Messages

1121

PoKeys / Re: How I made my pendant.

« on: August 05, 2009, 02:07:07 AM »

Thanks for the info Hood! It is much clearer now. I wonder, however, if there is an organized manual where it all is explained. And where can I learn to write my own Brains - I don't like copying without understanding.

Daniel

1122

PoKeys / Re: How I made my pendant.

« on: August 04, 2009, 01:49:21 PM »

Hood,

Why did you use a brain for the start, stop and hold buttons - isn't it possible to use hotkeys and make PoKeys emulate them?

Also, what are the numeric values of the analogue inputs corresponding to the max voltage and min voltage? Just don't yet understand the above formula completely.

Daniel

1123

PoKeys / Re: How I made my pendant.

« on: August 04, 2009, 06:53:43 AM »

OK, thank you Hood. Found the relevant post. Here is the link to whoever is interested:

http://www.machsupport.com/forum/index.php/topic,9163.10.html

Daniel

1124

PoKeys / Re: How I made my pendant.

« on: August 04, 2009, 02:52:16 AM »

Ohh... and why do you use Modbus inputs in the SRO brain? Is there a document out there explaining how to create such brains? The video tutorial doesn't seem to be enough.

Daniel

1125

PoKeys / Re: How I made my pendant.

« on: August 04, 2009, 02:32:43 AM »

Hi Hood,

Thanks for sharing your experience!

Where does the formula for analogue inputs, you mention in the word doc, come from? What if I wanted a max override of 200%?

Thanks,
Daniel

1126

General Mach Discussion / Re: Grizzly G0519 to a CNC

« on: July 26, 2009, 01:39:49 AM »

Hi Atv

Personally I would go with a belt drive. I think it is easier to make properly and more technically correct. The ratio has to be reduction and has to be calculated based on your speed and load requirements.

To determine the motors power have a look here http://geckodrive.com/support.aspx?n=493148
But I think they are missing the friction element in their formula (though may be it is taken into account in their normalizing constant), so I'd add to the heaviest weight 15% before putting it into the formula.

The ballscrew pitch, again, has to be calculated based on your speed requirements and has to be suited to the belt drive ratio and motor performance.

I'd say start with the motors you can find (not sure you have to be using servos for a small machine, unless you are willing to spend more money and time on servos), and then choose the right belt drive and ballscrews to achieve the performance you want.

Daniel

1127

General Mach Discussion / Re: Backlash Settings

« on: July 25, 2009, 09:09:00 AM »

Why would you thing you need to turn off the backlash comp off? With the amount of backlash you have, if you would have turned the backlash comp off your circles would have been egg shaped 

Daniel

1128

General Mach Discussion / Re: Backlash Settings

« on: July 25, 2009, 12:51:41 AM »

You are correct about the prep move, but if you're using software backlash compensation you don't need to do this, as this is exactly what the software does.

Daniel

1129

General Mach Discussion / Re: Backlash Settings

« on: July 24, 2009, 08:00:34 AM »

Hi Bill,

Basically, the correct way to treat backlash, and what everybody on this list would say is to try and eliminate the backlash mechanically as much as practically possible. On a router (or mill), if you have backlash, the cutting forces can move the table (head) to any direction within the backlash margins. Thus, the software backlash compensation can do nothing to help in this.

Having said this, many users benefit much from using the software backlash compensation. It all depends on the type of work you do and the forces acting. In my opinion, in most of the cases that you can't afford a ZERO backlash mechanical system, a software compensation will be very satisfactory solution. If you do a finish cut of say 0.05mm (or less), most probably, the cutting forces would be smaller than the friction in the system, not being able to move the table to unwanted directions.

If you have a constant backlash along the leadscrew and you can't eliminate it mechanically, you can define the value in Mach3 to compensate for. It is desirable that the mechanical backlash be as small as possible. I think that software backlash compensation for up to few hundredths of a mm can be of a huge benefit for some systems. You can cut very precise circles (up to 0.01mm tolerance) if you do several spring passes starting each one at a different location along the circle circumference. By probability theory it eliminates most of the possible errors caused by uneven leadscrew pitch or backlash compensation.

As to your backlash, I think it is too big and you should try to reduce to at least half of that, or preferably to the 0.002" region. You shouldn't be checking the backlash by the eye. The correct way to do this is using a dial indicator - you program a move towards the dial indicator and then backwards and the difference in the dial indicator reading is your backlash.

Daniel

1130

General Mach Discussion / Re: Restarting after cutter breakage

« on: July 23, 2009, 04:52:39 AM »

One other note - if you have subs in your code then run from here will not run as you expect. It has no means to determine which loop you want it to start from.

Daniel