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3D Printed 6DOF Robotic Arm

Robotic Arm with the look of a small Industrial KUKA KR Agilus robot but on a hobby scale and tight budget.

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My name is Jasper Cusiel, I'm 15 and go to Wakatipu High School, New Zealand. This robotic arm is for a school project for a Digital Technology's class and combines aspects of electronics, mechanical engineering, 3D modeling and 3D printing. Robotic arms sparked my interest when I came across a video on Youtube depicting the use of this style of robot for the movement of high end cameras to create CGI like video clips. It showed how the robot could create interesting, precise camera moves time and time again and ten times better than a human could. The price of one of these small commercial robot arms is close to that of a luxury sports car so it begs the question, could I 3d model and 3d print a similar robot arm for much less?

Why did I create this Robotic Arm?

It all started while watching YouTube when I came across a video titled "Dope Tech: Camera Robots!" and after watching the video was very inspired by the idea of building my very own robot arm.


So then what?

After that video I started to search if it was possible to build my own robotic arm and if so how much would it cost as the dope tech video mention the price for one of these things to be astronomical. That was until I remembered that I owned a 3D printer that I got for my birthday (Creality Ender 3 Pro) and that I was a fairly competent 3D modeler on Fusion 360. Now after searching for "3D printed robotic arms" I came across many videos similar to this.


Servos, Servos, Servos...

So while servos are easier to run as they don't need drivers along with having a potentiometer to ensure they always move to the correct position, they are quite jittery and can be observed in the video above. Below is a video I came across depicting the use of stepper motors for movement and is much smoother and makes the robot arm seem more professional in my eyes.

This video shows comical ways of using the robot arm but demonstrates the smoothness of the robot well.


Stepper Motors

On the other hand stepper motors are much smother and have continuous rotation meaning they are not limited to 180 degrees of movement (yes I do know you can buy continuous rotation servos but they are still jittery). Obviously servos end up being cheaper but not buy much as metal geared cheap servos come in at approx. $14 NZD from Banggood ( a more reliable Chinese electronics source and far cheaper than buying locally). Steppers from Banggood are around the same price but can only be found in the very common NEMA 17 size ( NEMA refers to the standard for stepper motors mounting and shape and was formed by the National Electrical Manufacturers Association and makes designing mounts for in the robot arm easy as stepper motor, eg: NEMA 17, the same size across different manufactures )

Where to buy Stepper Motors?

With some Googling I have found that on another Chinese goods website called AliExpress who sells Stepper motors for very cheap but I have used this website to purchase things before. It is hands down NOT reliable and with shipping time sometimes taking up to months is quite off putting. But I found a company on AliExpress who sells Stepper motors very cheap and goes by the name of "Stepper Online". It turns out they have their own online store with a whole array of steppers in every size possible and is a world wide company with warehouses in Australia which mean fast shipping to NZ!



Electronics

After deciding that stepper motors are the appropriate choice for my robotic arm the choices for an affordable electronics becomes more narrow. Researching other 3D printed robot arm I found that most "cheap" arm use the very common RAMPS 1.4 control board. 

The blue board pictured above is an Arduino Mega, this is the brains of the robot arm as such and interprets the Gcode file. The big red board is the break out board which contains all of the necessary electrical components to interface with the Arduino as well as the stepper motor drivers ( small red boards ). These boards go for around $15 on banggood and include the red board and stepper drivers while the blue board (the Arduino mega) goes for around $5 as is a cloned board. A cloned Arduino functions the same as a legit one from Adruino.com but is about a fifth of the price.

What about newer RAMPS boards?

The main differences between the iterations between the three boards is the heatsink added to the MOSFET's, Power connecter changed to screw type as the last ones were prone to over heating and melting. RAMPS 1.6 can also handle more power with better heat dissipation. Therefore I if the price is right I will definitely look to go with the RAMPS 1.6 as has much better feature


Stepper Driver 

In...

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  • Parts List ( so far )

    jasper cusiel7 days ago 0 comments

    Electronics

    NamePart NumberQty.
    Nema 8 Bipolar 1.8deg 4Ncm (5.7oz.in) 0.6A 6V 20x20x38mm 8HS15-0604S1
    Nema 11 Bipolar 1.8deg 7Ncm (9.91oz.in) 0.67A 3.8V 28x28x31mm 11HS12-0674S2
    Nema 17 Bipolar 1.8deg 44Ncm (62.3oz.in) 0.85A 5.3V 42x42x48mm  17HS19-0854S2
    Nema 17 Bipolar 1.8deg 60Ncm (85oz.in) 0.64A 10V 42x42x60mm 17HS24-0644S1
    Geekcreit® RAMPS 1.4 Control Board + MEGA2560 R3 + A4988 Driver With Heat Sink 3D Printer Mainboard Kit1
    3D Printer 42 Stepper Motor Drive Expansion Board 8825 / A49881
    40pcs 20cm Female to Female Jumper Cable Dupont Wire For Arduino1
    Geekcreit® 3D Printer Stepstick DRV8825 Stepper Motor Driver Reprap 4 Layer PCB1
    PSU ~200W, I am using a Liteon ps-5221-06 PC power supply1
    Emergency Stop Switch LAY371

    Hardware 

    NamePart numberQty.
    Flanged Rigid Coupling (for 5mm shaft)1
    GT2 x 6mm pulleys, 5mm Bore5
    Open belt GT2 x 6mm, neoprene, fibreglass cord (per meter)1
    Plain – ID 8mm OD 14mm Width 4mm MR148ZZ2
    Plain – ID 5mm OD 14mm Width 5mm 605ZZ2
    Flanged – ID 5mm OD 14mm Width 5mm F605ZZ2
    Plain – ID 8mm OD 19mm Width 6mm 698ZZ2
    Plain – ID 8mm OD 22mm Width 7mm 608ZZ3
    Flanged – ID 8mm OD 22mm Width 7mm F608ZZ1

  • Bearing and bolt provisions are now in place

    jasper cusiel7 days ago 0 comments

    After spending the whole weekend (9-5) using my mums more powerful imac, I have managed to add holes for appropriate sized bearing which I will purchase from https://mecha4makers.co.nz/ as the price is very competitive

    Just a few more bolts for covers to add then will be ready for 3d Printing!

  • Close to printing

    jasper cusiel11/09/2019 at 06:24 0 comments

    Axis 6,5 and 4 almost done with bolts and bearings to be added. Going to use a flange that is attached to the nema 8 stepper for adding tools to the end of the arm. Also added cooling holes for axis 5 and 6 as they are more inside the arm compared to others.

    steppers inside arm

    Motor ventilation and belt provisions.

  • Change Of Plans

    jasper cusiel11/07/2019 at 08:18 0 comments

    Change of plans, I'm running out of time so went on Kuka's website and found a 3d model of the robot arm I wanted. I have started on integrating the steppers motor and necessary hardware.

  • GT2 Pulley generator

    jasper cusiel10/31/2019 at 21:37 0 comments

    I have ordered the following stepper motors and will arrive soon thanks to the fast shipping from stepper online.

    I was struggling to find GT2 pulleys in the size I was after so turned to Youtube and came across this video which I followed in order to create a file that could generate appropriate size pulleys. Thus allowing me to make the pulley to the size I need rather than having to model from scratch a pulley every time I need one.

  • Getting sketchy

    jasper cusiel10/28/2019 at 07:06 0 comments

    I have begun designing how the base attaches to the shoulder on paper, it is easier than on the computer and I waste less time messing about in Fusion 360.

  • Modeling begins

    jasper cusiel10/27/2019 at 04:11 0 comments

    So it begins...

    Have begun work on the base with provisions for a NEMA 17 that is 60mm tall. Have shifted motor to outside to keep robot more compact as well as allowing for a larger pulley to be fitted. Also motor is upside down to not make whole robot sit not so high off ground to reduce leverage of the arm causing it to fall over. 

    Me trying to figure out how its going to fit together (pencil and paper is the way to go)

  • Decided on stepper motors

    jasper cusiel10/24/2019 at 00:48 0 comments

    Stepper motors I have decided on using, below is what Skyentific is using 

    Update - I have bee back and forth with the customer support at stepper online and I have decided that I will be going with 2x NEMA 17 steppers in stead of the NEMA 23 for the shoulder and 1x NEMA 17 for the base rotation, rest as per list.

  • NEMA 23 steppers

    jasper cusiel10/22/2019 at 22:45 0 comments

    Skyentific is using NEMA 23 steppers steppers that are rated to have a holding torque of around 200 newton cm. 

    But is geared down heavily. The problem I'm facing is that in the size he has linked for the NEMA 23 requires a stepper drive that can produce 2 - 3 amps of current and require a large stepper motor driver. These drivers need to be wired from the RAMPS board to the driver then to the stepper rather than plugging in the stepper driver onto the RAMPS board which is connected to the stepper. Also these bigger drivers can be around 4 times as much to buy compared to the small drivers. Below is a large stepper driver that can supply 4 amps.

    Below Is stepper online and it mentions that these motors are suitable for robotic arms!

    It also mentions that each stepper motor comes with a data sheet and torque curve. This will be helpful for calculating if my steppers will be powerful enough. Thats when I came across a very informative video series which explains how to choose stepper motors.

  • Stepper motor research

    jasper cusiel10/22/2019 at 22:28 0 comments

    Looking into stepper motors on Stepperonline and am following Skyentifics parts list. Find him on Github here

    Here he is using low amperage steppers which have high holding torques. At first I was confused as when looking on stepper online I came across stepper motors rated at 2 Amps where as he was using steppers with in the range of 0.5 amps to 1 amp with the same holding torque. So I contacted the customer support and the friendly guy explained that inside the stepper motor with the lower amperage had bigger stator coils that required less amperage to produce the same holding torque. He also mentioned the lower amp stepper would run cooler which would be better for my application as PLA ( 3d printer filament ) starts to soften at around 60 degrees celsius. Below is a picture of a stepper motor internals to help you understand where the stator coils are.

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