Very wide range of dyes for many applications

  • Good penetration, even very heavy carpets

  • Consistent and controllable spot color printing

  • Forgiving, little change in viscosity / pressure doesn’t change the color only penetration.

  • Light or Heavy weight has limited effect on print speed.

Disadvantages

  • Limited number of colors, depending on configuration of the machine

  • Designs need to be adapted to limited number of colors and resolution = higher design costs.

  • Changing colors = no production

  • Checkboard type design only small areas on original jets.

  • Original jets can’t be cleaned yourself (doesn’t apply to replacement jets)

  • Limited lifetime on original jets

Chromojet 800 from spot to process colors.

A new printhead technology having a resolution of 3 pixels per cm or 76.2 dpi should enable mixing of colors on carpet. This is and was the basic idea of the Chromojet 800 as a next step in the evolution of carpet printing. Like the previous spot color printing, dyes can still be mixed yourself using a wide range of dyes. Dyes are mixed using a thickener and than printed onto the carpet. Like the spot color printers, that speed of the head can be adjusted and the pressure of the jets can also be adjusted.

A typical Chromojet 800 has 16 colors. In the original setup 14 were used and 2 were left open to print special colors. Printing process colors is completely different than printing spot colors. When a light color as spot color is premixed on process a light color is printed by printing less dye onto the carpet. In order to still have good penetration a chromojet 800 is typically loaded with dark and light colors. For example 100% blue and a light say 20% blue. When printing a 20% blue, 100% of the 20% blue is printed. As the dye is mixed into a paste there is never be more than 100% dye paste begin printed. Would you print 200% dye, the dye past would stay on top of the carpet and print would become unsharp

When printing process colors it also means that colors are being blended on the carpet. Blending colors seems like an easy process but when blending colors that are mixed in a thickener it is not as easy as it seems. Imagine a yoghurt in 2 colors and blending these, not easy.

Nylon has the problem of so called cold fixations. This means that part of the dye fixates cold, before it goes into the steamer. Problem is that cold fixation prevents dyes from partly properly mixing. The rate of cold fixation is also determined by the yarn manufacturer. As most white yarns were not printed but backdyed, mainly fast fixating yarns have been made the last years.

Another problem is that different dyes have different rates of fixations. A certain yellow could fixate faster than blue. Blending yellow and blue should give green but when their fixation rate is different the blend will not be a nice uniform green but more a multitone green. We have seen this issue and many logo mat manufacturers struggle with this.

In order to print consistent blended colors, colors need to be calibrated. Like inkjet printing a rip software is made for the Chromojet 800. In the beginning the problem was that basically the rip software only supported 6 base colors. Although the machine has 16 colors, Blue and light blue would be part of the same single color. The same would apply to black, darkgrey, light grey and transparent, 4 colors seen as 1. Since several years the rip software can support up to 8 colors enabling a bit wider range.

Calibration might sound simple but it also depends that the calibration device used. Carpet being a 3d material will never have 1 single color compared to single color printing on paper. This means when scanning a colors 5 times, you will get a different value every time. The actual device that scans also has an impact in the consistence of the scan and profile.

In the beginning only 200 colors were scanned and profiles from this were bad. Colors could flip from one mixed color to another. Later 750 colors were scanned making the profile better but still not perfect. These days it would be best to use at least 2000 colors. Again when you need to scan 2000 colors each 3 times (3 times for average value) = time-consuming. This process can be automated if needed.

Calibration is really the last step and many people forget the fist steps, finding colors that blend, thickener used and more important controlling the dye.

Controlling the dye and especially viscosity is important. When printing spot colors a small change in viscosity doesn’t change the color. When blending colors it means that you print say 50% yellow and 50% blue to get green. When the viscosity of yellow becomes lower because of heat it means lower viscosity = more liquid. As the time and pressure of the jets do not change, when printing yellow more dye will be printed at a lower viscosity. More dye printed means my color will change as the amount of blue is the same but more yellow.

Above was and is one of the issues of the Chromojet 800, consistency in colors. For applications like mats, small differences are not problem. For B2B contract where large runs need the same colors or the color on the sample chosen by a designer to match other materials, it is important to be able to match the color time after time. For the Chromojet 800 this remains a big challenge as even a base color can change from batch to batch.

A good color kitchen is a must. A color kitchen preferably computer controlled dye mixing to guarantee consistent colors.

The other issue when setting up a pallet for color blending is the range. Depending on the base colors you choose a certain range of colors can be printed. If one expects to be able to print say all colors this will not be possible. Purple should be a color you could mix from blue and red, reality is that on nylon this will never be purple. Brown shades from red yellow black, forget it.

The problem is you could use 14 (7+7) colors and 2 for special. This will limit your total range or you could use all 16 colors (8+8) and have a bit wider range but not hit all colors.

Getting the best out of this printer is a challenge and so far we have seen most companies owning this machine struggle to get is to work as it should. The problem here is the knowledge needed is specialized knowledge in different areas, color kitchen technology, dyes, thickener,calibration and combining this.  There are less than a handful people worldwide that have this knowledge and unfortunately for you, the machine manufacturer will not be able to help you on this.

Would chemical suppliers be able to help. Yes but only to what they think is best, mostly they would like to sell you there chemicals, this to compensate for this or something else for that, all to make it complicated or compensate for a problem that could be solved better. Combined knowledge is needed but, this is very difficult to get. Doing it yourself, good luck, you will not be the first that has failed controlling this machine.

Once you are able to get the machine to work as it should it does have several advantages. Where designs on a spot color printer need to be converted to the spot colors used, on a process color machine you can choose from a very wide range and have to choice to let the machine choose the colors or use a pallet of say 200 standard colors you defined. The print resolution being 3 pixels per cm 76.2 dpi is much higher than the spot color technology. This means it is more forgiving for small errors in the design. The resolution of the carpet is still the most important, although you can print finer most twist / heatset carpets have a poor resolution. A line still needs to be around 3 mm wide. Instead of 3 pixels it not needs to be 9 pixels. If that line converted from a jpg varies from 8-10 pixels one can’t really see the difference when it’s printed. When the base photorealistic artwork contains 10 shaded in the similar blue color it doesn’t need to be converted to a single color for photorealistic printing. In general this means that cost for making designs are lower. Especially for logo mat printing designs cost are far lower and could even be partially automated.

Were penetration on a chromojet 200/400 is not a problem on the chromojet 800 penetration of some colors can be a problem. Typically this is a problem for lighter colors. Where spot color printing could penetrate even heavier carpet piles, the 800 can still penetrate heavier piles, but a bit less than the spot color printing chromojet 200/400

Speed of the machine can be changed by increasing the print head speed or increasing the pressure on the jets. When increasing pressure or speed on needs to make a profile for this setting. Changing pressure more on 1 color could affect the mix rate and thus a different color would be printed.

Advantages:

  • Very wide range of dyes for many applications

  • Medium / good penetration, even very heavier carpets

  • Light or Heavy weight has limited effect on print speed.

  • Lower design cost

  • Wide color range but not all colors are possible.

Disadvantages

  • Needs deep knowledge on dyes, thickener, mixing, calibration.

  • Expensive color kitchen to mix dyes needed

  • Profile is needed for every carpet type / construction

  • Profiles need to be checked regularly summer winter, spring autumn profile ?

  • Not all colors can be printed a range has to be choose based on the base colors.

  • Not forgiving, dyes thickeners need to be controlled ph, viscosity, thickener % for consistent quality.

  • Not all colors blend well, many for so called two tone effect where colors are not uniform but a blend is clearly visible.

Inkjet carpet printing

As controlling mixing colors using the Chromojet 800 technology was complicated a logical step would be inkjet printing. When using inkjet, dyes come premixed and no color kitchen is needed (huge cost saving on color kitchen tanks etc). Another theoretical advantage would be more colors can be blended using only 4 base colors. It all sounds to good to be true and when looking more close it is to good to be true.

Although inkjet printing on carpet / mats has advantages there are many limitations one has to consider when using this technology. When comparing inkjet printing on carpet to the previous carpet printing techniques I compare them like this.

Chromojet 200/400 spot color printing is like a tractor / work horse. Fairly easy to control, reliable speed on different materials, forgiving.

Chromojet 800 process color printing is like a sportscar. You need to work hard, have knowledge to be able to control this technology.  You can’t sit back and relax.

Inkjet process color printing is like formula 1 technology. You need to control every single, small details, over and over again. Loosing the smallest grip will mean you will finish last.

There is a huge different between inkjet printing and the previous valve/pressure jet technology.

Speed

On a chromojet 200/400 and 800 the speeds is controlled by the speed of the carriage going from left to right and the pressure of the jets. Typically when printing a higher pile the pressure on the jets is increased, meaning more dye is injected into the carpet pile. Alternative the speed of the carriage can also be reduced a bit for higher pile weight and increased for higher pile weight. Although there is a difference in speed between heavy and light carpet piles the difference is not huge.

On an inkjet carpet printer there is no option to increase the pressure of the jets. As a carpet needs a minimum amount of ink het only option is to slow down the carriage so more ink can be printed. Alternative for heavy piles you can print multiple passes.

For example a 300-500 gr/m2 carpet can be printed in 2 passes (1 going left, 1 going right) When printing a 700-100 gr/m2 carpet this needs to be printed in 4 passes. This means that the print speed and also line speed on a heavy pile is ½ of that of a light weight pile. Would you consider printing 1400 gr/m2 you might need 6 passes which is again slower meaning 6 passes is only 1/3 of the speed compared to 2 pass.

  • At 2 pass your linear line speed could be 3 meters per minute.

  • At 4 pass your linear line speed could be 2 meters per minute.

  • At 6 pass your linear line speed could be 1 meter per minute

Why is the above so important ?

When installing a carpet/mat printing line the printer is just one part. After printing the carpets needs to be fixated, washed and dried. When printing nylon typically is needs around 6 minutes for steaming.

When printing 2 pass at 3 meters per minute this means your steamer needs to be 18 meters.

When printing 6 pass at 1 meter your steamer needs to be 6 meters.

This is where the problem starts.

When installing a printer bases on a line speed of 3 meters per minute and you would print at 6 pass 1 meter per minute your steamer washer and dyer will have a huge overcapacity. Not only overcapacity but also energy consumption unless you are able to shut down parts of the steamer and dryer. But even if you could do this you have invested in machinery / capacity steamer washer dryer that you don’t need. Also you have invested is space for this machinery. So when investing in inkjet you have to carefully look at the qualities you would like to print and what capacity you will need for this. In the end it could be more economical to install 2 smaller lines if you need to print a wide range of fabric weights.

Typically carpet printing companies install overcapacity. Machines are hardly filled for 1 shift and before more volume can be reached years go buy. When looking at the inkjet textile printing market things are done differently. Most companies buy a printer, when it’s capacity is full they buy a second printer, 4 years later a third printer where this third printer might be using newer faster printheads. 6 years later the first printer they bought is replaced by newer generation.

Dyes

As you have read when using the previous 2 technologies you had to mix your own dyes. For these technologies a very wide range of dyes are available from different manufacturers for many different application. Typically for demanding applications dyes having a good wash/wet and lightfastness can be used.

For inkjet the choice in dyes are very limited. The reason is also simple, volume. As there are many different types of printheads that each require they own ink, an ink needs to be specifically made for each brand/type of printhead. For carpet printing only printheads that can print large volumes of dyes can be used. For the moment, the 2 printer manufacturers that build printers for printing carpet/mats use the Fuji Starfire SG1024 printhead. When looking at the rest on the inkjet industry this is not a very popular widely used printhead.

So far the dyes we have seen for inkjet are unable to match both the wash/wet fastness levels of the dyes used for Chromojet 200/400/800 printing. In our opinion and testing nylon dyes for inkjet printing are not suitable for contract market at the moment. For non washable mats, no problem. We have also seen 1 manufacturer printing inkjet on washable rubber backed mats. Again the performance of these dyes is very poor compared to other 2 printing methods.We would advice everyone to do thorough checking for your application before investing in inkjet.

Please also note that wrong dyes can cause printhead problems. when buying dye not from the machine manufacturer and problems will happen one will blame the other. This is what happens. In the inkjet industry brands like Vutek, HP, Durst all offer their own dyes as part of a total solution. For carpet printing one company does not offer their own dyes while the other does make their own dyes.

Penetration

There is a big difference between inkjet printing and chromojet 200/400 and 800 printing. The chromojet system uses high pressure between1.5 and 3 bar (air) to inject dye deep into the pile. This dye is also bound to a thickener so that it will be pressed to the bottom of the pile but because of the higher viscosity it will also remain at the top. When top liquid it would be at the bottom and little at the top, causing frosting. Frosting is where the tips will remain part white.

When looking at inkjet there is no thickener and the dye is very liquid. There is also hardly any pressure compared the  other technology. Penetration on inkjet is far less. For mats we have seen examples of maximum 3-4 mm. For some carpets we have seen a bit deeper but this all depends on the construction of the carpet. More open =more easy for the dye to go down the pile. More closed and penetration is a problem. For heavy piles more passes are also needed to get the dye deeper into the pile. Here it’s also important if 1 big drop is printed of several smaller drops. The bigger the drop the more mass and the more penetration it will have.

Penetration also depends on the type of material you are printing on. Nylon or Polyester make a big difference. Nylon absorbs dye into the outside of the fiber. When printing, there will be so called cold fixation that starts after the dye hits the nylon. On polyester there is no cold fixation and heat is needed to push the dye into the fiber. There is also a relation between dye and penetration.

Few people will know that inkjet dyes contain mainly water. The price and quality of the dye depends on the amount of dry weight color in the ink. As any fiber needs a certain amount of dry color, the % of dry color pigments in the dye is very important. This is often seen as a trade secret or or can say to hide a cheaper price.

The dry pigment weight in an inkjet dye is typically between 5 and 12%.

You will understand that when printing a 1 kg/m2 nylon you will need twice the amount of ink when loaded with 5% color pigment compared to a 10% loaded ink. It also means that at 5% you will have to use more passes = 50% slower speeds.

I would urge every user to ask their supplier for a written statement on the amount of dry weight color pigment in their dye. Only than can you compare dyes and optimize speed.

Designs / Print resolution

When using inkjet the design process is far less complicated than on Chromojet 200/400 or 800. As the resolution of print is higher 1 or 3 pixels difference should not make any difference. Still the carpet determines the print resolution. Designs can be easily printed, sometime without modification. This will lower your design cost. Especially for printing mats this will mean a huge saving in design cost.

When printing on a say 600 gr/m2 open twisted yarn, the print result when using inkjet will not differ much when compared to Chromojet 800 and sometimes even 200/400. The resolution of inkjet can mainly be seen on low or very dense carpets. There is still an advantage on the number of colors and the color range that can be printed using inkjet.

The color range when using 4 colors will be better than a well balanced Chromojet 800 but 4 color inkjet printing still has limitation.

Inkjet printing was and is mainly used for flat 2d materials. When printing say at 800 dpi on paper using 4 base colors. The fine raster will enable you to print a wider color range. This is mainly because the raster tricks the human eye.

One could say that 4 base colors printed on 800 dpi would give the same color gamut as 8 base colors printed on 400 dpi. This is truent but sadly for carpets it only works on paper. When printing on carpet the fine raster will not work as the resolution of the carpet is far lower. In the end colors will be blended. This is why I call printing on carpet a 3d inkjet printing, you have to think penetration = 3d.

The only option to get a wider color gamut is by adding 2 or 4 extra colors. The downside is that this will increase the cost of the machine but will not give any extra speed.

For color demanding application I would although suggest to have at least 6 or even better 8 base colors. This will give you a better color range and the ability to offer printed products in more color demanding markets.

Reliability.

For printing reliability is important. The ability to print the same quality all year round. This is why I call inkjet printing on carpet formule 1 technology. You need to control every aspect to be able to print reliable. In the inkjet market it is long known that temperature is key to reliable printing. When the temperature gets to high colors change. To low the same can happen. Typically inkjet on textile, or paper printing companies have different type of buildings than carpet printing companies. Typically a carpet printer is housed in a big building, many doors, open an close. As it is big there is little temperature control and during the year temperature can vary. Sadly we have seen that inkjet printers on carpet were sold and placed in regular production halls without any climate control. After some time it was than advised to place the printed in a climate controlled room. This should have been done at the beginning. But still placing only the printer in a climate controlled room is not enough.

Imagine the climate controlled room is between 19 and 21 degrees all your round. You load a big carpet roll into the machine but you still see a difference in color, why ? Again inkjet printing, formula 1 technology = total control.

Your big carpet roll is typically stored in a non climate controlled warehouse. Say 10 degrees C in winter and up to 30 degrees C in summer. Image what happens if you load a 10 degrees C stored carpet roll into the climate controlled printer room at 20 degrees C, or a 30 degrees C stored carpet roll. The result will be a different printed colors and for demanding b2b users this will cause a problem.

This will mean you have to for, example pre-wash you stored roll, or when not pre treated have it warmed up or cooled down to the temperature of your climate controlled print room.

One of the companies offering inkjet printers on carpet is new to the inkjet market and without having a history in building inkjet printers they started building a formula 1 inkjet printer. As you can imagine this is not easy and we have seen basic construction problems in these machines causing printheads to fail or having to be replaced because of these problems. At around $4000 a piece this is not cheap. Also replacing them can be time consuming. This construction issue has long been solved by other manufacturers that had previous knowlegde on building inkjet printers

So when buying inkjet look at the history of the company in the field of inkjet and their knowledge. Small things can make a big difference in reliability.

Think about what carpet weight you would like to print, what capacity you will need.

Advantages:

  • No color kitchen needed to mixed dyes

  • Very low design cost

  • Wide color range but not all colors are possible when using 4 base colors / 8 base colors could offer up to 95% of all pantone colors.

  • Good print sharpness on light low pile caprets.

  • Lots of software available form the inkjet industry to control your printing / workflow automation.

Disadvantages

  • Low/medium penetration.

  • Limited type of dyes to choose from.

  • Carpet needs to be designed for inkjet keeping it’s limitations in mind.

  • Lower wash/wet lightfastness on dyes compared to Chromojet 200/400/800

  • Light or heavy pile weight has big impact on print / line speed.

  • Profile is needed for every carpet type / construction

  • Needs a climate controlled environment for best result, including climate controlled or treated carpet.

  • Not all colors blend well, many for so called two tone effect where colors are not uniform but a blend is clearly visible (only on nylon not polyester)

As you can see printing on carpets has evolved but in this case evolution comes at many cost.

Where on the first generation you have spot colors, limited resolution you could print almost any white carpet even high piles and offer great wet/wash and color fastness.

The last generation inkjet has a wide color range, good resolution but limited penetration, carpet needs to be designed specifically for inkjet, wet/wash and light fastness are lower the the spot color printing.

In the end when looking at inkjet technology don't get blinded by samples from a lab. lab scale samples are not production samples and controlling inkjet in a small lab is far easier than in a big production location.

I hope the above information was helpful. Above information comes from my experience in carpet printing since 1995. Input of other experts in carpet printing field. Suggestions, remarks or advice needed when looking at carpet / mat printing, please contact me.

Above information is my personal opinion on carpet printing - Bob Balings