Crazy idea about feeder

[ayahoo 0]

Hi Guys, I have an Idea I would like to hear your comments .

We all know that having the feeder next to the extruder is the best design regarding the clogging and jammed extruders... BUT the problem is the size and weight,,, so I have an Idea to make is VERY SMALL & VERY LIGHT.

How? well using a solenoid! i'm an ENG in a factory that we are using many kinds of feeder system to our machines, one type of a feeder system is Pneumatic like this one:

You can see in the video that there are few steps for each cycle:

Hold the strip

Advance fix distance

Hold the end of the strip (so it wont come back)

Release the first gripper

Move back

and again...

Now I think we can make something similar to this to advance lets say 1mm every time, and the using pulses we can control the speed of feeding per second.

it would be possible to use solenoid with a brass collet of 3mm (Like this - http://i326.photobucket.com/albums/k418/scdscd8/cute/04/0402/04020115/04020115cute_w4_a.jpg) that would once the solenoid is moving forward it would mechanically lock on the filament and move it forward, once going back (with a spring) it would release the grip.

What do you think? is it possible?

 

[gr5 2,071]

I like the thought. This idea might trigger another. You should post a link to this current thread into this thread:

http://umforum.ultimaker.com/index.php?/topic/3174-ultimaker-rd-we-want-your-ideas/?p=23569

Someone else also talked about getting mechanical energy to the head - in their case using a rotating wire in a tube like for a speedometer cable in an automobile. This is similar to pneumatic energy transfer. In either case you need very good control of movement of the filament.

 

[jhertzberg 19]

Regarding using a rotating wire in a tube (bowden cable) to get mechanical energy to the head, chopmeister tried it and had no success. See http://umforum.ultimaker.com/index.php?/topic/2544-small-steppermotor-for-direct-extruder/?hl=hysteresis#entry18161. I have been playing around with the idea of constraining a loop of beaded chain under tension in a pair of PFTE bowden tubes with beaded chain pulleys wed to gears, within a housing, at either end. I previously built an articulated arm, attached to the head and the back of the frame, with a pair of pulleys bringing power to the head from a motor on the frame, but still don't have that working satisfactorily.

 

[ayahoo 0]

Thanks for the info it was interesting to see his try at this, but his design has many flaws... my idea is not using a motor at all! just using magnets today we are using circular motion (motor) to get linear motion (filament), I would like to stay at the linear motion without using the motor and the gears (fyi a solenoid weights around 25gr which is MUCH less than the motor & gear).

 

[gr5 2,071]

Your idea has many problems but I like it. I didn't want to tell you the problems because I think they can all be overcome. First know that the current extruder can push with 22 pounds of force. Can a 25gram solenoid do that? maybe. Secondly the movement is very precise. You need to be able to increase by .1mm smoothly over the course of 3 seconds with controlled acceleration and deceleration. Can a solenoid do that? Maybe - but you would have to add an encoder to feedback the position of the filament. How to do that? With a laser interfometer? With a spinning optical encoder? That would probably work well and be light weight. But the software now gets complicated.

Also with the drive on the head, retraction isn't as important but it is still important. Can a solenoid pull back on the filament also? Maybe. Maybe it could vibrate up to 1000 times per second pushing only the tiniest amount each time. Maybe a big solenoid for pushing and a smaller one for pulling?

The existing extruder stepper motor is very very heavy. But Servo motors are MUCH more powerful for the same weight. So if we could switch to a servo it could be made lighter. Not sure how much lighter. Right now Erik Zalm and rep rap people are working on the replacement to the arduino - a much more powerful computer. And the first thing they want to do is put in servo controller PID software for the servos. So.... improvements are on the way!

 

[jhertzberg 19]

I like your idea, but make sure you either take retraction into account, or consider a needle valve or shutter to stop flow when necessary. I would love to see some friction feed ideas that don't rely on a hobbed bolt. Can you make your increments both small enough to avoid visible pulsing artifacts, and fast enough to print quickly?

 

[ayahoo 0]

Well I think it would be nice, but difficult to implement and will require lots of time to play with :-), but using a servo motor would be easy to use, a motor like http://www.hobbyking.com/hobbyking/store/__9440__BMS_660DMG_HS_Super_Strong_Digital_Servo_MG_14_2kg_17sec_52g.html

All we need is a small board to control it and to change the firmware to support it.

[ayahoo 0]

http://arduino.cc/en/reference/servo

the board has servo control capability.

[gr5 2,071]

the board has servo control capability.

 

Oh. Maybe you are right - maybe there is enough cpu power left over for this but I had the impression that it was kind of at it's limit (cpu too busy to add much more functionality at speed). Anyway Erik Zalm himself seems kind of excited about the new Marlin to be run on a new kind of computer chip (arm):

 

The firmware will be a complete rewrite.

Many of the features you mentioned will be available.

Network, Encoder inputs, Webserver Touch screen etc. etc.

But the most important part are the better stepper drivers and increased diagnostic features.

The new electronics in combination with Youmagine will have very interesting features.

 

Posted here:

https://groups.google.com/d/msg/ultimaker/29O7CR6-r5k/tQxFpMipkucJ

 

[madoverlord 0]

Rereading this thread, a fairly insane idea occurred to me: how about a dual-solenoid system -- a solenoid-based feeder that pushes filament into the hot end, and a solenoid that retracts the entire feeder (!) to handle retraction.

I'm thinking there may be mass issues, and also reaction forces when the retraction solenoid fires. But perhaps this will inspire someone.

 

[irongland 1]

Actually I think you guys came up one a golden nugget about using a solenoid for retraction.

It sounds like it would be easy to code (whenever retraction occurs fire the solenoid) and it would reduce a bowden tube's issue with oozing and make the whole process go much faster. Imagine your ultimaker being able to make multiple retractions in one second.

I think that's a solid idea.

 

[jhertzberg 19]

I don't know if I understand your use of the solenoid for retraction correctly. I don't think that the oozing problem is solved by retracting the head. I think that the retraction of the filament creates a negative pressure in the heating chamber, and that slows the flow.

 

[irongland 1]

True, retracting the head might not be that helpful, but I think using the solenoid for retracting the filament is a good idea.

What I was thinking was using a solenoid to back out the filament near the hot end. By putting it closer to the hot end, there is less distance the filament must travel due the the "springyness" of the filament in the bowden tube. (we retract 4.5 mm, I think a lot of that distance is because the filament is being pushed towards the outer wall of the curved tube, when we need to pull it out, the filament must then pull back towards the other side.

This could also help speed up printing, for example, look at this thing:http://www.thingiverse.com/thing:131054

The ultimaker will have to make a very large number of retractions. lets say it takes a second to do a retraction. think of the time it would save.

Also the faster the retraction is made (as I understand it) will help create that negative pressure that pull the melting filament back into the nozzle. This too might improve quality. Certainly it would act more like a direct driven machine without the weighty head.

I think it's a good idea I might put a little effort into pursuing.

 

[madoverlord 0]

I'm sorry I was not clear. I was not talking about retracting the hot end, but moving the feeder up, so that the path from it to the melt chamber was increased, and thus the filament was sucked up.

In other words, one solenoid is a ratchet that does the normal feed, and one solenoid quickly retracts the filament -- not the hot end.

 

[irongland 1]

Ahh then we are on the same track of reasoning. I'm thinking though that we can eliminate the need for a direct drive (solenoid or otherwise) since having the perfect retraction would eliminate the need for direct drive in the first place.

Still, the use of solenoids for extrudes and other features intrigue me.

Hey does any one know how to wire one up to an ultimaker's electronics? I know we can get 6 and 12 v solenoids. unregulated these things look like they can draw .083 amps and produce 4 lbs (I don't think we need that much just for retraction, though for extrusion we probably will).

These things are kinda new to me, never done any work with em but they do seem quite simple.

 

[jhertzberg 19]

Thanks MadOverlord, that makes much more sense. How about using a miniature solenoid valve between the heat chamber and the nozzle? I know they make them small enough, I just don't know if the little ones can take the heat.