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  1. #1
    Engineer-in-Training
    Join Date
    Jan 2015
    Posts
    311

    Building a new machine, from scratch, 24"x24" design goal

    Hey everyone. I feel that I am ready to take on this project. I am not doing it for fun, I am doing it because the 9"x9" build volume is not cutting it for me anymore. I have a small company that uses 3D printing to produce parts. I am constantly asked to print things that are a little bit bigger than 9"x9". Also, my machines were bought, and modified heavily just to attain the level of reliability that I want. The problem is they are not the prettiest things in the world, and a lot of the parts need to be replaced or redesigned. For the most part they are reliable though.

    I want to create a big machine. The orientation of the motors will be identical to my standard 9"x9" size machines, so the firmware will be swapped right over with small changes.

    I am looking for this machine to have ABL that I currently use with much success. There will be no need for adjustment screws.

    The build plate will be aluminum, with a custom 24"x24" silicone heater pad bonded to it. I already contacted some suppliers to make me this size pad with a thermistor hole in the center and run off 110VAC.

    Standard ramps/arduino/marlin. Stepper drivers will be DVR8825 driving NEMA 23 motor for the Y axis, NEMA 17 motor for the X, Z and extruder axes. Reason I choose the NEMA 23 for the Y axis, I am anticipating that the bed will weigh quite a bit being that size, and it needs the extra power.

    Linear bearings, I am still contemplating whether I should bother getting the expensive linear bearings or just use the standard LM8UU bearings that seem to get the job done just fine.

    Axis adjustability. I have not built my own reprap printer from scratch. I just rebuilt and redesigned a printer that runs ramps/marlin. Because of that, I am not familiar with the tricks you guys use for alignment. What is the best way to measure/align rail parallelism, vertical/horizontalness, skew in different planes. Do you guys use long feeler gauges? Thats how I would ensure parallelism in plan, not sure how to do parellel out of plane though. Any input here is appreciated.

    I will be using an E3D-V6 hotend. Most likely the Volcano version for the huge 0.8 and 1.2mm nozzles to help speed up production. I dont intend to run a bowden extruder, I dont have experience with that yet.

    Other than that, the basic frame will probably be aluminum with some machined bracketry and some metal brackets currently available.

    What are your thoughts?

  2. #2
    Senior Engineer
    Join Date
    Jun 2014
    Location
    Burnley, UK
    Posts
    1,663
    Are you doing
    X moves head
    Y moves table
    Z moves head

    I have 3 machines here, one printer, one CNC mill and one laser cutter
    Of the three I like X moves head, Y moved table, Z moves head the best, that is my CNC router
    XYZ moves head is how my laser cutter is arranged and XY moves head, Z moves table is how my printer is arranged.

    That's your first decision. I am still not convinced about the need for NEMA23. The power available form NEMA17 is much more than you will need I think. I also think that your max power is still going to be limited by your drivers so 17 or 23 the power will come out the same anyway. It does depend on which motors you get of course.

  3. #3
    Engineer-in-Training
    Join Date
    Jan 2015
    Posts
    311
    Thanks mjolnir. The configuration is X head, Y table, Z head. Just like what you describe first. Thats how my firmware is set up currently.

    I will probably go with a NEMA 17 first, and design the bracketry to accept a NEMA 23 just incase the 17 cant handle the weight. Although I suspect it all comes down to the DVR8825 drivers as you say, being the bottleneck. I am sure if I boost the current to the 17 it would be a torquey motor, are you saying that 2 amps in a 17 is the same or close to 2 amps in a 23? Which motor works more efficiently?

  4. #4
    Technician
    Join Date
    Jul 2015
    Location
    Durban, South Africa
    Posts
    68
    Add ZorAxe on Thingiverse
    I'm definitely going to follow your build. Looks very interesting. I've got a CNC engraver that I built myself and now building a printer. I spend alot of time researching stepper motors when I was building my engraver. The NEMA 17's that I used are 60mm long. They were the most powerful ones I could find. The are 92 oz-in. (0.65Nm) holding torque, and I must say they are very powerful. I run them off A4988 stepper drivers with 24v PSU. Once the current limiter is set right in full step mode I cannot stop the shaft turning by hand. For engraving they are plenty powerful enough. I can engrave wood and aluminum.

    3D printing had ALOT LESS resistance in its moving axis as there is no cutting taking place, the extruder is simply laying down molten plastic. I don't see you having a problem with the NEMA 17's provided they are a bit more powerful than the standard ones. A big thing to consider is your linear rails and how much friction that have. If you are using linear bearings then you definitely will NOT have a problem with 17's. I used drawer sildes for my linear rails and they have MUCH more resistance then linear bearings, but the 17's I have don't slip or skip any steps, even when running at 1000 mm/min.

    There are many factors to consider, but remember if you use 23's then you will have to limit the current anyway, and when you limit the current you will limit the torque, so in a way you defeating the object of using the bigger motor.

    Let us know what you decide to do.

  5. #5
    Engineer-in-Training
    Join Date
    Jan 2015
    Posts
    311
    Thanks for your experience ZorAxe. I think I may just go with the long style 17s. Even though I am a little worried. Remember that bed is going to be 4 square feet of aluminum mounted on some type of rail, it will be a heavy sumbich. I have in my mind how I want the printer to look. But I have to now start designing it in UGNX6. Im probably going to have the parts machined out of aluminum.

    How do you guys build your z axis rail adjustability into the printer? Screws like the reprap?

  6. #6
    Engineer-in-Training
    Join Date
    Jan 2015
    Posts
    311
    I will be using the SMW3D linear rail system. I havent really heard of these guys. But designing my own rail system will take longer, these guys seem to have a solution at the right price.

    The only thing I dont like is the motors are cantilever with not enough support. And where does the screw go into the v slot rail? Is there a threaded hole in there somewhere? Not sure, cheap enough to try it out.

    http://www.smw3d.com/250mm-length-c-...tuator-bundle/

  7. #7
    Technician
    Join Date
    Jul 2015
    Location
    Durban, South Africa
    Posts
    68
    Add ZorAxe on Thingiverse
    It's a pleasure. My CNC engraver is about 900x700mm (thats around 3x2.3ft) and the 17's work for me. Remember it's not really about size it's more about what's resisting the motor. I do understand that the bigger in size the more weight it will be for the motors to move, but as long as there is as little friction as possible, then you will be ok.

    Don't let me sway you from getting NEMA 23's. I'm just giving you my perspective and what I've discovered with steppers. The more torque won't hurt, but just always check the holding torque and the amperage drawn. If you do go NEMA 23 then try to find one that will give you the most torque around 2A.

  8. #8
    Engineer-in-Training
    Join Date
    Jan 2015
    Posts
    311
    Quote Originally Posted by ZorAxe View Post
    It's a pleasure. My CNC engraver is about 900x700mm (thats around 3x2.3ft) and the 17's work for me. Remember it's not really about size it's more about what's resisting the motor. I do understand that the bigger in size the more weight it will be for the motors to move, but as long as there is as little friction as possible, then you will be ok.

    Don't let me sway you from getting NEMA 23's. I'm just giving you my perspective and what I've discovered with steppers. The more torque won't hurt, but just always check the holding torque and the amperage drawn. If you do go NEMA 23 then try to find one that will give you the most torque around 2A.

    Awesome. I was actually going to use the extra long NEMA 17s, but the SMW3D actuator package that I linked above, already comes with 23s. I will keep my eye on current though and adjust accordingly using the pots on the drivers.

    Also, are you saying these motors have a a sort of dyno graph? One NEMA 23 can make more or less torque at 2 amps vs another NEMA 23? I would hate to have to try and figure out now where to find this detailed information. These chinese motors dont usually come with this information.

  9. #9
    Senior Engineer
    Join Date
    Jun 2014
    Location
    Burnley, UK
    Posts
    1,663
    You would do better to stay away from the Chinese motors altogether if you can afford to. They are a low price because they are cheaply made. That presents itself in various ways, they are generally still quite reliable but their operating parameters are variable in that the steps can be uneven sizes and the current they will handle can vary within a motor for each of the coils along with the torque they produce per winding. Microstepping is where they really fail, the steps are hugely varied.

    As steppers are very reliable and rarely fail unless they are dismantled buy second hand. The cheapest way is to buy bits of a machine with them on usually.

    Stuff like this though this isn't a stepper.
    http://www.ebay.co.uk/itm/2719217173...%3AMEBIDX%3AIT

  10. #10
    Engineer-in-Training
    Join Date
    Jan 2015
    Posts
    311
    I wasnt planning on buy something like that.

    These guys will be my supplier, they seem pretty popular.

    http://www.smw3d.com/

    I will also be using www.openbuilds.com for a lot of parts and direction.

    openbuilds has tons of bundles of parts for reasonable price. check them out

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