DOES THIS HAPPEN TO YOU?
You’re running your gravure coater almost at full speed – not what the machine was designed to do, but what you can get out of it – and your web keeps wrinkling due to poor tension control. Or perhaps every time the temperature outside rises above 80 degrees the line speed set point drifts. Maybe you’re just plain tired of excessive downtime and buying replacement parts on eBay. Here are a few more of the issues that EDC commonly finds hampering their customers’ success:
- Lack of correct tension control – web runs too tight or too slack
- Rewind staring or telescoping
- Lack of proper pressure at the laminator section
- Inconsistent coating thickness or application
- Wrinkled or off-track web
- Improperly controlled temperatures
- Inoperative machine sections
- Slower than expected run rates
- Shift-to-shift variability
- Unscheduled and/or frequent downtime
- Failed automatic splices
- Unstable dancer
There are many ways to approach eliminating one or more of the above coating and laminating pain points. Here are some ideas depending on the nature of the issue, the time available to address them, and, of course, your budget:
Attack a specific component or two to relieve the pressure.
Stuff gets old. Components become incompatible. Dirt and grime cause all kinds of problems. Replacing just one item can make a world of difference. Here are a few examples:
- Check the wiring first! – EDC’s mantra and go-to before changing anything. Depending on the complexity of the controls (or the rat’s nest in your enclosure), a day of troubleshooting with a controls expert will pay for itself
- Replace the unwind I/P (current-to-pressure regulator) – it could be dirty or clogged or the analog circuitry is failing, preventing proper pressure regulation to the unwind brakes, which is directly related to tension control.
- Don’t forget to change the brake pads – just like for your car, these pads are only rated for so many miles and require routine maintenance
- Recalibrate the load cells – poor feedback leads to poor control
- Clear the air – make sure your compressed air source is clean, moisture-free and properly oiled. Stiction in pneumatic cylinders (think nips) is your enemy
- Motor checks, Part I – start by megging the motors to check for shorts or insulation breakdown. If you have DC motors, check/change the brushes. And while you’re down, make sure all the mechanical elements, belts and pulleys are tight. We have had plenty of drive service calls that turned out to be a loose coupling.
- Motor checks, Part II – A previous maintenance team may have swapped a failed motor for a lower horsepower, getting away with it because the frame size is similar enough. Now your line speed is compromised since you do not have enough torque. Likewise, if you want to increase your line speed, you’ll likely have to start by increasing motor horsepower and perhaps mechanical component sizes. Remember:
HP = LINE SPEED (feet/min.) x PLI (lbs per linear inch tension) x WEB WIDTH (inches)
For motorized rewinds and unwinds, multiply the resulting HP by the build-up ratio.
FOCUS ON A MACHINE SECTION
Unwinds, rewinds, flying splices, printing heads, laminators and accumulators – these are of course some of the sections of a coating and laminating line that need coordinated components to function properly. You may not need to retrofit the whole line or may not have the time and money to do so. Perhaps you can focus on a single problem area:
- As an example, some coating sections utilize three motors to get the job done. Replacing the motors and drives will breathe new life into that critical section. You may want to take it a step further and convert your old, hard-to-find DC motor to AC. Tying together the DC buses of an unwind and rewind will save energy and may eliminate the need for a regen drive.
- Maybe your PLC is a generation or two old. Instead of yanking out the entire rack, add a stand-alone CPU and use the rack and existing wiring as remote I/O. The PLC program can be converted and tested offline prior to installation saving hours or even days. This can also provide a foundation for modern-day machine communications (think IIoT) and manufacturing intelligence, helping you to capture and analyze key performance indicators (KPIs).
- Similarly, you may have what’s called “islands of automation,” where a line contains two or more independently functioning PLC’s or dedicated controllers. Again, utilizing the remote I/O strategy the PLC or controller can be replaced with I/O that can communicate with the main PLC. The code is moved to the single, main PLC CPU which has faster scan times, modern control capabilities and improved overall performance.
- Add a tension zone – if you’re having problems controlling tension between sections and there is no dancer or load cells, this could solve your problem. There are companies that build dancers that can be retrofitted into your line. You may already have an idler roll on which a pair of load cells could be added. Even if you do not, there are companies that can make very simple dead-shaft idler rolls to your specs. Whether you go with a dancer an idler roll/load cell combo, having a reputable controls integrator install, wire and program everything will be money well spent.
- Edge guides – Whether you have a linear guide at an unwind or rewind or a steering guide at your oven exit, these critical systems are often overlooked. Always check your bearings, guides and mechanical components first, but many manufacturers offer drop-in replacement controls and actuators that will reduce the changeover time. If you have a home-grown system, you may want to isolate it from the PLC to give your PLC one less thing to worry about.
- Has something changed in your process? Are you running faster or maybe using a heavier film or paper? Maybe an operator cranked up the pressure/tension, which is causing a machine section to under-perform. Again, by taking a sectional approach, you can likely isolate an issue and determine which inter-related components are causing the largest headaches.
FULL LINE RETROFIT
Now it’s time to bite the bullet. No more band aids, no partial fixes. You have budgeted the funds and are building up enough stock to cover you for the line being down during the turnover demo/installation window. Despite the fear that you may be feeling, an expert systems integration firm will help ensure you get another 20+ years from the newly installed controls. A full retrofit can encompass some or all of the fixes recently cited plus the following:
- Create PLC architecture that includes HMIs, remote I/O and drives all on the same communications network
- Eliminate outdated comms protocols or those with less bandwidth such as DeviceNet, ControlNet, Modbus, PROFIBUS, IO-Link, etc.
- Install HMIs that replace rows of pushbuttons, dials, meters and operators (keep the buttons you use most often!). Add recipe capability, alarm screens and user-friendly graphics.
- Replace analog or obsolete drives with late model drives networked to the PLC. Utilize advanced PID function blocks in the PLC rather than the drives
- Improve the overall safety of the line, perhaps utilizing a failsafe PLC and/or adding cable operated switches and interlocks to replace unsafe microswitch devices; replace existing E-stop buttons with illuminated versions that will tell the operator which button or zone has been depressed
- Replace load cells and amplifiers – ones that work all day, every day!
- Completely rewire the line to get rid of jumpers, splices and wires that no one knows where they come from. At the same time add proper grounding and shielding, perhaps using VFD cabling.
- Replace OEM-designed motors/geartrains or electrical components with off-the-shelf counterparts from major automation controls manufacturers (ABB, Parker, Rockwell Automation, Schneider, Siemens, Yaskawa, etc.)
- Consolidate disparate control panels into a new enclosure or enclosure group with proper electrical design, layout, labeling and no wires lying around in the bottom
- Resuscitate defunct machine sections and functionality
- Add an encrypted remote access device that makes it possible for the systems integrator or other vendors to troubleshoot your line from anywhere in the world. Have an overbearing IT ogre who won’t let you into the company network (who doesn’t) – use a cellular-enabled device or connect to your internet only when needed. One less service man’s plane ticket, hotel and meals will pay for it many times over!
If your coating and laminating line keeps you up at night or away from home on the weekends, there are many relatively small strategies you can employ to take a bite out of the larger issues. And if need be or if it is just that time, you can retrofit the whole line without needing to install a more expensive, completely new line for a fraction of the cost and in less time.
ADDITIONAL EDC CASE STUDIES
- Film Coating Line Downtime Resolved – Orafol
- Adhesive Coating Line Upgrade
- Multi-Axis Stepper Controls
If you need further help with your coating and laminating line, reach out to EDC today.