Stacking up savings with servo
A leading packaging manufacturer has made significant savings by installing an ABB motion control drive as part of the refurbishment of a sheet stacking machine
A leading UK manufacturer of corrugated cardboard packaging has saved nearly £70,000 by using ABB motion control products in a refurbishment project on a cardboard sheet stacking machine. Designed to allow the continuous stacking and discharging of cardboard sheets, the stacker at Smurfit
Kappa consists of two hydraulic lift tables each fed via five conveyor sections. The speed of each section was controlled by its own 7.5 kW servo drive to match the loading cycle of the lift tables but when this failed the company contacted ABB.
“We approached the stacker OEM for a replacement servo drive but were informed that these were now obsolete and no longer stocked,” explains senior electrical engineer Phil Davies. “Fortunately we could loan a spare drive from our sister plant in Dublin while we looked for a permanent solution.”
The OEM was able to offer Davies a newer servo drive at a cost of £7,600 per drive. “The company recommended that we had a service engineer on site to oversee the installation and carry out the subsequent commissioning. This would have required an investment of around £82,000 and a week’s shutdown to install had we decided to replace all of the drives in one go.”
Already a preferred supplier of variable speed drives at the plant , ABB offered two options: supplying an ABB industrial drive and a new motor gearbox; or an ABB ACSM1 motion control drive and reusing the existing servo motor gearboxes.
Weighing up the options
“The first option initially looked like the simpler solution, given the reasonably straightforward application of controlling the conveyor’s speed,” continues Davies. “However, the additional work involved with changing all the existing servo motors for standard AC motors made it physically a much bigger project.”
However the second option presented its own challenges as the company had limited experience with installing and commissioning servo drives. Davies was reassured that ABB could provide all the technical support needed. This option was less expensive than the one proposed by the stacker OEM with the cost for one servo drive complete with a filter, choke and resolver interface card representing a 70% saving on the alternative solution.
The first stage of the project involved installing an ACSM1 to prove the equipment which was completed over a weekend.
Cabling completed in advance
“We were able to install the new drive alongside an existing one and carry out most of the cabling in advance,” explains Davies. “This allowed us time to commission the drive and ensure the speed of the conveyor was correct.”
The ACSM1 worked with the original permanent magnet motor and set up and commissioning went ahead with no major problems. The next step was to decide whether to change all of the remaining drives or just enough to release some spares.
“As the stacker is in two levels, each with its own control cabinet, a sensible solution was to replace all of the drives in one level,” continues Davies. “This would help keep investment to a minimum while freeing up spares for the other level and for other plants within the group.”
As the replacement drive was on the lower stacker it was decided to replace all the servo drives in this unit including an obsolete AC drive controlling a vacuum fan. All of the old equipment was removed and one ABB general purpose drive and five ABB motion control drives installed along with associated control gear.
“As the new drives came with easy to use keypads that can display multiple lines of useful information we decided to mount these on the panel door to make programming, fault diagnosis and monitoring easier in the future,” says Davies. “As modern drives are more energy efficient than 20-year-old ones, we carry out an energy consumption comparison between the modified lower stacker and the original upper stacker. The eight-hour monitoring with an energy profile logger showed that over a year the modified lower stacker would save over £1000 in energy costs which equates to 7.9 metric tons of CO2 saved per year – in addition to the savings the project has already made.
Increased stacker life
“This was a very good solution in many ways,” concludes Davies. “We increased the serviceable life of the stacker for many years to come and saved around £70,000 by not using the OEM’s solution.
“In addition, we gained a better understanding of how our machines work through a process of in house development while building a good relationship, support network and trust in our supplier. By removing the existing drives on the stacker we gained a stock of spares to support several plants within the SK Group with the added bonus of saving over £1000 per year in energy costs.”
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