big wheels on the exstruder

hi all,

why are the wade exstruders liked? the ones with cogged wheels..

all i can think of is even with the gear reduction the top speed of the average nema 17 is fast enough to 'go faster', because the torque produced is much higher so no slipping.

is that the jist of it? or is there more to it? finer controll over the flow of plastic maybe?

I am using a typical wades extruder and really like it. It provides both more torque and finer extrusions than a direct drive. If you decide to make one, print out herringbone gears to minimize backlash.

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Prusa i3 Rework - Ramps 1.4 - E3d Lite6 - Full Graphic LCD Controller

Gear reduction decreases speed but increases torque. Geared extruders are most commonly used for 3mm filament because the torque gained through the gear reduction can apply more pressure to the filament going into the hot-end, which I think leads to fewer clogging problems.
With 3mm filament, the loss of speed isn't usually a problem. If you use a gear reduction to drive 1.75 mm filament and you have a high speed printer, you may find the overall print speed limited by the extruder.

When I was looking for a reliable extruder, I looked at a lot of designs, read a lot of forum posts about extruder clogs, and talked to several people about their experiences and came to the conclusion that 3mm extruders suffer fewer clogging problems than 1.75 mm extruders. Then I looked at why and found that 3mm extruders all use(d) a gear reduction. At the time, almost no one was using gear reduction on 1.75 mm filament. My conclusion, right or wrong, was that the extra torque provided by the gear reduction was responsible for the reduced clogging.

Further looking around led me to the BullDog XL extruder- 5:1 gear reduction and 1.75mm or 3mm drive capable. I got one, put it on my printer to push 1.75mm filament, and have not had a single clog or jam in the 8+ months it has been on the machine. The speed reduction compared to direct drive isn't a problem for me- I run my printer at a leisurely 50mm/sec.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

I recommend using a 3:1 geared extruder for 1.75mm filament, although 5:1 is OK if you have a short (i.e. low inertia) motor. Non-geared 1.75mm extruders can work too, but you should choose a long (high torque) motor with a rated current low enough for your stepper drivers to get close to without overheating.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

I've had mixed luck with direct driving off of the stepper shaft.
If the stepper builds up heat, maybe from being under sized and over-amped to give the torque, then the hot stepper will eventually soften the PLA at the tooth area.
I've used fans or selected big enough motors that can just run at low amps and provide the torque.
separating the motor using a gear pair takes the heat off of the tooth drive.

double and triple stack NEMA 17 are usually no problem for heat build up, but the 8 and 11 and even the 14 size can get really hot, without a fan on the motor.
If you're using a heated enclosure (for ABS) then a smallish motor can get to 90C pretty easily.

i've no idia what the motors are tbh.. theyre 48mm deep, and theres no miss stepping up to around 70mm/s, higher speeds on shorter travell, infill starts kicking a bit at that speed at around a 3 inch long a strip, every 5 ot 6 pass it clunk then shuts up for 4 or 5..


i've looked at the geared steppers, and it'll be a while before i think on buying a set up.. £125 is about the average i've been looking at, some are that price for just for the motors.

the motors i can touch with the back of my finger and theyre 'warm', if i have it right from charging batteries, 40C is warm to hot but holdable.. these are just warm and no discumfort.


i've got some big boy heads on the way, up to 1mil nozzles to play with laters. i'm still getting my foot in the door with setting's etc at the mo. Repetier is seemingly useable, and cura seems to like belting out a print verses slicers fidgity fidgity ee ee ee ee ee ee micro squirting as it goes lol...i'm guesing i havent got a setting up hi enough on that. (kisslicer is an intresting one, but i'm tired of resetting every up over and over again...really needs a good manual for it, so another later thing i think).
hmmmm, the retraction settings i've been procratinating on...spose it'll have to be played with sooner or later lol.


what sort of speeds do you get with the 3:1 reduction dc42? i'm going to give the volcano set ups a try.(1.75mm to start with).

and thanks all for the input.

Giving gear ratios for the extruder are meaningless unless you include the hobbed gear diameter (or even more correctly the diametrical pitch).

I'm using a 5:1 geared stepper with an 11.4mm diameter hobbed gear. It seems to be working fine at print speeds up to 150mm/s (I haven't tried it faster than this yet).

p.s. This is for 1.75mm filament.

Edited 1 time(s). Last edit at 09/04/2015 08:53PM by etfrench.

hmmm intresting etfrench.

Quote
etfrench
Giving gear ratios for the extruder are meaningless unless you include the hobbed gear diameter (or even more correctly the diametrical pitch).

I'm using a 5:1 geared stepper with an 11.4mm diameter hobbed gear. It seems to be working fine at print speeds up to 150mm/s (I haven't tried it faster than this yet).

That's true - and you are using an unusually large hobbed gear.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
etfrench
Giving gear ratios for the extruder are meaningless unless you include the hobbed gear diameter (or even more correctly the diametrical pitch).

I'm using a 5:1 geared stepper with an 11.4mm diameter hobbed gear. It seems to be working fine at print speeds up to 150mm/s (I haven't tried it faster than this yet).

p.s. This is for 1.75mm filament.

Actually, gear ratios and hobbed gear diameters and printing speeds are all a little meaningless unless you also specify the nozzle diameter, layer thickness and line width. At the end of the day, it is the volumetric extrusion rate that matters. A while ago I ran across some Ultimaker post indicating that with a 0.4mm nozzle, the maximum extrusion rate was about 10mm^3/sec. (I've found precious little other information regarding the practical max. extrusion rates.) With a layer height of 0.2mm and a line width of .5mm (pretty typical), 10mm^3/s corresponds to a 100mm/s printing speed.

I've been using a direct drive extruder with a ~7mm dia. hobbed gear and a 34mm long NEMA 17 and can get up to 15mm^3/s under ideal conditions, but practically speaking, I can only reliably get about the same 10mm^3/s over the course of a real print job. I'd love to know what volumetric rates other people are reliably able to achieve.

The hobbed gear is this one from Tridprinting.

The geared stepper is this one from StepperOnline.

Are there any good models available for testing extrusion volumes and speeds?

Edited 1 time(s). Last edit at 09/05/2015 10:12PM by etfrench.