When I run the machine at speeds under 500 mm/minute I notice a noticeable buzzing or almost grinding sound. When I speed things up to 1000 mm/minute it sounds pretty clean. I have checked most of the bolts and they seems appropriately snug and the belts seem tight enough as well. I cannot see anything that is vibrating but most of the sound seems to be coming from the region of the middle assembly. If I add some pressure on the belt while the machine is running on the between the pulley and the trailing end roller the noise gets better. Adding pressure anywhere else doesn’t seem to do much.
Has anyone run into this before? Is this a real problem or just an annoyance? Is there a simple way to fix this? I haven’t tried cutting yet but drawing with a pen at the slow speeds seems to work really well.