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  1. #21
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    There is also a difference between good and bad advice. What we can get away with in a jam is not good advice to give others. At best it is the absolute worst lowest end advice that might be still considered functional. But using auto parts on a 3d printer is just a bad suggestion. And to pwm a coil with an IC controlled board is to suggest to others that they go set their homes on fire. And I will correct that each and every time I see it. Here or anywhere else.

  2. #22
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    Quote Originally Posted by curious aardvark View Post
    honestly the linear rails will make absolutely no difference whatsoever on a delta. A 4 wheel carriage, properly fitted, will run smoother and faster with less potential vibration. As far as belts go - get decent ones but also use a tension based belt tensioner. They look like the middle of a cloths peg. Bascially they keep the belts at exactly the same tension, no matter what. One of the first things I did to my delta was add 2 to each belt. It also means you don't need complicated belt tensioning apparatus. https://www.amazon.co.uk/HALJIA-Timi...gateway&sr=8-5One thing you probably haven't considered is a kit from this chap. They'd used one on the duet3d stand at tct this week. http://www.zatsit.fr/english-summary.htmlDunno if you can buy them yet or not, the guy who builds the duet machines is a certified mechanical genius. So he probably got some ahead of the launch. But worth considering. On checking the kickstarter. It's a full delta kit and hasn't started shipping the kickstarter items yet. So worth a look, but it woupd need to be a diy setup. Magnets and carbonfibre rods probably a better bet.Unless i missed something and you're using the linears for the arms - I can see that working, lol ***Oh yeah (puts his mod hat on), autowiz and trakyan - play nice, there's a couple of good lads :-)
    If I can get you to take that mod hat off and talk to me from a perspective of design I would like to kindly and carefully argue your claim that a delta wouldn't benefit from linear rails over rods. Especially being the title of this thread is Large Format. as the print head moves about there is very much lateral torque applied to the rods even though the bearings only slide up or down. That is just how inertia works. And large format means long rods. That will very much flex in the middle under this sideways load from the print head skating about. Linear rails (one more time) get bolted to the frame every inch or so so there can be no deflection at any point in travel no matter how long the rail gets. The rod flexes more the bigger the print volume gets because there is no way to support the rod anywhere but at the very ends.

  3. #23
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    I've heard most people advise against those spring based belt tensioners, they basically introduce another stretchy element to the belt. Haven't had any experience with them myself so I don't know how true it is. The Zatsit is a neat bit of kit, I'd be interested to see how long the living hinges hold up, but it's really beautiful in its simplicity.Also for the third time, I never said to use PWM with a coil relay, I suggested bang-bang control. Aardvark, I'm trying, but he takes half of my first sentence and then jumps to conclusions, or skips over the rest of my post where I mention the stuff he complains about. Or just makes things up like the PWM on a solenoid relay.

  4. #24
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    Quote Originally Posted by Trakyan View Post
    I've heard most people advise against those spring based belt tensioners, they basically introduce another stretchy element to the belt. Haven't had any experience with them myself so I don't know how true it is.
    Did you even actually read that or did you just make that up? I would love to see "most people" advising against gt2 belt tensioners. Please can you provide me with a fistful of links to where all these people have advised against a belt tensioner? The belt tensioners get tightened to full open so there is no spring left and they just take up slack as the axis changes directions real fast. You don't have to tell us about your ill experience anymore. We get it.

  5. #25
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    Yes, I've read it. Most people on the reprap forum (not the one on this forum, the one from the reprap website) advise against them whenever they are brought up. Feel free to ask there if you don't want to take my word for it.
    The reasoning behind it is that people usually went to avoid elasticity from things like belt stretch, so adding a literal spring (something designed to stretch) is detrimental to that goal. If you tension the belt properly, there shouldn't be any slack for the spring to take up, seeing as you won't take my word for it go ask the manufacturer.

    I doubt you'll actually read these since you didn't look at the wikipedia link I sent on bang-bang control, but since you asked for them I'll oblige:
    https://reprap.org/forum/read.php?1,799484,800159
    https://reprap.org/forum/read.php?1,802522,803027
    https://www.reddit.com/r/Reprap/comm...elt_tensioner/
    https://www.reddit.com/r/3Dprinting/...ng_tensioners/
    https://www.reddit.com/r/3Dprinting/...ually_helpful/
    https://www.reddit.com/r/3Dprinting/...lt_tensioners/
    https://reprap.org/forum/read.php?14,836414

  6. #26
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    We are absolutely trashing this guy's thread. Those links are to discussions with arguments on both sides. And collectively there is less than a handful of people making those claims including you as one. Hardly "Most People". Any part is only as good as the installer and any installer is only as good as their level of experience. Go get some and come back with first hand knowledge on tensioner springs.

  7. #27
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    Of course for my machine running 2 steppers per axis having the tensioner spring in between the two steppers opposite the side the heatbed or extruder are on just sets a preload before the stepper motors are energized. And then there is no elasticity as I am pushing on one end while pulling on the other and vice versa. Really I can't believe more people haven't started running 2 steppers per axis. But I am proud to be one of the few.

  8. #28
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    Didn't see many people supporting spring tensioners, the majority explained what issues they can cause. The only reasons I saw people explain they should be used was it was better than a slack belt, but you shouldn't be slack in the first place. Or that it was an easy way to do things, which I don't think is a good enough reason especially if you want to spend extra money on profiled rails. The final thread did have someone arguing for spring tensioners, but he specifically mentioned they should be used with a damper, which the clothes peg springs are not.

    Finally, that's not how elasticity works. The belts and springs are elastic and can stretch no matter how many motors you put on them. You know what? Fine, I'm an idiot, you must be a professional mechanical and mechatronics engineer, doing things no professional machine would, like using two motors on one closed loop of belt. Let us not forget your breakthrough in belt technology: the belt you can push on!
    Quote Originally Posted by AutoWiz View Post
    Of course for my machine running 2 steppers per axis having the tensioner spring in between the two steppers opposite the side the heatbed or extruder are on just sets a preload before the stepper motors are energized. And then there is no elasticity as I am pushing on one end while pulling on the other and vice versa. Really I can't believe more people haven't started running 2 steppers per axis. But I am proud to be one of the few.
    Best of luck Reefsider, I hope your build goes well. I'm going to leave this conversation, it's not productive and I'm sure it's not helpful for your build, apologies for derailing your thread.

  9. #29
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    So you are now saying that stepper motors skip steps while a printer is running? Or are you implying that a tensioner spring is stronger than the holding torque of a stepper motor? well I guess if you are the one building or setting up the printer than maybe that should be a concern.
    Last edited by AutoWiz; 09-28-2019 at 11:40 AM.

  10. #30
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    Quote Originally Posted by Trakyan View Post
    Finally, that's not how elasticity works. The belts and springs are elastic and can stretch no matter how many motors you put on them. You know what? Fine, I'm an idiot, you must be a professional mechanical and mechatronics engineer, doing things no professional machine would, like using two motors on one closed loop of belt. Let us not forget your breakthrough in belt technology: the belt you can push on!
    I know it is hard to see the big picture when all you got is a small screen so to better explain my loose definition of function, on most printers when the bed or extruder goes in one direction the belt is pulled on the short side. that is there is a very short distance between the motor and what it is pulling, but when we move in the other direction we are now pulling against the tensioner spring, the idler, and a whole lot of length of belt. With a stepper motor at each end we are always pulling from the shorter side of the belt and with no idler or spring or anything in between. My reference to push and pull is to point out that the steppers are both moving in both directions so there is always 2x more torque applied. Now go see if you can make your honda run on PLA.
    Last edited by AutoWiz; 09-28-2019 at 10:28 AM.

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