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Thick8

Everything is about .4 mm too big

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Posted (edited) · Everything is about .4 mm too big

 

Hi All,

Total NOOB to making here so please be gentle.

I’m making some interlocking pieces. Basically a rectangular box made from 6 panels with tabs around the edges. I printed one out to measure; the overall measurement of the piece is .4mm bigger and all the tabs around the outside edges are .4mm wider than specified. And the area between the tabs is about .3mm narrower than specified. STL attached.
I printed it with a .4mm nozzle using the default .2 mm print setting. If I print it using the fine setting can I expect better results? I have smaller nozzles but I can't select the size I have in the core drop-down. Any help would be appreciated.

Thanks 

John

front.stl

Edited by Thick8

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Posted · Everything is about .4 mm too big

I printed the first few layers at .1mm, Same issue.

Is a printer similar to a CNC cutter? It would seem that the amount in excess is half the width of the line width x2 for an outside measurement. Do I need to take line width into account? Is there a way (like with a CNC) to choose "inside the line" instead of "on the line" so it will make the necessary adjustments in the software?

 

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Posted · Everything is about .4 mm too big

The nozzle width is compensated for by cura.  For example if you slice a cube that is 100mm on a side, the nozzle will traverse 99.6mm along each edge because it is printing inward towards the center of the cube by 0.2mm on all 4 sides (0.2 is the nozzle radius).

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Posted · Everything is about .4 mm too big

1) where did you measure your part - the bottom layer or two will usually stick out - this is important to get the part to stick well to the glass.  You can fix this (and I usually do) by setting "initial horizontal expansion" to around -0.25.

 

2) What kind of printer is this?  I might change all my answers depending on what printer you have

 

In general the slower you print the better the accuracy and it's also really good to turn off jerk and accel control if you want accurate parts and don't care how pretty they are (everything is a balance so you have to pick what is most important and in your case it is dimensional accuracy).

 

So the default profiles in cura never rarely change even though wonderful features are added every month.  Here is (from Ultimaker) the recommended settings for uglier and slower but dimensionally accurate prints (30mm/sec will be even better):

 

dimensional accuracy profile - engineering settings  - accuracy mode - meant for 0.4 nozzle
Line width: 0.4
Wall thickness: 1.2
Top/Bottom thickness: 1.2
Speeds: 35-40 (all 7 or so speed settings, except travel)
Jerks: 20
Horizontal expansion: -0.03
walls: 3
Inital Layer Height = 0.1
Slicing Tolerance = Exclusive
Combing Mode = off
Outer before Inner Walls = Checked

 

I recommend also turning off both jerk and accel control and setting initial horizontal expansion to roughly half the nozzle diameter.

 

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Posted · Everything is about .4 mm too big

Hello and thank you for the detailed response.

 

1. I first printed the part that I attached in it's entirety using the default 0.2mm settings. Then I printed the first 6 layers with the engineering 0.1mm settings. Both times I had the same amount of oversize.

 

2. It's a Snapmaker original printer. It's a neat little machine that allows me to print, engrave, and cut. I've used all three features for my flight simulator "stuff". Got it NIB from a guy on Craigslist for $500. Been wanting to do this for years but the price of 3 separate machine was WAY to cost prohibitive.

 

I used Fusion360 to built the components and save to STL files. 

I used the press/pull feature to make the .2mm adjustments to the file and am now printing it at the engineering 0.1mm setting.

 

Cura does seem like a very powerful piece of software. You have probably seen this https://all3dp.com/1/cura-tutorial-software-slicer-cura-3d/. I'll be spending some time with it this evening.

 

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Posted (edited) · Everything is about .4 mm too big

@gr5 You da man! I printed it with your settings and everything is within .02 mm.

THANKS!

Edited by Thick8
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