Motors do little steps, not big ones.

Hi there,

I'm building an i3, it's mostly complete. Electronics are Mega 2560 + ramps 1.4 running marlin. FYI I bought it all as a kit from these people via Amazon. It's been a mixed bag so far, but I'm generally pleased.The printed parts aren't great quality, some of the bits are wired wrong (end stops) and the instructions stop just after the basic frame construction, but all the bits were there, just required a bit of perseverence.

My specific problems:

Running pronterface, I can click the buttons to move the x and y. If I click for small intervals, there is movement. For longer distances, you get a shudder, then a whining noise and that's it. Any ideas?

The Z axis isn't working properly at all. All the steppers came with connectors on, but they are too large to fit two abreast as required on the Z axis. Initially I wired them together directly and connected to one row of four pins out of the available 8 pins.
What I have now is, with one motor connected I can repeat the behaviour seen for x and y (small movement fine, large movement, whine + click), but with both connected, you get some noise, but nothing concrete.

The Z motors are currently disconnected from the shafts, so they are not under load at all.

I've experimented with the order of wires for a single, unloaded Z motor, but nothing helps (Obviously the "bad" orders just don't do anything).


Finally, an easy one. I want to buy some connectors to rewire some parts.I've attached a picture of what I want (borrowed from NextDayRepRap.co.uk). What are they called? The author mentions Molex, but I'm only finding large power supply type connectors when I search for that.

Many thanks in advance.

Your max feed rate is probbly to high. once they get out of the accleration curve phase the steppers are trying to move to fast

try a contolled move eg G1 X10 f300, ie move to X10 at feedrate 300. This should move any distance, but slowly.

If you take a look at the top of pronterface there is a section x/y mm/min, this is the max speeds for manual moves in the X and Y direction. lower that till it works, then set your max fead rate to those numbers. then gcode cant move faster than your hardware limitations

Also, acceleration is set too high per default in most firmwares. 9000 mm/s² is ridiculous, 1000 mm/s² is much closer to what typical printers can achieve.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Thank you both, I will try that this evening and report back

Thanks again, that seems to have solved the first problem. I changed the X/Y to 300 which works a treat. Z I had to change down to 10. Any high and it won't work. I assume this is because one revolution of the motor spindles in Z represents less distance than one turn of the X and Y motor spindles.

Interestingly, the home buttons (sort of) work. X and Y do a high pitched whine, then suddenly whap the bed back to its homed position against the stop. Z just whines and does nothing. I'm guessing the home buttons home at a preset speed, I did turn on debug codes, but wasn't paying enough attention. I'm assuming they send a code for "Move towards minimum until endstop is triggered" with a speed that's too fast.

Question: I want to check the stepper drivers are configured with the correct output voltage. Any idea which pins I measure across? These are the drivers I have. From the picture it should be easy to probe the terminals at the pot, but in reality I can't hit those points.

The end stops and motors were all wired up backwards, I now have minimum Y as the bed as far from me as possible which seems counterintuitive to me. I should probably check that too.

Whining motors mean, they're working. Some firmwares require to set homing/endstop search feedrates separately from general max feedrates.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

For me it seems like problem with microstepping. Have you installed all jumpers under the motor drivers? Is it corresponding whit microstepping setting in your firmware?

Ah... Jumpers? I didn't configure any jumpers under the drivers, but now I think of it there are pins on the RAMPS under the drivers which I meant to look up. Do you have any idea how they are configured? I'll try and find some clues independently, but it's not in any of the build docs I've read so far.

This mentions them, so I'm going to try with three on each and see what happens. I'll update once I do it.

Thanks

3 under each driver will give you the full 16x microstepping.

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Waitaki 3D Printer

Yes, with three on each, I have silky smooth but very slow (scaled down) movements. Curiously the printer also hits an invisible max stop in all axes.

So two questions:

1) How do I ascertain what level of microstepping I require?
2) Will this necessitate a change in the Marlin code? I have another question related to Marlin which I will ask in the correct forum.

I've found the table defining the three stepper jumper setting options here

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UkIan
1) How do I ascertain what level of microstepping I require?

There's no fixed requirement, in principle all settings work. That said, 1/16 for belt driven axes and 1/8 for threaded rod driven ones is a good choice.

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UkIan
2) Will this necessitate a change in the Marlin code?

Not code, but its configuration. See e.g. [reprap.org] Adjust steps/mm for your microstepping, not the opposite way.

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Generation 7 Electronics	Teacup Firmware	RepRap DIY

Excellent guide. Thank you for that. Fingers crossed I'll be up and printing this weekend

It's working, but I don't know why.

The Z is not doing what I expect.

I've had to change my steps per unit to:

#define DEFAULT_AXIS_STEPS_PER_UNIT   {80,80,2000,237}

Where 4000 is expected.

In configuration_adv.h I've been playing about. We have

// Microstep setting (Only functional when stepper driver microstep pins are connected to MCU.
#define MICROSTEP_MODES {1,1,1,16,16} // [1,2,4,8,16]

Note: the values were all 16 to start with, I tried 1's to see if it made any difference to anything. They don't. My drivers are configured on RAMPS as X 16, Y 16, Z 8, E 16 (TBC).

Is there somewhere else I configure stepping? I'm now using the Marlin version direct from Github.

Thanks