Gecko G540 or?

[JW1977]

Sorry for changing the subject back and fourth, its just me but a question regarding the Electronics came to mind...
In my world its easy just to overdimension for example the steppers and the motors so that they should be able to cope with whatever i through at it.
Someone once told me that it isnt so and that the best thing is if the performance of the machine is optimised to what you should use it for... Which is right?

[EddyCurrent]

The optimum range of anything is where it operates in the central linear region of it's performance graph. If you oversize then it's not working hard and is in the lower non linear region of the graph, if you undersize it will work at the upper non linear region of the graph.

[JW1977]

The optimum range of anything is where it operates in the central linear region of it's performance graph. If you oversize then it's not working hard and is in the lower non linear region of the graph, if you undersize it will work at the upper non linear region of the graph.

Yes but a Porsche 991 works damn well to go shopping with. Question is, are there any disadvantages doing light work with a muscular cnc... Someone once told me so but i cant remember why...

[EddyCurrent]

I can imagine that if things are oversized they will use more energy to overcome their own inertia and losses than the energy used for light cutting. If this is the case I would expect the machine to be, 'not in control'.
A bit like trying to using a 50kg computer mouse for fast game playing.

[Ger21]

In my world its easy just to overdimension for example the steppers and the motors so that they should be able to cope with whatever i through at it.
.........................................Question is, are there any disadvantages doing light work with a muscular cnc

Adding larger motors can easily cause your machine to move slower, even though it may have twice the power at slower speeds.
Generally, the bigger the stepper, the slower it's capable of spinning.
Steppers are rated at their holding torque, when they are not spinning. The faster they spin, the less torque they have. With larger motors, the torque falls off more rapidly. If you gear them to spin slower, where they have more power, then you give up resolution.
I've seen cases where people have purchased large, inexpensive motors on Ebay. These motors are often too slow to get out of there own way. In most cases, these same people end up buying new, smaller motors. I've seen motors 1/4 the size make the machine 4-5x faster.

The best performing stepper motors will always be the smallest ones that meet your requirements. You should be choosing motors based on performance requirements.

[JAZZCNC]

Im still a bit confused about the motion control detail though. I can se why people like the Gecko G540 kit as it seems like an overall mid-level good compromise.

Ok well first the G540 isn't a motion control card at all, it's just 4 drives combined with a BOB. The drives are limiting regards motor amps and while they are nicely made they can't match the AM882 in performance terms. I've used both and I wouldn't buy another that's all I'll say.!

Yes but a Porsche 991 works damn well to go shopping with. Question is, are there any disadvantages doing light work with a muscular cnc... Someone once told me so but i cant remember why...

For a family of one maybe but try taking 4 kids and all the baggage that goes with them.!! You need a Porsche Cayenne for lugging kids and baggage around.

Think of the CNC machine as either Porsche 991 when optimised giving great performance at what it does best but limiting at other things.! OR . . Cayenne is still a Porsche and supposedly performance vehicle which will get your there with all your baggage and kids safely but not very excititng and rubbish around the nurburgring.!!
The Cayenne is the one with the Big engine not the 991. It's oversized and under performs because it's optimised for ever lugging kids around. This comes at a cost in both performance and Expense.? Your paying for performance vehicle which fails to deliver.!

The tuned and optimised porsche 991 does ONE job well and thats going fast. It's limited at moving kids but was never designed for that purpose so wrong to expect it too.

Now this gets more complicated with CNC due to way steppers work. Large steppers bring an all new set of problems which to get performance from requires expensive drives and motors.
This is why it's best to target the machine use and design to that with a generous safety margin and nothing more. More is less really is true when it comes to steppers. Anything above the safety margin is just wasted money.!

[JW1977]

Ok, i understand... Ive spent the last days designing the gantry and i will soon order the parts.
Thanks again for all the input. Ill be back 4 sure!

Btw and of topic.
I testdrove the new 991 Carrera S a couple of weeks ago. Bl... H... it was nice!