Low profile Spool holder with Scale by ksihota

Last crawled date: 2 years, 11 months ago

Updates01/06/2021
I replaced the Top Spool Holder with a slight variation that requires a little less support material when printed on end. Makes no real difference for those printing flat.
31/05/2021
I added a small safety feature to the top holder to test out. Its two small posts that screw into the side of the upper piece. They provide some side support in case the spool tips on its side. I used a small M3 threaded rod to tie the posts at the top, through the centre hole of the spool. This should also hold the spool from rolling off the holder. Of course the holder has to be held in place so that it does not slide. You could also just insert a short piece of coat hanger wire with one end bent at a 90 degree angle. If it slips out of the other side holder, put a small bend in the other side to provide a little friction, so it won't slide out easily.
I have not tested this other than to put it on while doing my last few prints. I haven't tried it while the filament has been caught or tangled. It was just an idea that I thought I would try.
Summary
This is a component designed to work with my custom filament dryer. Its size and construction is constrained by the parameters dictated by the dryer component it must fit within.
It can be used as a stand alone spool holder with scale or as a simple spool holder without the scale. Instead of using bearings I printed low profile bushings that ride on 5mm shafts. I used M5x25 button head screws, as the head holds the shaft in place. Smaller diameter shafts could be used as long as the bushings spin freely. The width of the holder is enough to handle between 60-70mm wide spools.
The scale portion requires a couple of components that can be found on AliExpress or amazon. I purchased mine on AliExpress for about $12 CAD (module and sensor) including shipping. On amazon they will run about double the price. I was unable to locate the control module on amazon.ca (it might be available in different countries.)
I used a 2KG load cell and an electronic module that includes the HX711 amplifier. An Arduino can also be used instead of the pre-built module. If you use an Arduino you will need a HK711 module with your sensor. There is information on the web on how to hook up and program an Arduino to report the weights provided by the load sensor. I just found the pre-built module easier to set up as it does not require any extra parts and is powered by a standard micro USB adapter.
AD Module: (AliExpress)
HX711 Load Cell AD Weight Pressure Sensor AD Module with Display 24-bit Weighing Instrument Electronic Scale
Sensor: (AliExpress or amazon)
Digital Load Cell Weight Sensor 2KG
The instructions for using the electronics (AD Module) are not very clear so I made up my own and included them here as a PDF.
If you are just using the spool holder without weight sensor you will require the top piece and the bushings. If you are using the sensor (filament scale) you will also require the base.
I have included a small case for the control module as well, but it is not integrated with the spool stand as the unit is meant to fit inside my filament dryer.
The plastic base is quite smooth so you will need to apply something to the base to keep the spool holder from sliding during a print. I have mine sitting on a silicone pad but you could probably just stick on some silicone feet to help keep it in place. There are also screw holes that can be used to fasten the unit onto a larger base.
Two M5x12 and two M4x12 countersunk head screws are used to fasten the load sensor to the base and top frames. The case uses a couple of M3x12 screws.
Depending on your setup, you may notice some spring in the scale which will vary your weight display. There will also be an increase in tension on the spool during printing which will display as a higher weight on the display. As the spool releases the tension, the number on the display will decrease. At the end of a print you can release any tension in the filament to get a more accurate reading. If your bushings are not running smoothly expect this tension to be quite a bit higher than when the spool rolls easily. On my original designs my tension varied from about 50g to 200g. On my latest builds the tension remains around 10g to 25g. I suppose that if you used an Arduino you could figure out the tension threshold (point where the tension indicates the filament is caught) and program a safe pause for the printer.
I have included 2 different bushing sizes. If you find that the 18mm binds on the edges you can replace it with the 17mm.
Keep a close eye on your spool, initially, to make sure that it rolls easily. If your bushings do not roll properly or the edge of the spool is damaged, the spool may roll or get pulled off the holder. Have something in place to ensure this does not happen or protects the spool and surrounding items from damage.