Re: [CAD_CAM_EDM_DRO] Re: Gecko differences

turbulatordude wrote:

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, Stephen Wille Padnos
><spadnos@s...> wrote:
>
>
>>turbulatordude wrote:
>>
>>
>>>Hi all,
>>>
>>>I am interested in the recent discount of Gecko drives and was
>>>pondering the idea of using servos on a machine.
>>>
>>>I did not see a detail listing the differences and similartitys of
>>>the different drives.
>>>
>>>
>>>What makes a 340 better/different than a 320 ?
>>>
>>>dittto for the 201/210
>>>
>>>
>>The 340 and 210 have the G901 pulse multiplier on their inputs.
>>
>>
>This
>
>
>>allows them to multiply incoming pulses by 2, 5, or 10 (or 1), so
>>
>>
>the
>
>
>>motor moves faster. It also gives the ability to work with a
>>
>>
>common
>
>
>>ground or a common supply for the optoisolators.
>>
>>
>
>I'm looking at a wood router and a plasma table.
>
>Both will probably be either rack or open belt, more likely the
>plasma will be rack and the router will be open belt.
>
>Any idea on what type of machine the multiplier is needed ? Or is it
>more for higher resolution or faster rapids....
>
>I'm trying to see the added benifit for my applications.
>
>Dave
>
>

With the multiplier, you can either increase your rapid speeds (at the
expense of resolution), or so you can keep up with high resolution encoders.

As an example, I bought used motors with 1000CPR encoders, so 4000 steps
in quadrature. I'm planning on using EMC or Mach2 to generate step
pulses, so (until I decide it's too slow and buy/build a step generator
:) I'll be limited to around 50k steps/sec. This translates to about
750 RPM at the motor. Since I'll be using a 2:1 drive, and I have 5 TPI
ballscrews, this translates to 75 IPM rapids - fairly slow. Very high
resolution, though - 4000 X 2 X 5 = 40,000 steps per inch. With the 2x
setting, I'll have 150IPM rapids, and half the resolution 20k
steps/inch, still plenty for me). Or, I can use 5x, limit my pulse
train to ~33k steps/sec, and have 250 IPM rapids (limited by the motor
max speed of 2500 RPM). This would be at 8K step/inch resolution.

If I buy or build an external step generator (like the Pico systems or
DeskCNC boards), then I can go back to 1x, and have full speed at full
resolution.

You can buy the G901 separately if you want to upgrade - it's about $10
more to buy it separately than for the combined unit. My understanding
is that the G901 is the only difference between the drivers.

- Steve