Compensating for blocked or deviated nozzles

As digital presses become wider and higher resolution, supporting additional inks beyond CMYK, the total number of nozzles required per press increases, which in turn raises the likelihood of at least one of those nozzles failing to jet or becoming deviated (and needing to be disabled). Each nozzle that is out will result in a lack of ink where it should have been in a straight line along the direction of print.

One obvious response would be to fix the problematic nozzles, when they have been detected, but this kind of physical intervention interrupts production and can be impractical. Replacing the affected printhead altogether is another possibility, but again this will have an unwelcome financial impact.

Our sister company, Meteor Inkjet, offers NozzleFix™, an embedded software/hardware solution to compensate for missing nozzles.  But for digital printing equipment which does not incorporate Meteor printhead electronics, software compensation may also be beneficial.  In this post, we will look at a software-based approach where good working nozzles can compensate for any misbehaving neighbors as required.

Nozzle-Out compensation in software

As the word “compensation” suggests, this solution works by telling certain nozzles to jet more ink than they otherwise would have to make up for a deficit caused by nozzles that were not jetting or had to be turned off because they had deviated.

For one-drop screening, this could mean that whenever a drop should have been output by a nozzle that’s out, a nozzle on either side could be asked to jet that drop instead. An alternative to this, which can accommodate any drop size, is to apply compensation before screening, working with intensities rather than drops.

Here’s how it works: when a nozzle is off, the intensity for each pixel associated with that nozzle is used to boost the intensity of neighboring pixels, which are then screened as normal.

This is best understood by way of an example. Consider an 8-bit continuous tone input TIFF™ which has the value 160 for every pixel. If we are using one neighbor on either side of a pixel to compensate, we will add 80 to their intensity before screening. If we are using two neighbors on each side, we would add 40.

The greatly zoomed-in images above illustrate the results after 3-drop screening for this example: the left image has one nozzle out and no compensation; the middle image shows compensation with one neighbor either side; the right image shows the use of two neighbors on each side.

Of course, the impact is best judged from the actual prints, where the combination of high resolution and ink results in an impressive optical illusion!

Image shows nozzles out and then a compensated version

 

The scans above were printed at 1200dpi. The image on the left simulates a number of missing nozzles, which can be seen by the presence of thin horizontal white lines (you may need to enlarge it for the full effect). The image on the right shows the impact of applying compensation to each nozzle neighboring a missing nozzle.

Rapid response and adjustment

A key benefit of this software-based approach is that a rapid response and adjustment can happen as soon as a problematic nozzle is detected. There is no need to wait for engineer and parts availability. Additionally, there is no trade-off to make between taking costly action each time a problematic nozzle presents itself or having a tolerance or threshold where nothing is done until a certain number of quality issues have accumulated.

Learn more about the technologies available to improve the quality of your inkjet output by visiting our website.

About the author

Ian Bolton, Product Manager, Direct
Ian Bolton, Product Manager – Direct

Ian has over 15 years’ experience in industry as a software engineer focusing on high performance. With a passion for problem-solving, Ian’s role as product manager for the Direct range gives him the opportunity to work with printer OEMs and break down any new technology barriers that may be preventing them from reaching their digital printer’s full potential.

Further reading:

  1. What causes banding in inkjet? (And the smart software solution to fix it.)
  2. Streaks and Banding: Measuring macro uniformity in the context of optimization processes for inkjet printing

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Is your printer software up to the job? The impact of rising data rates on software evolved from traditional print processes

Direct™ product manager Ian Bolton explores the impact of using software that has evolved from traditional print processes to drive digital inkjet presses as they advance to print faster, in higher resolution, a wider variety of colors and applications. In particular, Ian focuses on the impact that rising data rates have on the workflow:

Digital press software evolved from traditional print processes has already reached its limit. Digital presses are becoming higher resolution – most are moving from 600 dpi to 1200 dpi, quadrupling the data. They’re also becoming deeper, with up to 7 drop sizes – and these drops are being made from a wider variety of colors. Digital presses are also becoming wider, up to 4 meters wide, and faster,  up to 1,000 feet per minute!

And what if you need to print where every item is different? For example, fully personalized – like curtains, flooring, wall coverings, clothing etc. All of these require software that can deliver ultra-high data rates.

Let’s look at how those data rates scale up as digital presses advance:

The next generation presses demand ultra-high data rates
The next generation presses demand ultra-high data rates

 

If we start with 600 dpi, 20 inches wide, 3 drop sizes and 100 m per minute, then that’s 120 MBps per colorant, which is not too challenging. But once we move up to 1200 dpi, we’ve now quadrupled the data to 480 MBps, which is the read speed of all but the most bleeding-edge solid state drives today.

With printhead, nozzle and roller technology improving, the rated speeds also increase, so what happens when we go up to 300 m per min? It’s now 1.4 GBps and you will need one of those bleeding-edge solid state drives to keep up, bearing in mind you will now be writing as well as reading.

And if we go wider to print our wallcoverings at 40 inches wide, we’re now at 2.8 GBps … and we want our walls to look great close up, so we might be using 7 drop sizes, which takes us up to 5.7 GBps … and this is all just for one colorant!

Based on these numbers, it should be clear now that, for this generation of digital presses and beyond, a disk-based workflow just isn’t going to cut it: reading and writing this amount of data to disk would not actually be fast enough and would require ridiculous amounts of physical storage. This is where software evolved from traditional workflows hits a barrier: the data rate barrier.

To solve this we need to go back to the drawing board. It’s similar to the engineering challenge of moving from propeller-driven aircraft to jets that could break the sound barrier. Firstly, you need to develop a new engine and then you need to commercialize it.

So, if you’re looking for software to power your first or next digital press it’s going to need the right  kind of software engine that isn’t based on disk technology so that you can drive your digital press electronics directly and smash through the data rate barrier. In other words, you need to go Direct.

To learn more about the impact of rising data rates and how you can futureproof your next digital press, visit our website to find out more about going Direct.

If you’re interested in calculating data rates take a look at this blog post where you can download your own data rate calculator: Choosing the class of your raster image processor

Further reading:

  1. Harlequin Core – the heart of your digital press
  2. What is a raster image processor 
  3. Ditch the disk: a new generation of RIPs to drive your digital press
  4. Is your printer software up to the job?
  5. Where is screening performed in the workflow
  6. What is halftone screening?
  7. Unlocking document potential
  8. Future-proofing your digital press to cope with rising data rates

About the author

Ian Bolton, Product Manager, Direct
Ian Bolton, Product Manager – Direct
Ian has over 15 years’ experience in industry as a software engineer focusing on high performance. With a passion for problem-solving, Ian’s role as product manager for the Direct™ range gives him the opportunity to work with printer OEMs and break down any new technology barriers that may be preventing them from reaching their digital printer’s full potential.

To be the first to receive our blog posts, news updates and product news why not subscribe to our monthly newsletter? Subscribe here

Follow us on LinkedInTwitter and YouTube

Choosing the software to drive your digital inkjet press

When developing your first or next digital press, the software you use to drive it will be a key factor in its success, both for the data rates and output quality you can achieve. The time it takes to get your press to market based on the engineering effort involved to deliver and integrate that software is also a consideration.

A simple user interface to get  you started

The Press Operator Controller (POC) is an example front end or user interface available with Harlequin Direct™ , the software solution that drives printhead electronics at ultra-high data rates while retaining high output quality. The POC provides you with an initial working system, so you’re up and running without any significant in-house software development. We provide you with the source code so that you have the option to update and integrate it as part of your production system.

I have created a short video to show you its main functions:

You can find out more information about the Direct™ range of products by visiting our website: https://www.globalgraphics.com/products/direct

Further reading about considerations when choosing your digital inkjet press:

  1. How do I choose the right PC specification for my digital press workflow
  2. Future-proofing your digital press to cope with rising data rates
  3. Looking to reduce errors with simple job management, keep control of color, and run at ultra-high speed for jobs with variable data?

About the author

Ian Bolton, Product Manager, Direct
Ian Bolton, Product Manager – Direct

Ian has over 15 years’ experience in industry as a software engineer focusing on high performance. With a passion for problem-solving, Ian’s role as product manager for the Direct range gives him the opportunity to work with printer OEMs and break down any new technology barriers that may be preventing them from reaching their digital printer’s full potential.

Be the first to receive our news updates and product news. Why not subscribe to our monthly newsletter? Subscribe here

Follow us on LinkedIn and Twitter

How do I choose the right PC specification for my digital press workflow?

When planning the implementation of your first or next digital press, the PC specification you choose to run your software workflow will play an important part in the data rates you will be able to achieve. Assuming you are not bottlenecked by disk drive performance due to requiring intermediate disk accesses, you can generally expect data rates to rise with the computational power of your PC.

It might therefore make sense to review the PassMark scores for a range of CPUs within your budget and make your choice based on that, but this alone won’t be enough to tell you whether you’ll be able to drive your printer at full rated speed. Similarly, you may already have an existing PC system in mind but need to know if it will be powerful enough for your new requirements.

Ideally, you could set up an evaluation system to run some typical print jobs to get a definitive answer, but this could be costly and labor-intensive, especially if this is your first digital press.

It’s for this reason we created Direct Benchmark™: an analysis tool that exercises Harlequin Direct™, our ultra-high data rate RIPping and screening solution, with your choice of press configuration and print jobs, stepping through a tuning cycle to obtain a series of data rates and line speeds that can be achieved.

There are two main ways Direct Benchmark can help you: firstly, if you have an existing PC system to run on, you can install Direct Benchmark and gather your own results; secondly, you could base your decision on a database of Direct Benchmark results we are gathering here at Global Graphics Software from running a variety of jobs on a range of PC specifications.

Running Direct Benchmark yourself

Whilst a real Harlequin Direct system would be connected to printhead electronics and driving your press directly, the Harlequin Direct invoked by Direct Benchmark doesn’t require this connection. This makes it very quick and easy to install and start gathering performance numbers. The screenshot below shows the settings you can use to reflect your printer configuration and define the print jobs to benchmark.

During benchmarking, you will be presented with a screen showing statistics for each run and a real-time graph of data rate at the bottom, and then you will be able to export the results at the end. If you would like to see Direct Benchmark in action, you can view a short demo here:

Using the Direct Benchmark database

If you aren’t in a position to run Direct Benchmark yourself, we are in the process of gathering results for a range of press configurations and print jobs, running on a variety of PC hardware specifications. This is being conducted in conjunction with Proactive Technologies, who are providing access to some of the machines we’re using. Whilst it is too early to draw any conclusions or share our results at this stage, if you have some typical print jobs and a press configuration in mind, please get in touch with me, ian.bolton@globalgraphics.com, because we may be able to generate the results for you.

For more information about Direct, please visit globalgraphics.com/direct

To be the first to receive our blog posts, news updates and product news why not subscribe to our monthly newsletter? Subscribe here

Follow us on LinkedIn and Twitter

About the author:

Ian Bolton, Product Manager, Direct
Ian Bolton, Product Manager – Direct

Ian has over 15 years’ experience in industry as a software engineer focusing on high performance. With a passion for problem-solving, Ian’s role as product manager for the Direct range gives him the opportunity to work with printer OEMs and break down any new technology barriers that may be preventing them from reaching their digital printer’s full potential.

 

How to accurately calculate the ink costs for your digital press

There are many costs that can impact your profitability when running a production digital press, from power consumption to the substrate you’re printing on. One of the most variable costs is ink consumption, which often varies from job to job and therefore can be difficult to estimate. As you might expect, the content to be printed is the key determining factor, but you also need to consider the resolution, screening method, drop sizes and choice of colorants. This can bring quite a challenge for a press shop when quoting for a job, especially if the client is open to hearing a range of options.

Even with a static job that might be suitable for a test print run to get a cost that can be multiplied for the number of copies, it’s still not ideal to have to spend any time or other resources using the actual press. It’s much better to be able to get an accurate ink cost estimate away from the press, which is where our Job Cost Estimator comes in. It’s available as part of our Direct™ software range as well as our Harlequin Host Renderer™ and ScreenPro™ products. It uses the same setup that drives your printer, calculating a very accurate estimate of the ink cost for a specific job. Self-contained, it doesn’t require any connection to your printer, which makes it ideal when you want to give a job cost indication away from the print shop.

The screenshot shows a calculation performed using our Job Cost Estimator for a 1200x1200 dpi version of our two-page Direct brochure, screened with 4-drop pearl.

The screenshot above shows a calculation performed using our Job Cost Estimator for a 1200×1200 dpi version of our two-page Direct brochure, screened with 4-drop pearl. Under Cost Per Page, this is the average cost per page per colorant based on the two pages that were analyzed, with a final row showing the total (All). This is then multiplied by the total pages and the number of copies to get the Cost Per Job for each row.

Obviously, no costs can be determined without knowing how much the inks cost per liter, so you can set these within the application. Similarly, you will need to configure your printhead(s) to specify how many picoliters of ink are used per drop size.

As you can see from the left image above, we have assigned a different printhead for Black called Budget_PrintHead, which will have fewer picoliters per drop size than the Default_PrintHead shown on the right, to represent a possible response to a hypothetical jump in the price of black ink.

The Job Cost Estimator has been designed to be extensible, so it would be possible in future to incorporate other costs, such as paper, or factor in ink used periodically for nozzle refreshing, for example.

If you’d like to know more about the Job Cost Estimator, watch my short demonstration here:

For more information visit the Direct pages on our website: globalgraphics.com/direct

To be the first to receive our blog posts, news updates and product news why not subscribe to our monthly newsletter? Subscribe here

About the author:

Ian Bolton, Product Manager, Direct
Ian Bolton, Product Manager – Direct

Ian has over 15 years’ experience in industry as a software engineer focusing on high performance. With a passion for problem-solving, Ian’s role as product manager for the Direct range gives him the opportunity to work with printer OEMs and break down any new technology barriers that may be preventing them from reaching their digital printer’s full potential.

Future-proofing your digital press to cope with rising data rates

When we hear the phrase “big data”, we’re meant to think of extremely large data sets that are too complex to process in traditional ways. But, in the context of the next generation of digital presses, you’d be forgiven for thinking it refers to the ultra-high data rates required to drive them.

For example, consider a typical narrow-web label press: 13 inches (330mm) wide, 4 colors, 600x600dpi, running at 230 fpm (70m/min). This requires 0.9 GB/s of raster data to drive it at its rated speed.

Assuming next year’s press adds three more colors (Orange, Green and White) and is upgraded to 1200x1200dpi and expected to run a little faster at 330 fpm (100m/min), the required data rate will jump to 8.6 GB/s: almost a factor of ten increase!

Already this is a data rate far in excess of what the fastest solid-state drives can manage, so what hope is there for a traditional disk-based workflow when moving to 20 inches wide, duplex or 200m/min? Clearly, any part of the workflow involving a disk drive is going to become a bottleneck.

Ditch the disk with Direct
Ditch the disk. Rather than write intermediate raster files to disk between RIPping and screening, or between screening and the printhead electronics, everything takes place in memory.

This was one of the reasons behind the creation of Direct™, the integrated software pipeline we announced at the end of April. Rather than write intermediate raster files to disk between RIPping and screening, or between screening and the printhead electronics, everything takes place in memory.

There’s more to future-proofing your press than eliminating comparatively slow disk accesses, however. You’ll need a system that’s scalable and built from the fastest components, which is why Harlequin Direct™ is composed from a configurable number of Harlequin Host Renderer™ and ScreenPro™ instances working in parallel to make the best of the most powerful desktop PCs available.

When it comes to adding new colors or supporting duplex, the scalability extends to multiple Harlequin Directs across multiple PCs, one per print bar.

When it comes to adding new colors or supporting duplex, the scalability extends to multiple Harlequin Directs across multiple PCs, one per printbar.

An added advantage of this approach is that each printbar need not use the same resolution or drop-count etc. For example, you might wish to use a lower resolution and disable color management for white or varnish. Our Press Operator Controller user interface is supplied to manage your configuration, along with submitting and controlling your print jobs.

Our Press Operator Controller user interface is supplied to manage your configuration, along with submitting and controlling your print jobs.

The beauty of a software-only solution like Direct is that once you have built it into your workflow, you are free to upgrade your PCs over time for greater performance without any further software integration expense. A Direct-based system will evolve as your needs evolve, making it the ideal choice for future-proofing your next digital press.

For more information about Direct, please visit globalgraphics.com/direct.

To be the first to receive our blog posts, news updates and product news why not subscribe to our monthly newsletter? Subscribe here

Ian Bolton, Product Manager, Direct
Ian Bolton, Product Manager, Direct

About the author:
Ian has over 15 years’ experience in industry as a software engineer focusing on high performance. With a passion for problem-solving, Ian’s role as product manager for the Direct range gives him the opportunity to work with printer OEMs and break down any new technology barriers that may be preventing them from reaching their digital printer’s full potential.