Drive Screw
Posted by Anonymous User
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Re: Drive Screw December 12, 2008 05:17PM |
Thank you very much for the reply 
The angle is 1.8
Best,
arun
The angle is 1.8
Best,
arun
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Re: Drive Screw December 15, 2008 11:00AM |
Demented Chihuahua Wrote:
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> Yeah, I have the 1/4-20 all thread and a 200 step
> motor...runs horribly slow...I have a hard time
> slowing my extruder down enough to not overwhelm
> it. It's become a real problem for me.
>
I had the same problem with Tommelise 1.0. You should look at tin can steppers with about a 7.5-15 degree step to get the speed you need instead of those very fine resolution steppers. They just don't run nearly fast enough with the voltages, driver boards and software that you're using.
I shifted over to linear, tin can steppers for Tommelise 2.0 and have never regretted it. They're expensive, but you don't have to go through all the drama of worrying about how to connect steppers to lead screws, lead screw inertia and thrust yoke backlash because it is all built into the steppers.
-------------------------------------------------------
Hell, there are no rules here - we're trying to accomplish something.
Opportunity is missed by most people because it is dressed in overalls and looks like work.
Thomas A. Edison
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> Yeah, I have the 1/4-20 all thread and a 200 step
> motor...runs horribly slow...I have a hard time
> slowing my extruder down enough to not overwhelm
> it. It's become a real problem for me.
>
I had the same problem with Tommelise 1.0. You should look at tin can steppers with about a 7.5-15 degree step to get the speed you need instead of those very fine resolution steppers. They just don't run nearly fast enough with the voltages, driver boards and software that you're using.
I shifted over to linear, tin can steppers for Tommelise 2.0 and have never regretted it. They're expensive, but you don't have to go through all the drama of worrying about how to connect steppers to lead screws, lead screw inertia and thrust yoke backlash because it is all built into the steppers.
-------------------------------------------------------
Hell, there are no rules here - we're trying to accomplish something.
Opportunity is missed by most people because it is dressed in overalls and looks like work.
Thomas A. Edison
|
Re: Drive Screw December 16, 2008 02:41PM |
Demented Chihuahua Wrote:
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>
> @ Forest,
> Damn, that's expensive...too expensive. Bleh.
Huh?
-------------------------------------------------------
Hell, there are no rules here - we're trying to accomplish something.
Opportunity is missed by most people because it is dressed in overalls and looks like work.
Thomas A. Edison
-------------------------------------------------------
>
> @ Forest,
> Damn, that's expensive...too expensive. Bleh.
Huh?
-------------------------------------------------------
Hell, there are no rules here - we're trying to accomplish something.
Opportunity is missed by most people because it is dressed in overalls and looks like work.
Thomas A. Edison
|
Re: Drive Screw December 16, 2008 03:08PM |
Some numbers for Demented:
If you're using 3 mm filament, and a 0.8 mm/thread drive screw turning at 1 rpm, that's
3.14*1.5^2*0.8*1/60=0.094 mm^3/s (flow rate of plastic)
Divide that by your extrusion area, 3.14*(0.35/2)^2= 0.096 mm^2,
and you get 0.97 mm/s, which would be your ideal head feedrate. That's pretty slow - even my Z axis moves at 3 or 4 mm/s, at 400 steps/mm with the Kelling Nema23 motor driving 4 8 mm screws with gen 2 driver boards.
I think the lowest setting on the extruder exerciser needs some adjustment. There's probably a lower limit in the code, to deal with static friction; maybe you've got much lower static friction in your extruder compared to the usual one. Those low speeds are difficult without the magnetic encoder though; my setup ends up pulsing the extruder motor, but it results in a nice smooth movement, especially with the 1024 bit resolution on the encoder. It moves a bit like clockwork at that speed.
1 mm/s is pretty slow, but you could build yourself some faster parts. A bigger nozzle will help speed everything up though, at the cost of accuracy. I build all my parts with 0.5 mm filament, stretched from a 0.6 mm nozzle; stretching helps span the gaps.
Demented, how fast does your x and y stage go?
Wade
If you're using 3 mm filament, and a 0.8 mm/thread drive screw turning at 1 rpm, that's
3.14*1.5^2*0.8*1/60=0.094 mm^3/s (flow rate of plastic)
Divide that by your extrusion area, 3.14*(0.35/2)^2= 0.096 mm^2,
and you get 0.97 mm/s, which would be your ideal head feedrate. That's pretty slow - even my Z axis moves at 3 or 4 mm/s, at 400 steps/mm with the Kelling Nema23 motor driving 4 8 mm screws with gen 2 driver boards.
I think the lowest setting on the extruder exerciser needs some adjustment. There's probably a lower limit in the code, to deal with static friction; maybe you've got much lower static friction in your extruder compared to the usual one. Those low speeds are difficult without the magnetic encoder though; my setup ends up pulsing the extruder motor, but it results in a nice smooth movement, especially with the 1024 bit resolution on the encoder. It moves a bit like clockwork at that speed.
1 mm/s is pretty slow, but you could build yourself some faster parts.
A bigger nozzle will help speed everything up though, at the cost of accuracy. I build all my parts with 0.5 mm filament, stretched from a 0.6 mm nozzle; stretching helps span the gaps.Demented, how fast does your x and y stage go?
Wade
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