By spending a relatively modest sum on VSDs to refurbish their enamel spray paint line, oven manufacturer Glen Dimplex Home Appliances in Merseyside has saved thousands of pounds on replacement motors and an even larger sum on reduced downtime and improved production quality.
The drive chain system which transported oven components through the enamel curing oven, was powered through an ageing and bulky Carter variator gearbox. This gearbox failed on a regular basis, necessitating maintenance call outs at all hours and resulted in substantial production losses, halting production further down the production line.
Oil leakage from the Carter variator also meant that on a Monday morning after being unattended all weekend, the gearbox was empty and this in turn delayed production start-up. Meantime, the oil on the floor also represented a significant health and safety hazard.
Close speed control over the oven drive chain is essential to meet the varied curing times of the different sizes of oven components in production at any time, so George Kelly, the maintenance projects engineer, called in Danfoss Drives Partner, MR Engineering to advise on a remedy.
The solution was to dispose of the Carter gearbox and drive the line using a 3kW Danfoss VLT 2800 inverter to power the force cooled motor through a fixed ratio gearbox. Speed raise and lower pushbuttons and speed readout from a line mounted tachometer now enable the line operators full manual control over the enamel curing process regardless of the size of oven components on the line.
According to George Kelly The Carter gearbox problem was causing serious production losses, not just through stoppages but also in terms of scrapped product through unreliable finishing of the oven parts. With the improved reliability and controllability of the VSD solution, the line is completely trouble free and product scrap has been virtually eliminated.
The success and simple implementation of this project led to Glen Dimplex seeking a Danfoss solution to the motor losses on their electrophoretic spray plant. The 8 directly driven reciprocating spray heads, on a constantly reversing duty, were suffering several shaft breakages every week of the 0.37kW motors driving the spray heads.
In addition, the juddering of the spray heads when reversing was causing uneven powder deposition on the oven parts with subsequent quality problems. By converting the spray heads to inverter control utilizing Danfoss VLT 2800 series drives, both problems have been completely cured.
The smooth ramp-controlled reversing cycle of the inverters has eliminated motor stresses when reversing and saved countless motor shaft problems. The smoother control over the spray heads has also eliminated the powder deposition problem leading to improved production quality.
As George Kelly put it We've spent a few hundred pounds on inverter drives and saved ourselves many thousands in production downtime, improved product quality and saved hundreds of man-hours in maintenance.
We've a lot of Danfoss drives on site and I'm reassured going to bed at night knowing that Danfoss drives are taking care of another process and that I won't be called out in the middle of the night to another enamel line stoppage.