1 Topic by wompus

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Topic: Mods for Perfect Circles

Like everyone else, I love my SD and was thinking to myself, what can I do to make it even more awesome. I was hesitant to try this mod at first but after a while and seeing that it wasn't a big deal, I went ahead with it.  Pictures should explain it all.

If I had to do it again, I would remove the plate of the motor and use it to mark where holes that need to be drilled out on the frame instead of eyeing it through the threaded holes and marking the frame. Make sure where you are marking that you do not drill into the switch. It is not possible to secure it with 4 screws, but as you can see, I've gotten a great print with only two screws holding the motor to the frame. I used a twist tie to keep the coupler from coming apart.

I've also done a mod for my platform where I use a coupling nut instead of the standard nut. This keeps the rod straighter over a longer distance. The rod dances in the standard nut a little bit, the longer coupling nut reduces the dancing and keeps the rod straighter.

I've also printed out 100% infill brackets with clips to grab onto the frame. There is less flexing of the bracket and the pulley doesn't dance around on the bolt as much. I don't have a door so I can't say if this will interfere with it.

If there is a circle file that people use to calibrate, please post the link. I would like to try it out.

I'd love some feedback and to know if this helps anyone else!

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2 Reply by 2n2r5

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Re: Mods for Perfect Circles

http://www.thingiverse.com/thing:84795 here is a pretty good test for circle calibrations.

SD3 w/ mods:
Glass bed with QU-BD heat pad upgrade, threadless ballscrew w/ 8mm smooth rod, spectra line belt replacement, lawsy MK5 extruder, Lawsy replacement carriage, E3D hotend, Ramps 1.4 w/ reprap discount controller, DRV8825 drivers, 12v 30A PS, Acrylic case, Overkill Y-idlers, Filament alarm, Extruder fan + more.

2n2r5's Website

3 Reply by IanJohnson

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Re: Mods for Perfect Circles

I'm glad you did that with the Y motor, I had been toying with the idea for awhile.  I hate doing the dance of aligning the drive belt, and trying to get it tight enough to keep the backlash down without bending the rod or getting skipped steps.

You can give this mount a try and use a dial gauge to test the backlash in the Y axis - http://www.thingiverse.com/thing:69029

4 Reply by Tomek

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Re: Mods for Perfect Circles

nice mod indeed on the y-axis.

is there any reason for the spider style coupler instead of a rigid coupler? Is it just impossible to align things well enough for a rigid coupling?  I assume the spider/love-joy introduces backlash.

5 Reply by Hazer

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Re: Mods for Perfect Circles

Tomek wrote:

nice mod indeed on the y-axis.

is there any reason for the spider style coupler instead of a rigid coupler? Is it just impossible to align things well enough for a rigid coupling?  I assume the spider/love-joy introduces backlash.

Actually it doesnt, thats what makes it nice. Hard couplings have no backlash, but HAVE to be aligned. Helical couplings do not need to be aligned, but flex so much they have backlash. Spider coupling has no backlash and does not need to be aligned. But nothing holds it together either, the mounting needs to hold the coupling together.

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6 Reply by muddtt (edited by muddtt 2013-11-01 14:51:21)

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Re: Mods for Perfect Circles

What size was the spider coupler and what type of insert is in it? This looks easy enough to do with great results. Thx for the post!

7 Reply by wompus

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Re: Mods for Perfect Circles

Tomek wrote:

nice mod indeed on the y-axis.

is there any reason for the spider style coupler instead of a rigid coupler? Is it just impossible to align things well enough for a rigid coupling?  I assume the spider/love-joy introduces backlash.

The reason for the coupler I chose is because I didn't want any compression or expansion as with other couplers. Looking back at it, I also didn't want it fully rigid because I didn't know how well the motor will align with the rod.

muddtt wrote:

What size was the spider coupler and what type of insert is in it? This looks easy enough to do with great results. Thx for the post!

It's a 5mm / 6mm coupler. I'm not sure what you mean by the insert. Coupler is made of three pieces.

I'll try to make some prints over the weekend and post the results.

8 Reply by muddtt

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Re: Mods for Perfect Circles

Did you just use the original shaft?

someone said you used a spider/love coupler. It seemed like you order those with a separate insert. Thanks for the info.

9 Reply by wompus

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Re: Mods for Perfect Circles

2n2r5 wrote:

...here is a pretty good test for circle calibrations.

I gave it a shot. My settings probably have to be adjusted. I don't know if it makes a difference if it's ABS or PLA and how the material shrinks after it cools for this test. I'm using ABS though and it was pretty tight so I had to give the nickle a good wack to get it in there. If there's any deformities, there's a chance I may have stretched them out around the nickle.

muddtt wrote:

Did you just use the original shaft?

someone said you used a spider/love coupler. It seemed like you order those with a separate insert. Thanks for the info.

The coupler came as you see in the picture, all three pieces. No separate insert was ordered. A longer shaft is necessary for it to extend to the coupler so I had to order an SD3 6mm shaft for my SD2.

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10 Reply by ggoner (edited by ggoner 2013-11-17 07:28:23)

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Re: Mods for Perfect Circles

If a Nema 14 would line up with the shaft and fit inside the case, they may make a dual shaft version. With a dual shaft on the Y axis it would drive one shaft on the left and one shaft on the right. That way the whole assembly would be inside the case. That would be tasty!

P.S. Never mind... the y axis is a Nema 17 and it is too big to line up with the shaft from inside the case. They do make dual shaft Nema 17's I'm not seeing a way to align it to the shaft. They do make higher current Nema 14's, maybe a higher current version could drive it?

11 Reply by muddtt

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Re: Mods for Perfect Circles

definitely would be nice to do it inside. Outside is kinda strange looking.

12 Reply by ne14pez

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Re: Mods for Perfect Circles

I just ordered this: http://www.amazon.com/Amico-Stepper-Cou … m+coupling

I don't think alignment will be too difficult.  Besides, there is always a little play in the mounting holes.

Have any of you who have tried this already had any problems with the motor wobbling on those spacers?  I would be concerned that the torque from fast changes in direction could cause the whole thing to twist and introduce a new backlash problem.  Instead of metal spacers, why not design a printable rectangular spacer so that the motor can't rotate at all?  I was thinking something like this, but taller: http://www.thingiverse.com/thing:11429/#instructions

13 Reply by muddtt

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Re: Mods for Perfect Circles

Looks like a good idea. Take lots of pictures big_smile

14 Reply by ggoner

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Re: Mods for Perfect Circles

I drew up a crude concept model of an internal motor mounting for the Y axis for the SD3. I placed the motor on the right because it would block clear access to the Z axis stop screw on the left side. It only just fits. This will not fit on a SD2. The biggest clearance problem is the couplers (called spider, plum, or jaw couplers). The smallest are 20mm diameter by 30mm long. So with two couplers you need 60mm just for the couplers. A very compact coupler would make this an easier fit. As you can see you would have to cut a rectangular opening in the back for the motor to stick through. This may come into contact with the top of the spool mount. So it may be necessary to relocate the filament spool mount also.

This requires a dual shaft Nema 17 motor, two couplers, and the two motor mounts in the drawing.

This is just a concept drawing, not a working model. While it is close enough to determine whether it will fit, it is not a built and tested mod. Hope this helps anyone interested.

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Yaxis_MotorMounting.skp 914.09 kb, 20 downloads since 2013-11-18 

Yaxis_MotorMounting.stl 424.4 kb, 40 downloads since 2013-11-18 

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15 Reply by ggoner

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Re: Mods for Perfect Circles

First off I would like to thank wompus for his mods. This is definitely a step in the right direction.

Concerning my concept for mounting the Y axis motor inside the chassis I have made a few tweaks.

First off my thought is that a perfectly centered motor would not need flex couplers. A solid coupler would be better. Solid couplers can be made smaller and this would address the issue of the couplers taking up too much room. So I have drawn up printable couplers that are 14mm in diameter and 20mm long. The set screw holes would need to be tapped for 3mm set screws. I don't know if I have the diameter of the set screw holes correct for tapping. These couplers still may not clear the Z axis guide rods though they are at least closer to doing so. Someone may know of an existing coupler for 5mm to 6mm that would work better.

In order to align the motor properly we need to be able to adjust the alignment in both the Z and the Y axis. I have changed the motor mount holes to slots with .5mm play in both directions of the Y axis. I have changed the chassis mount holes in the motor mounts to slots to provide adjustment in the Z axis. This should allow the motor to be perfectly aligned.

I don't have a dual shaft Nema 17 motor. This plan is based on a motor model that I did not create. So final placement of the motor in the horizontal plane is not final at this point. This needs to be known before the rectangular hole can be cut in the chassis.

With the holidays coming up it may be some time before I can come up with the few dollars to order the motor. So someone may beat me to trying this mod. As a fair warning to those interested, this is only a concept at this time. I have not done this mod. This mod is design for the SD3. I don't think there is enough room to do this on the SD2.

I haven't split out the coupler and motor mount parts from the drawing because they are still concept parts. While you need two motor mounts and two couplers, they are identical so there is only two parts, but you need two of each.

If you have sketchup (it's free) you can select the parts, copy them (Ctrl C) and paste them into a new drawing to isolate them for modification and printing. There is a free plugin extension for sketchup to import/export STL files.

Have fun. wink

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Yaxis_MotorMounting1.skp 953.65 kb, 4 downloads since 2013-11-19 

Yaxis_MotorMounting1.stl 507.36 kb, 24 downloads since 2013-11-19 

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16 Reply by wompus

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Re: Mods for Perfect Circles

ne14pez, did you ever get around to implement the y-motor to the 6mm shaft? I'd love to see results from you or anyone else who had any success doing this mod.