Denford Mirac Electronics Refurbishment

[CHudson]

Hi Guys,
I'll start with a little back ground as this is my first post here!

I purchased a new RoutoutCNC CNC router at the end of 2009 with a view to milling PCBs for production of lighting control gear and after allot of mistakes begen producing decent PCBs. I then sat down and created full 3d drawings in Autocad for the actual light fittings and sent those drawings to various cnc machine shops.
After getting several ridiculous quotes (£800 + for a garden light fitting) I decided to give it ago myself.
My light design is 86mm in diameter so I ideally needed at least 100mm to allow for any play. I looked at various different lathes and kept my eye out on various used machine sites and ebay of course and eventually decided I wanted either a Denford or Boxford Lathe as both seem to have extremely high quality components and generally come with little use as they are often used in schools.
I eventually came across a Denford Mirac in near perfect condition. The ball screws and ways are like new and its seems to have only ever machined small plastic parts. It was also a steal at £875.00 excl VAT and in fully working order.
The problem is that the electronics in this lathe only work with DOS software and it seems plenty of Mirac owners out there have tried to get the existing electronics to work with windows without any success (providing their machine is pre 1994) leaving the only route of converting with new drives to work with Mach3 or similar.
The new drives are probably going to be the easy bit. The hard bit is going to be getting the automatic tool changer to work and spindle controls.
There seems to be at least 2 people out there that have successfully done a conversion but unfortunately have not posted a build log so its hard to work what they have done to get their machines to work.

Anyway on with the build:

I have so far purchased 2 Gecko 201x Drives and also the C11G breakout board from CNC4PC.

I will be posting pictures and more information very soon.

I have also posted this thread on http://www.cnczone.com/forums/showthread.php?p=746300#post746300 and http://www.denfordata.com/bb/viewtopic.php?f=40&t=2653&p=9617#p9617

[CHudson]

So far I have located a wiring schematic for the Denford Mirac which is attached courtesy of the guys at the Denford Forums

[irving2008]

Welcome aboard!

From a quick look at the wiring diagram, you should be able to drive the X and Z steppers (bipolar parallel wired, see sheet AC6-05) directly off the Geckos. Looks like steppers run off a seperate power supply integrated on slave board, but no indication of voltage.

X and Z homing (datum) sensors are 24v but should be interfaceable OK.

Spindle motor might be trickier, its 3-phase, and the spindfle and toolpost drive seems to be 1-phase in, 3-phase out but not clear at what voltages - suspect 415v. Spindle encoder goes back to slave board then a 2-core screened goes to spindle control board - I'm guessing thats a control voltage for spindle speed. Should be able to drive that direct from Mach.

[CHudson]

Thanks Irving2008, I'm going to try to get the geckos in place over the weekend as I believe the attempted delivery today even though I only ordered on Monday from the states! I'll have to take a good look at the toolpost/spindle drive as there is defiantly only 230 going on, I guess maybe its an 3 phase inverter.

I have attached a few pictures of the lathe, there not the best as my camera was going flat and I couldn't use the flash.

[CHudson]

Today I brought the electronic control box home and got the geckos out of their packaging. I was quite shocked how small they are but they seem to be excellent quality. Gecko shipped them very quickly, I received them within 3 days all the way from the US!

Anyway I sat down with the control box and started working out what's what. I have identified the X and Z axis's on the slave board and also the drive supply. I has hoping to work out what voltage the steppers run at by measuring it from the drive supply connector but it seems it does not output any voltage when not connected.

Does anyone happen to know what cables go to what on these steppers. If not can I just work it out by doing a continuity test?

Heres a few pictures:

[irving2008]

On the gecko's

A+ = Yellow
A- = Red
B+ = Black
B- = Orange

If the stepper runs backwards, swap Yellow and Red over...

[CHudson]

On the gecko's

A+ = Yellow
A- = Red
B+ = Black
B- = Orange

If the stepper runs backwards, swap Yellow and Red over...

Thanks Irving2008, I was hoping to give it a go today but unfortunately I have only just finished work! Any ideas what the supply voltage is?

[irving2008]

cant say, without a close look at the Power supply, but trace back to the smoothing capacitors for that supply rail and look at their voltage rating... generally the supply will be 50-70% of that. Or measure the secondary AC voltage of the transfomer that feeds it - the DC will be no more than roughly 1.4x that. I'd hazard a guess at 24 - 36v probably...

[CHudson]

I have made a little progress with the machine today. I worked out that I really needed heat sinks and fans for the Geckos as per the manufactures instructions for currents over 3A. I was told a little while ago that the steppers on the Mirac draw 3.5A under load (I also found out they run at 38V). I purchased 2 of these http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=158-556 heat sink and fan assemblies and have fitted them to the Geckos. I removed the slave board and then mounted the heat sinks to the large plate of aluminium where the slave board was.

I had to order 5 C15 Dual Relay boards from CNC4PC. They will be used for enabling the spindle and tool post, running the spindle and tool post in forward or reverse etc
It seems that the spindle and tool post are powered from the motor controller/inverter together and 24V relays are required to turn the contactors off and on to turn the motors off and on. Theres speed control and an encoder for the spindle but doesn't seem to be anything for the tool post other than a DC brake. I'm guessing that the tool post uses a worm drive and runs at a set speed and you just have to time how long you run the motor to get to each tool.

I'll post some pictures later on.

[CHudson]

After some discussion on the Denford forums I have stumbled across someones solution for the automatic tool changer on the Mirac:

After reading this thread http://www.denfordata.com/bb/viewtopic.php?f=43&t=2043&view=next

The automatic tool changer is making more sense. The VB script he used is here:
http://groups.yahoo.com/group/mach1mach2cnc/message/94962

As soon as I have the main board from CNC4PC I should be able to get pretty much everything working.

[CHudson]

Hi Guys, Sorry its been ages since I've last updated. I've been stuck twiddling my thumbs a little as I am constantly waiting for bits to turn up.

I wired up most the machine. I've managed to get both axis's working, the spindle turning and the tool post turning.

The Control card from CNC4PC is very limited in terms of inputs. I have had to purchase a further Parallel post card and breakoutboard to connect the home and limit switches to.

I'm struggling to get the spindle to turn at the desired speed. It seems to just stay to one constant speed even when using the mach3 tuning tool. I am also struggling to work out which core on the encoder goes to what, i.e are they pairs do they need 5V and Gnd etc

With regards to the tool post, that bit seems to be rather simple, all you need to do is tell mach3 to watch the grey code for the correct tool then stop and reverse then switch back over to the spindle. No voltage need to be applied once is fully locked in, though it wouldn't be possible to apply any constantly anyway as you can only have either the tool post on or the spindle on at any one time.

Oh and does anyone know how many steps per inch or whatever it is?

One final thing, any CAM recommendations?

[CHudson]

Well its been a while since I updated, I managed to blow up the breakout board so I had to fit some new chips anyway...

I have made some adjustments to the program to suit the Mirac the way I have it set up. So in Mach3 when the code
T0101 M6 Appears this is saying T offset, toolnumber then M6 is tool change macro

Heres the macro:

Dim Tool As Integer
Dim OldTool As Integer
Dim NewTool As Integer
Dim MaxToolNum As Integer

MaxToolNum = 8 'Maximum positions on Automatic Tool Changer
Tool = GetSelectedTool() 'Get the toolnumber from the command e.g T0101 M6 Tool number 1
OldTool = GetCurrentTool() 'Get current tool number


Call StartToolChanger

While NewTool <> Tool
Call CheckPins
Wend

Call StopTool

SetCurrentTool(NewTool)

'//// Subroutines /////////

Sub StartToolChanger
ActivateSignal(Output3) 'Turn on output signal to turn off spindle and turn on the atc
ActivateSignal(Output4) 'Turn atc forward
End Sub


Sub CheckPins
If IsActive(Input3) And Not IsActive(Input2) And Not IsActive(Input1) Then
NewTool = 1
End If
If Not IsActive(Input3) And Not IsActive(Input2) And Not IsActive(Input1) Then
NewTool = 2
End If
If Not IsActive(Input3) And Not IsActive(Input2) And IsActive(Input1) Then
NewTool = 3
End If
If IsActive(Input3) And Not IsActive(Input2) And IsActive(Input1)Then
NewTool = 4
End If
If IsActive(Input3) And IsActive(Input2) And IsActive(Input1) Then
NewTool = 5
End If
If Not IsActive(Input3) And IsActive(Input2) And IsActive(Input1)Then
NewTool = 6
End If
If Not IsActive(Input3) And IsActive(Input2) And Not IsActive(Input1) Then
NewTool = 7
End If
If IsActive(Input3) And IsActive(Input2) And Not IsActive(Input1) Then
NewTool = 8
End If
End Sub

Sub Stoptool
DeActivateSignal(Output4) ' Stop running the ATC forward, if you don't do this the inverter will stop and the whole unit
' Will need to be turned off and on again
ActivateSignal(Output5) 'Run ATC in reverse
Sleep 3000 'Wait 3 seconds to allow the toolpost to lock in
DeActivateSignal(Output5) 'Stop running ATC in reverse
DeActivateSignal(Output3) 'Turn off output to turn spindle back on
End Sub

I've yet to test it but it works fine in VBscript. Should have a chance to test it tommorow.

The outputs corrospond to the following:

Output 3 is the ATC power contactor and Spindle Power Contactor, the Spindle Power contactor is wired to the normally closed side of the relay and and ATC power contactor is wired to the normally open side of the relay

Output 4 is the ATC Forward Relay

Output 5 is the ATC Reverse Relay