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Drive Screw

Posted by Anonymous User 
Anonymous User
Drive Screw
December 12, 2008 12:21AM
I have a lead screw that says

0.10 in lead (10 pitch)

is this good for the mcwire

TYVM

Arun
Re: Drive Screw
December 12, 2008 08:35AM
What is the step angle for the stepper motor you're using?
Anonymous User
Re: Drive Screw
December 12, 2008 05:17PM
Thank you very much for the reply smiling smiley

The angle is 1.8

Best,

arun
Re: Drive Screw
December 12, 2008 07:53PM
What it means is that your stepper is going to go

(360/1.8)*10 = 2000 steps/inch

(2000 steps/inch)/(25.4 mm/inch) = 78.74 steps/mm

so your resolution will be

1/78.74 steps/mm = 0.0127 mm/step

Now suppose you wanted your axis to move 10 mm/sec. You would have to take

(10 mm/sec)/(0.0127 mm/step) = 787 steps/second

Without a pretty good driver board and a fairly high voltage power supply, I'd suspect that this would be pretty difficult to achieve. Nophead would be able to tell you more about whether the extant Darwin driver boards would be likely to deliver that kind of performance, I suspect.


-------------------------------------------------------

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
Anonymous User
Re: Drive Screw
December 12, 2008 08:29PM
So What you mean is that, i should ditch the Lead Screw and get the Specified 1/4-20.

Best,

arun
Re: Drive Screw
December 12, 2008 09:14PM
No, that just makes the situation twice as bad. Your stepper has to do twenty full revolutions to go an inch instead of ten.


-------------------------------------------------------

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
Anonymous User
Re: Drive Screw
December 13, 2008 02:32AM
humm...

the stepper on sale in rrrf.org is 1.8 deg
[www.kelinginc.net]

mcwre specifies a 1/4-20 Lead-screw...

aren't these a good match...

Best,

arun
Re: Drive Screw
December 13, 2008 03:19AM
Depends on how fast you can make the stepper run. If you're milling metal, that's one thing. It can be slow. If you're printing plastic, it needs to run fast.


-------------------------------------------------------

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 15, 2008 10:54AM
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.

Demented
Re: Drive Screw
December 15, 2008 11:00AM
Demented Chihuahua Wrote:
-------------------------------------------------------
> 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. smiling bouncing smiley


-------------------------------------------------------

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 15, 2008 11:29AM
How expensive is "expensive"? And, I have some junk steppers sitting around that I might use...assumably they are around a 7.5 to 15 degree step. They are NEMA 17's. Because of their smaller size and large step, would I be right in assuming I would get more power out of them using the Gen 1 driver board than I do out of the larger steppers? Or am I completely backwards?

Demented
Re: Drive Screw
December 15, 2008 12:26PM
Demented Chihuahua Wrote:
-------------------------------------------------------
> How expensive is "expensive"?
>
About $85/axis
>
> And, I have some
> junk steppers sitting around that I might
> use...assumably they are around a 7.5 to 15 degree
> step. They are NEMA 17's. Because of their smaller
> size and large step, would I be right in assuming
> I would get more power out of them using the Gen 1
> driver board than I do out of the larger steppers?
> Or am I completely backwards?
>
I've never heard of a NEMA 17 stepper with a big step angle so I couldn't make a reliable guess. You'll just have to try it and see.


-------------------------------------------------------

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 11:43AM
Hey Demented, when I was first playing around with Zach's magnetic encoder, I got my extruder to run at 1 RPM very smoothly, just to see how slow it would go. That's the same speed as the second hand on an analog clock. Too slow to be practical for RepRapping, but it should go slow enough for your purposes. That would get you up and running at least.

Wade
Re: Drive Screw
December 16, 2008 01:01PM
@Wade,
I can run it at a setting of 1 on the Extruder Exerciser...that wasn't the problem...it's that even at that speed with a .35 mm tip, it was pushing out too much plastic. I'm not sure what RPM that translates into but it seemed really slow. Like, ridiculously slow.

I've bought the Magnetic Rotary Encoder and plan to get it together and on my machine eventually but the PIC electronics don't support it so it's kinda a mute point at this time I think.

Instead, I simply installed a larger tip--.85mm I think--and we'll try that once I get a new PTFE barrel. Till then, we wait.

@ Forest,
Damn, that's expensive...too expensive. Bleh.
Re: Drive Screw
December 16, 2008 02:41PM
Demented Chihuahua Wrote:
-------------------------------------------------------

>
> @ Forest,
> Damn, that's expensive...too expensive. Bleh.

Huh? confused smiley


-------------------------------------------------------

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. smiling smiley

1 mm/s is pretty slow, but you could build yourself some faster parts. smiling smiley 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
Re: Drive Screw
December 16, 2008 03:44PM
Wire your motors in bipolar parallel and they should go four times faster. You won't be able to supply the full rated current but then you should only need a small fraction of the max torque for a McWire.


[www.hydraraptor.blogspot.com]
Re: Drive Screw
December 16, 2008 08:51PM
I get about 2.7 mm/sec. Sad. My z gets about 1.5 mm/sec.

I haven't worked out how fast my Extruder is truning yet, not as easy as the axis to figure--and I'm lazy--but it sounds like it is turning much faster than that...one more issue to tackle when I get my machine back online...bleh.

Demented
Re: Drive Screw
December 16, 2008 08:52PM
Ah! That's a great idea, Nophead! I'll do that...awesome!

Demented
Re: Drive Screw
January 18, 2009 10:31PM
Does anyone use 1.8 deg per step stepper motors for driving the plastic filiament ?

If not, is it just a question of needing another channel of stepper motor control ?

Graham.
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