Layer smash revisited...

My Z setps are: 3200/1.25 in Marlin

When I tell Pronterface to move Z 200, the X stage stops 200mm from it's start.

I've printed objects at .2 with little visible issues, however I printed this at a .15 layer height and got really bad layer smash.

I was watching and could see the trace thickness change from ok to rather think to 'Way too close thick' then the next layer is way too thin.

The resulting print is of course brittle at the junction of too thick a trace and too thin.

How can I fix this?

Thanks,

Hi, I have the same problem, will be following this thread. Printing on 0.25 with a 0.4 nozzle, it smashes some inbetween layers, but not all. I will open a new topic, with a video and pictures because there is more going wrong with my printer.

Are you printing at a layer height that is an even number of whole steps for your motor? Microstep positions are not accurate with a screw-driven Z axis (not sure about belt and cable systems on Rostock and Tantillus), so some layer heights will be too low, resulting in too much plastic for the real layer height.

Dale Dunn Wrote:
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> Are you printing at a layer height that is an even
> number of whole steps for your motor? Microstep
> positions are not accurate with a screw-driven Z
> axis (not sure about belt and cable systems on
> Rostock and Tantillus),

Although this is true it does not work as most people think. The only way it works is if you disable the microstepping on the driver board itself. The reason is when you home it will stop on a microstep and from that point on taking whole steps you end up stopping on the microstep every single layer. At that point you may as well be relying on the microstepping stopping at any point or take the plunge and disable the microstepping on the board.

With all that said I can not offer any help on the question at hand.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

Just another thought on this. Be sure you are not disabling the Z motor between moves. If you disable the Z motor between moves then relying on microstepping is a very bad idea for sure.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

Sublime Wrote:
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> Just another thought on this. Be sure you are not
> disabling the Z motor between moves. If you
> disable the Z motor between moves then relying on
> microstepping is a very bad idea for sure.


If these are the lines in Marlin,

// Disables axis when it's not being used.
#define DISABLE_X false
#define DISABLE_Y false
#define DISABLE_Z false
#define DISABLE_E false // For all extruders

I think I'm not.

Sublime's post made me think in other directions and I hate sitting and waiting for someone else to figure out my problems.

I re-checked the filament size and found I had transposed the last two digits. 2.79 vs 2.97.

Did a smaller print and it worked great, but still had very small lines in it.

Then it hit me! (Ouch.)

The Wallace I'm using in this print has a vertical X carriage, and I had noticed that when I hit the plate with the hot end, it was rotating upwards. ... (It shouldn't do that. It's on liner bearings... Unless....)

It turns out I had only tightened the lower bearing retaining screw enough to capture the belt. it does double duty. This allowed the X carriage to rotate on the top bearings a little.

I have now cranked that screw down. There is no longer any rotational play in the X carriage.

I'll post a pic of the next print.

Ok,

I thought it was the floating head problem I had before with a loose hot-end extender, but tightening the X-carriage on it's bearings didn't make the ridges go away. Although the appearance of thicker and thinner traces in the layers had gone...

So, I tried some other settings.

Different heights actually produce ridges at the same heights...


Remembering all the previous prints had been single wall and these have been double wall, I tried the outside first setting in Slic3r.


It reduced the visibility of the ridges, but they are still there.

So, the problem is definitely not rounding error in the firmware or a floating head.

....

Looking as the ridges next the the Z-rods, I AM now experiencing Z wobble.

I'm guessing when I fixed the filament size and tightened the X-carriage, it fixed the Layer squash, as watching the prints each layer now looked good, but because I was still seeing ridges, I thought it was still there.

The results of squash and wobble do look similar.

Now to look at the Z coupler I was having problems with...

Just an Update.

Worked on the Z-wobble issue.



Not completely gone, but much reduced.

I am now suddenly having the same issue. I fixed my hotend issue (it was not attached well enough in my extruder) and now I get a nice line profile all of a sudden.

Which I didn't have before! What!?...

Not sure what you mean by 'nice line profile'.

In my case, I'm using a Wallace design here and the Z motors are only mounted on one edge.

After I tightened the Z-Coupler that had gotten loose, I noticed the motor oscillating up and down as the rod spun.

I figured the motor must have been on an angle (being held only by the edge) when I tightened the coupler.

So, I designed a set of Z-motor support ends and installed them. Then I loosened the coupler and re-adjusted it with the motor vertical.

The prints are looking much better now.

I will be uploading those parts and more on Thingiverse soon. (Testing at the moment.)

Ah, I'm using a reprap Air 2, but will soon move my Z-motors to the bottom. I have found another guy who has done the same.

Yesterday I have ordered 2x aluminum Z-couplers. I wonder how they hold on to my stepper motors, because my stepper motor doesn't have a flat part so this means I have to tighten the bolts a lot on the couplers. I really hope they wont slip, but am thinking of making a flat side on my Z-axis stepper motors.

With 'nice line' I meant that I was getting a very bothering repetitive pattern on the sides of my prints. I was calling it 'nice' as a joke...

Nice to hear you have solved part of it! I am getting very close to having a new kind of heatbed/printbed design that diminishes the effect of heatbending on the heatbed. I am running into a very busy project week at the academy, so actually realising this design will take a few weeks from now, but when it's there I promise to share it.

Okay, I have solved most things, but now all of a sudden sometimes, I have the idea the Z-axis skips a few steps? It doesnt get hot, it doesn't really have much friction in going up or down, but just randomly it sometimes doesnt move up when it should and this means it prints two layers on the same height which means that small gaps are immediately closed up and the next layer it moves up, so it's actually 3 layers squashed in the area for 2 layers. It takes 2 more layers for the squashed layers to normalise again.

I don't know why this is happening, the motors don't shut off, and I can just manually move the Z-axis as much as I want.

I bought a digital caliper to calibrate my axes and I am sure that my axes are correctly configured. I have the values all with maximum of 5 decimals.

Should I maybe set even less decimals in my firmware, or can it be that there is a different problem?

I have locked my hotend completely, no movement up nor down, left nor right. The heatbed doesn't just jump up or anything, I have been constantly measuring and I sometimes can print nicely and sometimes randomly it just messes up a few layers.

This is driving me nuts.

That sounds like your Z-motor driver on the RAPMS(or other) board may be over heating.

It'll just pause long enough to cool down.

I ran into that when I first tried a real print on my Wallace. The cubes were small enough to not be a problem. Bigger prints soon had problems.

Usually when things are going wrong, I pause the print and raise the Z by 20mm. The over heating stepper driver caused this motion to be start-stop-start-stop rather than smooth motion.

Even more evident when homing the Z from a height.

I backed down the stepper driver voltage adjustment and been fine since. (Until the heat sink fell off today. )

Lance

Actually I can move the Z-axis up and down for 130mm and more in a continuous flow without any problems, the way back also no problem, even giving multiple commands which cause it to go 100mm up, down, up down so in total 400mm movement up and down, no trouble. I have improved thew Z-axis so much already, I have added good lubrication that is usually used for bearings, not oil but grease which stays in the thread.

I thought exactly what you mentioned, so I checked, calibrated the power to the Z-stepper and it's not this overheating problem..

It's incredibly unclear to me what can cause this.. I have noticed it doesn't happen on some prints, you can see my other topic with some pictures from what happens. And sometimes doesn't happen.