This is a modification for the spool holder on a Lulzbot Mini. I started checking them out when I had a bit of a feed issue with the standard holder. Of course it turns out the feed issue was caused by the tail of the filament sticking too far out the inside of the spool and hanging up the rotation on the standard holder. It did make a pretty loud CLUMP when it finally pulled over (check your spools before you load them). So this is really the answer to a question that nobody asked. The standard holder works fine. It did however provide a good excuse to print something! I originally wanted to use bearings in the design but could not justify them given how easily the ABS parts spin on the spindle bolt. In fact the spool may spin too freely with this mod. I have had one new spool unwind a turn or two just sitting there due to the memory in the filament.
OK, there is definitely not enough friction with this setup. I have added some spacers to fit between the knob and the hub. Select a spacer that allows you to get some friction without having to tighten the nyloc nut too much. 19mm worked for me with spools with a recessed center. I also added a revised spindle holder. With this one it does not matter which way the hubs go on. The spacing will stay the same. The old one was designed for a bearing hub.
One nice thing about the design is you can print multiple hubs and leave them in the spools if you change material or color often. You could even color match them to the material.
The hubs are designed for spools with a 52mm i.d. and a width of 50mm to about 70mm. This worked for spools I had from Lulzbot, MatterHackers and Ultibot. I could do other diameters or lengths if there is any interest.
The spindle holder attaches to the stock support and uses the stock attachment bolts. The 8mm x 120mm spindle bolt is pressed into the spindle holder and is retained by a ridge on the inside of the hex hole. Of course you can adjust the bolt length to meet your requirements. The knob has an 8mm nylock nut pressed into it (nylock out). It is also retained by a ridge in the hex hole. I used a nylock because the knob does not need to be tightened up to the hubs to hold them in place, they float on the spindle. It just keeps everything from falling off the end. Just snug against the nylon should hold it because, unfortunately, the spool spins lefty-loosey. The hubs have a standard 3/4"x 6 acme thread.
Print the spindle holder and the knob with the hex hole side down. Support material has been provided in the part design, just pull the little rings out after printing. The hubs print wide side down. The clearances for the holes and the threads are based on how my Mini prints. I hope they will work for others as well.
Added rear hub file with threads extended 10mm.
Supports are provided as a part of the STL files.