Visualizing 3D Printed Thread Dimensions

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Quark
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Re: Visualizing 3D Printed Thread Dimensions

Post by Quark » Tue Nov 17, 2015 11:13 am

Very nice!

Calpoog
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Re: Visualizing 3D Printed Thread Dimensions

Post by Calpoog » Sun Nov 20, 2016 6:00 pm

I'm having trouble getting my first layer correct. I was able to get the wall thickness just about right by adjusting the extrusion multiplier, but the first solid layer is always so thin. My first layers do not at all look like the beautifully squashed layers of the blue lines in the initial picture. My first layer does not appear to be squished at all. Infill on the top solid layers are squashed and actually touch, but a single bottom layer on these thinwall boxes, the lines for the infill easily separate and don't even touch in most places. I used a metal .25mm feeler gauge for a nice tight fit, so it shouldn't be a question of my z-height.

Check out the attached picture. That's the thinwall box provided from the tutorials with a single bottom solid layer. The wall thicknesses are pretty consistently .40mm. The height of the model is 2mm and the height comes out at 2.17mm. I have my layer height in S3D set to 0.25mm. Is this just a property of the fact that 0.25mm heights can't add up to 2mm? Also, what would happen if I used the standard S3D medium quality layer height of 0.2mm? If the bed is set to 0.25mm manually, does it know to adjust smaller if I choose to print at a higher quality with smaller layer heights (or is that where first layer height should be adjusted?).

My biggest issue is how sparse the first infill layer is. The top layers of other items I have printed are very flat with no gaps between threads. I guess I'm mostly confused that I did a bed leveling with 0.25mm, my extrusion width is 0.4mm and yet it doesn't appear to be flattening the first layer. Any help would be greatly appreciated!

EDIT: I took Jule's advice about adjusting the Z-offset in the g-code tab. It helped immensely! Is this something I would need to do every time I adjust the layer height for different qualities? Should I re-level the bed with a 0.15mm feeler gauge so all my future z-offsets will be positive? Or should I just be okay with the 0.25mm bed leveling that I did and have potential negative and positive z-offsets based on what layer height I'm using? (many thanks jules). I guess my final question would still be why then if I leveled at 0.25mm with a 0.4mm extrusion width and proper wall thicknesses was I not getting the first layer I needed without adjusting the z-offset? Understanding all these individual things is definitely helping me along.
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Jules
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Re: Visualizing 3D Printed Thread Dimensions

Post by Jules » Sun Nov 20, 2016 6:36 pm

Your nozzle is still just a hair too far away from the bed. If it starts a little bit closer, it will squish the thread just a bit more like it is supposed to.

I'm guessing you have the Rev.E? The easiest thing to do to fix it, because you are just about as close as you can physically get it using a gauge, is to adjust the starting height using the codes Steve posted here:
sthone wrote:
From the Command line in S3D

First Type M501 to read the EEPROM parameters
Look for the M206 line. (it should look something like M206 X0.0 Y0.0 Z4.20)
You can then adjust it using M206 Z[new value] (so add or subtract your .02 to what ever yours was to raise or lower the starting height)
and then M500 to save it to the firmware.

This is an excellent way of fine-tuning the gap between the bed and the nozzle. If you add +0.02 to the Z value from the M206 line, you will move the bed 0.02 mm closer to the nozzle, making the gap smaller.
If you subtract -0.02mm, you will increase the gap and move the bed farther away.

You could make an adjustment of about 0.04 mm, and it should tighten that right up. :D

(And Ed, who did the initial post, is a Thread Master.....it might take you a while to achieve the perfection he can whip up. Don't worry about it too much if it doesn't look quite the same. Just make sure it is solid.) :lol:

Calpoog
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Re: Visualizing 3D Printed Thread Dimensions

Post by Calpoog » Sun Nov 20, 2016 6:56 pm

I took your advice from another thread and set the z-offset to the difference between the desired 2mm and the 2.17mm it came out. That made the first layer nice and flat and shiny and actually connected! It also made the height 2mm exactly. However, I do wonder (-0.17mm offset seems like a lot) that if some of the difference in final height was due to the fact that 0.25mm doesn't go evenly into 2mm. For instance, if I changed my layer height to 0.15 or 0.2 and reprinted, would my -0.17mm z-offset make the nozzle drag?

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ednisley
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Re: Visualizing 3D Printed Thread Dimensions

Post by ednisley » Sun Nov 20, 2016 7:53 pm

Calpoog wrote:-0.17mm offset seems like a lot
Remember that 170 µm is about as good as you can get with a mechanical setting; it's 200-ish wavelengths of deep red light and two or three hairs. To get closer than that, you must tweak the offset in software.
0.25mm doesn't go evenly into 2mm
All the coordinate values get converted into steps and the hardware doesn't care about anything else. The Z-axis stage moves at 400 step/mm (*), so each step is 2.5 µm and (for example) the difference between 0.20 mm and 0.25 mm amounts to 20 steps: not a problem.

The initial Z offset ensures the hardware will produce the correct first layer thickness, regardless of that thickness: you're promising that you've measured the actual thickness and have provided the offset that makes the answer come out right. After you've defined the Z=0 position, all the layers Just Work.

(*) The New Shiny Z-axis takes smaller steps, but you get the idea. When you use stupid-small layer thicknesses, then you must take mm-to-step rounding into consideration; that's why smaller Z-axis steps are now a thing.

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Jules
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Re: Visualizing 3D Printed Thread Dimensions

Post by Jules » Sun Nov 20, 2016 9:32 pm

Do you have the Rev E machine? Or one of the older ones? You need to use the right method for your machine if you want to be able to fine-tune the output, and the steps are different for the newer machines. (Just want to make sure you went to the right place.....did you use the QuickStart App to set your initial gap?)

Calpoog
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Re: Visualizing 3D Printed Thread Dimensions

Post by Calpoog » Sun Nov 20, 2016 10:11 pm

Yep, quick start app on the Rev E machine using a new metal 0.25mm feeler gauge!

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Jules
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Re: Visualizing 3D Printed Thread Dimensions

Post by Jules » Sun Nov 20, 2016 10:39 pm

Calpoog wrote:Yep, quick start app on the Rev E machine using a new metal 0.25mm feeler gauge!
Okay....it's pretty important that you only use the techniques that work for your machine, and when you said that you had to make a 0.17 mm adjustment I suspected that you got hold of one of the posts that was written for the old machines, not yours. The new machines are not adjusted using an offset to the Global Z-Offset in S3D...mainly because you generally have to make a really large adjustment before it registers.

It has to do with how the starting point is calculated in the new firmware - it's different from the old machines. (Yours zeros at the bottom, theirs is at the top of the Z-shaft.)

You can modify your gap using the write-up here:

viewtopic.php?f=3&t=3666

And you want to read the Beginner's Guide here for more explanation of what is going on with the newer machines:

viewtopic.php?f=3&t=3542

There are a lot of conflicting instructions on the forum because of the machine change. Some of them no longer apply to the new machines, but folks who still have the old machines still need them so they get left in place.

You did figure out what the issue was, so that should take care of it. (And with the new machine - you only have to do this ONCE. You do not have to re-set the gap every time you switch filaments.)

:D

Calpoog
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Re: Visualizing 3D Printed Thread Dimensions

Post by Calpoog » Mon Nov 21, 2016 3:13 am

I did work through the Rev E beginners guide. But I guess I may be a bit more confused now... According to the perfect first layer post let's say my layer heights are supposed to be 0.25. Why then do I do z-height adjustments (with M500 and whatnot) after having gone through the entire bed leveling process with a feeler gauge of 0.25mm. Shouldn't the first layer be perfect without any adjustments? Or is that why things were too tall on the first layer to begin with: because I did it with a feeler gauge of 0.25mm and the first layer assumed a bed leveling with the piece of plastic at 0.13mm, and therefore the 0.12 left over it normally would assume instead makes it 0.37 (and therefore too tall)?

I guess what I'm trying to ask is: When I tell the machine, say, I want layer heights of 0.25mm, I would assume that it also assumes the first layer should be 0.25mm. Does it do a gcode command to set the height to 0.25mm (and add in EEPROM z-adjusted settings) or does it assume a height of 0.13-0.15mm default of the nozzle being off the bed and set the initial gcode to go to 0.12mm to print the first layer? Every layer afterward is a simple previous+0.25mm but what's confusing me is what factors and assumptions are made by the machine for the first layer. :?

Thanks for all the help, headway is being made lol.

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Jules
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Re: Visualizing 3D Printed Thread Dimensions

Post by Jules » Mon Nov 21, 2016 6:06 am

You actually want to use the gauge of 0.13 to 0.15 to set the gap for your machine, because the firmware compensates for it. (That's the ideal gap - not the ideal layer height.) The machine will move away enough to give you the correct layer height for whatever you tell it you want it to be.

(Really don't have to worry about that sort of thing if you set the gap correctly once. Makes the new machines very easy to use.)

Use the Perfect First Layer post only to see what a perfect first layer looks like.....the instructions are written for the older machines, where we had to actually take all of those things into consideration. :D

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