smaller filament by stretching? I want to make my own 1mm dia filament from 1.75mm filament. Can I use a heating element and a geared spool drive to stretch the hot filament with a given gear ratio? The spool for the thin filament would run 1.75 times faster. ASCII art: o__________O ***** ~~~~~ o= small gear O=big gear *= cooling ~= heating https://reprap.org/forum/read.php?1,663639,663639#msg-663639 Thu, 13 Aug 2026 04:51:27 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?1,663639,664390#msg-664390 Re: smaller filament by stretching? https://reprap.org/forum/read.php?1,663639,664390#msg-664390 Was it 1.75mm filament with a 5mm dremel tool? With smaller filament and a smaller grinder tool, the job would be much easier, I guess.
I think, with a quick release bit holder, we could put the diamond bit in acetone over night to keep it clean.]]> o_lampe General Mon, 16 May 2016 08:58:18 -0400 https://reprap.org/forum/read.php?1,663639,664384#msg-664384 Re: smaller filament by stretching? https://reprap.org/forum/read.php?1,663639,664384#msg-664384
Quote
o_lampe
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Srek
You will be very hard pressed to get a constant diameter. Any specific reason why you want to use 1mm filament?

The reason is to be able to use smaller extruder motors for direct drive. I have the idea to use a diamond powder coated dremel tool as drive gear, which has a very small diameter.

I gave a diamond coated dremel bit as a drive gear a chance some time ago:

[attachment 78191 DiamondDremelBitExtruder.png][attachment 78227 GrindingBit.jpg]
- Diameter 5mm, grit size 252 (MAFRA d-s109 Diamond grinding bit)
- Did nicely push the material (3mm filament), very constant feedrate resulting in smooth printed surfaces
- After some time one of the grits seems to have detached from the bit and clogged my nozzle (0.4mm)
- Subsequent grinding did fill up the diamond coating with plastics. Material did not fall off by itself - missing taper angle of the grits and undercuts kept the material sticking
- Cleaning the nozzle and the bit was quite a pain...

Improving the grinding bit parameters could probably solve these issues - please keep going on and let us know.

PS: See also the No-hob extruder using a Dremel bit #196]]> powdermetal General Mon, 16 May 2016 08:42:53 -0400 https://reprap.org/forum/read.php?1,663639,664308#msg-664308 Re: smaller filament by stretching? https://reprap.org/forum/read.php?1,663639,664308#msg-664308 A filament stretcher to convert it to 1.75mm would come handy, if one would have a huge demand for filament.]]> o_lampe General Mon, 16 May 2016 03:36:20 -0400 https://reprap.org/forum/read.php?1,663639,664306#msg-664306 Re: smaller filament by stretching? https://reprap.org/forum/read.php?1,663639,664306#msg-664306 The heating tube would be off aluminum or copper and the heating element ( Ni-Cro wire ) would be on the outside. It would be movable to find the best suiting temp-profile.
I don't want to start a mass production, just produce enough filament to test my extruder ideas.
[VDX] mentioned somewhere else, he had 0.5mm filament ( from toothbrush production?) at hand. I'd like to experiment with that too.]]> o_lampe General Mon, 16 May 2016 03:32:48 -0400 https://reprap.org/forum/read.php?1,663639,664005#msg-664005 Re: smaller filament by stretching? https://reprap.org/forum/read.php?1,663639,664005#msg-664005
You can not use the spools. You need rollers that will not slip or skip steps otherwise you will get inconsistent width. From the feed side you might need multiple rollers to counter slippage. The filaments needs to be cold enough before reaching the puller rollers otherwise the puller will flatten the filament. As [frankvdh] mentioned you really need good (correct) cooling.

You might also need filament width sensors on both ends to control the process.]]> Frans@France General Sun, 15 May 2016 06:47:08 -0400 https://reprap.org/forum/read.php?1,663639,664000#msg-664000 Re: smaller filament by stretching? https://reprap.org/forum/read.php?1,663639,664000#msg-664000 Frans@France General Sun, 15 May 2016 06:35:30 -0400 https://reprap.org/forum/read.php?1,663639,663985#msg-663985 Re: smaller filament by stretching? https://reprap.org/forum/read.php?1,663639,663985#msg-663985
Quote
Srek
You will be very hard pressed to get a constant diameter. Any specific reason why you want to use 1mm filament?

The reason is to be able to use smaller extruder motors for direct drive. I have the idea to use a diamond powder coated dremel tool as drive gear, which has a very small diameter.]]> o_lampe General Sun, 15 May 2016 06:18:54 -0400 https://reprap.org/forum/read.php?1,663639,663980#msg-663980 Re: smaller filament by stretching? https://reprap.org/forum/read.php?1,663639,663980#msg-663980 I also believe some ingrediences will disappear by melting it.

The idea is to feed the filament through a wider tube ( say 10mm inner dia ).
Air is blown through the tube from the 1mm side. A heating element in the middle of the tube will heat the air and also the filament. That way I get a continuous temp gradient.

My math was wrong, I took the circumference formula instead of the cross section 8-)]]> o_lampe General Sun, 15 May 2016 06:13:01 -0400 https://reprap.org/forum/read.php?1,663639,663878#msg-663878 Re: smaller filament by stretching? https://reprap.org/forum/read.php?1,663639,663878#msg-663878 thejollygrimreaper General Sat, 14 May 2016 17:49:19 -0400 https://reprap.org/forum/read.php?1,663639,663857#msg-663857 Re: smaller filament by stretching? https://reprap.org/forum/read.php?1,663639,663857#msg-663857
Except that this depends on both spools having the same diameter. If you're planning on unwinding 1.75 off one and winding 1mm onto the other, then the spool diameter of one decreases and the other increases over time. So you can't just drive the spools... you have to control the filament speed.

But I suspect that it wouldn't work, although I don't know. I suspect that strength (and therefore "stretch") of the filament is inversely proportional to diameter. So once a thin point develops, it just rapidly gets thinner until it breaks. Maybe if you cooled it immediately that it was down to 1mm, so that it regains its strength, it might work.]]> frankvdh General Sat, 14 May 2016 16:54:15 -0400 https://reprap.org/forum/read.php?1,663639,663678#msg-663678 Re: smaller filament by stretching? https://reprap.org/forum/read.php?1,663639,663678#msg-663678 Srek General Sat, 14 May 2016 06:04:55 -0400 https://reprap.org/forum/read.php?1,663639,663673#msg-663673 Re: smaller filament by stretching? https://reprap.org/forum/read.php?1,663639,663673#msg-663673 www.thingiverse.com]]]> Frans@France General Sat, 14 May 2016 05:50:45 -0400 https://reprap.org/forum/read.php?1,663639,663639#msg-663639 smaller filament by stretching? https://reprap.org/forum/read.php?1,663639,663639#msg-663639 Can I use a heating element and a geared spool drive to stretch the hot filament with a given gear ratio?

The spool for the thin filament would run 1.75 times faster.

ASCII art:

o__________O
***** ~~~~~

o= small gear
O=big gear
*= cooling
~= heating]]> o_lampe General Sat, 14 May 2016 03:49:09 -0400