Mitch's AR2 Build Log

This is a great thread! Thanks for sharing all your build progress.

I had to take a long break from mine because I didn't have a way to drill and tap the sprockets. I've since taking an intro to machining class and now have a much better appreciation for all the machining that goes into the metal builds.

Spent a little time this weekend working on the controller's heat sink. It's an exact copy of my previous one, but this time I was able to cut it on the VMC instead of manual milling (no VMC in 2009!).

It's just three aluminum plates. I won't need fancy heat dissipation, those little NEMA17 motors won't make these controllers very hot.

https://anninrobotics.com/wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_3.avif

Cutting the heat sink plates

https://anninrobotics.com/wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_4.avif

45 minutes later...

https://anninrobotics.com/wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_5.avif

Easy assembly

https://anninrobotics.com/wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_6.avif

It's pretty compact; size is about 8" x 3.5" x 4" (200 x 90 x 100 mm approx).

Tonight I'll assemble the PCB (first level, power distribution, same as the CNC router).

Next, I'll look at the Arduino+RPi carrier that will mount on top of the power board. Looking at the other designs here it's definitely the right way to go!

/Mitch.

If I get truly adventurous, I might try a new PCB vendor my friends have ben using (jlcpcb, for those that are curious). I'll fab a second board that sits on top of this one and holds the Arduino, passing the signals to the board above. (so, a 2-board stack). This will eliminate almost all the wiring, just need to run the stepper phases to the bottom board and the limit switches to the top one. End result is about 8 x 4 x 4" not including the power supply.

Will post progress as it happens.

(maybe for Chris) - I haven't looked at the Arduino software yet, but I assume the steps/rotation is something I can change. The Geckodrives are natively 10-microstep devices, those these G201X units do have programmable microstepping.

/Mitch.

I'm back! FIRST Robotics season is over, the school year is about to end, and I'm ready to transition from making robots... to making robots. Time to get my AR2 up and running.

Next up on the agenda: The controller. While I do have the step drivers from SteppersOnline, it occurred to me that I might be able to make an even more compact package by building a copy of the controller I built for my homebrew CNC router.

Conveniently it can hold up to six Geckodrive modules. Photos below:

https://anninrobotics.com/wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_7.avif

Geckodrives in carrier module

https://anninrobotics.com/wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_8.avif

Custom PCB (includes instrumentation)

https://anninrobotics.com/wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_9.avif

Finally found the rest of the blanks (8 years ago!)

While I wait for McMaster to deliver more M3 set screws, I can test fit the J5 cover.

It looks like I'll need to modify the model for the cover sides, since they interfere with the timing belt pulley. I will hollow out the inside face like the tensioner end is and print a new set.

My Ultimaker does a pretty good job, so I don't think it bloated the walls of these parts; will compare with the model to make sure that didn't happen.

Chris, you might consider modifying those pieces in a similar way.

The FIRST robotics challenge ("Destination Deep Space") was released yesterday, it looks awesome, kids are really excited about it. I'll likely not make as much progress on my AR2 for the next several weeks, but I can begin the controller and start sourcing parts I don't yet have.

/Mitch.

https://anninrobotics.com/wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_10.avif

I'm nearly there for the mechanical assembly...

I had to bore out the J6 motor housing, the motor didn't fit.

I also ran out of M3x5mm set screws; it looks like I used the wrong ones on the linear slide piece, and I'm not going in there to get them out :-).

All that remains is the J5 belt and J5 limit swtich, plus the covers.

I don't yet have a gripper, so my robot won't be able to do much more than wave.

Then... of course... wiring. Lots and lots of that. I may need to slow down a little, since FIRST robotics starts tomorrow, but I'll sneak an hour or two in to get the controller and wiring set up.

Super pleased with the colors, once I have the other cover on I'll post more photos.

OK here are my assembly comments:

P51 - the turret housing screws are all 10mm (the flat heads are also 10mm). 14mm screws are too long and bottom out on the J3 spindle.

P51 - M3x14s are only just barely long enough for the motor housing. I suggest deepening the counterbore by 1-2mm (double check against the motor holes). only a few threads holding the motor on.

P53 - When mounting motors, some indication of which way the wires should exit would be helpful, it's hard to figure out from the pictures sometimes.

P54 - The set screw that goes through the tube should be 10mm, the 5mm one is too short to see the head protruding on the inside.

P54 - there is only one hole in the J4 shaft for the set screw to protrude through.

P55 - the J4 motor mount bracket's holes are too small for a close fit M3 screw to fit through. They can be drilled with a 1/8" drill.

P56 - the POM nut fit is too tight to J5 carrier. I drilled mine out with a 0.5" drill and now it's still a press fit.

P56 - a deburring tool is a nice hand tool for creating the countersink manually and accurately (a power tool might remove too much material).

P57 - the J5 carrier looks like 2 pieces in the photos but is actually 1 pice. The small clamp piece looks like it is better secured with a SHCS instead of a flat head.

P57 - There aren't any M3x4 set screws in the klt. I used the longer ones. (to hold the 3mm bearings)

P57 - the 3mm rods were already cut to 85mm.

P60 - an M4x10 is too short to mount the J5 bearing to the tension block. I used a M4x14. Could bore the post a little deeper.

P61 - my housing has no hole on the back side, and the one on the front side is tapped for M4., not M3. I lost an M3 somewhere in there, I can't find it :-). Used an M4x5. However, this means that my housing could be 180 degrees out of whack, so I'm looking it over again. Removing the housing will be problematic if I need to take it apart, the fit was snug.

P62 - Manually rotating the J5 motor shaft is easier said than done.

P65 - J6 motor fit is very tight, even with the sticker removed. I may need to bore out the J6 housing to get it to fit.

The pile of parts is getting smaller!

I'm up to J5 and J6 now. I have lots of assembly comments (will put in next reply).

But first the photos!

https://anninrobotics.com/wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_16.avif

J5 motor

https://anninrobotics.com/wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_17.avif

J5 housing and linear slides

https://anninrobotics.com/wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_18.avif

J5 housing installed

https://anninrobotics.com/wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_19.avif

J6 housing

OK, to go with the progress so far tonight, here are my comments about the assembly manual:

P47 - Securing the J3 bearing cup. The kit comes with M3x20 flat heads, not M3x25.

P47 - both the 8mm key stock and the 2mm key are already sized appropriately.

P49 - One of my sprockets was not bored to 8mm, but the other was. sprocket is marked 04 Z13B3

You might mention that the set screws are best located 6.5mm from the top of the sprocket, this centers the screw hole between the bottom of the sprocket and the fillet on the opposite side.

P49 - The kit included 44 links + one master link. The chain did not need to be cut and fit perfectly without any modifications.

/Mitch.

Here's tonight's progress so far: We're up to J3!

I received my limit switches today, so I'm installing them as I go. I plan to make the wiring harness later after I see where all the wires need to be.

As I get the steppers installed, I am definitely liking the black anodize color (I had considered a different color, but the black goes with the gearbox housings).

https://anninrobotics.com/wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_20.avif

J3 bearings

https://anninrobotics.com/wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_21.avif

J3 chain installed

https://anninrobotics.com//wp-content/uploads/2025/07/Mitchs-AR2-Build-Log_22.avif

Another view

Absolutely no need to apologize fore anything; part of the "open source" bit means we get to contribute too! I'll collect my notes and the places where the manual didn't make sense and post them at some point.

/Mitch.

Thank you, I apologize - I do need to update the manual. I did shorten the length to 50mm as this is a standard length I can split shafts into and there was no need for the 53 - its just what I ended up with when I made the first one.

Couple of things for the next manual update:

- (pg47) : My keyed shaft is 50.24mm long, so it is a little hard to cut down to 53mm. I think that I'm ok with it, seeing how it is used I think the missing 2.75mm should not present an assembly issue.

- (pp45-45): My kit shipped with two different sprockets, with two different bores (same # of teeth though). I'm not sure I need to modify one of them, will know when I get there :-).

I have a #25 chain breaker/assembler; it should be close enough to the 6mm chain that I can use it to make the chain loop without needing the master link.

Here in the Silcon Valley (South SF Bay) I paid $120 to have 24 pieces anodized. It was the minimum charge from the vendor, mostly to cover the setup costs. Relative to the rest of the robot's cost, it didn't seem like a big number. I'm very happy with how it came out.

I asked the vendor to be the absolute last priority, schedule me when they could, and I chose black, a color that they always have ready. Given how close to Christmas I sent the parts, they got to it within a week.

If you do anodize, defintiely choose a dark, opaque color like black. The kit parts are all machined a little differently, and there are witness marks from the tooling everywhere that you can see through the anodizing. I had to reassure the vendor that I'd be pleased with the results :-).

I colored only the parts that would be visibile from the outside, so some of the tiny ones didn't get anodized.

Clean the parts thoroughly with acetone or mineral spirits before you drop them off.

It should go without saying that best practice is to be nice to your vendor, especially if they're used to much larger jobs. Very often these people make thousands of the same part, so when you show up with 24 unique pieces they will need to track them carefully not to lose any.

Anodizers have other metal finishing services as well; I could have had the parts bead blasted first, which would have removed the witness lines,

/Mitch.