Print quality is getting better and more consistent

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Here’s a few recent prints from my Reprap.  After a fair amount of tuning the quality has dramatically improved, but more importantly, the consistency and repeatability is getting to a point where I can print many simular and different parts, and they fit together with simular tolerances.

Ball-chain pulley for upcoming drawbot project

Ball-chain pulley for upcoming drawbot project

The Ultimachine filament I picked up seems to have greater dimensional stability than the Faberdashery samples I have, although the colors of the Fab filament are nicer as the texture is a little more pleasant as well so I can see why it’s popular.  For my purposes engineering accuracy is more important so I’m happy the Ultimachine filament is fitting the bill in that regard.

Open-Source Hardware logo, upside-down

Open-Source Hardware logo, upside-down

One thing that came to my attention through the last tests is that I have one of my axis inverted.  This seems like something you’d notice but since a lot of the things I print are symmetrical  it wasn’t apparent until I printed some objects with letters on them (or this iPhone case with the camera opening on the wrong side…).

Domestic Violence Awareness iPhone case (prototype, apparently)

Domestic Violence Awareness iPhone case (prototype, apparently)

 

Category: 3d printing, Desktop Manufacturing, Hardware, Project Updates | Tags: ,

5 comments on “Print quality is getting better and more consistent”

  1. Hello, Are you interested in selling a physical print of the ball-chain pulley shown in this article? I need a few for a project I am working on. Thanks!
    Reply
    • Sure Jordan, I'd just want to make sure I print you the right size :) This is the pulley in the photo: http://www.thingiverse.com/thing:33231 If this is exactly what you want let me know and how many you need; if not just let me know what you'd like (a link to a model would be ideal) and I'll give you a price for the lot. Thanks!
      Reply
      • Actually, maybe you can help me out. I am trying to make an automatic blind opener. The blind is the configuration where you pull the chain loop and the screen moves up and down. I can get a piece of the chain and mail it to you so that the size of the pulley is correct, but I am unsure as to what stepper/motor controller would work for this application. It takes a fair amount of force to pull the chain on the blind so I am guessing the motor would have to be fairly strong and the grooves in the pulley will have to be sufficiently deep to handle the force. Any suggestions?
        Reply
  2. I don't think you'd need to mail the chain, it comes in a few standard sizes so you'd just have to measure it (offhand I can't remember exactly what you'd measure but I'll look it up when I have a chance). Theres a few things to consider when planning on driving a chain like that. The first is how you're going to tension it, I don't know if the chain hangs loose now, or if it's strung between two pulleys but that will be a factor. The other as you mentioned is what you're going to drive it with, and you can go a couple of ways here. Like you said these tend to require some torque. You could probably get a beefy stepper motor that could handle it (or a gear it down to do so) but it's much easier to find a DC gearmotor that is up to the task, and depending on how much control you need that might be the better option. A stepper will give you very precise control throughout the rotational range of the motor, but if all you want to do is open and close the blind you could use a limit switch (mechanical, optical, etc.) to signal the open and closed positions and then use a "dumb" gear motor that just spins one way or the other until the limit switch closes. If that will work for your application you can get away with a much simpler (and cheaper) motor controller, and you have a wider and cheaper selection of motor options (one of my favorites for high-torque applications are the innards of cheap battery drills :). However, if you need to be able to stop the motor anywhere in-between open and closed then you're probably going to need a stepper motor and the associated control electronics. For controlling individual steppers I've used Sparkfun's EasyDriver (https://www.sparkfun.com/products/10267) in the past. It's' pretty easy to interface to an arduino and can probably handle the power you'd need for this application (you might need to add a heatsink). It's hard for me to give you advice on the specific stepper motor you should go with since we don't know exactly how much torque is needed. One old-fashioned method I've used to get a ballpark on torque is to pick up a fishing scale (the kind you hang the fish from) and find a way to use it to pull on the load you're trying to measure. This will give you a very rough idea of what you need in ft-lbs. I'm sure there's better ways to figure this out but that's the only one that comes to mind at the moment :) Hopefully this helps, I'll see what I can find out about measuring your chain and see about printing some pulleys that will fit.
    Reply
    • Wow, Jason, thank you so much for all of this information! I didn't think of just getting a DC gear motor, that's a great idea. This application is for a new place that I am moving into. Next time that I am down there (hopefully in 1-2 weeks) I will measure the chain (which is actually a continuous loop pulley so tensioning should be easy right?) and also do a torque test and then we can go from there. Thanks again!
      Reply

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