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Old 08-27-2010, 07:39 PM   #1
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Default Another Sieg X2 CNC conversion

For the last year or so I have been gradually gathering up various bits and pieces to do a CNC conversion on my X2 mini-mill, just as and when I have had the spare cash and when I see things on offer.

Now I have got my Paddleducks engine running my attention has turned to working on my machines, and the first thing I wanted to so was to get started on my CNC conversion.


So for the last few days I started working on the electronics side of things.

A long time ago I played Bass in a little band, and I also did the PA duties. Anyway, the point of this seemingly pointless story is that I built myself a stereo 150Watt per channel PA amplifier for the band and mounted it all in a nice 19" rack case. Now this amplifier has been serving very usefully as a footstool under my desk for the last few years, so I decided to recycle it.

I stripped out the 2 150watt amplifier modules and all the wiring and pre-amp section, and this left me with a nice big 6U 19" rack case with a toridal transformer rated at 500VA, 35V. Once rectified and smoothed that will give me approx 40-45V at about 14amps, and that will provide that power for the stepper drivers.

Here is a pic of the transformer fixed in place, along with the stepper motor drivers placed roughly in the position that they will be fixed. Also pictured are a couple of small transformers that will be used for powering low voltage stuff.




The reason I have 2 little transformers is to give me 4 power supplies ( each transformer has 2 secondarys ) that are completely isolated from each other. Why do I need this? Well, to protect the controlling PC from any voltage spikes and surges from the steppers, I have a isolated interface that goes between the PC and the stepper motor drivers, but this requires a 5Volt supply that is seperate ( ie, isolated ) from the PC's power supply. ( that's one isolated power supply )

I also have got one LCD voltmeter and one LCD Ammeter for monitoring the main power supply voltage and current demands ( not really needed, but I like dials and displays ), and each of these displays needs its own power supply that is exclusive to each LCD meter. ( so thats 2 more isolated supplies )

Then I have one more that I'm not totally sure if I need it at the moment, but it may well come in handy.



Anyway, I have also done some metalwork on the front and back panels of the case. It has been interesting trying to cover up all the holes originally made for the amplifier with the new holes for the new application.

Here you can see that I have installed a fan, this is positioned so that it will draw the heat away from the stepper motor drivers as seen in the 1st pic.

Also you can see the cutout for the 25way "D" connector for the connection to the PC, and the 4 4way XLR sockets that will connest to the stepper motors ( X,Y,Z and A (for the rotary table) ), these are of a locking type because if you unplug a stepper motor from its driver while it is powered then most likely you will have to replace the blue smoke in that motor driver, they really dont seem to like that. So hopefully having locking connectors will prevent disconnection thru vibration or pulling of cables.





Moving on to the front panel, I have got the 2 lcd meters to mount, and also I have 4 moving coil ammeters and 5 switches to mount.

This is as far as I had got up to yesterday.




Then today I milled out the holes for the LCD's and also another hole for a switch.


And this is what I ended up at the end of today.




So on the front panel I will have a master Voltage and current readout on the 2 LCD's, and individual readouts for each of the stepper motor drivers. I will also have a switch for each stepper driver to easily isolate any motor ( especially helpful for swapping the Rotab for say another axis without having to power down the whole system.

There is also a master power switch ( the green switch )


Anyway, that's as far as I have got. That is pretty much all of the metalwork done on the electronics box, now I will be working on wiring it all up.


Tim



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Old 08-28-2010, 01:34 PM   #2
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Default Re: Another Sieg X2 CNC conversion

very nice! I love the amp meters and the switch per axis!



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Old 08-28-2010, 04:46 PM   #3
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Default Re: Another Sieg X2 CNC conversion

Quote:
Originally Posted by vedoula
very nice! I love the amp meters and the switch per axis!
Thanks Vedoula, all the ammeters are not strictly needed, but I love seeing whats going on.



I dont have a whole lot to show for todays work, I spent most of this morning arranging and then re-arranging all the components to try and get them fitting with enough space around them, and with enough airflow thru to the exhaust fan to ( hopefully ) keep the drivers cool.

Then it was just a case of bolting it all down and then this afternoon I set about wiring up the drivers to the 4pin XLR sockets. And that's all I got done.

But I did finish off by probably doing the most important step, I took a photo of the progress.

So here it is, I've added a few labels to hopefully make clear what some of the bits are for.




I still have to mount the smoothing capacitors, mount the bridge rectifier and wire them, wire the breakout board, make up a rectifier and regulator for the breakout board, and a whole bunch more too!!


Stay tuned for more updates,


Tim
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Old 09-03-2010, 05:15 PM   #4
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Default Re: Another Sieg X2 CNC conversion

Well I left you all hanging on the edge of your seats, ( you were all on the edge of your seats, weren't you? if you weren't on the edge of your seats, please could you do so now or the whole effect will be ruined )

Anyway, I have not been completely idle since the last post, I have been working on the wiring and fitting a few more little bits into the box.


Here's a pic of the whole progress as of today.




Here's a few closer shots.

This is a closer shot of the bridge rectifier. I mounted it on a piece of Ali heatsink that I had left over. I drilled and tapped it M8 so that it would be able to fit it onto the bolt that secures the transformer to the case. Then I drilled and tapped a M4 hole to mount the bridge rectifier to it. That should keep it cool even when under full load.
I have yet to hook up the positive to the smoothing caps, this is where I will be putting 3-4 diodes to drop the voltage to keep it within the limits of the stepper drivers.




This is the next part of the power supply chain, the smoothing capacitors, 2x 10,000uF. Also beside it you can see the power relay that will switch the transformer on and off as described above in my post about my substitute for a charge pump.




Here is the bank of 4 relays that are switched by the front panel switches, these feed the 45V dc from the smoothing caps to the actual stepper drivers. The reason for using relays for switching instead of just using the front panel switches are, firstly, the switches are illuminated, but they need to be switching 240Vac in order to light up (ok, not a really important reason, but I like lights and dials), and secondly when the main transformer is switched off the relays will immediately isolate the stepper drivers without waiting for the caps to discharge.
Also you can see a ferrite choke to hopefully suppress any interference.




A closeup of the stepper driver wiring.



Showing the wiring of the ampmeters and switches. Each meter is wired across a shunt ( a short, extremely low resistence link, in this case about 0.015 ohms ) You cant see the shunt directly, but in the picture above of the stepper driver wiring you may have noticed a single terminal block sticking up. The reason it is sticking up is that the shunt is inbetween the terminal block and the terminal of the driver. ( the actual shunt I had to make myself out of some resistence wire I had, it turned out to be about 14mm long was the needed length )




A closeup of the back of the LCD displays.




So that's as far as I have got, I have just been taking my time trying to keep the wiring as tidy as I can, it makes troubleshooting a bit easier ( I hope )


Stay tuned for more updates ( you dont have to stay on the edge of your seat this time )

Tim

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Old 09-10-2010, 06:34 PM   #5
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Default Re: Another Sieg X2 CNC conversion

So here's a little update on this.

I fitted a bigger transformer for powering the breakout board and for powering a speed controller board that I just got from the states, and possibly a spindle speed monitor circuit that I also just got. The original transformer only gave me 0.3Amp output, but this one gives me 1.3Amp, plenty to play with.

I also made up 2 sets of Bridge-rectifier and 5volt regulators along with electrolytic capacitors. I just hard-wired all this lot together, mainly as I had mislaid my vero-board ( which will no doubt appear as if by magic when I have finished doing all things electronic ).

You also might note a little yellow blob attached to the regulators in the pic below, these are Tantalam (woeful spelling) Bead capacitors, like electrolytic caps they are polarized and will go bang if connected the wrong way. A little cap mounted close to the regulators will help to supress interference.




I also modified the wiring on the back of the ammeters. Because I am using home-made current shunts which may differ slighty from one to another, I need some way of adjusting and setting each meter to read a true value. So I got some 100 Ohm 10-turn trim pots and fitted them in-line with one lead of each of the meters. (100 Ohm is a lot higher than I need, probably 30 ohm would do, but I only got 100 Ohm ones, but being 10-turn should give me the range of adjustment I need )




Then I had to create a little relay driver circuit to interface between the breakout board and the main power relay (my poor-mans charge pump system). The problem I faced was this, the breakout board's output ports are active low. What that means is that when the computer sends a signal to turn a particular pin on, the breakout board will actually connect that output to ground. This would not create a problem if the breakout board could handle the current to operate a relay, but alas it cant so I had to come up with a little circuit.

It is a very simple circuit, just a PNP transistor, a 1k resistor, a diode and a relay. The PNP transistor will turn on when the base pin is brought low, ie ground. Then the current can flow through it and into the relay, turning it on ( which will then allow the main psu relay to turn on ). The diode is there to suppress the back EMF when the relay is de-energised.

Again, not having any stripboard or veroboard to mount the circuit to, I mounted the diode to the relay, secured it with a dab of hot-melt-glue. then I hot-glued the transistor to the side of the relay, and then soldered the whole lot up. By mounting it all together it meant that I only had to bring 3 wires to the relay from the breakout board, then I could position this relay close to the main power relay, thus saving having to run 240Vac lines all over the place.

Here's a couple of views of the relay and associated circuit.




I then ( very tentitively ) plugged the power in, but before switching it on I unplugged the power supply wiring that goes into each stepper driver ( handily these stepper drivers have easily unpluggable connectors for all their wiring ) Then I switched on, and ....... well nothing went bang. Then I realised that my poor-mans charge pump circuit was doing its job, preventing the main transformer from switching on until Mach sends the signal to the right pin.

Not wanting to ( potentially ) fry my pc, I bravely decided to just over-ride the need for connection to a pc and just used a little piece of wire to link the output pin to ground, thereby energising the little relay. Then I was able to press the power switch on the front panel and ....... again, no bang or flash, just the Lcd's lit up showing 0.00v and 0.00A ( because I havent connected up the main Positive from the bridge-rectifier yet ).


So, the only thing left to do before testing with actual stepper motors and pc attached, is to work out how many of these power diodes are needed to bring the voltage down to a safe enough level for the stepper drivers. Then I will be able to do initial testing and setting up of the ammeters, and then the electronics side will be complete. ( barring a complete meltdown and explosion !!! )


Tim

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Old 09-10-2010, 07:28 PM   #6
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Default Re: Another Sieg X2 CNC conversion

Tim, looks like you're having fun with the wiring and the power supply circuits. I'm guessing from the size and quality of the components you're using, you have access to an electronics inventory somewhere since some of that stuff can be pricey if purchased off the shelf. It brings me back to the time when building amplifiers was my hobby and profession for many years where I had access to anything I wanted for components and hardware.

I'd say you could have mounted the full wave bridge to the chassis instead of the finned heat sink but what the heck. I doubt you'll need the chassis fan.

Good luck, looks like you've got a handle on it.

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Old 09-10-2010, 08:10 PM   #7
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Default Re: Another Sieg X2 CNC conversion

Thanks Trout,

Quote:
Originally Posted by Troutsqueezer
Tim, looks like you're having fun with the wiring and the power supply circuits. I'm guessing from the size and quality of the components you're using, you have access to an electronics inventory somewhere since some of that stuff can be pricey if purchased off the shelf.
I've been having a ball with it. A lot of the bits have come from previous stock, others I got specifically for this build.


Quote:
It brings me back to the time when building amplifiers was my hobby and profession for many years where I had access to anything I wanted for components and hardware.
Snap!! I also had a hobby of electronics for years, mainly audio electronics and wiring up my dad's model railway show layouts ( I still do a little of that now too ). Most of the power supply has been permenantly borrowed from a 300watt PA amp I built and a 150Watt Bass amp. ( I still have a 300VA toridal transformer spare if I need any more power, and another 40,000uF of smoothing caps ( including 2 10,000uF Elna caps ) but I think that would be overkill on the smoothing front, and would most likely blow every fuse when 1st switched on!!! )



Quote:
I'd say you could have mounted the full wave bridge to the chassis instead of the finned heat sink but what the heck. I doubt you'll need the chassis fan.
You're probably right, but it ended up being better for me because I didnt relish the thought of stripping the case down to clear it for drilling the chassis. Using the mounting bolt from the transformer made it easier for me.


Hey ho, onwards and, um... sideways


Tim
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Old 09-12-2010, 08:18 PM   #8
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Default Re: Another Sieg X2 CNC conversion

Just a little update, I dont have anything by way of pictures to show, but I have had it powered up tonight without letting any of the blue smoke out, so that is a bonus.

I ended up using 3 diodes to bring the voltage down to a safer level which turned out to be 47 volts with no load attatched. Now that the power supply was complete I set about calibrating the analogue ammeters, an easy job as I was able to apply a load to one channel at a time and then compare to the Lcd ammeter.

Then, just for laughs, I plugged the power leads back into the stepper drivers, hooked up all 4 steppers, donned an upturned saucepan on me head, stepped away and bravely switched it on with a wooden broom handle.


Well actually I didnt use a broom handle, but I did switch on and nothing went Booom.

Buoyed by this tremendous and overwhelming success I progressed on to switching on each individual channel, and with no smoke emerging I switched all the channel switches off.


It was at this point that I realised that the main Lcd ammeter was still giving a small reading :scratch: I pulled the cover off the box and saw that 2 of the stepper drivers Power LED's was still lit.

The problem is that a couple of the relays that are for isolating the power to each stepper driver are tending to stick in the on state. Not good!!

I should have known that they could be a problem area, the inrush of current at switch-on tends to weld the contacts shut. So I will just do a little re-wiring and run the power straight to the front panel switches.


Oh well, only a minor setback that will be easily fixed.


Tim

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Old 09-13-2010, 05:39 PM   #9
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Default Re: Another Sieg X2 CNC conversion

I took the camera out to the workshop today, so here's a pic of where I put the 3 diodes to drop the voltage for the main Stepper drivers.





I got a bit more done today, I started on taking out the faulty relay and it's 3 companions and just wired the power feeds direct to the front panel switches. That done I turned to mounting the speed controller board into the case. I fabricated a few brackets out of Ali.





And I also made up a couple of ali brackets to mount the little spindle speed detector board in the case.





I then wired the 2 boards up as seen in the pics above.

I was thinking of mounting both the speed controller board, and the speed detector ( tach ) into the mill's own electronics enclosure, but then I realised that if I convert my lathe over to cnc too, then I'd need to buy or make a 2nd speed controller and Tach. But if I had the 2 boards mounted in the stepper driver case, then I would only need to have a switch to change over between lathe and mill.

Anyway, I think I am now at the point of bringing a pc out to the workshop to hook up to it, and then hopefully make the steppers turn according to my command. Then I will have to have a tidy up ( as the workshop is looking like a bomb has gone off in an electronics dump ) before starting on the modifying of the mill.


Tim

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Old 09-18-2010, 03:15 PM   #10
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Just a little update on this. I brought out a PC and hooked it all up, installed Mach3 and then set about working out how to configure Mach3.

What is a little overwhelming is the shear amount of options and customisability ( I think I just made up a new word ). At 1st when I tried to move any of the axis's all I got was a quiet squealing noise from the steppers, but a quick trip into a connections menu to change the "active low" setting on each axis to being on solved that. And so I have motors spinning on my command. I have to say that I was really pleased that I had managed to wire all the stepper motor phases up correctly for each axis, I was half expecting to have to re-wire some of my leads.

Anyway, I spent the rest of that afternoon playing with Mach3 and it's settings.


That being done and found to be working ok, I have now turned my attention to the task of working on the mill itself. Over the last few days I have been gradually breaking it down into it's componant pieces with a view to cleaning them, setting them up better, and also seeing just how I am going to mount the Ballscrews and nuts when they arrive.

I have spent this afternoon working on aligning the head of the mill with its upright column so that the spindle axis is parallel with the dovetails. I ended up having to shim the bottom of the head casting by 0.16mm to get it close.( I say close because I have still got a runout of about 0.08mm over 12 inches of travel, but I got fed up with taking the head off the dovetail to adjust it. The error when I started was over 0.3mm over the 12 inches of travel)


I have a number of parts coming in the next week or so for this, some oldham couplings, some Angular contact bearings a few other bits that escape my memory at the moment. So until they come I am a little stalled. I have to re-assemble the mill though, so I'll be getting on with that, as well as working out what sequence I need to follow to make the various brackets and fittings for the conversion.


Tim



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