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  1. #1
    Join Date
    Jul 2012
    Posts
    4

    CNC-ish project. Need suggestions

    I am going to design a 4-axis positioning mechanism for my research, and it will use 4 steppers. Therefore what I need is very close to a CNC configuration (motors, drivers, linear movement, microcontroller to integrate everything).

    I made something like this a decade ago using nema17, Arduino, and Pololu drivers. It worked fine but the motors did get quite hot and were very noisy. I want to make an improved version now. If possible, without reinventing the wheel. The main difference with a 'classical CNC' is that my system should carry a camera, not a spindle. And the camera is pointing horizontally, not downward (therefore this would not really work).

    The 4 axes are XYZR, where R is the rotation (or tilt) of the camera. I plan to control each axis with a stepper such as Nema17 or Nema23. I am not interested in speed whatsoever, but I am very interested in high-precision positioning. Instead of doing it myself from scratch, this time I thought about buying/building a semi-ready CNC kit and then adapting it for my needs. The motors would be closed-loop because I read that they are more silent, more temperature and power-efficient (they only draw power when are not idle, unlike normal steppers), and that since they have an encoder you can avoid missing steps.

    The main use is to control de motors in real-time, manually using a joystick. As an additional functionality, it would be nice to be able to program it by sending GCODE to execute defined-locations travel.

    In principle I thought of buying close-loop NEMA motors and drivers and connecting everything to a Raspberry where I can use Python to make a fine control of speed, rotations, distances, using GCODE, etc. Therefore I wanted to ask you guys first if you know something like this.

    For example, I could buy this CNC kit and then add the mechanical parts myself. I'm more interested in finding a ready-to-work software and/or electronics so I can take care of the physical configuration and start working.

    What would you do in my case? Are you aware of Open-Source, or even commercial solutions that do what I need? Any information will be very welcome.
    Last edited by roccent; 07-03-2024 at 06:21 PM.

  2. #2
    Join Date
    Apr 2004
    Posts
    5770

    Re: CNC-ish project. Need suggestions

    There are stepper-powered camera control systems on the market. They tend to be quite expensive, but if you're making a feature-length movie, that's not a big deal. You can also rig things up with linear rails, rotary tables, and steppers, like this;

    https://makezine.com/article/maker-n...motion-system/

    If the distances you're trying to cover aren't large, you might be able to convert a 3D printer frame to do what you want;

    https://www.instructables.com/Motion...me-Lapse-Rail/

    Another approach might be to cobble together some automation actuators that have the spans you need. These can contain high-precision ball screws and slides set up to run together. Even if you have to replace the motors, they can still cost less than the components bought separately.

    Beware of so-called "kits" containing motors, power supplies and drivers. Often these contain the cheapest examples of both, with high-inductance motors (that require high voltages) weak power supplies, and low-voltage drivers that will blow up if supplied with the voltages to adequately drive the motors. If you're going to do this yourself, do the research to put together a set of components that actually work well together.
    Andrew Werby
    Website

  3. #3
    Join Date
    Jul 2018
    Posts
    6553

    Re: CNC-ish project. Need suggestions

    Hi Roc - Stepper motors require power all of the time, whether they are hybrid or normal types. The noise issue comes down to the electronics not the hybrid capability. Most stepper controllers have settings that reduce current when idle. However if there is considerable torque on a motor at idle then this is not a good thing to do eg if there is a large offset load on your rotating axis then this could overload the motor if current reduction is applied. All of these aspects are design considerations. So to have "nosieless" controllers look for the Trinamic types. Most 3D printers use these as they are used in a domestic situation and noise can be an issue.

    https://www.analog.com/en/lp/001/sec...erate%20speeds

    I suggest you look at Dynomotion controllers. They are well supported, you can write your own control code for them and if you use std steppers you can use feedback to control them like hybrids if you wish. I'd use std stepppers as I don't think the added cost has value, may as well put that into better bearings. Dynomotion has a forum in the CNCzone so have a look there. The Dynomotion owner and developer is very good with support so I see no issues achieving what you describe for your machine.

    https://www.cnczone.com/forums/dynom...kflop-kanalog/

    The other aspect of Dynomotion controllers is that they have jerk control. If you intend taking shots while the camera is moving the motion will need to be very smooth. Dynomotioon controllers will provide excellent motion control, other controllers can be shaky in this area. Are you going to use a belt drive for XYZ? Many vision systems do as they are low inertia, scalable to very large sizes and they are smooth. Peter

  4. #4
    Join Date
    Jul 2012
    Posts
    4

    Re: CNC-ish project. Need suggestions

    Cool, that gave me a lot of great ideas. Thanks a lot!!

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