DIY CNC Milling Machine From Scratch

**routercnc** · 17-03-2016

I messed around for a while with those for my control box but in the end I could not get them to do what I wanted. I think I was trying to use them to switch the main toroidal power supply using a DC circuit or something like that.

I used a contactor in the end which works a treat and is the right thing for the job. Why so many and what are they switching?

By the way, loving the machine so far.

**totts** · 17-03-2016

Thats what i wanted, using them with my 24v psu to switch on the toroidal ps, spindle, cooling, estop, program estop and coolant. Using the 24v for switching. I hope it all works lol

Simon

**JAZZCNC** · 17-03-2016

Solid state relays are not always good thing to use because they often fail ON.!

**totts** · 17-03-2016

Yeh ive heard that, the electricians in work have told me a few stories, which im surprised the fail on, i have two relays operating on the estop so i hope thats enough otherwise i will go back to normal relays.

Simon

**Davek0974** · 18-03-2016

Please only use normal relays or contactors for e-stop, SSR's are really only safe for loads like heaters and lamps, i learnt this years ago when i was doing R&D for printing process and finishing machinery. They fail regularly and 99% will fail ON not off. Even when used for heaters you need to use sensors for over-heat which happens when they fail.

If using for motors, always fit a good snubber network to help protect the SSR.

Loving the build BTW;)

**totts** · 17-08-2016

Morning all, managed to get it up and running and wondering if anyone can give me some electrical advice,

I'm currently using an akz250 (usb Bob) no I know that u need a stable 5v to run? Also using dq860ma steeper drivers.

The problem is when I run a long program like the one in the picture, I loose steps in the x axis, one roughing cut depth is different to the next.

Now I've tried slowing the motors down and changing the acc, and the problem still happens.

I had a quick look at my wiring and ran a multi meter over the terminals, I have 4.45v going to (can't remember if it was step/dir) and 2.7v on the other terminal,

Also my drive has an enbl + / - terminal, do I need to wire 5v signal to this? As my drive is working without it?

Thanks

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**Clive S** · 17-08-2016

Nice to see you have it up and running. I don't know anything about that board but are you powering it via the USB if so can you power it from a separate power supply?

Are you running the drives at about 68V?

You don't need to connect to the enable terminal, that won't effect missing steps etc.

**JAZZCNC** · 17-08-2016

Possibly due to the Step pulse being on the wrong side of the slope. Commonlly step pulse is on the rising edge but in some cases drives may be set so on the Falling edge. If this is the case and on wrong side then can lose one step with every direction change.

To check this write program that goes back n forth few hundred times on that axis. Mark the start point and check it goes back to same point after the moves.

If doesn't then change the Step low active in Motor Outputs. This will put the Step pulse on the opposite edge.

**totts** · 17-08-2016

Originally Posted by JAZZCNC

Possibly due to the Step pulse being on the wrong side of the slope. Commonlly step pulse is on the rising edge but in some cases drives may be set so on the Falling edge. If this is the case and on wrong side then can lose one step with every direction change.

To check this write program that goes back n forth few hundred times on that axis. Mark the start point and check it goes back to same point after the moves.

If doesn't then change the Step low active in Motor Outputs. This will put the Step pulse on the opposite edge.

This would make sense as the toolpaths have a lot of direction changes due to it being an adaptive toolpaths, so if I change step low active will this run the motor in the opposite direction?

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**JAZZCNC** · 17-08-2016

Originally Posted by totts

This would make sense as the toolpaths have a lot of direction changes due to it being an adaptive toolpaths, so if I change step low active will this run the motor in the opposite direction?

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No it shouldn't but if it does then just go into Homing and Limits and select Reverse. You may need to change the Home direction.
Don't Change the Dir Active leave that the same as it can have an affect on drive.

However Like I said wouldn't change it without knowing for sure and the only way is to mark and run test code.