A redesign of the GUS Arm for easy external stringing

Re: A redesign of the GUS Arm for easy external stringing

Postby Jfriesen » Sun Apr 10, 2016 11:37 pm

Okay I got my first arm printed/assembled and I re-did the test described on the previous page to estimate actuator error using my calipers. I'd put my measurement error at at least around 0.05-0.1 mm because the calipers aren't mechanically attached to the arms ( I actuate the arm out of assembly and measure from the inside of the motor arm bolt to the inside of the slave arm bolt, pressing the calipers gently between these two bolts). The plot shows a marked improvement in accuracy! The maximum error in my previous test was +- 0.25 mm and it is now down to +- 0.15 mm. That's a 40% improvement so I'm very satisfied.

The arm also has a much higher apparent stiffness as the new gear profiles seem to produce a stiffer mate. Anyway I think I have finally arrived at my final design but we will wait to see how the calibration cube print goes!

Let me know if any of you have other thoughts on tests evaluations concerns etc.
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Re: A redesign of the GUS Arm for easy external stringing

Postby ekaggrat » Mon Apr 11, 2016 5:41 am

:mrgreen: great cant wait to see the prints.!! one question .. how do you ensure that your hotend is perfectly vertical to the hub? if it is not i affects the print as the hot end twists with the position of the arms.
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Re: A redesign of the GUS Arm for easy external stringing

Postby Viproz » Tue Apr 19, 2016 8:38 pm

Quick update on my build with a quick question.
So I bought everything and exploded my budget (https://docs.google.com/spreadsheets/d/ ... =838216683) quite a lot of stuff already arrived, I'm going to start printing the pieces in a few days, I think I'm going to start with the things like the wade, the small parts and the hubs and I'll end with the arms.

Do you recommend waiting to print the arms that you finalized them or can GUS print them without too much issue ? (My main concern is that I won't be able to print too much stuff with the printer I'm going to use to print the printer so I'd like to be sure that I'll be able to print replacement parts with my printer)
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Re: A redesign of the GUS Arm for easy external stringing

Postby Jfriesen » Tue Apr 19, 2016 9:11 pm

I have run multiple prints on GUS and I think the last commit to the GUS repository is probably going to be my final revision to the arms. I haven't yet print a GUS arm on GUS but I did print the first few layers of a GUS arm and it looked great. I need to buy some more PLA before I print a GUS arm with GUS.

The one thing I will say is I noticed you order the 623v pulleys which will be incompatible with the latest arms which has screw holes for m4 screws instead of m3. I strongly advise to switch to the U604ZZ pulleys I am using as their quality is significantly better. I picked mine up off amazon which was a bit pricey (you need 48 of them) here:

http://www.amazon.com/FORWORD-10pcs-Pri ... ge_o03_s00

But it appears you can also order them from multiple places on alie-express, this one looked reasonable to me but I can't vouch for the quality:

http://www.aliexpress.com/item/4mm-Walk ... c79d31b4ef

If you want to try with your current 623v pulleys you could easily edit the arm files in solidworks to reduce the hole size again. If you aren't able to edit let me know I can modify and add STLs for m3 bolt arms.
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Re: A redesign of the GUS Arm for easy external stringing

Postby Jfriesen » Wed Apr 20, 2016 12:52 am

Here is a quick timelapse of a print with the latest GUS rev2.5:

https://youtu.be/yPdXjGgnkIU
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Re: A redesign of the GUS Arm for easy external stringing

Postby tommythorn » Wed Apr 20, 2016 6:37 am

Wow that looks really good. How does calibration cubes fare? Straight and dimentionally accurate?
If I'm not mistaken, the extruder isn't part of your github STL collection, right? If so, which are
you recommending? (My very modded QU-BD TwoUp have been revived and improved so I'll be
starting my prints soon).
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Re: A redesign of the GUS Arm for easy external stringing

Postby Jfriesen » Wed Apr 20, 2016 6:48 am

The cubes aren't quite perfectly straight along the sides but they are close enough that the sides only stray from true by about 0.4 mm maximum. And the over all cube is squared up and coming out dimensionally accurate within about 0.3 mm error margin. I'll post some pictures tomorrow. I have been printing 75 mm cubes by the by.

I use the e3d v6 hotend but any hotend with the same form of attachment should work more or less the same.
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Re: A redesign of the GUS Arm for easy external stringing

Postby Viproz » Wed Apr 20, 2016 6:54 am

The extruder is in the STL folder, here it is : https://github.com/Jfriesen222/GUS_CAD_ ... s-wade.stl + biggear + smallgear. And here is an approximate BOM for it https://docs.google.com/spreadsheets/d/ ... =920633918 (in the bottom on the tab "Detailed BOM", I'm not 100% sure hat I have all I need I'll see when I'll build it and I'll update the list if I find anything wrong).
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Re: A redesign of the GUS Arm for easy external stringing

Postby Jfriesen » Wed Apr 20, 2016 7:22 am

Ah yes you said extruder not hotend... clearly I'm tired. I just use the very common wade extruder. I don't love the bowden extruder setup though. Even with large retraction settings I'm still getting some strings off of the prints. I am going to look for some advice on cleaning up the bowden setup or maybe see if I can get away with something closer to a direct drive.
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Re: A redesign of the GUS Arm for easy external stringing

Postby ekaggrat » Thu Apr 21, 2016 8:41 am

i have been using a bowden for some time on my delta . the only ratio that works well is a 1:3 . the wades edtruder is 1:5 so that causes difficulty in quick retract. i have a belted version for my delta and for the gus i used a 1 :3 gear set which fits on any wades extruder . if you need that i can share it .
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