Monthly Archives: September 2013

First lathe parts for my DARwIn-OP Robot Clone

Now that I am finished setting up my Sherline CNC lathe to cut my missing DARwIn-OP parts (FR07-F101, HN07-i101, and RX28-CAP), I am doing the first test cuts.

HN07-I101 and RX28-CAP
HN07-I101 and RX28-CAP (my cuts on left and original on right)

I manage to cut the HN07-I101 and RX28-CAP.  I have an original set that I bought, so I am able to compare, the ball-bearing fits tight enough. I still have to make the holes, but I’ll device some tools to use on the mill for this. Then I still have to polish and anodize.

I used some spare 20XX aluminum that I had, a 1″ bar for the HN07-I101 and a 5/8″ bar for the CAP, I am still waiting for some 6061 aluminum 15/16″ and 3/8″ bars to do the final pieces. The G-code cut programs are available on the Code section of my sourceforge project, they require a quick (or automated) change tool post with this setup of tools.

Sherline Lathe Quick Change Setup

So, to continue with my DARwIn-OP Robot Clone, I need to make a few parts on the Sherline lathe.

For this, a quick change setup is really practical.

Quick Change Tools Setup
Quick Change Tools Setup (updated)

Using quick change tools allows to calibrate each tool once. Later, when cutting parts, the tools can be easily swapped in a few seconds, settling back again to the same positions with minimal margin of error.

The basic tools I use are (updated):

  1. Right Hand Cutter (55° insert)
  2. Boring Cutter (for hole boring)
  3. Left Hand Cutter (55° insert for back face cutting)
  4. Cutoff Cutter (for cutting off the part from the stock metal)
  5. Left Hand Cutter (minimum radius tip for corners)
  6. Left Hand Cutter (in position for right facing)
  7. Right Hand Cutoff Cutter (tool #4 but calibrated for right and cutting)

The quick change tool post must be aligned specially for the cutoff cutter to be aligned when cutting. I use the headstock to do the alignment.

Quick Tool Post Alignment
Quick Tool Post Alignment

For CNC operation, the tools have to be configured in LinuxCNC’s tool table. So the software can compensate for the offsets for each tool.

Tool Table Configuration
Tool Table Configuration

Several test cuts have to be made to properly calibrate the tools X and Z offset, also the tool nose diameter can be setup to compensate on diagonal cuts.

Anyway, using a lathe (and a CNC version) have to be done cautiously. A wrong move could hit a cutter or its holder with the metal block you intend to cut and the CNC software won’t notice, plus the quick change tool post will get misaligned and all the calibration will have to be done again. It is also good to follow some safety guidelines like always turning off the lathe before switching tools or drills.

ODROID-XU for my DARwIn-OP Robot Clone

Today I got my ODROID-XU (ARM Cortex-A15) board. While writing my DARwIn-OP Clone Leg Test post I noticed that HardKernel was doing a presale of the board. I ordered one and got it fast!

ODROID-XU
ODROID-XU

The specifications are:
– ARM big.LITTLE architecture.
– Exynos 5410 Octa, with Quad Cortex-A15 1.6GHz CPUs and Quad Cortex-A7 1.2GHz CPUs.
– 2GB RAM.
– USB 2.0 and 100Mbps Ethernet.
– Runs Android or Ubuntu.
– Can use an SD or a eMMC module (8 to 64GB) as hard drive.
– 2 USB 3.0 and 4 USB 2.0 ports.
– 94x70mm board.

The board is very small and low profile. It should be an excellent choice to put on my DARwIn-OP robot clone. The eMMC module comes with Android preinstall, so I’ll be installing Ubuntu and doing some tests.

Source Repository for DARwIn-OP Robot Clone

The source code repository for cloning the DARwIn-OP Robot is at sourceforge at:

http://sourceforge.net/projects/darwinopclone/

I started to load gcode files for milling the first frame, the fr07_s101.

The files are at the Code section in a Subversion repository. Under the mill folder are the gcode files and the 00_README.TXT text file explaining the usage. I’ll be uploading more frames as I clean and check the files.