Hi this is my second time on the forum. I draw a compression spring in 3 parts useing the cyclinder tool and then pull/helix tool and tried to combine them into one spring, but it will not combine. The dementions of the spring are 13mm ID, 15mm OD with a 1mm diameter wire. The centre section was L 20mm, Pitch 2.5mm. The two end sections were L 2mm and pitch 1.1mm. After combining them, I try to select it but only one section will hi-light. I use the Ctrl to hi-light the other two dections and try to move it. It will move a little way then weard things start happening to the image. Could the problem be because it is hollow? How do you change it from hollow to solid?