Talk:Wade's Geared Extruder

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Thanks for the clean-up Casainho, but I think I'll put the testing methods back in there. I think that good testing of a new design is as important as the design itself, if not more. Wade

I did "clean" the page. I think the extruder is stable since many people printed and use it. I feel the need to have a clean and informative page. Anyway, any info can be recovered from last versions. --- Casainho

Hey Johnnyr - nice photos! At first I was thinking, strange, I don't remember uploading those pics, and then I realized it was your copy! Very nice. Almost indistinguishable from mine, just some slightly different washers!


What bolt sizes are you using to attach this to your Mendel? Those should be added to the bill of materials (even though technically they're between projects). Those of us in the US sadly can't walk down to a hardware store to buy nuts/bolts if we want to stay consistent - we have to buy them all online with shipping costs, etc.  :( By chance I had some M4 12mm and M4 20mm bolts (to reduce shipping I added components for a future Adrian's extruder build too), and I was able to determine that 12mm is too small but 20mm would work if I used enough washers to space it out.

The real problem though is that the bolts can't be too long, because otherwise they'll hit the X-axis smooth rods! I thought I had it worked out great on the first bolt, but the second bolt was the one beneath the stepper motor, so I had to lower it to mount the stepper motor, bringing the bolt dangerously close to scraping the bar. I can dremel a bolt down to size I suppose, but for others building this, it'd be good to hear what size worked for you. (and whether you need "low" sized heads instead of standard, etc). Thanks! - Jkeegan 20:26, 2 September 2010 (UTC)

Jkeegan, ask Wade here in the Super-secret RepRap Developer Mailing List.  :D --Sebastien Bailard 01:23, 3 September 2010 (UTC)

Jkeegan, use whatever fits.  :) I think various builds end up with various thicknesses, so slightly different bolts are required for each one. A hex head bolt under the stepper motor will let you remove the extruder without unbolting the stepper, but it's not easy - that's the main flaw with this design, imho. The next version will have more clearance around the mounting bolts. I don't know exactly what size bolt I used, but I will check next time I disassemble it. That could be a while though; I'm only on complete replication #3 with my Mendel; I think Nophead's went for almost 20 full prints before he had to rebuild it.

Oh, and always buy extra bolts.  :)


Hey Wade can we move this to "Wade's Geared Extruder," since that's what everyone calls it anyway? newbies will spend a lot of time trying to find this page before they figure it out, and there are other pages with almost the same name as this one (which should also be moved to "Adrians Geared Extruder") --Buback 21:03, 22 October 2010 (UTC)

Go for it - I'm busy at the moment, but might as well call it like it is.  :). Wade

Could someone please provide better specifications for the springs? To make it easier for people to source themselves, springs should be specified by Outside Diameter or Shaft Size, Length, and either Load or Spring Rate (ideally, a usable range for either). The current specifications are, frankly, useless. --Nether10 19:11, 25 April 2011 (UTC)

I build the springs from 1 mm music wire, with an OD of 10 mm (wound on a 1/4" mandrel (drill bit) in a handheld drill), and stretch them to fit - thus the specifications. I don't have a good way to accurately measure the total load or spring rate of these home built springs, but spring calculations suggest a max load on the order of 10 to 15 kg for all 4 springs together; those calculations are notoriously error prone though. Any spring that you can fit on the bolts, and has a wire diameter of close to 1 mm, should work well. 3 kg max load, in other words, and an unsprung length of 10 or 12 mm - I'll update the page. Wade. Edit - actually, now that I re-read the page, everything you asked for was already there - Max Load (100 N) OD (10 mm), the only thing missing was the unsprung length, which you can work out from the 4 active coils spec, and which doesn't actually matter anyway. I'll update the "useless" specs later when I have more time.

"4 active coils" doesn't give a length (as there's an undefined distance between the coils), and the 100N load, as it was written, seemed to be a random example. Thus, I considered the specs useless (although I suppose I should have been more kind and said "insufficient"). I'll update it for you. Thanks for the reply. --Nether10 19:36, 26 April 2011 (UTC)

Pressures, strengths, torque and scaling for 1.75mm filament

The text says the design can do a pull tests at >15.25 kgf. I was wondering how that would scale for other filament sizes.

15.25 kgf = 149 N on a 3mm filament. Turning that around, it seems capable of producing a pressure of 21MPA in the printhead: 149 N/ 3.14159 / 0.0015^2.

For an equivalent max pressure on 1.75mm filament, that would require 50N, ( = 21MPa * (Pi * (0.00175/2)^2)).

149 N on the 4mm lever arm of a 8mm hobbed bolt would be 59 N*cm. Geared at 39:11 gets to 16.8 N*cm. Compared to the 40N*cm min requirement, that's 42% or a * 2.37 build-up factor.

With an 8mm hobbed bolt that would need a torque of 20 N-cm, and geared 39:11 that's 5.64. Applying the same build up factor, that would be 13.4 N-cm (19 ozf-in, 1.36 kgf-cm).

It seems like a 20 ozf-in, 1 amp, 6 oz NEMA14 like would be similarly adequate for 1.75mm filament. ~ Dave

That sounds about right; for a given pressure, the force varies with the square of the filament diameter, so going from 3mm to 1.75 should take about 1/3 the force to extrude. Nophead's work indicates that there is more at play than just the nozzle pressure though - filament buckling, the varying friction on the walls as the moving filament melts, etc. I went with way more force than I thought I needed, just to make sure that pushing filament wouldn't be a problem. Feel free to update the wiki with some data on 1.75 mm filament extruder experiments. ~ Wade
I'm still at the box-of-parts stage, so actual experiments would have to wait. I was checking feasibility of whether one could use a set of interchangeable motors for the whole thing. ~ Dave

Filing and hobbing the bolt

How much does one file the bolt? To make a certain major diameter of the hobbed portion? Or just enough for the tap to take? Are you aiming for something like engaging and interfering with maybe 90 degrees around the filament? DaveX 21:36, 6 February 2012 (UTC)

Answering my own questions: First, choose a tap size and how much you want the threads to nest into the worm. 90 degrees of nesting would need a depth of (1-sin((90-nestAngle/2)*pi/180))/2=0.146 of the tap's minor diameter. Per an M5x0.8 tap has a minor diameter of 4.134, so a groove 0.605mm deep will carve out the bulk of the material for a 90 degree nest for an M5 thread. M5 will leave will make teeth of heights around 0.433 mm. If you file a 0.6mm groove into the 8mm diameter to make the groove/worm gear's major diameter 6.8mm, the pitch diameter will be about a 6.8-.433=6.367mm, and the number of teeth on the worm would be the circumference divided by the tap's pitch, or (6.8-.433)*pi/0.8=25.003 teeth. Since I dulled and broke my cheap M3x0.5 tap, I winged it and used a bigger SAE tap, 10-32, in an eyeballed groove, carved with a 5/32" drill bit. Reviewing the page after the fact, positioning the tap with washers is an excellent idea. Next time, I'll use that trick for positioning the tap's minor diameter drill against the shaft, and for positioning the tap in the groove. But for now, the sloppy, handheld & eyeballed 10-32 tap is working fine in my Wallace. DaveX 17:14, 1 November 2012 (UTC)


Was the page name accidentally renamed from Wade's Extruder to "Экструдер Уэйда"? I don't know much about how the multiple language convention is done, so I don't feel comfortable reverting anything, but it seems like that might have happened. --Jkeegan 10:04, 17 February 2013 (UTC)