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John's AR4 build

AR4 robot arm

Built by John Dammeyer8 chapters
Model
AR4
Status
In progress

The build, step by step

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  1. Chapter 1 · Jul 18, 2025

    AR3 with Castings for many of the metal parts.

    I've started to build the AR3 since I already have a number of encoders in stock. So I'll order the AR3 series motors instead. In order to create some of the castings instead of machining bar stock I've used a combination of the 2D drawings and imported via either an old version of GeomagicCAD or a friend has used Fusion360 on the STL files to grab some of the measurements that aren't immediately obvious on the 2D drawings. Got about half the 3D printed covers done. Have both Teensy 3.5 and 4.1, Mega3560 and pretty well most of the bearings. I'm using AlibreCAD to do my drawings. Will use AlibreCAM to machine the castings and other metal parts. /images/forum/media/72f90a7f3d9cde7a.avif

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  2. Chapter 2 · Jul 18, 2025

    AR3/AR4 Build in Victoria,BC

    I've started building the AR3 with some of the AR4 changes. I have both the Teensy 3.5 and now a Teensy 4.1. I have a number of encoders so I'm going to do it that way rather than use the StepperOnline motor/encoder pair. Same with a bunch of stepper motor drivers in the parts bin. I've created Alibre PART files from the drawings which was a really useful way to learn how it was put together. Most of the bearings have arrived from various suppliers. And I'm pretty well done all the 3D printing. To make the metal parts I'll first make patterns and then cast the rough blanks out of scrap aluminum. Then use my CNC mill and ELS controlled lathe to take them to completion. Here are the first photos. I have my ducks in a row on the 3D printed parts. /images/forum/media/82ce5b094735b9cb.avif /images/forum/media/468b5a15f1734040.avif

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  3. Chapter 3 · Feb 2, 2026

    J2_MotorSupport

    Finally finished the milling on the modified J2 MotorSupport bracket. I started and had all the holes drilled and counter sunk for the original AR3 version. But then the AR4_MK4 showed up and I like the idea of not taking apart the motor planetary drive to mount it. But the AR3 J2 motor is no longer available and the AR4 J2 motor is larger in diameter and longer. So the 3D printed version didn't fit my AR3 J2 motor. So back to Alibre to first create the slot to lift out the motor and then design from scratch the inserts to be 3D printed. I still can't get really nice finishes on the edges with my mill. Not sure if it's the cutter, the speed or backlash but at least it's done. Now to find a piece of 1.75" thick aluminum to replace the 3D printed piece which has no strength. Oh and the drawing for the J2 Tension Ring was incorrect so I made one that is too thick. Have to thin that down to 3mm so there's better clearance for the J2 motor. The arm is 3D printed just to give me a feel for size. I have a piece of 1/2" plate for this. Hard to believe I started this project 3 years ago.

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  4. Chapter 4 · Feb 18, 2026

    J4 Main Shaft Construction

    I'm building the AR3 that will use the Teensy 4.1 and the AR4 software and inexpensively as possible but not totally 3D printed. Buying the J4 Main Shaft as a long piece of stock aluminum was too expensive. Then I stumbled on some folding lawn chairs that used 1" OD aluminum tube. Problem is that it's really thin wall and likely even just trying to drill it may compress it out of round. As it is it turns nicely in the bearings and the rest of the parts are all a friction fit onto it. So what to do? Easy. 3D print an inner liner that is a slip fit into the tube and has a 12.7mm hole down the middle for the joint lead screw. I'll epoxy it in place and then I can easily hold it and drill/tap the 3 holes.

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  5. Chapter 5 · Feb 20, 2026

    Control Cabinet Drawing

    I've attached an initial revision of my control cabinet and how I'm going to put mine together. Since I'm using the Teensy4.1 and the latest AR4-MK4 software I will likely also wire in the support for MODBUS. Especially since I have the software tools from https://www.modbustools.com/ for both master and slave. But I also want to add CAN bus support so the drawing shows how I'd use pins 30,31 (CRX3, CTX3) and switch the J5,J6 limits to 32,33. The problem is that I see in the newest Teensy4.1 code that these pins are assigned to J8 step/dir. If I switch the declarations in the Teensy4.1 sketch and remove references to J8 will that confused the HMI software running on the PC?

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  6. Chapter 6 · Apr 8, 2026

    AR3 Control Box

    Finally, after more than 3 years I have essentially finished the control box. Still to wire up is the second controller and the wiring for the air solenoid gripper control. Still some work to do on the arm itself. I was doing a number of the parts in PLA-CF but lately Carbon Fibre filament is starting to look like asbestos. Which is too bad because it prints so nice and is so strong. I do have a question. The AR4-MK3 HMI interface talks to my Teensy 4.1 which is now powered from the external 5V supply rather than the USB. I can't find anything in the user interface that reports the status of the limit switches. I'd like to be able to actuate them and see if they are correctly interpreted. As in I have them wired correctly. Or does that feature not exist and perhaps it should?

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  7. Chapter 7 · Apr 11, 2026

    Modified AR4-MK3 J5 Motor Bracket

    I'm using this on my AR3 and since I'm keeping the single ended encoder cables physically separated from the stepper motor cables. One for each side of the motors. The problem is that they butt up against each other and although I could split them so they don't touch then it requires two tie wraps. So instead I converted the STL file to a STEP file, trimmed the ends and printed them Now I can use one original and one shorter new version together and they don't touch. (Or just two of the newer ones). I've renamed it AR3MotorBracket since I'm using this on the AR3 arm not the AR4 and on more than one joint.

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  8. Chapter 8 · Aug 23, 2026

    Working Surface Size

    I'm at the point where I need to bolt down the AR3/4 to some sort of table. I don't have a spare table so I thought a box with a tick counter top type work surface. Rough dimensions: 60L x 30W x 16H. (24"x12"x7"). The top could be a bit longer to take into account the reach of the arm. So say I did create and top surface say 80cm x 30cm (32"x12") and I wanted to create a grid pattern. If using imperial then 1" squares? If using metric 25mm squares? Or should they be bigger squares? Should may table top be larger? The box part will be have openings at the front and back to allow access to the connectors at the back and the ESTOP switch etc. at the front. Likely the control box will sit on a piece of plywood attached with drawer slides to the inside of the box.

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