Hi!

A few years back I looked at Mach 3 and what it took to hook it to steppers to work a small router .... put the plans on hold while I got married and moved across the US (married a woman who is parlayed and needs 24/7 care .... want to set up a small home shop to make a living while watching her .... http://mcsele.shutterfly.com ).

I have just found a small bed mill with bad electronics that may be a good candidate for Mach 3.

It has 3 axis servos as well as several MPG's, limit switches and such. 

First question .... is there enough outputs from parallel ports ( I assume I can still find / build a computer with two ports) to make a full blown mill work ?  What is the most cost efficient interface board made that I can use to interface the ports with the servo amplifiers / controllers ( may need new ones also depending on what is presently on the mill)?

If I need (or should) look at a motion control board, again, what is them most economical to use?  I see a few out there ( although most are for steppers and I need one for servos).  I am hopping to get the mill for less that $1000 and am on a very tight budget.  I don't want to spend several thousand on a board to interface the computer and mill.  Electronics is a hobby of mine.  Is there any plans or kits out there that would reduce my cost?

Any advice would be greatly appreciated!

Thanks .... Mike

 

This will all depend on what kind of servo drives you have on the mill. It is likely they will be analogue only amplifiers and the feedback would have gone back to the control, if that is the case then you have a few options, external motion controller or get new drives.
The controllers that come to mind are the
DSPMC   http://www.vitalsystem.com/web/motion/dspmc.php#Mach3
KFlop     http://dynomotion.com/
Ajax      http://www.ajaxcnc.com/
Galil       http://www.galilmc.com/

I have no experience with any of them so best do some searches

Depending on size and type of servos there are lots of drives available, see here   http://www.machsupport.com/forum/index.php/topic,12233.0.html    for a write up Simpson did on various ones, looks like the Dugongs are nice drives.

If however your drives can accept Step/Dir signals then you could connect direct to the parallel port but I would advise to go with a smoothstepper, I use them on all my machines and love them.

So basically you need more info before more concrete advice can be given.

Hood

If you go the stepper route, Hobby CNC  makes a kit for 3 axis for less than 100 bucks. Great kit, well built and organized.

Looks like the machine has a Milltronics controller presently on it.  The machine was built in 1995.

The servos are: Milltronics Type- MT30M4-38 NO- S06279 C/Stall Torque -26 LB/IN 8.6 A Max -3700 RPM 140 V47

The only thing I was told is that the servos have been rebuilt a few years back.

The controller is back (or maybe the amp ) as the unit right now had one "run away" servo when powered up.

Thanks for the advice ... will know if I get it this week.

I figure at $1000 for even a "stripped" machine with no electronics, I will be getting a good deal ... ??

Thanks .... Mike

They seem to be SEM motors, If you dont get the amps the Dugong drives should be perfect for them

Hood

If I want to go with the Gecko servo drives ( which seem to be the most popular ) ... what is the chances of just putting a final drive transistor ( a large mos fet) off the drive  ... OK, it is a little more complicated since it must go positive of negative but there must be a fairly simple circuit design to just drive more power out of these units ( 140 volts rather than 80 )

Thanks ... Mike

Guess I should ask what the output of a servo drive looks like???

I was just assuming it is a pulsed output of either 80 volts with positive on one wire and zero on the other or vise verse  to get the servo to go the other direction ..... is this correct ?

Thanks ... Mike

The output of the drive will be a voltage up to the Max depending on the speed that is required and reversed polarity for the opposite direction, it is not pulsed. If you boosted the voltage you would be in trouble as the drive is deliberately putting out a voltage and monitoring the encoder to see that it is where it is meant to be, if you boost the voltage externally then things are not going to go well
I suggest you read Simpsons write up on all the various drives, linked to above, as it seems to confirm all I have heard over the years regarding servo drives that are commonly used. Dont skimp on servo drives or you will regret it if you are planning on making a living from the machine.

Hood

As a happy user of the DSPMC from Vital systems I wholeheartedly recommend it but since you are on such a tight budget, I am not sure that you will want to spend the money.

Mike

Thanks for all the advice ... will be asking a lot more soon.

I got my mill ... a MB-14 Fryer CNC bed mill ... all 5000 lbs of it ( http://cgi.ebay.com/Fryer-MB-14-CNC-Bed-Mill-Milltronics-Control_W0QQitemZ150390712129QQcmdZViewItemQQptZBI_Mills?hash=item2303fc2741 )

It has electrical problems so I figure it will be a great candidate for a Mack 3 conversion!

Mike