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Digital drives are essential.

Why Digital Drives Are Essential for Accuracy, Consistency and Resolution

“Servo motors are the lifeblood of Delta ModTech machines,” explains Rob Hattling, Senior Electrical Engineer with Delta ModTech. “They allow us to master the motion of nipped rollers, rotary dies and spindles.”

Rob Hattling

Rob Hattling, Delta ModTech

We first started using servo motors in 1983, when Delta ModTech owner Dave Schiebout decided to boldly go where no converter had gone before.

He replaced the mechanical approach with servo motors, and accuracy improved by 25 times (even without a sophisticated control).  This allowed us to achieve tight tolerances for the converting industry.

In recent years, as Rob Hattling, Senior Electrical Engineer with Delta ModTech explains in the video below (and throughout the rest of this post), the accuracy has increased significantly as we’ve entered the digital age.

Digital drives taking us to a whole new level

The credit for recent increases in accuracy goes to our switch from analog to digital drives in 2002, according to Hattling.

Analog drives use machine components to represent the passing of time.  In a watch with a minute hand, time is measured by how quickly the minute hand sweeps across the face of a watch.  It’s a representation, or analogy, of time. (Source)

With a digital drive, this representation takes the form of digits. Information is converted into these digits, then displayed and stored. When a servo drive goes digital, it allows for several significant advancements:

Digital signals avoid errors.

Consistency and Accuracy – Because the signal is digital, we avoid the inherent errors of an analog system.  The feedback from the sensor is always the same. Analog feedback can vary, which can make all the difference when you’re dealing with microns.

Resolution – The advent of digital controls is similar to the evolution of TV sets.  From the days of CRT tube TVs of the 1990s to today’s 85” 4K LED TVs, resolution has taken a quantum leap.  The types of resolution translate to the digital controls.

Check out the advancements in our machines as we’ve converted servo drives to digital.  

2002 – Partial transition to digital drives


  • 32x better resolution
  • Greater consistency in turning and permanence
  • Electronic accuracies of 0.00003” (1 micron)

2007 – Complete switch to complete digital systems


  • Synchronization of larger systems
  • Generate faster response and greater accuracies
  • Electronically gear up to 256 servos

Building "impossible" systems.

“The ability to add up to 256 servos allows us to build systems we previously would have considered impossible,” Rob said.

2009 – Switched to the next generation of digital drives, the Sigma 5 Controls

Gained 10x, down to nearly 0.1 microns of accuracy, or 0.000004”

We’re also now moving to the Sigma 7 controls as the standard for new machines.  These deliver 16x better resolution than previous drivers.

Accuracies are down into the submicrons.

“We’re getting electronic accuracies down into the submicrons. 2E-7” (0.006 micons) or over 4 million counts/inch,” said Rob.  

What does greater accuracy, consistency and resolution mean for converters?

How does the transition to digital drives better serve converters?

Accuracy improvements up to 100x

Rob notes that we’ve seen accuracies improve up to 100x, which will translate into improved accuracies on the web with your materials.

Greater speeds with the same repeatability and tooling

You should generate higher throughput with the same piece of machinery. With an analog machine, if you increase the speed, the accuracy suffers, which limits your machine speed. Digital controls allows for greater accuracy with increased speed allowing greater production rates.

Increased speed allows greater production.

Improvements with Camming and island placements and P-Camming

You get a lot cleaner transfer and allows for greater speed – 1000 parts / minute and

Accuracy – 20x improved.

Improved tension controls

We were able to improve the algorithms on the digital drives to help with tension control.  We’re now able to get stable tensions down to half a pound.

Integrating vision systems for even greater accuracy

The advantages of the digital drives get an added boost by our integration of MOD-Track Vision Systems.  By using the feedback/data generated by the vision systems, and then doing some averaging, we’ve been able to generate even greater accuracy by:

  • Adjusting die registration offsets to track the web
  • Steering guide for cross web
  • Adjusting positions for printing

Good to great: The digital divide continues to widen

Writer/blogger/entrepreneur Jonathan Fields wrote, “In art, business, and entrepreneurship, there is no coasting.  There is no neutral. No sideways…there’s only up and down. Leading or trailing.”

The use of servo motors ushered in a new world of possibilities to the converting industry.  The advent of digital controls has ensured there was no “coasting” or “neutral.” It’s allowed us to reach further than we ever dreamed possible.  

And if the past is prescient, it’s a sign we’re just getting started.