Advice on upgrading smartstep/3 controller

[Simon P]

Hi All,

Further to my post in the machine section,
I have an early model (97) Novamill / Smartstep3 Controlled that I'm having some issues with,
The machine was working fine then suddenly developed a fault on the X- and Z- axis's which is causing an error message *Control Communications* to be displayed,

I'm not having any luck trying to resolve this issue so I'm now considering upgrading to usb / ethernet (mach3) and wondering what I would need to carry out such a conversion, I would like to use as much of the original electronics as possible and I'm hoping I can simply remove the control board from the smartstep/3 driver board and replace it with something like the smartstepper board, (I say smartstepper only because a local CNC retailer has these boards in stock) this of coarse is assuming that the driver board is not at fault in the first place...

A brief description of the problem and what I've tried so far,
If I attempt to Jog continuous I noticed that the axis readout only appears to be working in the + direction now and will only display *-------* whilst trying to jog continuous in the - direction on either of the X or Z axis's, Y axis is still reading / working normally in both directions, Jog Step works fine on all axis the problem only accures if using jog continuous - or I attempt to run a code,
The machine still boots up and homes fine, the control board reads *H* whilst it's homing followed by an *8* as it normally does,
Just to mention repeated resetting of the error eventually makes the machine work normally again but it only works for a few minutes before it reverts back to the error message,

I suspected it was most likely going to be a connection / wiring issue so I carried out a continuity test on the rs232 cable pins, I also tried a direct cable link between control board and pc port just to prove to myself and double confirm it wasn't the issue, I've tried using a different pc, however this was xp based and i had to install an additional serial port card, running from a dos screen in xp fanucmd.exe found mint and connected first time (i was surprised) but it made no difference and the axis problem remained the same, I've removed the control board and used a hot air gun to re-heat all the solder as it was looking a little oxidised, this has made no difference either so starting to think it maybe a fault on the board itself...

Not being that clued up on the electronic side of things I'm hoping someone can help with suggestions on the best way forward with this?

[Denford Admin]

We have some smartstep top cards which have come from working machines (in fact there are two coming in today)
Might be worth trying one before you go ahead with the upgrade ?
Make an offer if you want to try one (of course we can't supply any warranty)

[Simon P]

Thanks for the offer though i'm now pretty sure the top card isn't the issue,

Having checked the top card for connection/solder problems but not finding any I decided to remove the driver board and check that aswell, I'm pretty sure that I've found the problem as there's a dark coloured residue leaking down pins 5 - 6 on one of the L297 Ctrl chips and also a tiny pinhole blown in the front of one of the L298 Driver chips, I've ordered a pair of replacement chips from rs and will swop these out when they arrive however I'm now wondering what would have caused this failure, i've checked the motor wiring for shorts but couldn't find anything wrong there, other than a shorted motor which i don't believe it is as it works fine plugged into any other axis port, i don't know what else i can check - anyone got any ideas on what could have caused this or is it a normal age related failure on these boards?

Guess it's a case of fit the new IC's and keep my fingers crossed...

[Denford Admin]

Putting them on sockets might be a good idea, there's some info here if you haven't already seen it:
viewtopic.php?t=2615

If the motors and wiring are OK, it could just be down to wear & tear...those driver chips get very hot and could well be worth investing in a cooling upgrade (bigger better fan, more fans etc...)

[Simon P]

Yes agreed fitting sockets would be a big advantage over the direct fittment,
It wasn't that difficult to replace them but if it needed doing more than once then sockets would definately be the way to go...
Sadly replacing the chip's has made no difference to my issue and the none reading fault remians the same, if anything a little worse.

I've decided to go ahead and upgrade so have ordered the nesessary drive's bob controller psu etc,
The drive's i've ordered are the adjustable type from 1.0 upto 4.5 Amps and will be powered from a dedicated 36vdc open psu,
Am i correct in thinking the original steppers were run at 2. Amps half step?

Also with regards to the spindle speed, the bob I've ordered already has an onboard pwm / 0-10vdc converted output ideal to control the spindle, however strangly this output is the only one on the bob that is not opto isolated...
I'm wondering if anyone has any ideas on solving this issue, the only thing I've found so far is this isolator unit from RS http://uk.rs-online.com/web/p/signal-co ... g/0629516/ but the price is rather high and if theres a cheaper option I'm all ears...

I do like tinkering with electronics but really can't claim to know anything about what i'm doing!

Thanks for you help,

[Denford Admin]

Am i correct in thinking the original steppers were run at 2. Amps half step?

Yes the Baldor stepper drives were 2 Amp half-step

the only thing I've found so far is this isolator unit from RS http://uk.rs-online.com/web/p/signal-co ... g/0629516/

For that sort of money, couldn't you get a new drive ?
I'm not sure if it'd work, but the Sprint 400i appears to have isolated circuits, maybe worth investigating another DC drive?

[Simon P]

Thank you DA,

I didn't know this 400i drive was available,
The cost is about the same from what I can see however the 400i is a far better option as it would be a direct connection from BOB to Drive and so will avoid the time delays that are associated with the RS Isolator unit...

Excellent!

I installed most of the upgrade bits n pieces yesterday, it was very simple and straight forward to put it all together, Mach3 is fairly easy to set up and after powering it up everything appears to be doing what it should - it's quicker smoother and a lot quieter now, the motors are running much cooler as well...

I have set it up Metric at 200 steps per unit however measuring the table travel against the dro it is falling short by approximately 0.001 - 0.002 per mm of travel so there's some slight tinkering to do here but otherwise I'm very pleased with it so far,

Off to order a 400i dc drive now...

Thanks for you help - it's appreciated

[angel-tech]

with the existing pulleys on the machine it should be 200 steps, what do you have for velocity and acceleration ?

[Simon P]

Hi Angle,

I haven't had any time to play with it yet - it's currently set up as...

X= Step: 200 Vel: 1270.2 Acc: 1159.9872 Pulse 5/5
Y= Step: 200 Vel: 1270.2 Acc: 1159.9872 Pulse 5/5
Z= Step: 200 Vel: 1270.2 Acc: 825.7536 Pulse 5/5

To be honest I'm not sure how I ended up with this config, I didn't think these settings had any effect on the travel distance, I thought it was strickly motor speed?
It's falling short by approx 0.001 - 0.002 per mm at the moment on all three axis,

[angel-tech]

i would change the acceleration to about 10% of the velocity, you've got way to much acceleration on atm. 120 would be about right.