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Snappy V2.0: Land of confusion.
#1
Apologies if this gets longish.  I have not yet built, and have many questions.

I am planning to build a Snappy V2.0.

First problem:  I need a 3D printer to print the Snappy parts.  Oh, I guess I should mention (for those who are not aware): The Snappy is a **true** RepRap.  Literally, the entire thing is 3D printed.  You need motors, electronics, a bearing, and a couple of tiny nuts and bolts, and that's it.  Everything else is printed.

Anyway, I have a friend who bought/built a 3D printer kit, and is happily printing.  So, I am going to approach him with all the STL files, and the filament (around 2.4KG), and see if he is willing to help out.  As for the other parts, I am scavenging an aborted OneUp kit.

Second problem:  My OneUp kit came with only four NEMA17s and I need five for the Snappy.  I believe that the motors that came with the OneUp were Wantai 42BYGH610 from China (cannot confirm - hope we get the old fabric8r contact back soon). I would like to have all the same motors, as I think it simplifies things.  However, the 42BYGH610 is hard to find.  A set of three is for sale on eBay ($33 - pricey, as I only need one).  aliexpress.com has the motor advertised by (I believe) the manufacturer, for $8.95, but says that it is no longer available.

Another option would be to simply use a different NEMA17 for the fifth motor.  mpja.com has a motor who's specs come close:

Model:  32177 MS
Step:     1.8 degree
Lngth:     1-7/8" (47.625 mm)
Coil:   ~6 Volts/??? Amps/7 Ohn/15 MilliHenrys.
Wires:  4
Polar:  2-Phase, Bipolar
Torq:   ???
RI:     ???
DT:     ???
Wt:     0.75

Model:     42BYGH610
Step:     1.8 degree
Lngth:     40 mm
Coil:     6.5 Volts/1.2 Amps/6 Ohm/13 MilliHenrys
Wires:     4
Polar:  ???
Torq:     3000 gcm (41.662159670238 ozin)
RI:     54 g(cm^2)
DT:     220 gcm (3.05522504248412 ozin)
Wt:     0.24 Kg

Abbreviations:  RI=Rotor Inertia, DT=Detent Torque, Wt=Weight

So, this leads to all kinds of questions.  First, how does my RAMPS board know that one motor (which I will probably use as the extruder motor) is different?  Do I have to configure that in the firmware?  Is there a good tutorial out there for configuring firmware for differing motors?  Is it wise to even have an oddball motor in this scenario?

Also, I am planning to use the anubis print head that came with the OneUp kit.  Anybody have any hints/tips for using that head?

If anyone can verify the motors, or if using one oddball will help/hurt, or can offer any advice on this endeavor, please advise.

Thank you all in advance.
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#2
Hi mr_intensity,

Welcome to the forum.

>>> First problem:  I need a 3D printer to print the Snappy parts.

Well, that is a problem Smile. You could beg your friend to print the parts for you (by the way, no matter who prints them, it seems like it will take a very long time to print everything). You could finish the OneUp first, and then print the Snappy Smile. And then there are numerous printing services, but that will drive your price up.

I have looked through the content of the old forums (which is a mess, which is why posting it here is on the back burner), and I found two references to Wantai motors. The first one is clearly from the RPM printer, and the model number there is "57bygh800". The second mention, it is not clear which printer they are talking about, but that info is: "WANTAI STEPPER MOTOR Model : 42BYGH610P2-X 1.2A (U) 1.8deg/step".

I have no idea if either of those is actually correct.

I am no expert on the firmware for these things - I've never messed with it. So, my opinion isn't worth much on this, but I don't think there will be an issue if you use a similar motor - I'd just make sure that you match the two steppers for the z-axis. Hopefully, someone else can chime in on that.

I would also just run with the hot end you have - if it gives you trouble, you can solve the problem then or worry about replacing it.

Best of luck in your adventures - maybe you could explain a little more about why you want to do things this way. There are numerous cheap printer options today that will run rings around the old OneUp (my OneUp worked very well), don't have the roadblock of getting the parts printed, and will generally be a much less painful experience getting started. See other threads here, just did that myself.
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#3
Thank you, MisterAcoustic, for your quick response.

(2018-01-08, 06:13 PM)MisterAcoustic Wrote: ...maybe you could explain a little more about why you want to do things this way.

My OneUp horror story is documented in what was (I believe) my only old forum post (subj: IS THERE ANYBODY OUT THERE). Essentially, I had one missing part and one broken part, and Q3D would not even respond to me, let alone ship me two cheap melamite parts. Heck, don't even send me the parts. Just E-mail me the CAD files for the two parts, and I can have them made local. But they would not even respond.

Anyway, OneUp had issues with the single Z-axis motor design causing "droop" of the X-axis. Some clever people dreamed up a Kevlar line-and-printed pulley system to stabilize the X carriage, and eliminate the droop. But when I went out to thingverse, the things (and the author) were no longer there.

So, I have a project that is down two frame parts, and will droop/crash the head into the platform versus something completely 3D printed, with no droop, is simpler to assemble, and can use my existing motors/electronics/extruder. Snappy wins, if I can get the parts printed.

My friend and I belong to an aviation club (EAA), and our chapter does "build nights," every Monday, for people building their own airplane/ultralight/LSA. For those who are not building an aircraft, bring in a project to work on. The reason I mention this is that he does not need to print all the parts all at once. Just print me enough to do a sub-assembly on Monday night. Snappy can be my "Build Night Project" for a month or so.

Then, I got to figure out all this firmware stuff.
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#4
Hi mr_intensity,

First, I'd just like to recommend that, if you have any budget at all, that you pick up a different printer altogether. I believe that you will save more in time and sanity, and get printing more quickly if you do. I just bought a cheap chinese printer, and I have to say that it's amazing for the price.

Okay, back to your actual comments....

) OneUp broken/missing parts: You haven't said which parts. I originally bought a OneUp, and then upgraded it to a TwoUp. This means that there were parts that only fit the OneUp that were left over. I may have them somewhere, but I will need a while to search. If instead the parts are used on both OneUp and TwoUp, I have a second TwoUp that needs to be re-assembled (It wasn't put together quite well enough by its original owner). This means that I should be able to document any part from that machine, if that would interest you.

) Fixing OneUp droop: First thing is, I never had that problem - it depends on how lucky you get with the parts you have. If you want to fix the droop, you don't have to have the printed solution to the pulley system. In fact, I invented my own, using sliding door hardware from the hardware store (after my TwoUp got damaged and needed help). You can see a picture of this system on the fabric8r.com/site page. The main image cycles between three pictures. The middle one shows my TwoUp after I installed some printed upgrades. The pulleys are still on the machine, even though it doesn't need them with the upgrades. If you're interested in that, I can explain how I attached and adjusted the string/wire.

I'd also like to point out that I think it's likely that a fully 3D-printed printer is going to have quite a few design trade-offs that will make it less desirable in both assembly and use than it might seem from the drawings.

Having said all of that though, if you are interested in making and learning, then it will probably be quite rewarding to make your own. I have been happy with my One/TwoUp for that reason. But now I'm very happy to be moving forward with my new printer.
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#5
Okay, if you want the gory details: This is a "V2" OneUp kit. There were supposed to be three EIFRAME pieces, but I only got two. One was missing. Also, one of the two SIDEBRACE pieces was broken (photo attached).

Thank you for staying with me, this far, and giving me good advice. My budget at this time is little to zero, as I am unemployed and my unemployment has run out. That is one of the things that makes Snappy attractive. With hardware in my OneUp Kit and the 1KG spool of filament that I bought with it, last year, all I really need are 2KG more of filament ($30 at Micro Center) and some screws and nuts (pennies), and I got a Snappy. Also, looking at the assembly instructions for both printers, and the OneUp pieces parts, the Snappy just appears to be a easier and more solid build.

I should be seeing my buddy on Friday. Let's see how receptive he is to printing a snappy, and move on from there.


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#6
Hi mr_intensity,

I don't know which piece the EIFRAME piece is, but if you have two others, then you might be able to make a third one, or have it made. When I get time to look in the docs, maybe I'll have more to say.

The piece you posted a picture of - I bet I have broken that piece 20 times or more Smile. It's really not critical. You can put your broken pieces together on the other gantry pieces, and put a little drop of glue on it. It will be fine.

I think you might be closer to having a OneUp than you think. If all you can spend is time, that's all it costs to try to work though the issues with the OneUp. I only used glue in a couple of spots in my build, and I could take it apart to grab the motors in half an hour. I think you could finish the OneUp and have a printer. If you don't like it, you can print some parts of the Snappy along with your friend and get that done sooner.

Whatever you do, have fun Smile
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#7
Back to the original topic, pretty much any common 3D printer stepper that fits will work. Given a choice I'd use a Kysan 1124090 (quiet, reliable, lots of torque) but you may have a space issue (my also non-functional 1^ parts collection is two floors up or I'd check). From a quick look the Wantai you list should work.

You want a motor voltage that's less than 12V (the driver current setting will protect it), and less than 2A, around 1.5A is better, for most 3D printer driver boards including RAMPS, and most likely 200 steps/rev. A 400 step/rev motor will work, but I'd back off to 8 microsteps on the driver.

You configure the motor by setting the current limit on the RAMPS board (you can do it empirically, up the current until it hits the 5 second limit (you can hold your finger on it for 5 seconds without having a high pain tolerance) then back it off a little bit). Steppers are designed to run at higher than you might think temperatures, despite the urban legends running pretty darn warm won't hurt them. For a standard 200 steps/rev motor at the standard 16 microsteps/step the calibration will be the same regardless of who made it, if you run across a 400 step/rev motor then either set the driver for 8 microsteps/step to get the same results, or double it if you stay at 16. Since microsteps are notoriously inaccurate, think as much as +/- 20%, you're fooling yourself if you think more tiny steps somehow magically make it better. Actually motor steps can have pretty high tolerances too. Since you set the current with a tiny screwdriver, and if you use a motor/microstep setting that matches the stock motors (200 and 16, or 3200 steps/rev) you can use the stock firmware without any changes.

You might be able to trace/cut/sand to fit your missing MDF pieces out of MDF, hardboard, or something similar since you seem to have an example.

Aviation club? Way back when, in the early 80s, we bought a Quickie Aircraft Q2 kit and got it about a quarter assembled over a couple years of evenings and weekends. We then moved (back to a farm the bank and I owned in the north woods) where I didn't have a good place to work on it, had 3 daughters, plus a high-travel time job and a high workload small farm, and the semi-completed kit has been sitting in several outbuildings for around 35 years now. Like most homebuilts it'll likely never get completed Sad I'd like to build a power chute, these days going nowhere slowly would be a lot more run. 200 hr PP but haven't flown since the wife/mortgage/kids/etc thing kicked in, it was a lot easier when I owned a trailer on a small airport and kept it there rent-free in exchange for night watchman, minor mowing duties, and paying a $6/month hanger light bill.
------
Original Printrbot Plus, modified
Kickstarter Thingybot Delta
QU-BD One Up (parts, received with bad motor)
QU-BD RPM (incomplete box-o-parts, milling package never received)
Maslow CNC (4'x8' chain driven router, Arduino and custom controller)
Zenbot Mini (6"x8" router, LinuxCNC)
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#8
Mr A:

The EIFRAME is part of the Extruder Sub Assembly (photo attached).  All three of them are kind of stacked as a spacer, and a couple of long M3 bolts are run through the holes, to one of the NEMA17s.

Wish I had a caliper to get some really accurate measurements on this thing.  I'm gonna try to reproduce this thing in OpenSCAD, and have the part as an *.STL file.  That way, if my buddy balks on printing the Snappy,  I can ask him: "Well, could you at least print this very small part for me?"

I am really not too keen on building the OneUp, as it looks more rickety than does the Snappy.  They put together a whole bunch of melemite parts in a sub-assembly, while the Snappy prints one part that does the same thing.  Snappy just seems more sturdy.

I have dug out the kit.  And yes, I still even have the broken part.  I was going to super glue the broken part, independent of anything else, but then I re-read your post.  I was wondering how I was going to make sure I "glued it straight."  By lining it up in the assembly first, it should hold it straight whilst I glue.

Not sure what I am going to do, at this point.  We'll see if my buddy balks at the Snappy, and I am going to see how the EIFRAME definition goes.


Moose:

Thank you for your input.  I have never adjusted the current limit on one of those controllers before, so I am sure I will ask many stupid questions whenever that time comes.

Some friendly advice:  Don't EVER give up on an aircraft project.  Try to do something small on it, every now and then.  If you are absolutely sure it is over, then look to sell it, take the money, and do something that you want with it (like the Powered Parachute). Don't let it lay around, gathering dust, until you pass, and then your daughters are stuck having to get rid of it.

Of course, another option...Any of those daughters good with tools, and looking to become a pilot?


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#9
OMG! That was so BRAIN DEAD STUPID SIMPLE.

(see attached)

The dimensions were 4 cm x 1 cm x 0.5 cm.  Standard clearance hole for a M3 bolt is 3.4 mm.  Holes were centered, and equidistant from all three edges.

The toughest part was figuring out the radius for the circular cut.  That took not only Pythagoris, but dragging Binomial math out of the recesses of my brain.


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#10
Hey man, why use Super Glue?

I'm CLOSE with the SIDEBRACE piece (see attached).  As accurate as I can get, with just a tape measure.  It says this piece is 0.6 cm thick, as opposed to 0.5 cm thick with the EIFRAME piece.  I'll have to compare the two and see if one is a millimeter thicker than the other.

My initial game plan was to take the good SIDEBRACE piece, and scan it at high resolution, then do a bitmap-to-vector conversion (probably to Encapsulated PostScript [*.EPS] format) and then use pstoedit to convert the drawing to *.DXF, and import into OpenSCAD.  This failed for multiple reasons.  So, I took the broken piece, and a tape measure, and have something that is pretty close.

The two circular cutouts are just "guesses," and I do not have the big curve in the SIDEBRACE, because it is non-circular.  I am thinking of printing out some millimeter graph paper, and tracing the curve onto it in order to get a close approximation with very small line segments.

So, the board meeting of our Aviation club has been canceled due to weather concerns.  So, I will not be seeing my buddy tonight.  I may just E-mail him the two STL files (once done) and see if he can print them up for me.


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