Messages

1781

General Mach Discussion / Re: edge finding/2.5D probing

« on: May 14, 2009, 05:01:38 AM »

pilotjunky - thanks for the feedback - hope you get some good results. I'll take a look at cnc4free. Thanks.

markhammill - Have you successfully installed and run Start Menu / All Programs / Probe Utilities/ ProbeCtrl which apart from other things provides init values for probe25D.tap. The reason for your error is that there appears from what you say to be no values in the Mach vars - you can check this out via the Mach menu Operator / Gcode var monitor.

stevespo - Looks to me like the macros are being run at startup - and they shouldn't be. As you know - when you load a gcode file into Mach, it is processed to calculate the path. Often however it's desirable to NOT have Mach run macros during this phase. A way to achieve this is to set the checkbox in Config / general config / ignore M calls while loading. Another way is to build into the macro the test "isLoading". I've chosen to use the latter with the intention of making things easier for the user which certainly used to work fine. I'm wondering if something's changed in Mach and "isLoading" is maybe not working - but that's just a guess at the moment. Try setting the "ignore M calls" checkbox to see if that helps.

1782

General Mach Discussion / Re: Saving DRO Values

« on: May 04, 2008, 09:47:59 AM »

Hi Carl - Not sure if this is pertinent to what you want but... If for example you're intending saving the axis position DRO values it may not achieve what you want. If you're using steppers and microstepping there are issues with motors staying where you left them and starting them anew from where you left off. One good reason for allways starting with a ref all. Like I say, this may not be an issue for you but just thought I'd mention it just in case.

1783

General Mach Discussion / Re: Hot stepper Motor

« on: May 04, 2008, 06:01:27 AM »

There are a variety of factors that can lead to excessive motor heating. Of course at the moment we don't know whether yours is excessive but anyway - considering the quick wins first....

Your motor appears to be a 6-wire 2Amp 2.9V 1.46 Ohm (unipolar rating) motor.

What follows depends on how you have it wired.

IF you have it half-winding connected then your PS voltage of 56 volts is giving an overdrive ration of 19.3:1 which is actually quite high.

Over voltage maintains torque at speed which is not perhaps of primary importance for a tangential knife rotator. The downside of high overdrive is increased motor heating - so this may be one of your problems. Particularly when you consider that a knife control spends a lot of time stationary (holding) - like a Z axis does in 2 or 2.5 D in use. A popular myth is that the current in a stationary (holding) stepper is low, zero or negligable. In fact that's when it's at its highest!

I'm guessing you do indeed have it wired thus because you've set your gecko to 2Amps.

IF on the other hand you connect it full-winding (series) you will have the following rated values for your motor.

1.4 Amps, 4.1 Volts, 2.92 Ohms.

In this case you should current limit your gecko to the 1.4Amps. However at the same 56 Volts of your PS, you'll reduce the voltage overdrive ratio to 13.6:1. Still perhaps a little high for your knife rotator but better than before. This should reduce heating. Please note that heating is reduced in this scenario NOT because there is less current in the coils but because there is less voltage overdrive. The heating due to current will be virtually the same in both cases because the electrical power is virtually the same.

Finally - the worst scenario: IF you already have it full-winding connected then your current overdriving (2A instead of 1.4Amps) and this is definitely not what you want. This WILL lead to heating from over-current and is a good way to damage your motor.

1784

General Mach Discussion / Re: Macro Code

« on: May 03, 2008, 04:24:31 AM »

not intended as condescention - more born of frustration - you don't hold the franchise .
If you'd just said what you wanted to actually achieve in the first place (like you were repeatedly asked to do) I think you'd have been pointed at the solution you appear to think you've discovered within the first reply. This has been done so many times it's kind of patronising of you to think you've discovered it. Try a search - hint - "touchoff" - NOT "disable reset"
Nobody mentioned "probe" because you never once said what you were trying to do. FWIW I didn't mention it with my code fragment because I assumed you'd know that G31 and the probe input go hand in hand - obviously I was wrong.
BTW - the probe input isn't the only input that doesn't cause a reset - there are loads of others. In fact about the only input that does is - guess what - limit - because that's its purpose.
A friendly tip - whatever the other things are you want to do - see if you can actually tell us next time - it'll save us a lot of time and you from putting Mach on ebay.

1785

General Mach Discussion / Re: Macro Code

« on: May 02, 2008, 08:06:50 AM »

stirling - While that code will work to set Z0, the final outcome is wrong. Using that code, it will

set Z0 at the height of the touchplate and raise the head .75". This leaves Z at 1.248.

Oh come on... so set 0.498 instead of zero - whatever. Do you really think you're the first person ever to want to do toolheight with a touchplate - the forum's litered with the CORRECT way to do it.

Also, this is only one of a couple of things I want to do that require referencing a home switch, but they all require the head to be able to move again after touching a home switch, without intervention by the operator.

I don't get it - you feed dribs and drabs but never actually say what it is you're trying to achieve.

I'll be VERY suprised if whatever way you finally achieve what you want it couldn't have been done far easier if the above is anything to go by.

1786

General Mach Discussion / Re: Macro Code

« on: May 02, 2008, 04:26:22 AM »

Is this what all this stuff about reset has been about?

code "G31 Z-100"
while isMoving()
wend

set zero

G00 Z0.75
while isMoving()
wend

1787

General Mach Discussion / Re: Noobish Question On Motors & Drivers

« on: April 30, 2008, 11:30:03 AM »

Hey Hood - No argument from me - you the servo man  - I was just letting you know what I'd read.

Cheers

Ian

1788

General Mach Discussion / Re: Noobish Question On Motors & Drivers

« on: April 30, 2008, 09:07:38 AM »

Hi Hood - well I did say "I'm no expert on servos as I've said - but I think I'm right in saying..." - that'll teach me to stick to what I know 

.....That said.... 

Here's why I said what I said....

http://www.allbusiness.com/sector-92-public-administration/justice-order/1177040-1.html

1789

General Mach Discussion / Re: Stepper motor power supply

« on: April 30, 2008, 08:11:54 AM »

Just read through this thread again and I'd like to ask some (rhetorical) questions.

1) what is "root2" and how does it relate to the rectified/smoothed DC voltage of AC?
2) For an LR driver - what is the max current the PS will need to supply for 3x2Amp motors?
3) If a stepper motor is standing still (holding) what current is it "drawing"?
4) How many rated currents do 8 wire motors have?
5) what is "root2" and how does it relate to single, series and parallel wiring schemes?
6) Why can 2.5Amp chopper drives NEVER source 4Amps - EVER?

1790

General Mach Discussion / Re: Noobish Question On Motors & Drivers

« on: April 30, 2008, 06:20:59 AM »

trekky - don't be too easilly seduced by size - big is generally better - but not allways. Nothing comes for nothing - everything's a compromise. Large stepper motors can introduce problems such as difficult tuning due to large detent torque. etc. etc.

Question: why do we need lots of power in our drive motors? - answer: to push the tool through the stock? - WRONG! - We need power in the spindle for that. A good spindle will go through stock like a knife through butter - a bad spindle will never go through it no matter how hard we push. We need torque in our drive motors to accelerate the mass of the gantry and we need power to maintain that torque accross our speed range.

But what speed? - well - the right speed for the job, our spindle and cutter (with maybe some to spare - for luck!). OK so you have a rig that will travel at a Km/sec - but your spindle and tool will only cut at 1mm/hour - that was money well spent then!!!!

That said, Hood is absolutely right - accel is also hugely important - you can never have too much, because what we'd actually like is instant speed, i.e. infinite accel. I'm no expert on servos as I've said - but I think I'm right in saying that at lower speeds, steppers will out accelerate servos by a gazillion miles (per sec per sec ) because they have more low speed torque. To get torque out of a servo - they have to be spinning fast. - so what happens at low speeds? - in order to work - you have to gear them down. That makes me think I'd want servos for either really high speed applications or really heavy rigs - course - that's just my opinion.

So..... read up - then do the maths - it may turn out that you'll have way more power than you need from 360 inoz Nema 23's. It may turn out you need 800 inoz Nema 34's OR it may turn out you need to buy Hoods servos 

Tip for the day - learn about inductance and what it means to your motors - it's far more important than a seductive holding torque. Remember holding torque only tells you how good the motor is at standing still