Stepper Resolution

Hi, I want to do a project that requires more precision than the layer height and the nozzle size can deliver. What I'd like to do is wiggle the nozzle, effectively utilizing the stepper resolution to make an accurate data encoded print. Can anyone tell me what the X, Y, and Z stepper resolution is?

Thanks in advance,

Les

 

The steppers are 1.8degree per step.

The X and Y are 80 steps per mm

The Z is 2267.72 per mm for 5/16 and 2560 for M8

 

Mike to the rescue! Is there anything he DOESN"T know about the mighty ROBO? Let's play a game of "stump the chump".

Mike, what is the maximum load capacity of the heated bed and compare that to the maximum power sourcing capacity of the RAMPS 1.4 board?

Les

 

And a follow up on those stepper stats: I can believe 80 step per mm which is truly excellent, but 2k+ steps per mm seems a bit out of the ballpark, that's equivalent to 2+ steps per micrometer is this true or are we off by some factor?

Lea

 

The heated bed is rated at 1.4ohms at 12v. This gives a max power output of around 130W.

According to the calculation this should be able to barely sustain 100C, with the assumption that the surrounding air has increased to around 45C. The cork board backing should increase this temp capacity as less energy is being wasted cooling the underside of the board.

The ramps 1.4 board uses a MFR1100 polyfuse which is only rated to 11A at ambient temperature. The robo has these swapped out for 1400 so they can handle 14A. They're only rated to 16v so the maximum power you can get from the ramps board is around 190W if we assume the polyfuse can handle 12A at steady state.

That's because 5/16"-18 has a thread pitch of 18 thread per inch. Or around 1.41111111111 mm per revolution. This rounding error gives that weird 2267.72 value which is why you need to use off even value number 0.1058 to get an even number of steps per layer. Otherwise you get rounding errors which leads to bulging.

 

Looks like I'm the chump who got stumped! So Mike would you recommend buying a new RAMPS 1.4 board since mine is now charred and melted on the heated bed connections, or should I wait for the RAMPS 1.5 board? And if I buy a RAMPS 1.4 board do I need to replace the PolyFuse? (i can solder well enough to do it).

Les

 

I think the 1.4 is just fine and even when the 1.5 is released (which will be a while) it will probably be more expensive than it's worth at first.

What I, and most other people, suggest is pulling the 1100 polyfuse out and replacing it with an inline automotive fuse, something rated to 15A is preferred, but 20A is fine as well.

Like these:



Another nice thing is I believe this allows you to run 24V if you wanted to upgrade your power supply to that. Just remember that the bed can pull upwards of 400W on 24v which is around 20A. I believe the mosfet is rated to 60v http://www.st.com/web/en/resource/technical/document/datasheet/CD00002690.pdf

 

OK I'll do that Mike, thanks.

Les