Build Issues - Z-axis

OK - I've found some issues with my build that have brought up questions I have for Sublime. I also hope that pointing these out might help other builders.

1 - max build height I'm getting is only ~93mm. I'm wondering how I can eek out that last 7mm? (see image)

2 - still having issues with getting the build platform any closer to the extruder than this. (see image)

3 - I'm getting interference between the platform and the SD card reader. I've reduced the Arduino standoff heights from the recommended 5-10 mm, to about 3mm, and shifted the Z-axis over as far as it will go, but there's still interference. (see images).

Thanks!

ernchesto Wrote:
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> 1 - max build height I'm getting is only ~93mm.
> I'm wondering how I can eek out that last 7mm?
> (see image)

See the answers below.

>
> 2 - still having issues with getting the build
> platform any closer to the extruder than this.
> (see image)

The endstop needs to be higher. The wires can be bent over easily, its just the shrink wrap that is making them feel hard.

>
> 3 - I'm getting interference between the platform
> and the SD card reader. I've reduced the Arduino
> standoff heights from the recommended 5-10 mm, to
> about 3mm, and shifted the Z-axis over as far as
> it will go, but there's still interference. (see
> images).

This is my fault. I switch to SDramps from a universal SD card reader and then tested it on one of my earlier machines which must have the Ramps board mounted lower. Just leave it for now and I will get a cable made up for everyone to relocate it. This will also allow the bed to go down lower and increase the Z height. I should be able to send all the parts off to everyone next week.

I apologize for any inconvenience these things have caused anyone.

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Anyone have any ideas why one wouldn't be able to nudge the z-axis upward (Z+) - it refuses to move any closer to the endstop than about 40mm. When I Z-home, it immediately blasts right up to the endstop.

The reason I ask (aside from the obvious) is that I've shifted the endstop as high as it will go, and I don't want the extruder tip to smash the glass.

Strange, I thought I responded to your post Brad, but I don't see it here. Must have hit a wrong button.. It went something like this:

- Thanks for the answers. No worries about the inconveniences, it's a pretty complex piece of kit.-

Well - I just experimented with jamming the extruder tip through the glass.

Background: my X has been somewhat absent since I messed with the servo pot bidna. I actually swapped it out with the extruder one and it worked a bit - so I turned it up (clockwise) a few degrees, and there it was - gone! My Y works pretty well in one direction, but the other is limited.

Anyway, I just hit X-home -> no response; hit Y-home -> somehow this was interpreted as Z-home I watched closely, like a deer in headlights, as the bed came right up to the tip, and glanced off it thanks to it being at the furthes point on the X+ location.

Needless to say, had the print head been in 99.9% of the other potential places it could have been, I would have had the pleasure of smashing the glass. Feeling rather lucky. Had to share.

LOL nice little story and good use of emoticons, I actually kinda felt like I was there with you.

So does this somehow mean that the Z-axis moves when you hit Y-home as well as Z-home?

No idea on your Z-axis question above btw.

Glad you enjoyed Eric - to be truthful, I've been dying to use the beers clanging emoticon. That thing is awesome

Yeah, pronterface thinks Y-home is Z-home. To be fair, I've not yet set a home location. So I'll cut it some slack until then..

ernchesto Wrote:
-------------------------------------------------------
> Anyone have any ideas why one wouldn't be able to
> nudge the z-axis upward (Z+) - it refuses to move
> any closer to the endstop than about 40mm. When I
> Z-home, it immediately blasts right up to the
> endstop.

Z+ is down.

It will never go negative any further than it has gone positive unless it is homing. To work around this you can type in G92 Z40 in the little text field at the bottom right. This will tell the machine it is already at 40mm+ so you can go negative as much as 40. Use any number you would like up to 100. Be careful it does not try and go to high. My suggestion is to lower the bed all the way down and then press the Z home button and while it is moving try pressing the endstop and see if it stops. If it does not stop you will need to unplug the machine to stop it. If it works then you should lower the endstop and press Z home.\ and slowly raise it up until it makes the bed stop right at the glass. You can fine tune the Z starting height in Slicer (Z offset)

>
> The reason I ask (aside from the obvious) is that
> I've shifted the endstop as high as it will go,
> and I don't want the extruder tip to smash the
> glass.

---

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ernchesto Wrote:
-------------------------------------------------------
> Background: my X has been somewhat absent since I
> messed with the servo pot bidna. I actually
> swapped it out with the extruder one and it worked
> a bit - so I turned it up (clockwise) a few
> degrees, and there it was - gone! My Y works
> pretty well in one direction, but the other is
> limited.

Let me think about this one. I am not sure what would cause this. If it is the driver I will just replace them do not worry.

>
> Anyway, I just hit X-home -> no response; hit
> Y-home -> somehow this was interpreted as Z-home
> I watched closely, like a deer in headlights,
> as the bed came right up to the tip, and glanced
> off it thanks to it being at the furthes
> point on the X+ location.

Home X ad Home Y are disabled in the firmware because it does not have X and Y endstops.

Can you try typing in G28 Y0 and see if the Z moves? If it moves it is a problem in the firmware that i will have to look into. If it does not it is a problem with the pronterface button.

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Home for X and Y is the back right corner and you just put it there before turning on the machine.

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>"Can you try typing in G28 Y0 and see if the Z moves? If it moves it is a problem in the firmware that i will have to look into. If it does not it is a problem with the pronterface button."

tried it and it set Z - home, nothing more.

BTW - I learned last night not to 'put' the XY anywhere while the machine was powered on! I did in a fit of fatigue and f*^ked all the cable tension up!! Good practice. Not fun practice.

Also - BTW - I think I've got the bed levelled to a place that "I'm happy with" - we'll see what the extrusion thinks of it..

ernchesto Wrote:
-------------------------------------------------------
> >"Can you try typing in G28 Y0 and see if the Z
> moves? If it moves it is a problem in the firmware
> that i will have to look into. If it does not it
> is a problem with the pronterface button."
>
> tried it and it set Z - home, nothing more.

What do you mean it set Z home? Did you type it in the little text box on the bottom right?

>
> BTW - I learned last night not to 'put' the XY
> anywhere while the machine was powered on! I did
> in a fit of fatigue and f*^ked all the cable
> tension up!! Good practice. Not fun practice.

Yeah you may be able to tighten the bolts that hold the cable a little tighter but you will never be able to move it with the power on. The motors produce a few kg of holding force.

>
> Also - BTW - I think I've got the bed levelled to
> a place that "I'm happy with" - we'll see what the
> extrusion thinks of it..

Small prints will work but odds are that large ones will show how one corner is a few micron low or high. Levelling the bed is always "Its perfect" and then "never mind it was still out a little". This happens with all the machines.

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Quote

Let me think about this one. I am not sure what would cause this.

It is because the sense resistors are replaced with zero ohm links.

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[www.hydraraptor.blogspot.com]

nophead Wrote:
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> Let me think about this one. I am not sure what
> would cause this.
>
> It is because the sense resistors are replaced
> with zero ohm links.


Have you even tried yours yet? Last time you said they were no good but never tested them so how do you know? I have many running and do not have problems.

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Sublime Wrote:
-------------------------------------------------------
> ernchesto Wrote:
> --------------------------------------------------
> -----
> > >"Can you try typing in G28 Y0 and see if the Z
> > moves? If it moves it is a problem in the
> firmware
> > that i will have to look into. If it does not
> it
> > is a problem with the pronterface button."
> >
> > tried it and it set Z - home, nothing more.
>
> What do you mean it set Z home? Did you type it in
> the little text box on the bottom right?
>
Z-home meaning endstop. Roger that on typing the G-code into the little box.

Sublime Wrote:
-------------------------------------------------------
> Have you even tried yours yet? Last time you said
> they were no good but never tested them so how do
> you know? I have many running and do not have
> problems.

Yes I tested one. All the adjustment is in the first few degrees of the pot as would be expected. The only reason it works at all must be the parasitic resistance of the links and the PCB traces.

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[www.hydraraptor.blogspot.com]

nophead Wrote:
-------------------------------------------------------
> Yes I tested one. All the adjustment is in the
> first few degrees of the pot as would be expected.
> The only reason it works at all must be the
> parasitic resistance of the links and the PCB
> traces.

I have some of these same stepper drivers. What resistance should the sense resistor be so I can order a few on my next electronics order? And the sense resistor is the one located right next to the pot, right?

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The sense resistors should be 0.05 ohms on a Pololu. There are two of them close to the motor connector. The incorrect ones are labelled 000. The ones I have from Pololu have no markings and are green.

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[www.hydraraptor.blogspot.com]

So does this mean that the stepper drivers/heat units we have with our Tantillus kits are not what we should be using? I'm confused, because my Z and Y seem to be working fine. My X doesn't work aside from the odd hellscreech it gives out (without any notable motion), if it cares to give that much. And I've not seen my extruder motor turn yet (I'd replaced the stepper driver with the one I'd tried adjusting the pots screw [I think that's what it's called] to get the X working.

So it seems that they work fine, unless I go and try to increase the voltage with the adjustment screw, which I'm at a loss for finding any feedback mechanism for - visual or tactile - aside from: turn>re-plug-in machine>test >> repeat.

I'd really like to get this figured out so that I can start testing. I did just send a test print through (no filament loaded), and it came alive, fans worked, everything was great - except that the only motion was along the Y and Z axis.

I've not had much luck finding documentation on this aside from what's been said in this forum and this, from [wiki.ultimaker.com]:

Tuning the stepper motor drivers
On the little stepper driver boards (see picture on the right) that are inserted into the electronics, there are trimpot's that can be screwed clockwise or counter-clockwise.
The pre-mounted Ultimaker stepper drivers come pre-configured with a sane setting, but you might want to tune it to work better in your climate. Below are some instructions.
If a stepper board overheats, it will shut down for a short while, leaving the motor alternating bewteen a powered and unpowered state. This means they are overpowered and/or undercooled. You should lower the power setting by turning it counter-clockwise, slightly. For the extruder motor, you might experience this as a clicking or ticking sound, like in an old antique clock.
To know exactly how much you've turned it up, please turn it counter clockwise first. It will go until about 7:30 O'Clock, where it reaches a stop. The top is half-way.
Note: the instructions above seem to be outdated. The potentiometer on the UltiStepper driver shipped with current Ultimakers doesn't seem to have mechanical end-stops.
Warning: from personal experience, it seems to be possible to destroy the UltiStepper by tuning the potentiometer while running in Laid-back mode without cooling. Don't do that. On the plus side, reducing the current really does wonders against the noise. --Maxy 22:47, 28 June 2012 (CEST)
The potmeters on the motor drivers should NEVER be turn up more than half way.

No there is nothing wrong with the drivers except the current adjustment is more sensitive then the Pololu ones. There are hundreds and hundreds of these driers from RepRapDiscount out there in use and no one that I know of has had a problem due to the difference. If you do find one that does not work I will be happy to get you a new one.

To get the current just right you can adjust it while the power is on and you are trying to move the axis. Just be careful not to short anything out on the board with your screwdriver and do not turn the driver up to high (over 50%).

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Well that sure speeds things up by not shutting the power off each time! I was being cautious. BTW - the one for my X axis is labelled as a Pololu md09b - so I'm guessing that this is supposed to be less sensitive/easier to adjust. Well, I must be really bad at this because I can't seem to get this guy to wake up. I've increased the current in ~ 5degree increments all the way around. Did a bunch of cclockwise turns to 'reset' to zero (if this is possible. Anyway, no luck on this one.

Is there a way that I can test the extruder motor that I'm not seeing in pronterface? When I did a dry run (no filament), the extruder wasn't turning, and I'm not sure if it's just smart that way, or if it should have been mindlessly feeding imaginary filament. Thus my question - what is the easiest way to test that the stepper driver is working for the extruder?

And one last question - any ideas on why my Tantillus interprets the Y-home button as Z-home?

Thanks!

To test the extruder you need to have the hotend heated. Or type in M302 which will allow cold extrusions.

The z moving when pressing the y home is a bug in marlin that I need to find and fix.

---

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Sublime Wrote:
-------------------------------------------------------
> Just be careful not to short anything
> out on the board with your screwdriver and do not
> turn the driver up to high (over 50%).

50% ?

On a genuine Pololu that would be 2A which is not achievable due to poor thermal layout. About 33% is as high as you can go. Temperature rise is proportional to current squared so it is very critical at the top end.

With the zero ohm links it is super critical because it is less than half, so about the first 6th of the pot's range is usable. It will vary from batch to batch because the trace resistance depends of the plating process, which is very variable. That is why the Prusa heated bed has not be plated.

Edited 1 time(s). Last edit at 08/23/2012 05:32AM by nophead.

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[www.hydraraptor.blogspot.com]

Sublime Wrote:
-------------------------------------------------------
> To test the extruder you need to have the hotend
> heated. Or type in M302 which will allow cold
> extrusions.
>
Sweet - Gracias.

> The z moving when pressing the y home is a bug in
> marlin that I need to find and fix.

Good to know, thanks!