Messages

4851

General Mach Discussion / Re: spindle

« on: April 08, 2018, 08:50:06 PM »

Hi,
yes there are controls for the spindle but you've given us nothing about your machine or BoB or any thing else.
We aren't mind readers.

Are you using a parallel port?
What BoB are you using?
What type of spindle and spindle driver are you using?
Can you post manuals for the BoB and spindle driver?

Craig

4852

General Mach Discussion / Re: Only X-axis motor is working

« on: April 08, 2018, 08:45:51 PM »

Hi,
yes they'll do fine if there a sung fit. The 'lost motion' due to torsional flexure of the cheap couplers is 4um.
Quite frankly chasing 4um is not high on my list of things to do.
With the 10:1 gearbox my steppers are rated at 705oz.in With a 5mm pitch ballscrew of 20mm diameter that means a
rated thrust of 1480 lbf! I need some sort of mechanical fuse and the wee couplers do the job well, it was not my
intent, it just worked out that way. I don't want couplers such as the ones you've pictured, it would mean a blown
gearbox if I had a crash.

Craig

4853

General Mach Discussion / Re: Only X-axis motor is working

« on: April 08, 2018, 06:26:50 PM »

Hi,
all my ballscrews are direct drive. I use those el-cheapo aluminum couplers with a spiral slot in them. They flex a bit
and result in 'lost motion' which is not desirable but what has happened is on the odd occassion where I've crashed
the coupler shears off rather than wrecking the gearbox/stepper/ballscrew. Something like a mechanical fuse.


Craig

4854

General Mach Discussion / Re: Only X-axis motor is working

« on: April 08, 2018, 03:01:59 PM »

Hi,

I don't know how much my PC would have to perform to get the kernel to run at 45mhz but it's a clean computer. The only thing it will be doing is running the Mach3 program.
I'm also not above upgrading that as well. In fact, it's part of the plan in the long term

Don't bother upgrading the PC, you'll likely never see the difference, get yourself an external motion controller like an ESS or 57CNC and never look back.

I really do wish I could put together an encoder feedback. I know it can be done but that's above my pay grade for a while

Correctly specified steppers, drivers and powersupply used within their ratings will NEVER lose steps and therefore encoder feedback is a complete waste of money.
My steppers came with 500 ppr encoders already fitted. Once I got them sorted and they haven't missed a step for years I took the encoders off.

The companies who push these hybrid stepper servos are playing on your fears. If a standard stepper is going to lose steps because its overloaded then a feedback stepper of the same
size is also overloaded and will lose steps, the feedback may mean it tries to catch up, but it will fail....its plain overloaded and feedback wont save it, it'll fault 'following error'. Don't waste your
money on these things, learn whats required to have ordinary steppers perform as designed and the limits within which they'll work.

If you want more performance than that go to AC servos, genuine AC servos....not those really expensive Clearpath things....there again another company playing on your fears to print money.

Craig

4855

General Mach Discussion / Re: Mach 3 - driving beyond soft limits ?

« on: April 08, 2018, 03:12:21 AM »

Hi,
establishing how this error accumulates is going to be the key to solving the problem.

There is three ways I can see it happening.
1) The machine is missing steps on an occasional basis and an error is building up over a period of minutes before a move is attempted which results in a crash
2) There is some fault which causes an axis stall but shortly, several seconds, after the stall the axis resumes but now is well behind the Gcode contolled point.
3) There is some fault in Mach which is causing some instantaneous jump in the machine coordinates.

This last possibility could be detected by a suitably written macro running repeatedly with the macro pump.
The macro pump runs every 40ms or so. If the machine coordinates between successive passes through the macro pump differ by more than the maximum allowed by virtue of max motor tuning speed you
would have your smoking gun.

Craig

4856

General Mach Discussion / Re: Only X-axis motor is working

« on: April 08, 2018, 02:53:39 AM »

Hi,
Roger is right, if you get these things and leave Machs kernel at its standard 25kHz then the maximum speed for the steppers would be 750 rpm and with 5mm pitch
ballscrews that works out to 3.75 m/minute, still plenty damn good!

If you get these things and put a 70V power supply on it whats the bet you will have no need to change your motors, these drivers will make them sing.  Whats more they'll keep doing it for years.

Craig

4857

General Mach Discussion / Re: Only X-axis motor is working

« on: April 08, 2018, 02:39:07 AM »

Hi,
by way of a reminder, say you wish your stepper motor to spin at 1200 rpm at maximum speed, that is 20 rev per second.
With microstpping fixed this would mean the driver would need to be pulsed at 20 X 2000 =40,000 or 40kHz to rotate that fast.  Mach's standard parallel port is only 25kHz.
You could of course set Machs kernel speed to 45kHz, in fact you'd have to. Upping Machs kernel speed ups the pressure on your PC to perform.

An even better way to resolve it is to use an external motion controller, but they are not free. A good modestly priced controller  in the range $100-$200.

Craig

4858

General Mach Discussion / Re: Only X-axis motor is working

« on: April 08, 2018, 02:32:10 AM »

Hi,
yes very good value for money and Gecko is the leading brand.

Did you note that there is only one resolution, that is to say micro stepping is fixed at 10 per full step or 2000 step per revolution.
This is good in most circumstances but not all. Provided your design is good with 2000 step/rev then go for it.

Craig

4859

General Mach Discussion / Re: Only X-axis motor is working

« on: April 08, 2018, 01:55:33 AM »

Hi,
Vexta make two and five phase steppers, don't confuse the them.

My steppers are 23 size and fitted with a low backlash 10:1 planetary gearbox. Even second hand they were over $250 each and the drivers were another $200 each.
The motors and drivers are matched at 1.4A per phase. With a five phase steppers four phases are active at any given instant. Thus the total current in the motor
is 4.6A. I run them at 1A per phase so they run a little cooler.

The gear reduction means my machine is quite slow, rapids of 1200mm/minute but great torque, the stall thrust through 5mm pitch ballscrews is over 5000N. I got what I wanted but paid
a premium, knowing what I know now I think I could have spent more wisely and still achieved a good result. I would think long and hard before getting five phase steppers, they are good
but somewhat rare and all of them are expensive.

Craig

4860

General Mach Discussion / Re: Only X-axis motor is working

« on: April 08, 2018, 01:05:30 AM »

Hi,
ditch the TB6660, they are rubbish. Even if you get them to go right the moment you try to decelerate your motor hard the back EMF will blow the driver chip.
Get a decent driver, there are some experienced CNCers who recommend these Leadshine units and plenty more who recommend Gecko.

Craig