I have a brother and with this machine it does not matter when I do...
On my Vikings it does not matter. Sometimes I turn on the machine only to find out that the design I want to use is not on there so I take it out, put the design on and put it back in. No problems. I also take it out while the machine is in use as it does not affect the design being sewed at the time. That design is loaded on the machine. Hugs. Nan
Not sure about other machines but at Bernina we were taught machines OFF USB in - Machines OFF USB out!xx
HI Mary, I don't have a Janome, but I take it out of the machine when it's stitching a design and go to my computer to download another design and put on it. Then I just put it back in whilst the machine is going. I've never had any trouble doing that! Love Chris
I always add the USB while the machine is off and do the same when removing it. However I went to class once and the instructor just plugged it in while the machine was on. I do have Baby Lock machines and I am not sure if Janome needs to be treated different.
I insert the USB regardless if the machine is on or off. So far, it doesn't seem to matter.
I don't have a Janome 500e, but on my Baby Lock Ellisimo, it doesn't matter when I plug in a USB...