Welcome to Our Community

Some features disabled for guests. Register Today.

C-Bot

Discussion in '3D printers' started by Carl Feniak, Sep 29, 2014.

  1. trublu832

    trublu832 Well-Known
    Builder

    Joined:
    Jun 10, 2015
    Messages:
    127
    Likes Received:
    65
    One other thing I was going to do along with that mod is cut the lead screws short enough so that there's no chance that the hot end could ever bang into them if it was moving about.
     
  2. CapnBry

    CapnBry Well-Known
    Builder

    Joined:
    Jun 13, 2015
    Messages:
    100
    Likes Received:
    54
    I meant to say that too! If anyone else does this mod they should either add like 50mm to the leg height or be prepared to cut the lead screws shorter. Carl's measurements give you plenty of room for a variety of hotends and carriages on a regular build (where they're out of the way) but the extra length can definitely ruin your day with them out in the "playing field" like that. I've already slammed my hotend to a lead screw at 250mm/s and it left a gouge on the fan housing. I've been trying to decide if I wanted to get two more pieces of extrusion and replace the legs with longer or just cut the screws but I'm pretty sure I'll just cut em.
     
  3. trublu832

    trublu832 Well-Known
    Builder

    Joined:
    Jun 10, 2015
    Messages:
    127
    Likes Received:
    65
    I just planned on cutting my lead screws down from the start, no need to re-do the legs
     
  4. Carl Feniak

    Carl Feniak Journeyman
    Builder

    Joined:
    Mar 18, 2014
    Messages:
    654
    Likes Received:
    246
  5. CapnBry

    CapnBry Well-Known
    Builder

    Joined:
    Jun 13, 2015
    Messages:
    100
    Likes Received:
    54
    I wanted a Hall effect endstop for my Z axis so I made one that is a little cube you can thread the wiring into and clamp down an A3144 unipolar hall effect sensor. The sensors are like 25 cents each from China, or as much as 70 cents from Amazon prime. They're not supposed to work on 3.3V which the Smoothieboard puts out on its endstop lines, but it does. I can just move the power to a 5V pin if I feel ambitious later. There's no cool LED though.
    [​IMG]
    [​IMG]

    I'm having a hoot with this printer. The two Z axes are incredibly difficult to keep level. It sort of worked but then I put some super lube on the lead screws and now it is right f*#$ed. The lead screw nuts now don't have enough friction to hold the bed in place when the stepper current is off so one of the two sides ends up slipping down. Even if they don't slip, the slightest bed pressure (such as trying to remove a print) will trigger it. I had them positioned 220mm from the back of the printer (of 405mm arm length), although the majority of the weight was on the shorter half due to the weight of the bed. I pushed them back as far as they would go until they hit the power supply, 160mm from the back extrusion. At this point there was slightly more friction and they'd pretend to hold a little longer before slipping.

    I'm going to give it one more try, moving them as far back as they can go without hitting the corner brackets and moving the power supply to the other side of the bar, but I've given up for today. It might work better with the OpenBuilds nut block, but they were out of stock when I ordered. This brass lead screw flanged nut has some play in it. I'm not sure if that's how lead screw nuts are normally as this is my first build with them.
     

    Attached Files:

  6. Carl Feniak

    Carl Feniak Journeyman
    Builder

    Joined:
    Mar 18, 2014
    Messages:
    654
    Likes Received:
    246
    Nice on the hall effect. Let us know if you think it is more accurate. Interesting issue on the z axis. I noticed this on mine when I first oiled it and pressed down on it by hand. It doesn't move unless I press on it pretty firmly but my bed is not as heavy as yours. I am using a bike chain oil that has some tack to it so maybe that also works in my favor. Switching to a lower pitch lead screw is a costly option. Anyone else have ideas?
     
  7. trublu832

    trublu832 Well-Known
    Builder

    Joined:
    Jun 10, 2015
    Messages:
    127
    Likes Received:
    65
    Thanks for the update, I think I might have the same lead screws, if I hold one vertically with the brass nut at the top it will spiral down the screw via gravity. Ive considered pinching the brass nut to make it slightly oval.
     
  8. CapnBry

    CapnBry Well-Known
    Builder

    Joined:
    Jun 13, 2015
    Messages:
    100
    Likes Received:
    54
    Exactly how mine are too. I did come up with a completely inelegant temporary solution, which is to take a 2lb sack of bolts and tie it to a piece of fishing line, tied to the Z bar and thrown over the top bar. The boltsack acts as a counterweight and is enough to prevent the bed from easily slipping. I'm looking on eBay now for a piece of steel remnant that I can use to build a slightly better solution. I figure a 1.25" round steel bar weighs about 4.1lbs which would counteract most of the bed weight. I have some thin stainless cable in the garage from another project I can loop over the top on a pair of V-groove bearings.

    Looking forward I'll probably now replace the dual Z direct drive system with a single Z motor and a belt sort of like @adamcooks Triple-C build, except with just two lead screws. That way I'd really have to go out of my way to get them out of sync. I can get 8mm bore 40T GT2 pulleys for the screws and a 5mm bore 20T GT2 pulley for the motor, which would give me a 2:1 gearing so the motor wouldn't have to work so hard and I'd get a nice even 0.02mm per full step. Can anyone see a reason why this would be a bad idea?
     
    #818 CapnBry, Jul 4, 2015
    Last edited: Jul 4, 2015
  9. Carl Feniak

    Carl Feniak Journeyman
    Builder

    Joined:
    Mar 18, 2014
    Messages:
    654
    Likes Received:
    246
    No, that should work gearing wise. There has got to be a much simpler solution though as a few other guys are basically using the same setup as you and not having this issue (as far as them not mentioning it). I am thinking sheffdog and Ak Eric as two recent builders that went with a 12 by 12 bed and two lead screws. You can take a look at their blogs to see if they did anything different. Could it be as simple as using a tackier oil?
    I would not recommend ovaling the lead screw nut as you may cause jamming if you go too far and may also impact you z accuracy slightly.
     
  10. AK Eric

    AK Eric Journeyman
    Builder

    Joined:
    Mar 31, 2015
    Messages:
    179
    Likes Received:
    129
    For what its worth, my build platform ain't goin' nowhere on its own accord: It spins freely when the steppers are idle (I can adjust it by hand), but not enough to actually have it travel down under its own mass. I lubed the leads-crews with the remainder of the lithium grease that came with my makerbot.
     
  11. CapnBry

    CapnBry Well-Known
    Builder

    Joined:
    Jun 13, 2015
    Messages:
    100
    Likes Received:
    54
    I didn't try moving my steppers back to Carl's original position. I didn't have the tee nuts loaded in the Z bar for it and I really didn't want to take everything apart to get them in there. Maybe that's the secret, having them attached to the Z bar ties them together more rigidly? When they steppers are out on the arms, the arm can have a little flex to it that allows the weight to be unevenly distributed and one just moves a bit. The arm on that side lowers a bit, only a portion of which is transferred as torsion to the Z bar (because there's a bit of flex at the arm joint), and only a portion of that is transferred to the opposing arm for the same reason. The whole thing sort of twists slightly.

    If they're both attached to the Z bar, they only one can be lower than the other is if the Z bar tilts left or right. The wheels in the V-rail do a good job of preventing that from happening so they there's no slip.

    At least that's what I'm thinking must be going on. I'd rather not attach the motors a the Z bar because with the weight of the block of aluminum bed, the whole thing can bounce like a diving board (not as flexible, but in that manner) and I'd be concerned about it moving up and down tiny amounts while printing at high speeds as the inertia of the print head shakes the whole structure. The 2lb bag-of-bolts counterweight I have on there currently seems to be working pretty well so far, but I will be upgrading that to a more permanent solution with a heavy steel rod and some V-groove bearings over the top.

    I think like Carl's said, making your own problems and solving them is half the fun of building a printer!
     
  12. AK Eric

    AK Eric Journeyman
    Builder

    Joined:
    Mar 31, 2015
    Messages:
    179
    Likes Received:
    129
    I am experiencing some bounce... I'm just getting started with this thing so I can't say yet how bad it is. Once thing I've been thinking about is move one of the leads-screws to the middle of the back, and the other to the front of the bed. This seems like a great solution... we'll see if I get that far ;)
     
  13. ruggb

    ruggb Well-Known
    Builder

    Joined:
    Jan 11, 2015
    Messages:
    135
    Likes Received:
    16
    Mine is a 3 screw setup and it is not too hard to rock the single screw side but it is stable under operating conditions. I only have a single wheel at each of the 4 corners. I would be very leery of just 2 screws without more wheels on each corner or a smooth rod and linear bearing arrangement to keep it from rocking. OH the thought of that is making Carl cringe. But that also asks for binding issues to exhibit themselves.

    As far as the pulleys go, mine is running well (after I got it aligned correctly) on 4 36T pulleys on motor and screws, but I can see and advantage to a 2:1 gearing. The Z motor doesn't work very hard anyway since it is one small step at a time - unless u home from full down. Then, I also have 76 oz-in motors.
     
  14. Carl Feniak

    Carl Feniak Journeyman
    Builder

    Joined:
    Mar 18, 2014
    Messages:
    654
    Likes Received:
    246
  15. CapnBry

    CapnBry Well-Known
    Builder

    Joined:
    Jun 13, 2015
    Messages:
    100
    Likes Received:
    54
    Thanks, @AK Eric and @ruggb for the input on your designs. Everyone is so friendly and collaborative in this thread, it definitely helps.

    Those 1-start screws would probably have been the best to start with for the simplest design, not so much for the torque but because the angle of the thread would divert the downward force enough to prevent them from auto-turning. I think I'm going to prefer having both lead screws linked though, because once they're locked together at equal heights, they'll stay that way forever. My current i3, one side of the Z very slowly gets out of whack. Like on the order of 0.01mm per 4 hours of print time so every few days I have to grab the motor and give it a little turn to keep it at the same height. I'm hoping with this new C-Bot that I'll never have to do this again-- that things that are level will stay that way until there's a disaster.

    My belt loops (got a couple sizes) and GT2 gears are coming from robotdigg in China so I guess I'm going to be quiet for the a few weeks. Thanks for the help, guys!
     
  16. trublu832

    trublu832 Well-Known
    Builder

    Joined:
    Jun 10, 2015
    Messages:
    127
    Likes Received:
    65
    Does anyone have a sketchup or an stl model file of a v1.2 endstop switch?
     
  17. João Fernandes

    Builder

    Joined:
    Oct 27, 2014
    Messages:
    6
    Likes Received:
    0

    Attached Files:

  18. adamcooks

    adamcooks Well-Known
    Builder

    Joined:
    Nov 6, 2014
    Messages:
    244
    Likes Received:
    65
    I know there are a few prusa i3's around with a belt coupled a axis.

    Wow, been away for a few weeks switching sides of the country and quite a few new printers popping up. Did finally get my shop setup, made the mistake of modifying my tempered glass build plate. I found out that tempered glass explodes with tremendous force. IMG_20150630_111003:nopm:.jpg
     
  19. trublu832

    trublu832 Well-Known
    Builder

    Joined:
    Jun 10, 2015
    Messages:
    127
    Likes Received:
    65
    Thanks for the upload of the endstop files!

    I couldn't resist doing a preliminary dry fit build while I wait for my MrMetric hardware to arrive. I didn't have a banana for scale so I used an egg. Going with an 8"x12" bed with 12" build height. Parts are being printed on a Robo3D.
    IMG_5382.JPG IMG_5383.JPG

    For anyone looking for a good cutting method for the rails I had some great success with this $25 blade, it gave perfect burr free clean cuts of the v-slot with a miter saw:
    http://www.amazon.com/Concord-Blade...=1436882538&sr=8-3&keywords=non+ferrous+blade
     
    Carl Feniak and Mark Carew like this.
  20. Mark Carew

    Mark Carew OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

    Joined:
    Jun 28, 2013
    Messages:
    2,759
    Likes Received:
    2,438
    @trublu832 thanks for the blade tip, thats a good price. :thumbsup:
    Mark
     
  21. Carl Feniak

    Carl Feniak Journeyman
    Builder

    Joined:
    Mar 18, 2014
    Messages:
    654
    Likes Received:
    246
    Nice, what pitch lead screws are those? Looks more shallow than 8mm so should avoid the issue CapnBry had (but kinda hard to see in the pic).
     
  22. trublu832

    trublu832 Well-Known
    Builder

    Joined:
    Jun 10, 2015
    Messages:
    127
    Likes Received:
    65
    8mm lead screws
     
  23. Carl Feniak

    Carl Feniak Journeyman
    Builder

    Joined:
    Mar 18, 2014
    Messages:
    654
    Likes Received:
    246
    Well in theory you should be fine anyway as you will have the same Z force component as me and the wheels should take all the moment forces. Was just curious as it looked different in the pic,
     
  24. CapnBry

    CapnBry Well-Known
    Builder

    Joined:
    Jun 13, 2015
    Messages:
    100
    Likes Received:
    54
    Yeah lookin' good @trublu832! I linked the same blade a couple of pages ago, except the 80 tooth version which was $1.50 cheaper at the time. 80 teeth was still sufficient for me to cut without needing any cleanup on the edges of the parts, and I cut through all 4x 2040 legs at the same time no problem.

    I am still waiting on my belts and GT2 gears, but my bed heater finally showed up. It is that 120V 750W Keenovo silicone heater with integrated 100K thermistor. For reference it heats up my aluminum build plate (12 x 12 x 1/4, 3.5lbs) from 25C to 100C in under 3 minutes. I measured the temperature at the top and it lags by about 5-10C, but in under 5 minutes it is fully and evenly heated edge to edge. To maintain the temp the PWM runs at ~15% power (40 of 255, or 117W). The cheapo "fotek" 30A SSR I had removed from another project doesn't even get warm during the heatup, but it is clamped to the extrusion so it is effectively heatsunk if it does generate any heat.
     
    #834 CapnBry, Jul 15, 2015
    Last edited: Jul 15, 2015
  25. mgagnier

    mgagnier New
    Builder

    Joined:
    May 28, 2015
    Messages:
    2
    Likes Received:
    0
    What are the dimensions for the bearings that go in the v wheels (625ZZ bearings)? It looks like the OD needs to be 10mm to fit in the wheels and ID has to be 5mm to fit on the M5 bolts, but I can't find any bearings with these dimensions. Am I doing something wrong?
     
  26. trublu832

    trublu832 Well-Known
    Builder

    Joined:
    Jun 10, 2015
    Messages:
    127
    Likes Received:
    65
    5mm ID 10mm OD 4mm thick is what I'm using, I bought the wheels and bearings separate. Here are the bearings I used http://www.ebay.com/itm/291206716216
     
    Carl Feniak likes this.
  27. craftygeek

    Builder

    Joined:
    May 1, 2015
    Messages:
    9
    Likes Received:
    0
    I'm making progress on my build slowly but surely. I'm now collecting the electronics as i'm nearly ready to start installing it all.
    Question:
    Fans - what type/sizes, how many & for what purposes are you all using?
    Any guidelines on airflow/cfm?
     
  28. Carl Feniak

    Carl Feniak Journeyman
    Builder

    Joined:
    Mar 18, 2014
    Messages:
    654
    Likes Received:
    246
    Thanks for pointing these out, was curious myself as I just bought all mine through the open builds store. The sides of my bearing didn't have the type listed on the side (probably to small) and I didn't bother trying to sleuth it out.
    For others, just search "MR105ZZ" in ebay and you will get all kinds of options.
     
  29. Carl Feniak

    Carl Feniak Journeyman
    Builder

    Joined:
    Mar 18, 2014
    Messages:
    654
    Likes Received:
    246
    My E3D hotends each came with their own 30mm axial cooling fans for the hotend fins.
    For part fans, I went with two axial 40mm fans on 12V (for ramps anyway).
    Try to get as high a CFM as possible. You don't need to get really pricey ones, but don't get the $0.90 ebay specials either... I did and they have low output and bearing sleeve life. Bought 4 and three have died, just consuming the last one.
    Something like this would be good:
    http://www.ebay.com/itm/Mini-40mmx4...781?pt=LH_DefaultDomain_0&hash=item3cdf7b6d15
     
  30. AK Eric

    AK Eric Journeyman
    Builder

    Joined:
    Mar 31, 2015
    Messages:
    179
    Likes Received:
    129
    Just an update: First 'really big' print. 20" tall, 11" diameter, just over 3 hours with the 1mm Volcano nozzle @ 500 micron.
    bigInstagram.jpg
    http://www.akeric.com/blog/?p=3300
    Very happy withe the printer so far :)
     
    sheffdog, Raldan and Carl Feniak like this.

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice