Denford Mirac Electronics Refurbishment

[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/s...duct&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/viewtop...2043&view=next

The automatic tool changer is making more sense. The VB script he used is here:
http://groups.yahoo.com/group/mach1m.../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