Messages

471

General Mach Discussion / Re: Hot Stepper Motor

« on: June 29, 2008, 01:36:56 PM »

These are exactly the same motors I use, with the Gecko's.

You cannot allow the Gecko drive unlimited freedom - they can (and will) pass up to 7 amps - I am sorry, I have missed what voltage you are using while I am writing this reply. I am using 24 volts. (Do not use less than 24 volts)

With the motor wired  in parrallel as you have drawn it, you need to limit the Gecko to about 4 amps, by putting a resistor in the two left hand terminals - there is a list of what values to use.

Mine still get hot to touch when I am working them hard, but generally stay touchable

472

General Mach Discussion / Re: Mach3 pausing during move

« on: June 29, 2008, 01:29:51 PM »

You are over-running your motors - nothing can come to a dead stop from 200 ipm - you are talking a lot of momentum, unles you are moving feathers.

Try cutting you acceleration down quite drastically - to say 1/10 of what it is. This should cut out your problem.  If it still persists then you will have to cut your speed.

Build the acceleration back up  until the fault re-appears, then back it off again until it becomes reliable.

473

General Mach Discussion / Re: Stepper motor size

« on: June 29, 2008, 01:24:36 PM »

Are you stepper motors 8 wire, and if so, how have you got them wired.

474

General Mach Discussion / Re: Power supply in parallel

« on: June 29, 2008, 01:15:58 PM »

When you say it is not powerful enough, what do you mean.

What are you trying to power.

If your main axis need, say 4 amps each, then power each axis from it's own supply - it makes no difference to the driver cards where the power comes from. As long as the leads to each motor are not interconnected, then you will be fine.

If say your Z axis needs another 2.5 amps, then  use  one of the supplies to power this as well.

I am thinking of powering my x and y axis from 36 volts (Gecko drives) and the Z axis from 24 volts (Routout drive) to see if I can increase speed and reliability on my X and Y.

475

General Mach Discussion / Re: Stepper motor size

« on: June 29, 2008, 04:32:19 AM »

I used Routout 2.5 amps drives on my machine to drive 220Ncm steppers. These were 8 wire motors rated at 2.5amps at 7.5 volts

Originally I wired them in series, and, like you, I found them lacking - only moving my lathe at 4 inches pm (reliably). (Mine is geared down at 3 to 1)
I wanted then to "rewire" the motors in parrallel. The problem was, of course, when I checked the windings and did the sums, the rating was for a single coil, and as soon as I put the coils in parrallel, I neede more omph than the Routout could provide.

To be fair, the Routouts did run the parrallel set up, better than when the motors were in series, but they were limited to 2.5amps and 24 volts.

I got a Gecko from a friend (and have since bought another) - and these are in a different league. They are adjustable, and rated up to 7 amps, and up to 80 volts. Fastening these on (using the same motors at 24 volts - same as Routout) my speeds went up to 40 ins per minute. I admit they are not reliable at that speed and I have dropped them down to 20 ins pm but a five fold increase is great. I am still using the Rotout card to run my milling head - but when I have the cash to invest in a third Gecko, I will then try a higher voltage - maybe 36 volts, and see what improvement that brings.

Before you rush to change motors, I would honestly fit yourself up with 3 good drives - the Gecko 201's are ideal. The beauty about that is you have the capacity to change current and voltage to your motors, without have to change your drives again. You can then see if you can coax any better performance from your motors.

476

General Mach Discussion / Re: velocity

« on: June 27, 2008, 01:30:48 PM »

That was simple -

But you now, if you want to be accurate, need to set your steps per unit (inch) to an accuurate figure, instead of just setting them at a figure to suit a speed that you want to achieve - otherwise how are you going to draw out what you need to cut.

This means calculating the number of steps.
How many steps do your motors need per revolution (A) is there any gearing to your leadscrew (B) {1 for direct drive}: how many turns does your leadscrew make to move 1 inch (C).
Multiply A x B x C = number of steps per inch.
Set this in your motor configuration and then adjust the speed upwards to what you need to achieve. Increase the speed first til it complains then back off til it runs smoothly, then increase your acceleration until it complains then back off.

477

General Mach Discussion / Re: velocity

« on: June 27, 2008, 10:27:39 AM »

I cannot see how changing your steps per unit will affect your velocity, one is a distance, the other a speed.

The only way to change your velocity is, either get the motors to turn faster, or reduce or introduce step up gearing between the motors and the table (or cutter).

If you increase the gear ratio between the motor and table (or cutter) then your accuracy will suffer, in that each step will mean a move of greater distance. Your steps per unit seem an odd number anyhow at 15,245 how do you arrive at that.

As far as the motors turning faster is concerned, I take it you have altered the distance per minuter upwards and your motors are now complaining and will not turn any faster - are they steppers or servo's. I recently increased my steppers by a factor of 10 by rewiring, and you can also increase the voltage to get them to turn faster. Servos I don't know much about.

I don't know what you are trying to move - is it a gantry? Is it smooth enough to move at that speed. There will be a physical limit to the weight your motors can accelerate (and decelerate) - and it may be that your motors have reached their limit, and to move faster, larger motors will be necessary to get over the inertia.

478

General Mach Discussion / Re: Tool Depth Stop

« on: June 27, 2008, 04:37:14 AM »

Use Locktite glue or something similar - I glue railway wheels onto axles and never had any come loose in 10 years.

No heating, no fuss, no little screws flying about. Just glue the collar on.

479

General Mach Discussion / Re: 0 return not precise.

« on: June 26, 2008, 04:00:32 AM »

I am just musing, because I don't know the answer on such limited information :-

Logic tells you that the system is loosing steps when moving to the right ( it cannot gain steps). I do not know what your steps per inch is set at, therefore it is difficult to follow that much further , other than to say 1/4 of an inch in 62.5 is 40 thou per inch - how many steps is that..

What if you start the tool on the left and move the whole 123 inches, and back - does it finish where it started.
Similarly, if you start the tool on the right and go 123 left and back does it return to where it started.
I assume you have measured the movement left and right to see if the table is travelling short in one direction. You can certainly measure to 1/4 inch with a tape measure.

Logic says that the table must stop short, and the most likely place is to the extreme right of travel - is there any movement past the 62.5 inch mark or are you approaching limits - I know you have cleaned it all, so you have thought of that.

I think you need to do a little bit more detective work to find where the movement is being lost, before we can point to a solution.

There is no limit on Mach 3 to my knowledge - certainly not in one direction only.

480

General Mach Discussion / Re: How to increase circle resolution?

« on: June 25, 2008, 01:17:56 PM »

As you talking about circles, i.e. true circles, which could be rewritten into G2 or G3 commands, or are these just odd bits of curved lines.

The problem with many of the drawing packages is that they do not draw circles - so from that point of view Mach 3 out performs many of them

If it is a circle, you may be able to put in one line of code that cuts outs many, many lines. G2 or G3 command is basically  - move from herre to a new position and (on the way) describe a circle radius R.

e.g. G2 X7 Y10 R6  - If you were at 0,0 then go to X7 Y10, but on the way describe an arc of a circle radius 6

This on simple command might save you 100 lines of code if your arc had been made up of 100 straight lines.