Used properly, an overlocker sewing machine can save you a great deal of time and excess work. You will be able to sew several threads together at the same time, trim all your excess fabric, join the seams and finish the cut edges with high efficiency. Yet if the machine is not working properly, then the opposite may be true, and if you feel that you're going backwards rather than forwards at the moment, you may be tempted to take the machine in for a service instead. What will the technician look at?
With time, residue will build up in all the nooks and crannies. Threads, fluff, lint, dust and other debris can accumulate and when it does so, it will certainly slow down the efficiency of the machine. To begin with, you will need to get all of that residue cleaned out with a compressed air gun.
The knives are crucial, and you must make sure that they are still as sharp as possible, or you won't make much progress. They can easily become blunt over time as they come into contact with those thick seams or metal pins, and if so, the pair of knives will need to be sharpened.
Your machine will not run as efficiently as it could if the drive belt needs to be adjusted. Eventually, it will lose its tension due to a lot of use, while it could also pick up some damage to the "teeth" and not be able to grip as effectively as it once could.
If you're not too happy with the accuracy of your stitching, it could be something to do with the forming pin. If it's out of line at all, then your accuracy will be suspect, and you will need to get it recalibrated.
You may also need to adjust the loop tolerance, in relation to each other and to the needles. The gap in between each of these parts may need to be readjusted.
Finally, ask the technician to lubricate the drive shafts. While these components will normally last for a long time without too much maintenance, a little oil here or there may help to free them up and improve the efficiency of the machine.
Always take you overlocker into a qualified repair specialist for their expert advice, so you can get back to your high levels of productivity as soon as possible.