Zenbot Resurrection – Part 2

The Rebuild Begins

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Back in April I had 2 months off with some of my long service, it was around this time I wanted to do this project, but as it happened I ended up going to Shenzhen with Hacker Camp 2016 and when I got home I renovated a bathroom, so I didnt start the rebuild, however in anticipation of this I had already started ordering the parts for the project and already had just about everything I needed.

Out with the old

Here are some photos of it as it is with the old controller and external stepper drivers. The spindle shown is the current model of the Wolfgang Engineering WW-650 as I’ll be upgrading from the previous one. This one will allow me to get up to 24000rpm. These stepepr drivers were bought online somewhere and came with limited documentation, they worked well, but for the life of me I cant find the documentation I had as there are no external marking on the case. These will be filed away for re-use when I have a bit of time to work out what the dip switched do.

Wiring in the Limits

First thing after removing all the old wiring is to install the limits, this was a very simple achievement as there is plenty of room on all axis to install a limit where it can access the moving carriage only one I haven’t installed is the Z-axis ++, which will be used for the touch probe.

I initially intended to wire them all in N/C configuration 1) to improve noise problems and 2) in the event of any wiring problems it will fail safe open. However the CNC shield a V3.0 (chinese copy from Aliexpress) only supports N/O contacts, apparently the newer version of the board has been changed to allow for either, so to allow for either in the future I wired both the N/O and N/C contacts on the switches using 3 servo cable I happen to have on hand, unfortunately I didnt have any shielded signal cable so will see how it goes in terms of noise. The limits I’m using are just simple mini micro switches mounted onto the frame.

To maximise my working area I installed the limits so that when the axis was prettywell at their extent it would just be at the trip point of the switch, from there I can fine tune by adjusting the leaf of the switch if required. This machine has a fairly small work area (150mm x 200mm x 70mm) so every mm counts

GRBL CNC Shield

I’ve decided to try the CNC shield (V3) running GRBL and if I have any issues will look at TinyG. Mounting on the back of the x-axis carriage as a temporary test fixture is via the use of double sided tape, once I get things working I’ll look at something a bit more permanent, from my initial search of thingiverse there are a number of likely candidates the Spindle control is achieved via an electhouse 20A single channel Motor Driver, is really compact and more than covers the motor I’m using

To improve noise protection I’ve added ferrite cores to all incoming cables includign steppers and power to the board.

Here you can see why you dont put in a bit when you do testing…..have a close look…look closer. First casualty of the rebuild dammit! It didnt see any cutting time….RIP 🙁

The problem with a belt driven machine is on loss of power to steppers the Z head will drop. I’ve since rectified the problem with a counter balance spring on the Z-Axis, so no more head crashes when I remove power, either intentially or unintentionally.

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Author: Stephen Eaton

Geek at heart. Loves to tinker and find out how things work, which inevitably leads to items in pieces and not working for much longer :)

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