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Emco compact 5 cnc lathe with Welturn

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Emgee01/12/2015 15:06:19
1531 forum posts
219 photos

Mike T

Which method did you use to bypass the on board computer ?

Emgee

mike T01/12/2015 15:23:45
173 forum posts
1 photos

Emgee

I designed an interface board using L297D chips to convert the incoming step /direction pulses into the four phase drive signals required by the Emco stepper drive boards.

Later I replaced the Emco steppers and driver boards with M542 drivers and new steppers, just as John Stevenson did.

What did you do to control the Emco spindle motor?

Mike T

sam sokolik01/12/2015 15:43:32
60 forum posts

iirc the stepper drives in the emco control each phase. The same linuxcnc config could be used I would guess. (I am setting the interface card in the emco 'pc' to use phase control. I don't know if you would need a buffer/bob as I don't know what the input control voltage to the existing drives are.

sam

Emgee01/12/2015 17:22:37
1531 forum posts
219 photos

mike T

Am I correct in thinking the L297D interface board was fitted between the parallel computer port and the Emco stepper control pcb ?

Did you use Mach for control ?

Both my Compact 5 cnc lathe and F1 mill are still running original controls, I use MFI for writing any lengthy programs required or if only a few ops needed it is simple and quick to enter direct at either machine.

I have program control of the spindle stop/start and speed by using an add-on board from Henk Versuren. the stop/start is std M03-M05 and speed control by using M22 for cnc speed control and M26 to set the speed parameter as % of belted speed. Once programmed the M22 is global so only M26 needed to provide further speed changes in the program.

Emgee

Emgee01/12/2015 17:31:59
1531 forum posts
219 photos

Hi sam

I can only guess the inputs to the Compact 5 steppers will be as used on the 5PC model, I'm sure they were the same steppers.

You mention buffer/bob, electronics is not my forte so that means nothing to me although I can recognise some components and make up simple ccts from schematics.

Emgee

mike T01/12/2015 17:41:51
173 forum posts
1 photos

Emgee

Correct, the L297D interface board (three chips) sits between the 25 Pin parallel port and the 2 (3) input connectors on the Emco stepper drive card. The connectors are disconnected from the on-board computer, which I no longer use. The interface board is simple enough to be hard wired, does not need a PCB.

As I said in an earlier post, I use DeskNC control software or LinuxCNC. The 25 pin parallel port will also be compatible with Mach.

Do you have contact details for Henk Versuren? I cannot find him with Google

Mike T

Emgee01/12/2015 19:53:57
1531 forum posts
219 photos

Mike T,

check your PM inbox for a message.

Emgee

Fatgadgi02/12/2015 14:24:44
162 forum posts
21 photos

Hi Mike

First an erratum ..... should have been Homann not Hofmann and the boards are called "Digispeed"

http://www.homanndesigns.com/store/index.php?main_page=index&cPath=1&zenid=sm3s1t10peg5d5cj57itvukvh3

Secondly about where the 0 to 10v comes from, the jist from my simple Mechanical Engineer's brain is as follows:

This breakout board takes signals from Mach3 and outputs them again (and inputs as well of course), but in a protected way. So if anything happens to the lathe electrics, ie it lets out smoke and I get a nasty damaging electric spike from it, it's not passed down to the PC. So it provides (opto) isolation for inputs and outputs.

It also modifies and isolates the spindle speed control signal from Mach3.

Mach3 can provide output to control a spindle, but (I believe) it uses a digital signal (PWM). The breakout board modifies this output from the parallel port to provide an old school analogue voltage that varies between 0 to 10v, which probably came about to emulate the potentiometer control in the first place ??

Anyway, this can be used to control VFDs (or all the ones I have come across at least) in a simple manner - not as accurate as PWM, perhaps, but for my needs perfectly practical.

And somehow I'm sure I can use it to replace the manual potentiometer, perhaps by changing the voltage to suit. I'll know shortly when the Emco runs again and I can do some measurements.

Feedback from the spindle speed can be fed back into Mach3 as well from the shaft encoder. The resolution of the original Emco disc was too fine for Mach3 and so I have made and fitted a coarser one (ie less holes per revolution). Don't know how good this will turn out to be and whether fluctuations in spindle speed can be handled quickly enough, but we'll see.

Emgee02/12/2015 15:41:30
1531 forum posts
219 photos

Hi Will Bells

Sorry about the earlier typo, Which model Digispeed have you decided on ?

Emgee

Fatgadgi02/12/2015 15:50:24
162 forum posts
21 photos

Hi Emgee - I'm guessing my breakout board does exactly the same thing as the Homann ones do. I'll try what I have first .... if it goes pop, I've only wasted £14 (cheap compared to one of the ballscrews I had to replace !!!!!)

Fatgadgi07/12/2015 00:40:51
162 forum posts
21 photos

Had the old girl jogging under her own steam today using Mach3- the Emco that is.

So still want to finish adding homing and limit switches, but just mulling over whether to integrate the tailstock or not. I can see how to add one on the X axis (cross slide) and two on the Z axis, with the one near the chuck adjustable.

But what happens if I leave the tailstock clamped and the limit or homing switch is behind it ? I want to keep it on the lathe, so I'm thinking that I should add a forth sensor and have the limit on the tailstock itself

Anyone done this ?

(And, the spindle speed control pot was measured at 8.5v. Result)

John Stevenson07/12/2015 01:03:50
avatar
Moderator
5068 forum posts
3 photos

Disconnected mine.

Found out they were more trouble than they were worth.

Every time it went into machine co-ordinates it shot off to the home switches at the far end of the bed, spent more time travelling to home than it did cutting.

Eventually set machine co-ordinates same as work co-ordinates as they are always on the end of the bar you are turning and spent the time writing decent tool change macros so it went just far enough away in both the plus axis to swap tools safely and then get back to turning which is what it's paid to do.

Fatgadgi07/12/2015 09:54:18
162 forum posts
21 photos

Mmmm ..... never thought of that, but I guess the saddle legs it to the pre-defined tool change position at the far end of the bed every time a change is called up.

Guess for me there is a high chance of causing damage by hitting the limits by mistake and a low chance of worrying about cycle time.

Emgee07/12/2015 11:25:03
1531 forum posts
219 photos

Hi Will

Could you please send detail of the method and settings in Mach that enabled the use of the Emco spindle controller.

How did the new speed indicator disc work with Mach and do you still have ability to thread ?

As for the Z limit why not have the home switch behind the carriage fitted to the bed but adjustable by sliding to suit the length of the workpiece. Like John says put a line of code in to move the saddle away in Z before the toolchange line then after the toolchange move back by the same amount, tool offsets will be used in the toolchange line to ensure the tool is at the correct place.

Sending the carriage to a home switch positioned at the tailstock end of the bed creates far more use/wear on all components than necessary.

Emgee

Fatgadgi07/12/2015 21:43:06
162 forum posts
21 photos

Hi Emgee

Sorry to fall short, but the spindle speed is not connected to Mach3 yet - I will attempt to do that in a few weeks time I think, probably over Christmas. I have a relay connected to the breakout board to start the spindle though, which was straight forward enough to set up.

It cut metal on Sunday in manual mode, which was a nice milestone. Just aluminium and a fine cut, but the finish, even with a lot of overhang, was pretty good. Next weekend I will try to run a short g-code program.

I haven't connected the encoder sensor either yet, but I'm going to bypass the breakout board for that and temporarily hack straight into the parallel connector. If that works, I'll set up a second parallel port.

I will not get a chance to do much before the weekend though, so I'll see how far I get on that.

Fatgadgi02/01/2016 01:23:45
162 forum posts
21 photos

Just a quick update on the compact 5 update to Mach3 - basically everything I wanted to change has been done with the exception of the speed control being directly controlled from the program (sorry Emgee, but the voltages on the pot are not what I wanted after all - 10v across the pot, but 50v to ground, which I need to think about before going further).

So it all seems to work nicely, just the external motor wires to tidy up a bit.

I've added limit/homing sensors and modified the photo interrupter and encoder disc on the spindle to feed Mach3, which I want for screw cutting which I'm going to try tomorrow (just bought the license to unlock this feature in Mach3) and run some longer programs.

My original intention was to add the computer into the box at the back, but after a bit of deliberation, I've chopped 6 inches off the top of the cabinet and turned it into a 5 PC. So the computer is stand alone and the rest of the control stuff is in the box.

Also used Fusion 360 to write the gcode after a bit of messing around with the standard Fanuc turning post processing settings.

Cheers Will

Emgee02/01/2016 10:55:35
1531 forum posts
219 photos

Hi Will

Thanks for the update, seems you will need the Homann DC06, just then need to wire from the speed pot connections on the Emco control board to the Homann board, this part of the board will then be at mains voltage but is isolated from the electronic side and earth, just be aware.

The other connections on the board are all to provide Mach control of spindle on/off/speed/direction and will be similar to your b/o board connections.

Keep us posted.

Emgee

mike T02/01/2016 11:16:08
173 forum posts
1 photos

Hello Will

You are making good progress with your machine update program. Well done.

I am not clear about what you discovered about the voltages on the Emco motor speed board pot. Can you give a bit more detail?

I made some triangular pieces to fit under the lathe base to tilt it forward until box at the back was vertical. This gives a semi slant bed, which improves visibility and helps clear the swarf . You also gain a flat surface on top of the box to put stuff.

Keep up the good work

Mike

mike T02/01/2016 13:46:57
173 forum posts
1 photos

Hello Will

According to my Emco circuit diagram for the motor spindle speed board. The speed control pot (50K) is connected between +12 volt and ground via a 27K dropper resistor. Therefore the voltage across the pot should be about 8 volts and the voltage on the pot wiper should vary between + 8 volt and 0 volt.

I cannot understand where the 50 volt to ground comes from. Make sure you are measuring using the chassis earth ( connector X21 pin 6) and not mains neutral.

Hope this helps

Mike

Muzzer02/01/2016 14:45:46
avatar
2904 forum posts
448 photos

Mains neutral and mains chassis earth / ground should all be the same potential, within a volt or so. Neutral is grounded at the substation.

Have you connected the control system "ground" to anything earthed? If it's floating, the voltage to earth could measure 10s of volts AC and/or DC.

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