Big filament drive wheel?

Has anyone tried to use BIG filament drive wheel?
Everything uses the M8 bolt option, but looking at MIG/MAG welding machines these uses very large wheel for sub 1mm line.

That makes perfect sense too, that way you get more lateral (length wise) grip area, so has anyone tried using 20mm+ drive wheel? What was the results?

Mig welders use around 25mm rollers for feed, they are smooth with a groove where the wire sits, this works as the idle roller has a very high spring tension on it that would crush plastic filament. Not sure what if any advantage a larger hobbed bolt/wheel would have. The current designs can already build up enough pressure to destroy the filament if it's not feeding correctly.

Think of it like this, your car tire only has about 1" of contact with the pavement no matter the tire size (with a few industrial exceptions). So the filament is still only going to come into contact with a very small portion of the roller regardless of the size or roller.

Here is a Mig feeder

Look at this test: http://airtripper.com/

Edited 1 time(s). Last edit at 01/25/2015 05:42AM by Ano.

"Think of it like this, your car tire only has about 1" of contact" this is completely incorrect!
I've actually spent time calculating tire contact patch areas.

Diameter of tire affects the longitudal area, and width affects the - well sideways area Tire pressure affects overally to both directions.
With the right tire size compared to bad you can almost double the contact patch area *despite* the fact that larger the rim diameter usually the lower the profiles available which necessitates stiffer sidewalls and thus decreasing longitudal contact patch area.

With the weight, tire pressure and tire size my racing car currently has about 380mm2 per tire contact patch area, i could increase this upto around 460mm2 per tire by going MUCH bigger tire (increased inertia, increased rolling resistance and other issues would largely negate any benefits tho in my case). regular street sport tires which are 20mm wider than my racing slicks i think had around 310mm2 per tire contact patch area.

" The current designs can already build up enough pressure to destroy the filament if it's not feeding correctly."
Crushing the filament is about the pressure, which is a function of force against an area. if you have 1sq.inch and 10 lb of force you have 10psi, or if you have 10sq.inch and 100lb of force, you again have 10psi of pressure.
Hence, we can quickly conclude that pressure is an irrelevant measure of grip on the filament. the area + pressure however is not, and can also be represented by area + force.

So filament getting crushed BUT not feeded through means too small contact area. Increase contact area and you will not have filament getting crushed against the same backpressure.

Also using exactly like mig welder has would probably not crush the filament because MIG welder doesn't have hobbing, hence the load is spread on much larger area.

Elementary physics.

Quote
Ano
Look at this test: http://airtripper.com/

That was quite informative, but as the writer noted the large diameter would require gearing, or even lowering the microstepping to begin with.
He unfortunately did not compensate for the gearing difference, or even calculate "final force".

Let's do a simple comparison by force * effective diameter:
Plain insert: 27.58
Raptor: 17.89
Mk8: 29.4
Mk7: 29.57

So in essence Mk7 with larger diameter wins *marginally*, but in real world Plain insert, mk8 and mk7 perform pretty much equally.

Gearing is *very* important and microstepping heavily influences available torque as well.

Im using a mig welding wheel on my large format printer I am building. Can't really comment on feeding for cause I need tensioning springs, but it looks promising.

---

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HUGE 3D PRINTER PARTS SALE!!!

I've done a lot of contact patch size calculations in the past as well, which are different from available TRACTION calculations, in which contact patch size is only one factor.

Something far more relevant though is what compound the tires are made from, as it affects how well it can grip the pavement.

Apply this to your filament, and what you get is that how well the hobbed portion of the belt can really grip the filament. Generally it does this by having a textured surface apply pressure to the plastic, which probably does some deformation of the plastic, allowing it to transfer power from the bolt to the plastic. In this case, I'd bet it would far more effective to change the material to something more plastic, like rubber, and give it enough pressure to deform against the filament, allowing a large contact area, and therefore better traction. Of course this also makes the drive variable, as the effective diameter of the drive starts to change. This is where a larger diameter would help, since the deflection becomes a smaller percentage.

Of course the flipside is that the larger the wheel, the less force is available from the available motor torque. Once you have more traction than you have torque, there's no point in more.

Edited 1 time(s). Last edit at 01/28/2015 02:06PM by SupraGuy.