Getting your machine serviced regularly is important, as the engineer does more than just cleaning the machine. However if you try and clean the bobbin case area yourself every month, you'll save on how regularly the machine needs a service.
This weekend I cleaned out my 6 janomes, and boy where they grimey underneath the bobbin case!
The instructions below are for cleaning out a top loading machine. First thing is to get out your manual, and see how they advise you to clean the machine. Most top loaders can be done in the same way as the instructions below. I lay my screws and removed parts in a mirror of how they came out of the machine, making it easier to put it all back in the right order. If you're worried about forgetting where something came from, then take pictures at each stage.
1 -To remove the bobbin case on a top loader, you need to start by removing the sole plate, which may be screwed on.
2- You now need to remove the bobbin case which is the black plastic holder in the centre.
3- Once the bobbin case is removed, you can now see how much hidden fluff, and dust there was beneath it! Use the brush that came with your machine to get it all out. A can of pressurised air is also a useful tool to blow the dust out of hard to reach areas
4- Using the sharp pointy end of the cleaning brush, hook out any other areas of fluff around edges of all the metal bits you can see
5- Fluff also likes to collect at the top of the needle, and on presser foot, so make sure you give those areas a once over too.
6- The underneath of your bobbin case should hopefully now look lovely and clean
7 - There are screws that allow you to get to areas further inside your machine. I generally don't go any further, as the more small bits I remove, the more likelihood there is that I won't be able to get them back in! I save that for when the machines are serviced.
8- You now need to put the bobbin case back in, there is a tiny split at the front which will give you a guideline. Then replace the sole plate. Your machine will thank you for giving it a little clear out!