Small rigid router - Design advise needed

**TonyD** · 31-01-2015

Mitchejc, its totally feasible just take your time.
When I started I looked into the electrical before the mechanicals (which was a mistake) and I think in the end had I not stopped I'd have had 3 iterations of my control box, the first one had no safety and Jazz and Andy intervened to help.

I would start with power, get the PSU's in and working, then get the safety system arranged to kill the power as needed with the combination of limits and estops. Then I'd go for the bob and make sure that the safety circuitry can send the right signals to that. From there I'd work on home and limits to the bob and then you've got the guts of a working control system, motors and drivers are usually a function of the right wires in the right place, not much scope for creativity or screwing that up, maybe there's some motor tuning via drivers but that’s icing once the rest is done, not saying its not important, just most likely done near the end.

The critical thing in IMO right now is figure out the safety and control (limits and home), there's lots of good advice on the forum, limits NC, estop the same etc.. Personally I found it challenging to get into all the relays and drew comfort from the reliability of the pilz, they are available second hard and if you can get one I don’t think you'll regret it. Even starting out with some power and a pilz with a reset button and the estop circuit will build your confidence a lot.

Lots of folks have great advice, some of it is a bit overwhelming when you're a beginner, I'd proceed as outlined and add the frills like spindle control, water pump, etc once you’ve got power, safety and comms to the PC via the bob sorted.

Ps. I needed a bigger box each time I added a new feature, either get one bigger than you need or figure out the basics without a box first.

**EddyCurrent** · 31-01-2015

The panel for my own machine was called "OTT for DIY" at the time but I disagree, for me it was just normal. For example if you could easily produce mechanical items to a particular tolerance and finish, why would you choose to make one inferior ? I can see that cost is a factor but that does not mean you make it less safe, you just have to reduce the number of features while keeping the core safety aspects.

**mitchejc** · 01-02-2015

Originally Posted by EddyCurrent

The panel for my own machine was called "OTT for DIY" at the time but I disagree, for me it was just normal. For example if you could easily produce mechanical items to a particular tolerance and finish, why would you choose to make one inferior ? I can see that cost is a factor but that does not mean you make it less safe, you just have to reduce the number of features while keeping the core safety aspects.

Thx Eddy, I get what you are saying. What is the absolute minimum core safety aspects considering I'm the only one who is ever going to be using this machine and I do have 100's of hours machining time on my old router so I've got a fair idea of what can go wrong from an operating point of view? In my mind estop is a nice to have as long as I have a nice big circuit breaker handy that will cut power to everything :-)

**mitchejc** · 01-02-2015

Originally Posted by TonyD

Mitchejc, its totally feasible just take your time.
When I started I looked into the electrical before...

Tony, thanks for the info and reassurance. Your suggested approach makes sense and I'm going to follow that. I had a look on the PILZ website but there's a lot of stuff. Sorry for my ignorance but what does this thing do on a high level and where does it fit in? Which model number should I be looking for to get some docs?

**Neale** · 02-02-2015

Originally Posted by mitchejc

Sorry for my ignorance but what does this thing do on a high level and where does it fit in? Which model number should I be looking for to get some docs?

In crude terms, imagine two relays in parallel, both powered by a feed via the normally-closed estop switch. Each relay has a normally-open contact and these are wired in series and used to supply a control voltage to the external system - exactly what it does is up to you. So, in operation, both relays are activated, both relay contacts closed, and external system enabled. Hit the estop, the relays drop out, and the external system is disabled. Two relays mean that even if one contact sticks, the estop still works. For greater reliability, the two relays can be fed via a double-pole estop switch and two cables although I'm not sure if many people go this far. As it stands, though, the system would restart when the estop button is released or unlocked, so the safety relay box has a couple more relays which are associated with a reset or enable external switch which has to be pressed to get the main relays into their operational state. My Pilz relay actually has three sets of contacts so it can control three independent external systems/devices (maybe enable inputs on stepper drivers, ditto on VFD, and estop input to Mach3, for example). And that's one of the simpler Pilz devices! I bought mine as a new-but-obsolete version from eBay so the model number isn't very relevant (and I can't remember it off-hand).

As to where it fits in - a normal estop setup can only switch one circuit. Generally, you want to switch more than that (as per comments above) so you are going to need some kind of relay setup or somesuch to handle multiple independent circuits, but for emergency use it needs to be reliable which a single relay might not be. Add in the need for an explicit reset switch so if estop is hit, then things really stay off, and it gets a bit more complicated still. The Pilz "relay" packages all that functionality into one box. You might want to trip the relay with the limit switches as well as estop but that's a decision for the machine builder.