Heated Spool Box
Just a small sneak peek at a project that I am working on. This is a heated spool chamber capable of supporting up to 8Kg spools. I currently have 5Kg spools that will not fit anything commercially available. The chamber on this is not designed to dry filament, but rather keep it just above ambient temperature. The box and front cover are manufactured from polycarbonate, fully capable of handling elevated temperatures. Spool rollers are printed concentric to keep the spool in the center of the rollers. The support shaft is hardened bearing rod and will support the larger spool loads. Bearings are Abec 7 ceramic hybrid, extremely low friction. The support frame is designed to fit on top of the Pulse/Prusa enclosure. I will post more pictures as the project matures.
Maximum spool diameter which will fit is 405mm x 250
Most large scale printer companies use a center spool roller instead of dual edge rollers. There is science behind this.
While dual rollers are convenient, there is a large amount of rolling resistance with the larger spools. Small spools are light weight and the friction is easily overcome.
The problem lies mostly with the internal bearing resistance. An easy way to explain this is through a gearing example.
My large spool is 12 inches in diameter or 405mm. My original roller is 1 inch or 25mm in diameter. So with this we have a gear ratio of 12:1.
A 1 kg spool is about 8 inches in diameter, so the ratio is less near 8:1.
To compensate, I have increased the diameter of my rollers by 3. This now yields a gear ratio of 4:1.
To help further, I have purchased Grade 7 ceramic hybrid 608 bearings and packed them with TinkSeal.
Now I will have an open roller system which will accept 500g to 8Kg spools with no center bar or roller adjustment needed.
I was a little short on my roller design. I have designed newer, larger rollers.
1 Kg spool on the new rollers looks tiny, but rolls smooth and prints perfectly. No adjustment is necessary from 1Kg to 5Kg which makes it very convenient to just drop a spool and feed it.
I have dropped a few desiccant packs in there temporarily to absorb moisture while I print. Unfortunately this was not enough to keep my material dry.
And for the 5Kg test, 'room to spare'! There is enough room for an 8Kg spool. Prints well as the larger rollers are able to lower the friction and sustain the higher weight.
I have redesigned a desiccant box to fit this filament box.
Printing in progress, filament coming off the 5 kilogram spool above.