Meduzas "bolt-on" belt geared feeder upgrade for UM2

[meduza 189]

I have been thinking a lot about making a bolt-on upgrade for the UM2 with a belt-drive, that would increase the pushing power, and also remove the thermal coupling between the feeder motor and the knurled bolt, since it has been shown that excessive temperatures at the bolt can decrease the performance of the feeder.

I did a few sketches during the last year, even did a printed mock-up that i posted on the old forum, but never got around to completing it. Yesterday i sat down and did a redesign in CAD, printed the pieces and now decided to post it here on the forums for your feedback

It is a very simple construction with a minimal BOM, only two GT2 pulleys (one 20T and one 36T), a 110mm long GT2 belt loop (55T), a 5x40mm cylindrical pin, two MF695 flanged bearings, some M3 screws & nuts and a few printed parts. Total cost should only be about 15€ says a quick look at eBay prices.

It functions as a gearbox that moves the knurled bolt a few centimeters outwards and upwards, and provides a new nema17 hole pattern which means that it will work with any feeder that is designed for the standard feeder position at the UM2, including the @IRobertI feeder and the original UM2 feeder, it gives you a gearing of 1.8:1 and removes almost all thermal coupling between the motor and the knurled bolt.

The only change needed to use this geared feeder upgrade is to change steps per mm in Marlin to the original value times 1.8, thats it!

All STL's and BOM: https://www.youmagine.com/designs/belt-geared-um2-feeder-upgrade

CAD Pictures:

Photos:

So, what do you guys think about it?

Edited August 14, 2015 by Guest

[neotko 1,376]

I love the idea. Just a bit worried by the backlash of a belt on retractions and the tension on the belt on the long run. But I love it.

[meduza 189]

The backlash of the curvilinear GT2 tooth profile is very low by design, and since there are quite many teeths in engagement (actually about 50% of the teeths are in engagement at any given time) on a very short belt, i do not expect backlash to be a very significant factor at all, especially since the gearing reduces the impact of backlash even further.

Belt tension is very easy to adjust for, if it ever would become a problem.

Edited August 12, 2015 by Guest

[neotko 1,376]

I already love it. Can't wait to see the stls and build it.

[meduza 189]

I will probably post the STL's to YouMagine tomorrow, just need to do some small adjustments first.

[meduza 189]

@neotko and everyone else interested, the files are now available on YouMagine: https://www.youmagine.com/designs/belt-geared-um2-feeder-upgrade

Edited August 14, 2015 by Guest

[neotko 1,376]

Just ordered the parts on ebay for 2 extruders. I'll post as soon I get the stuff =)

[MrByte 4]

This looks really interesting.  I've ordered the parts and I'm going to give this a try.

[MrByte 4]

My parts came in today. Started putting this together. I'll provide an update when I've got everything assembled and the firmware tweaked.

[ultiarjan 1,125]

Thanks to the new forum I totally missed this one... looks very promising !!!

[ultiarjan 1,125]

Maybe @tinkergnome can put a "step mutiplier factor" in his custom firmware so people don't need to get into marlin...

[MrByte 4]

Okay, couple of questions from me, since I've never modified the firmware before:

1) If I compile the source from https://github.com/Ultimaker/Ultimaker2Marlin without alterations, this will compile a default UM2 firmware, correct?

2) Assuming no other alterations required from above, what settings do I actually modify to change the step rate for the extruder?

[neotko 1,376]

Maybe it's easier to do it with USB and do a Pronterface:

M92 E(number of new steps)

M500 Write data to EPROOM

?

As far as I see on ultimaker 2 marlin it has the gcodes

[neotko 1,376]

If you mess with something you can always do a

M502 Restore factory settings

M500 Write data to eproom

[MrByte 4]

I found what I need to modify, but having issues getting even the unmodified source to compile right now.

So I'll probably try your suggestion with the g-code.

[ultiarjan 1,125]

Think if you read this you'll understand how to compile the firmware;

https://ultimaker.com/en/community/view/7436-more-information-during-print?page=6#reply-97906

[MrByte 4]

Setting the steps/mm through g-code appears to work as expected.  Did an extrusion test and got decent results (I've never been able to go above 6 mm^/s without a total print failure, but this went all the way to 10 mm^3/s, but with noticeable under-extrusion issues starting halfway through 7 mm^3/s), but I'm going to do some more fine tuning on this.  I don't think I got the belt lined up perfectly.

Edited August 30, 2015 by Guest

[ultiarjan 1,125]

nice... maybe share a little video?

[meduza 189]

Nice, i have not had the time to actually mount my prototype to my UM2 yet, so you are actually the first person trying it @MrByte, huge thumbs up for that!

[MrByte 4]

Biggest problem I ran into is that I use @IRobertI's feeder design in conjunction with his low friction spool holder design. The casing for the new extruder pushes the feeder out just far enough that the screw prevents a spool from being mounted on the low friction spool holder.

I'm temporarily using the stock spool holder while working on a mount design for the low friction spool holder that mounts the spool holder using the unused NEMA hole pattern on the opposite end of the machine. Making a few final tweaks to that design and once it is mounted and working, I'll post the STLs here for others to use, if they wish.

[neotko 1,376]

I was starting to assemble the stuff but my 5x40mm pins can't fit the bearing or pulleys. I bough this http://pages.ebay.com/link/?nav=item.view&alt=web&id=361324052257&globalID

So that doesn't work. Can I use a simple m5x45 screw? Or anyone could paste a sample of what to buy on ebay so I can search something alike that could really work?

[MrByte 4]

Since I don't have a lathe, I wound up putting the pin in a power drill and using some sand paper to get the pin down to size so that there was a snug enough fit with the bearings and the pulley.

[neotko 1,376]

I did try that, but they are freaking hard. I tryed putting it inside the drill agaist a metal file, and after 10mins, it still didn't fit in. Really really hard little pin. I suppose if I do it for 30mins I would make it, but my idea was to make 4 extruders... I would prefer to just buy the correct stuff.

[meduza 189]

The pins i used (had them at home, dont know the source) did work right out of the box with no sanding, it surely was tight but i did not need too much pressure to fit the bearings to the shaft.

@neotko, it sounds like you have got hardened pins, those are as hard as the file so thats why almost nothing happens. You can soften it by using a small gas burner to heat it to red hot and let it cool in air.

A M5 screw is not that good of an option, i would look for a piece of silver steel rod (a good hardware store) or just a 5mm stainless steel shaft (hobby/rc stores can be a local source), both can also be bought on ebay.

[neotko 1,376]

Well @meduza I just bough the perfect (imo) product for the 5mm shafts.

This are Axis 5mm for Motor Emax GT3520 and I bought them on a R/C Hobbies shop for 1,34€ each (so really nice) they fit perfectly on the bearings and gt2 pulleys, the fit it's just perfect, smooth and without any hard or easy slippery. So finally I'll be able to assemble the feeder upgrade this week.

Also imo they are perfect since they are (edit) 60mm+ long and I wanted to add a 8mm/5mm coupler to purge the feeder manually. There are also 50.5mm long versions but they where 3,50€ each.

Edited September 9, 2015 by Guest