Host software - Test generator

Hi,

This page discuss the print quality and a test case generator. But the link on how to use it doesn't go anywhere and this other page comes back to the wiki home.

Can you please indicate how to access the generator.

Thks

Ok, I created the missing wiki page (https://github.com/repetier/Repetier-Host/wiki/Test-generator)

If you want to test the advance algorithm of Repetier-Firmware, use version 0.60 with updates from 9.4.2012. It fixed a little bug in the advance algorithm.

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On that page you state pressure is proportional to v^2 but my understanding it is proportion to v.

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[www.hydraraptor.blogspot.com]

Linear would be cool, but bernoulli without frictions is

v0^2/2+p0/rho+g*z0=v1^2/2+p1/rho+g*z1

You see pressure p is a linear term and v is always quadratic. Or is there an error in my logic I haven't seen?

For a more detailed description read the extruder part of this: https://github.com/repetier/Repetier-Firmware/wiki/Hardware-settings-and-print-quality

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repetier Wrote:
-------------------------------------------------------
> Ok, I created the missing wiki page
> (https://github.com/repetier/Repetier-Host/wiki/Te
> st-generator)
>
> If you want to test the advance algorithm of
> Repetier-Firmware, use version 0.60 with updates
> from 9.4.2012. It fixed a little bug in the
> advance algorithm.


Thank you very much.
One thing : I currently use the Mac version and the Printer/test menu is not there. In fact before my first email I even looked at the code and couldn't see a ref. to the test generator; but as I am not an expert in programming ...
I'm not currently using your firmware but that will come ... I'm still learning and trying to master all these, so one thing at the time.

This page [galileo.phys.virginia.edu]: says viscous flow through a pipe is linear with pressure, inverse fourth power on diameter.

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[www.hydraraptor.blogspot.com]

@Francois

If you are using the native Mac version - it is complete rewrite and doesn't contain the test generator. If I have collected more tests I may add it, but only this test is not useful enough.

@nophead

Your equations are for an open tube with no more obstacles. So if you extruder with the diameter of your filament this should be correct.

But what happens if you have a reduction in diameter, like our extruder have? It would work like a venturi nozzle and then you need bernoulli and the dependency becomes quadratic.

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I think it moves far too slowly for Bernoulli to be relevant. Yes the flow accelerates when it goes from the large pipe to the small pipe, but the speed is always pretty slow and the mass minute. The pressure needed to make it flow through the nozzle exit dominates.

My mental model is a reservoir of springy material (the 3mm melt chamber) and then a small pipe. The pressure at the start of the small pipe will depend on how much plastic has been forced into the melt chamber minus what has already flowed out. The flow rate through the small pipe is proportional to the pressure, so you have a first order differential equation which means a step change in filament feed speed makes the flow rate change on a negative exponential curve, much like and RC filter.

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[www.hydraraptor.blogspot.com]

I see what you mean and it could explain why Matts advance algorithm doesn't work perfect. When I get some time, I will change it to linear and see if it is better as the quadratic dependeny derived from Bernoulli. I think the truth is somewhere between both. The only question is morr linear or more quadratic. I hope the tests will give some answers on this.

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Repetier-Software - the home of Repetier-Host (Windows, Linux and Mac OS X) and Repetier-Firmware.
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