1 Topic by magstang1775

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Topic: PWM to change speed

Hi all,

I am working with some really tricky polymers, and am finding it would be worthwhile to slow down the speed, esp. at the beginning of extrusion. Obviously I could change the limits on the stall protection board, but that's hardly an efficient method. Has anyone experimented with adding a PWM controller? Any advice on how to do so? I'm not super knowledgeable about electronics, but this seems like a relatively simple upgrade.

Thanks in advance for any advice/input!

2 Reply by elmoret

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Re: PWM to change speed

The stall protection board is itself a PWM controller, there's no harm in using the CV potentiometer to adjust speed.

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3 Reply by magstang1775

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Re: PWM to change speed

Right, I got that part. It would be nice though to have a dial on the outside-- one of the polymers in particular basically comes out as a liquid, so I need to slow way way down at the beginning of extrusion, then speed up to a more normal rate once it's established a bit. Basically, I'd like to be able to adjust on the fly without having to open the enclosure. Is that possible with the stall protection board? Not sure if this is making sense.

4 Reply by Kronikabuse

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Re: PWM to change speed

Isn't that what the acceleration setting is for?

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5 Reply by elmoret

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Re: PWM to change speed

There's no acceleration setting on a Filastruder.

Why not mount the stall protection board on the outside of the enclosure? You could replace the potentiometer on the stall protection board with one that has a knob if you like, too.

Daisy chaining PWM controllers can have strange effects, but you're welcome to try!

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6 Reply by magstang1775

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Re: PWM to change speed

Oh, duh, that seems like an obvious solution. Okay. I'd much prefer to use what's already there than to make it overly complicated.

Can you describe how I would go about replacing the potentiometer with one that has a knob? Even with it mounted on the outside, I think a knob would be the most convenient. I may be able to find an engineer around here to help me if it is complicated or tricky.

As an aside, thanks for your very prompt responses, Tim!

7 Reply by elmoret

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Re: PWM to change speed

Just remove the existing potentiometer, measure its resistance (don't remember off the top of my head, but can measure one if needed) and choose a replacement that has a matching resistance.

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8 Reply by magstang1775

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Re: PWM to change speed

I'm checking out potentiometers at McMaster and I'm not really sure what I'm looking at.

You mentioned I need to match resistance. That aside, do you think one of the (A) knobs would work? http://www.mcmaster.com/#potentiometers/=122bxcg

To remove the old pot, do I need to desolder from the board? I don't really have that capability, so it may be simpler to try daisy-chaining.

9 Reply by elmoret

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Re: PWM to change speed

McMaster would be a super expensive supplier for potentiometers.

If desoldering is off the table, I'm happy to do one up for you, at the cost of a stall protection boad on the website ($15). You'd just order one and when it shows up it'll have the knob ready to be remote mounted, so you'd just replace the one you have. If that works, get in touch via email to handle the details. (how long you want the wire to be, etc)

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10 Reply by magstang1775

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Re: PWM to change speed

I'll get in touch via email. Thank you!

One more question (figured this would be better answered here in case others are interested)-- will this change remove the built-in stall protection? Or will that still function?

11 Reply by elmoret

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Re: PWM to change speed

This would replace the stall protection board you have. It is an identical board, I'm just doing the work (of replacing the potentiometer) for you. You would remove the stall protection board you have and replace it with the one I send.

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12 Reply by magstang1775

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Re: PWM to change speed

Okay, got that part. What I meant was: will the motor still have stall protection in terms of limiting the max current draw, or will that only be limited by the knob?

Just want to make sure that if I have the knob turned all the way up, it won't damage the motor if it starts drawing too much current (from a jam or whatever else). Does this make sense?

13 Reply by elmoret

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Re: PWM to change speed

Yes, there's two knobs on a stall protection board. One is voltage (which is proportional to speed) the other is current (which is proportional to torque).

Normally the voltage is set to unlimited to allow for maximum speed, I'd be replacing that potentiometer with one that could be remote mounted. The current limiting pot and all of that functionality would be untouched, and I would set the current limit for you ahead of time.

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E3Dv6 All Metal Hotend - the premier 3D printing hotend

14 Reply by magstang1775 (edited by magstang1775 2016-04-20 20:02:09)

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Re: PWM to change speed

Ah, that makes sense. Thanks for clarifying. I mixed up current/voltage and what they do. Sorry for the confusion!

It's probably a good thing you'll be doing this and not me!