Ideas for the next Wally.

Ideas for the next Wally.

Postby Feign » Thu Jun 26, 2014 6:47 pm

Hi, Concept Forge folks... Bored engineer here with some ideas.

I've been sort of interested in the Wally printer for a while and have been lurking here for a while, though this is my first post. From the looks of things, getting the z-axis to behave is the root of most of the woes here, and I've come up with a basic idea that I posted to the RepRap board a while ago, but have decided to make a thread about it here to get some discussion going.

Moving both the arms and the print bed in synch to keep the bed even with the arms in the y direction. In the example picture below, I've added a z-axis arm for the print arms with various belting methods to keep the two arms evenly mirror-imaged to each other as they travel. (the belt is the bold line for clarity in each example)
Wally_Z-Axis_Ideas.JPG
You'll need to view it full size, for it to show correctly.
Wally_Z-Axis_Ideas.JPG (81.49 KiB) Viewed 75319 times

In the left two examples, the z-motor placement is pretty obvious, but they all can use the belt as an idling device, mounting a motor to many other places on the frame to pull the arms in the z-axis whichever way they need to go.

Any ideas? Could this be applied to existing Wally builds?
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Re: Ideas for the next Wally.

Postby see3d » Thu Jun 26, 2014 7:18 pm

Your ideas are clever and could find practical applications, but according to Nicholas (in last nights post), the Z axis is not causing a problem for Wally current builds. It seems to be a software issue with getting the right equation implemented for the X,Y cartesian to Wally polar mechanics. I don't think it makes sense to try to add such complexity to the current Wally before solving the root problem first. Once Wally works as designed, then its shortcomings can be addressed.

That being said, I am personally interested in alternative Z axis designs. Your design to have a relative linear Z motion between the head and table with counterbalanced rotary motions is intriguing. :geek:

Your design has another advantage: The more than doubling of the practical Z motion range for a given 4 bar linkage arm length. I guess we would have to call it a dual 4 bar linkage or an 8 bar linkage. :)
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Re: Ideas for the next Wally.

Postby Nicholas Seward » Thu Jun 26, 2014 7:27 pm

@see3D: One of the reasons I am leaving Wally is that the XY and the Z are problematic. Right now XY is the biggest problem but it would have a chance of being compensated for if the Z wasn't changing all the time also. (Obviously, nothing is impossible but it is a rough design to get calibrated.) My next design will have a boring linear Z but I really like this idea and it will be fun to play with.
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Re: Ideas for the next Wally.

Postby Feign » Thu Jun 26, 2014 7:40 pm

see3d wrote:Your ideas are clever and could find practical applications, but according to Nicholas (in last nights post), the Z axis is not causing a problem for Wally current builds. It seems to be a software issue with getting the right equation implemented for the X,Y cartesian to Wally polar mechanics. I don't think it makes sense to try to add such complexity to the current Wally before solving the root problem first. Once Wally works as designed, then its shortcomings can be addressed.

Hmm, when I initially read that post I thought he said the problem was the x-y being dependant on the z, rereading it really changes the story! Though to be honest, this would make things a lot easier to caibrate, since there are only two polar coordinates to worry about rather than three.

In either case, the Wally style arms could be replaced with Morgan style arms (or the single arm Nicholas has been mentioning) just as easily.

see3d wrote:Your design has another advantage: The more than doubling of the practical Z motion range for a given 4 bar linkage arm length. I guess we would have to call it a dual 4 bar linkage or an 8 bar linkage. :)
Not just doubling the travel for a given bar length, but making it so the build are isn't restricted by the arc of the z-axis arms.

Actually, with this I was thinking each z-axis arm would be 3 bars rather than 4, since the non-driven bar can be placed in the middle of the carriage on both the top and bottom arms in all cases without affecting the print. This makes it a bit less complicated, and potentially adds stability, eliminating the potential for torque to lock up or break the bars.

EDIT:
Nicholas Seward wrote:@see3D: One of the reasons I am leaving Wally is that the XY and the Z are problematic.

Knowing that you're leaving it make me want to save it more. :lol: I've always had a soft spot for fixing abandoned things. Now of course, I've got my eye on the arms and how I could force the math to get better there too.
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Re: Ideas for the next Wally.

Postby Simspeed » Fri Jun 27, 2014 9:30 pm

I for one am looking forward with great anticipation to Nicholas' one arm scara design. I've been working on a three leg delta frame design that uses the "boring" linear slide Z axis ;) .....but I've progressed through many different XY ideas to settle on the one arm scara concept. (See attachment). Many thanks to Nicholas for his support and suggestions to help me get to the current point.

I originally thought to add the Wally XY axis mechanism to my chassis, but the one arm scara concept is turning out to be more practical in my application. I'm anxious to start my build but I think it best to wait and gather as much from Nicholas' scara as I can before finalizing mine. Every component needs to be set conceptually before beginning the process of acquiring pieces and then scaling it all to fit together.

Interesting projects all....excited for the next steps. Thanks...TP
Attachments
Delta Scara 026.JPG
Delta Scara 026.JPG (158.48 KiB) Viewed 75296 times
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Re: Ideas for the next Wally.

Postby realthor » Tue Mar 31, 2015 7:59 am

Hello guys, I have just registered with the forum to express my support for the WALLY project and to state that it was (is?) on of the most promising projects out there as minimum vitamins and specialized parts are concerned. I was pretty disappointed to learn that the math is too heavy or complicated.
My questions are:
1) is WALLY still a WIP project? I would be as happy with a Morgan XY arm but the Z - apart from some scissor lift ones i've seen in different corners on the web - is the one I am after.
2) is the WALLY math already in Merlin firmware?
3) is the next WALLY (as i've heard) as low on parts as this one? Also without radial bearings?
Attachments
screenshot.200.png
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Last edited by realthor on Fri May 08, 2015 5:50 pm, edited 5 times in total.
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Re: Ideas for the next Wally.

Postby Nicholas Seward » Tue Mar 31, 2015 8:27 am

I am certainly not working on Wally any more. The arms require a ridiculous amount of math which is compounded by the non-linear z which makes calibration a nightmare. Great prints can be made but they are not very accurate. If you could hook up a RaspberryPi and a webcam then you could get it to map the errors in 3D but I haven't gotten around to playing with that level of autocalibration. It was a fun project to explore a few ideas. I am currently starting work on a 1-arm scara that will travel up and down a column (2 rails). All the steppers will be in the base and it will mostly use the Morgan firmware. It will be simple stupid and will have an insane print volume when compared to the Morgan or wally. I really want to get rid of the Z rails but sanity and simplicity and practicality are preventing me at the moment.

Side note: I have a student working on testing bearingless boltless joints (mostly for an experimental Simpson as if Simpson wasn't experimental enough) to see how good we can make them and how they will hold up under the demands of 3D printing.

Bottomline: For Wally to survive let me suggest a few changes. Move the steppers to the arm (easy math) or replace the arms with Simpson style arms (stupid easy math). This should make the xy easy to calibrate. The Z need to be linearized. Rails would do it but in the spirit of Wally check out this.
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Re: Ideas for the next Wally.

Postby realthor » Tue Mar 31, 2015 1:19 pm

Even though it looks quite overkill with so many needed bearings (compared with just a couple) for the vertical axis linear bearings, it might still be a better option when linear rods are included in the total price.
Has anyone considered printing the bearing's housings on a 3D printer and fill it with steel balls? Considering that 3d printing is dealing with low weight plastic parts, they wouldn't get that much of a wear.
I am thinking something along these lines: https://www.youtube.com/watch?v=Qw1yGYdkNBk

Thank you.
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Re: Ideas for the next Wally.

Postby Nicholas Seward » Tue Mar 31, 2015 3:50 pm

Why even use steel balls? Plastic BBs are super cheap and super round.

I personally want to look into getting rid of the balls all together. Two spring loaded point contacts can make a very low friction joint. With 3D printing loads we may be able to get ride of all the bolts and the bearings.
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Re: Ideas for the next Wally.

Postby realthor » Tue Mar 31, 2015 10:45 pm

I am very interested in this. Is it too premature to create a separate category for the "bearingless boltless joints" project that is going on? I am sure many more would be interested in some CAD/sketches.

As for my comments on wally, I am pretty sad it is going to be discontinued at some point but hope for better alternatives. I am more of a general idea, exploring possibilities guy with no current experience in 3d printing, thus there is little I can contribute but hey, everybody starts from somewhere.

Keep up the good work and thanks for your commitment.
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