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PrintAir CoreXY

Discussion in '3D printers' started by Keith Davis, Oct 3, 2015.

  1. Keith Davis

    Keith Davis Master
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    Keith Davis published a new build:

    Read more about this build...
     
  2. DarkAlchemist

    DarkAlchemist Veteran
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    Hmmm, a rather funky design. Have any idea the total cost of the parts alone and how many printed parts are needed?

    I heard some bad stuff about Core XY designs being a pain but I have never used one so what is its major advantage and this design's advantage?
     
  3. Keith Davis

    Keith Davis Master
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    Cost of parts will be around $400, give or take $20 depending on sourcing. The V Slot extrusions alone are $95. There looks to be 33 printed parts total, including 3 parts not shown. I figure print time at 20 hrs.

    The advantage of a Core XY is the small amount of mass being moved, effecting speed, especially acceleration. On a Cartesian design the Y axis moves the build plate and the object, putting a speed limit on acceleration. A box design like the Q3D Revolution instead moves the mass of the X motor(s) even if a Bowden extruder is used. While an H-Box design like Ultimaker's also moves only the extruder carriage, the belting is more complex to layout.

    The main drawback of the Core XY I've built for testing is the amount of processor needed for constantly calculating the two motor movements. High speed Delta designs have similar processing requirements. On my test a RAMPS could keep up with 200mm/sec but I had to go to the 32 bit processor Azteeg X5 to flawlessly run over 300mm/sec. I'm going to try this with a RAMPS just because of the price difference ($40 vs $110). Considering it is a Bowden, no printing of flex filament is envisioned, so I plan on using an all metal E3D which can move enough filament at 300mm/sec w/.4 nozzle.
     
  4. DarkAlchemist

    DarkAlchemist Veteran
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    The printer I designed had only 3 printed parts and everything else is from here or ebay because I am not too keen on printed parts but because of the lack of printed parts the cost of it is 500-590 dollars.

    I don't move the bed like a Prusa design (bad show on that as I found out so I will never have another printer that the bed moves in any direction but up and down) and move it like an Ultimaker in the Z direction only. A shame these parts cost so dang much as it is keeping me gun shy to try anything with them.

    As far as the 32 bit vs 8bit goes it really isn't so much the bit count but the clock speed and instructions per second because a ramps has a hard time keeping up past 150mm/s on a Delta.
     
  5. Keith Davis

    Keith Davis Master
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    Ah.:)

    I have way too many RAMPS boards laying around to not use them :(. And some of my Mega 2560 boards are the 16MHz R3 version while others are the old 8MHz. Maybe....

    But still, the expensive Azteeg has a 120MHz ARM chip.....
     
  6. DarkAlchemist

    DarkAlchemist Veteran
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    Yep, due to the speed and the instructions per cycle it does it can easily blow away even an Arduino 2560 o/c (in liquid nitrogen) to 120mhz because the ARM is just so streamlined. I have two 2560s (1 on the ramps and 1 never used as a backup) and once I get a new printer up and running I will go for something ARM based but they are not cheap.

    By the way the rod is that 5mm and is it flat on one side? If not you will need to do something to prevent the gears from slipping. If it is I am looking for a seller for just such a beast. Basically I am after the same deal as a stepper motors shaft but at what ever length I need (with the flat side as well).
     
  7. Keith Davis

    Keith Davis Master
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    Do you know of any other ARM based processors for 3d printing? I haven't researched all the stuff out there, just the Azteeg.

    Actually I plan on cheating on that 5mm drive shaft. I plan on using a stainless steel threaded rod. I figure they are strong enough to take the torque. The set screws on the pulleys cut into the threads quite handily, creating their own "flat" at anywhere on the rod rotation. If I used a rod with a flat cut at each end and in the center, all on the same plane, then I'd have to have exactly matching belts. I really don't want to get into closed loop belts or count hundreds of belt teeth, so I'm going to see if I can "monkey fit" it. And I just assumed that finding a 400mm long 5mm shaft with a flat milled the entire length would be difficult. Just in case I need one, I'll be asking you later if you found such a thing.
     
  8. DarkAlchemist

    DarkAlchemist Veteran
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    My Z screws on my i3 rework boat weight is SS and you are right they tear the threads up but I must confess I can't easily get 5mm all threads anymore so I am stumped. edit: I know from experience that allthreaded 5mm rods wobble so are not dead straight like a smooth rod would be (reason I am looking for it).

    As far as the ARM based processors there is the Smoothie which the Azteeg X5 is based off of. There are some controllers based on the Arduino DUE which is a Cortex M3 based CPU but I can't remember them off the top of my head.
     
    #8 DarkAlchemist, Oct 4, 2015
    Last edited: Oct 4, 2015
  9. Keith Davis

    Keith Davis Master
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    Yes, 5mm threaded rods do wobble, but I don't think that will make a difference, the set points will remain aligned. I get my 5mm threaded SS from Tacoma Screw, but then I have a local Tacoma Screw store for pick up. A 3/16 rod with one wrap of masking tape will work as an alternate for 5mm too (0.18750 vs 0.197).

    Another knock off of the Smoothieboard is the AZSMZ, priced like it was made in China (which it is) half the price of the Azteeg. I might try it, even though I haven't yet seen how to setup corexy in their firmware samples (I think you just set arm_solution to corexy).
     
  10. DarkAlchemist

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  11. Keith Davis

    Keith Davis Master
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    Thanks for the controller links! I just woke up, I'll check them out.

    Just as I was crawling into bed it occurred to me that I have 8mm threaded rods. And, oodles of 2oT 8mmID GT2 pulleys from another design for the shaft ends. And, a handful of 40T 8mmID GT2 pulleys for the shaft's middle I can run against a 20T 5mmID GT2 on the motor for speed reduction/torque increase. Z shaft solved.
     
  12. DarkAlchemist

    DarkAlchemist Veteran
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    Well, I am no lover of 20t pulleys because if you do the math 16t pulleys/gears are evenly divisible which matters for Z (you can read up on Z banding). 16t is 10 micron layer height using a gt2 belt 1/16 microstepping where as a 20t is 12.5 micron which is fractional so you have to make sure you never have Z end up on an odd step with a 16t I never have to worry about that when slicing as I can use any layer height I choose. One thing I will say is a 2:1 is great and stick the 16t on each end that way the torgue is increased AND your resolution is increased.

    What I am trying to figure out is if I have a 40t and a 20t then slap 16t on each end what did I just do? Did I just make my 200 steps into a 400 steps and the 10 micron is now 5 micron for the height? I think that is what would happen.

    Oh, I still can't find 16t 8mm bore and I can't find 5mm smooth rod in any lengths greater than 400mm from Misumi so seems I am stuck (I need a 510-540mm M5 smooth rod in h5 or g6 if I have to or some pulleys with 16t and 40t with all having an 8mm bore). The 20t would be 5mm bore directly on the motor which is butt easy to find.
     
  13. Keith Davis

    Keith Davis Master
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    Good point on the 16T pulley!

    It doesn't look like there is enough meat left on a 16T pulley for an 8mm bore.

    Maybe - use a 5mm 16T pulley mounted to a 5mm bolt through the pulley and bearing and a 5mm/8mm flex coupling, then the 8mm threaded rod and same 5mm 16T & 5mm bolt with 5mm/8mm flex coupling on the other end.

    I think you're right, 10 micron would be 5 micron with a 2:1 reduction requiring a doubling of steps_per_mm in config.

    Back to the AZSMZ board - this thread started as a printed case for the AZSMZ LCD and turned into a pretty good configuration.txt thread http://www.thingiverse.com/thing:745001/#comments. Seems that AZSMZ (cxandy) has pretty much taken over Smoothieboard development.
     
  14. DarkAlchemist

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    Smoothie was supposed to have pro versions coming out but I think China is whipping their buttocks. Smoothie was/is a far superior design BUT was just too over priced and the pro versions were going to be yet another 1.5 to 2 times the price of the current versions. I was reading and the AZSMZ uses two different pins (I forget which ones now) so if you take a Smoothie config those two pins have to be changed. I forget where I found that bit of info at.

    I thought about the coupler but the coupler cannot be flexible so I am not sure if that is even available.

    edit: Just went looking and found it - http://www.ebay.com/itm/2pcs-5x8mm-...r-Transmission-Connector-D14L25-/251977382666
     
    #14 DarkAlchemist, Oct 4, 2015
    Last edited: Oct 4, 2015
  15. Keith Davis

    Keith Davis Master
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    Hey thanks for the ebay link pal! I was headed out to the shop to look for a round to chuck in the lathe when I saw this. Considering my time and their price, I can't afford to make this. But blue? Cobalt Blue? Oh well, I'm going to have to powder coat the Tee Brackets anyhow. Jesus....

    Ordered an AZSMZ from czandy. He says he'll get me the firmware code for the new version ESP8266 WiFi adapter next week, says it's an easy setup. His board should be here by then. I love his LCD, small, and case bolts right into V-Slot. He's easy to work with. He has Delta and Cartesian config samples and I suggested he add the one line to the Cartesian for running Corexy instead and he did.

    I read a number of forum threads where people had problems with Panucatt's Azteeg X 5 (mostly bad solder jobs) and used ASZSMZ instead with no problems. If cxandy's AZSMZ is as good as his support, I've found bacon.

    Looks like I need to get started on construction this weekend.
     
  16. DarkAlchemist

    DarkAlchemist Veteran
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    LOL, I found some others but were all copper and just didn't look as sturdy and cobalt blue would look nice against black Extrusion, lol.

    As far as the wifi thing I was told WiFi for print jobs was a bad idea and I was told this by a lot of people were the creators of the Smoothie as I would have loved WiFi printing but in this house no way Jose' and what they were talking ab out was if the wifi was right next to the transmitter so nothing would happen as the protocol is a bad dealio for it but I have no idea about any of that.

    I would like to try an AZSMZ but I don't have a printer anymore as my boat weight (i3 Rework) left the building last April and that made over 1 year of thousands of hours of fiddling and "maybe" 2kg of printing and .5 kg of useful prints. People looked at it and could not figure out what was the issue so a boat weight it became. Now I just want a printer that works and I don't have to eff with once setup. No more spending 16-18 hour days trying to dial it in to get 1 print sort of nonsense.
     
  17. Keith Davis

    Keith Davis Master
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    I'm thinking of doing the plastic in Green Apple, and Cobalt Blue doesn't quite fit. And brass? Saw those. Brass?

    The way to use WiFi on AZSMZ is just to upload to the SD card, then trigger the print off the card with the computer/tablet/phone, and disconnect. Wifi adapters are limited to 115200 baud and when using a 32 bit ARM that would be like putting horse shoes on your corvette's wheels instead of tires. Even with the best of signals you couldn't keep up. AZSMZ needs 250000 over USB, that's why it, Smoothie and Azteeg, all have an SD card - so it can print from itself.

    Sorry to hear about your i3 Rework. I think "i3 Rework" must be a brand because there are a LOT of them. I bought a Makerfarm i3 kit 2 yrs ago. Unpacked it, without looking at the plywood parts put them back in the box and threw the box in the dumpster. I just wanted the hardware and electronics. XYZ needs a solid frame for reference. I didn't care for Bart Dring's offset v wheels on the makerslide so I was experimenting with running his v wheels on 1/4 inch square bars turned 45 degrees nested in 8020 extrusion slots to center the wheels. It actually worked. But Mark is a lot smarter than I, he turned the concept inside out and stuffed the wheels into V-Slots. The minute I saw it I ordered (I am that smart). My V-Slot based i3 is BldrBot (http://www.openbuilds.com/builds/bldrbot.632/). I have one running right now in the workroom - it has over 7,000 hours and has printed every day for 18 months. The only problems have been keeping the two z axis motors in sync. I finally solved that by cutting the wires to one of the motors (dead motors have good bearings and make a handy pillowblock) and running a belt-pulley drive from the driven rod to that dead rod. Even with the old QU-BD v9 extruder it prints PLA & ABS all day at 100mm/sec and has never had a bed level change since I went to the single motor. I use it mostly for 7 hr prints for a RAMPS box. It's that trusty.
     
  18. DarkAlchemist

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    My lord so their WiFi isn't even G? OUCH!! Why in the world should I care if I just pop the card into my PC and save to it instantly? I personally do not like printing via a SD card as I much prefer going directly from my computer as the controls on the screen are just too rudimentary for me.

    I3 Rework was designed from the French and it was based on the i3 Einstein variant with more fixes. Right off the bat the first thing wrong was the Z endstop holder. Caused me 3 months of hell but now my printer (after a couple of hundred dollars to fix) will not lay down the first couple of layers. No matter who has looked at it, and checked everything out, all I could get is a "WTH? Why is this <bleep> still not working?" from them and they just get disgusted. Basically the printer can't be fixed and it only happens in the middle of the bed so I am hoping to try and level it one last time and print the parts I need in a corner. Oh, the first thing people checked was the bed itself and no issues so they thought it must be heat related so go buy this and same thing.

    I am no lover of Josef Prusa's designs (as is well known) and I went on the reprap forums and someone laid out to me why his designs, in very great detail, suck. Josef Prusa made a design (i2) that propelled the 3d printer in so many homes and for that I take my hat off to him and acknowledge his contribution but his designs are made to to lowest denominator. What turned me off to Josef Prusa, after half a year of hell on the boat weight, was him finally acknowledging, on his blog, he designed the I3 to be aesthetically pleasing so a wife wouldn't be upset at it on the kitchen counter top or living room tabel AND was NOT designed to be functional. After that I felt betrayed but that is for the Prusa lovers to attack as they always do, lol.

    BldrBot I have heard very good word about but I just don't want another 3d printer where the bed moves in any direction other than Z.
     
  19. Carl Feniak

    Carl Feniak Master
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    For the Z banding issue, I think the recommendation is to only use full step increments and not micro steps. The reason is that the true position of a micro step is less accurate than a full step position.
     
  20. DarkAlchemist

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    That is the theory also a moving bed causes ghosting AND for tall prints can, especially if fast printing, just shake the model clean off. None of those happen with a non moving bed (much preferred is a real fixed bed but very hard to implement).
     
  21. Mark Carew

    Mark Carew OpenBuilds Team
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    You may want to look into gear reduction in place of micro stepping.
    Take a look at this write up of Micro stepping vs. Gear reduction it may shed some new light on the subject.

    Also wanted to say very cool looking build! I really like the way you were able to use the T Joining Plate on the Z run, great idea. :thumbsup:
    1.jpg
    Keep up the good work and thank you for sharing.
    Mark
     
  22. Carl Feniak

    Carl Feniak Master
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    Probably bad communication on my part. I was simply recommending choosing layer heights that correspond to full step positions rather than micro step positions. This only applies to the Z axis of course.
    Edit: just read Mark C's linked article... good explanation of why you'd want to do the above. Just for the Z layer height. I still micro step my Z axis so it is smooth for homing, I just choose a layer height that correspond to a full step for my printer. In my case, increments of 0.04mm.

    Mark,
    Nice design, interesting Z axis! Looking forward to seeing build pics in the coming weeks.
     
    #22 Carl Feniak, Oct 6, 2015
    Last edited: Oct 6, 2015
  23. Keith Davis

    Keith Davis Master
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    Thanks for the link Mark. It's good to see the engineering behind what I've been experiencing. It's not just my imagination.:D

    As for the use of the Tee Plates, notice that the Y axis is also running on the same Tee Plate/V Wheel setup. I've used this elsewhere and drill the two outside holes to 7mm for the eccentric spacers. Works great.
     
    Mark Carew likes this.
  24. Keith Davis

    Keith Davis Master
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    DarkAlchemist, I really thought you were making up the name "Reworded". Now that I've looked at pics, I suspect that you would indeed have problems that appear to be bed level. Look at later designs that have a wing on each side of the frame plate that extends back and is affixed to the rear of the Y frame. The reason: the joint between the frame plate and the Y frame is the weak part of the design and the wing creates a triangle reinforcement. It may not appear that there is wobble on your frame plate, but I bet if you run a ribbon of scotch tape from the top of the frame to the rear bar on the Y frame you'll see that tape dancing while printing. If so, that is likely putting your nozzle closer to the bed on the ends and higher in the middle. It doesn't take much vibration like that to get the problem you've described. Anyhow, that's the explanation I've read for those wings on later designs.
     
  25. Keith Davis

    Keith Davis Master
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    Carl, I think you are the one who encouraged me to build the corexy I'm using here back when it was on my CoreXY Enclosed. I abandoned that design because I couldn't realize a Z axis I liked. That encouragement has haunted me every since. Well, I now have a Z axis I like. Thanks!
     
  26. DarkAlchemist

    DarkAlchemist Veteran
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    I have a brace on each side and I made sure it was plumb and there is no wiggle. This is where the problem comes in at when people look it over. A really horrible design and the main reason it has been sitting in the den untouched since April-ish as I can't even look at it because I get nausea. So much wasted effort, expense, and time on a hunk of junk.

    So, I am just going to build/buy something that does/did it right or I may just forgo 3d printers all together and use the money instead on a CNC router. That last part is especially if just the mechanical parts alone is going to run me 500-600 bucks.
     
  27. Nick Foley

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    Are the forces in a CoreXY really so well corrected that you can get away with a compression-only XY gantry like that? Even when making fast Y moves with the effector near min/max X? Awesome if so.

    Great design. Mine has deviated a bit from your previous one due to a desire to keep everything as off-the-shelf as possible. I should start the build in the next week or so and will post when I do.
     
  28. DarkAlchemist

    DarkAlchemist Veteran
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    What does that mean "a compression only XY gantry"?
    Mine was designed to do that and because of that the price skyrocketed.
     
  29. Nick Foley

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    The gantry only has internal wheels on the rails - no outer wheels clamping against the back side, too. If you were to twist the gantry about the Z axis hard enough, the rails would bow / the gantry would buckle, and the wheels would come off the rails. I'm not saying that this is a problem, BTW... in reality, everything may be stiff enough and the forces low enough for that kind of failure to be irrelevant. I've just never seen it before and am curious if it has been tested or used elsewhere.
    upload_2015-10-10_18-23-9.png
     
  30. Keith Davis

    Keith Davis Master
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    Nick Foley, I got the idea from David Bassetti's design linked on the Build tab. I'm running the wheels against 20x40 outside rails whereas his design uses only a 20x20 - and he's running a direct drive's mass on his X axis instead of the bowden's lighter mass. But, he never mentioned what kind of speed he's getting, so we'll see.

    And David is bolting his X axis to the two wheel plate with only one bolt, where as I'm using the regular Tee Plate and two bolts to hold the X axis bar perpendicular to the wheels. I'm amazed he got away with only one bolt but probably did it to cut down overall width.

    [​IMG]
     
    #30 Keith Davis, Oct 10, 2015
    Last edited: Oct 10, 2015

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