Quantum for "Shopbot" style machines, why?

[Apples]

Why is Quantum and the smoothing function for acceleration settings really good for Shopbot style machines as opposed to other machines?

I have a large 10ft by 6ft plasma table, very similar construction to a shop bot.  Rack and pinion drive, no ballscrews etc.

Why is this style of machine going to get better results than others?

Cheers
Peter
Australia

[Brian Barker]

Hello Peter,
The low steps per rev and the low accel kills the shopbot tables. With the low accel the corner rounding is very large The best way to fix this is to run a higher accel but as soon as you do that the machine will start banging and jumping all over the place. To get around this we had to go to a 3rd order planner. This takes care of the jerk that the shopbots can't take and will make them run much faster!

Is that any help?
Brian

[Apples]

Brian,

Yes that helps.  My gantry weighs in at about 120lbs.  I have 2 x 1200oz-in steppers on the long axis.  There is plenty of power there, but gee.... it shakes and rattles and jerks when the acceleration is set right up.  Sounds like this might be a good thing for my system.

I was just about ready to give it a go on the machine, when all of a sudden I derailed the gantry.  I was playing with the sherline mode and normal mode.  And in the sherline mode I could use 1us step pulse, then when I changed back over to normal, it was still set on 1us not 5us that it has to be.  I had my finger on the buttton to jog and then all of a sudden, there was a massive noise grrrrr! and the thing jumped of the vee rails.  Now the gantry is derailed and two bolt heads have jambed up.  One from the table and one from the gantry trucks, and I can't budge the thing left, right up or down to pick it back up onto the tracks again.....sigh....  Gunna get the hammer and try to knock it out of the jamb.

This is called Murphy's law.  Have you heard of it? 

I will let you know how Quantum goes on my system once I sort out this gantry thing.


I also take it that, you plan on making Quantum into a fully working stable version?  Intergrated into Mach? Or just Mach and Quantum?

Cheers,
Peter
Australia

[Brian Barker]

This is called Murphy's law.  Have you heard of it? 

I will let you know how Quantum goes on my system once I sort out this gantry thing.


I also take it that, you plan on making Quantum into a fully working stable version?  Intergrated into Mach? Or just Mach and Quantum?

I think Murphy is a little SOB and follows me all over the place!!!

Great I wuld love to hear what quantum will do on your system. Be sure to set your accels 3-5 times higher and to limit your jerk to about 1000 and start taking it up from there (BTW it will only work for Gcode moves)

Quantum will someday be the next mach3... It will need a new license file and should not cost to much to upgrade.

[Apples]

Brian,

I gave Q a go on the plasma table.  For some reason I can not get it to run properly.  I can fiddle with the numbers from 1000 to 50,000, and yes the accelerations are slower or faster.  I have also mucked around with the accelerations.  Normally I have it set to 500 in Mach3, and this gives me the best acceleration/ smoothness ratio.  But in Q I can wind it up to 50,000 and it will still jerk around the corners and nodes etc.  Maybe I missed a setting somewhere?

Any ideas?

And what is the "Adaptive jerk" box thing for?  The value is 2 and the box is ticked.  Do I have to do something there?


Peter
Australia

[Brian Barker]

Uncheck the adaptive jerk and replace the 2 with the 2000 that should get you up and running. at 2000 your table should be very slow to get up to speed

[ynneb]

Hey Apples, I remember seeing a video of your machine rattling, on CNC Zone. Yours should be a great candidate for Quantum.
My machine was also loosely based on the shopbot too. It new how to shake at times too

[Apples]

Brian,

I unchecked the adaptive jerk, and changed the value from 2 to 2000.  There was no difference.  It still slows down at every node/segment end.  I have changed the acceleration values etc.

What else should I check??? 

Ynneb,

Yeah, if I turn the acceleration right up it will go "bang" "bang" "bang" at every direction change.
Do you still have your cnc router?  How's it going? 


Peter
Australia

[Brian Barker]

I have no idea why it is not working for you if you put in 2 you should have a very bad accel... 

See that you have your settings right (Look at the pics)

[Apples]

Brian,

I have 2000 in the adaptive jerk box and it is unchecked, should I try for a larger number?

I have anywhere from 1000 to 50,000 in the max units per jerk box.  There is a noticable difference in the acceleration here. 

Peter
Australia