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johnd
Oct 03, 2023
In Questions
Watching the tutorials on the camera part I'm puzzled why the X and Y appear to be swapped from the conventional approach where X positive is to the right and X negative to the left while Y positive is upwards on the page and Y negative is downwards.
Search XY coordinates on the web (or look in a math book) and you see this sort of thing.
https://www.techtarget.com/whatis/definition/x-and-y-coordinates
So why on the video part is the X upwards?
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johnd
Aug 28, 2023
In Questions
I'm planning on casting the J5 housing from scrap aluminum and then doing the final machining on my CNC mill. This is all hobby and I'm not that experienced at machining yet. However, I did 3D print the J5 housing to get a feel for size and possibly to and filler and turn it into a pattern for casting.
Looking at the drawing the radius of the inside corners is 2mm or would require a 4mm cutter. A bit of research on line shows that that size cutter doesn't come in a length that would reach the bottom of the J5 part. I then took the 3D print and the drawing to a friend who owns a CNC machine shop and asked him about that.
His comment was that it wasn't possible to mill to that depth and 2mm radius. The photos in the assembly manuals are a bit unclear.
So my question is: What size cutter is used for the J5 housing sold in the kit of parts? Is the radius actually larger or has some manual work been done to square off the inside corners to allow the J5 Belt Carrier full travel.
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johnd
Mar 06, 2023
In Robot Builds
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.
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johnd
Mar 02, 2023
In Questions
I've been reading through both the AR3 and AR4 manuals. Other than the J1 Base Enclosure and the alternate RJ connector holes, no 2 pin avionics connectors I don't see any other hardware modifications. (belt verses chain is possible on both). And of course the motors have the built in encoders. Are there any other hardware changes? I remember reading that the chance from the Teensy 3.5 to Teensy 4.1 was to move much of the motion code into the Teensy out of the PC. But why the change from the MEGA 2560? Does that mean the AR4 software won't work with the MEGA 2560? Is there an overall detailed differences list between AR3 and AR4?
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johnd
Feb 27, 2023
In Robot Builds
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.
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johnd
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