SOLVED Everything is about .4 mm too big

[Thick8 1]

 

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 March 22, 2020 by Thick8

[Thick8 1]

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?

 

[gr5 2,172]

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).

[gr5 2,172]

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.

 

[Thick8 1]

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.

 

[Thick8 1]

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

THANKS!

Edited March 23, 2020 by Thick8

[paxpring 4]

On 3/22/2020 at 7:43 PM, gr5 said:

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.

 

 

I know my message is a bit late considering this thread took place back in March but I was struggling with this issue too. I know now what the solution is thanks to your response, yet, I am still left with one question. 

 

I am into 3D printing for several years now and for my employer I've bought the UMS5 and your statement (highlighted above) got me puzzled. How come 'dimensionally accurate' goes hand in hand with 'ugly' prints? Would you be willing to elaborate on this? 

[m12lrpv 0]

On 8/3/2020 at 11:08 PM, paxpring said:

 

I know my message is a bit late considering this thread took place back in March but I was struggling with this issue too. I know now what the solution is thanks to your response, yet, I am still left with one question. 

 

I am into 3D printing for several years now and for my employer I've bought the UMS5 and your statement (highlighted above) got me puzzled. How come 'dimensionally accurate' goes hand in hand with 'ugly' prints? Would you be willing to elaborate on this? 

 

There's no correlation whatsoever between dimensional accuracy and the visual quality of the print.

 

I too have been printing for years and it wasn't until I got a printer where I could adjust the step's /mm of the printers x, y and z axis and e-steps for managing wall thickness to tune the printer to be dimensionally accurate in all 4 dimensions (wall thickness being the 4th) that i realised that compensating for it in the printer is the right way to do it.

 

If you don't have the ability to do that then cura has some options to try and help compensate which is great and why so many people use it.

 

[ftoons 5]

Hello,

Just wanted to add that the settings posted by Smithy in post linked below are great for improving tolerance.

Here it is:

 

[ftoons 5]

1 minute ago, ftoons said:

Hello,

Just wanted to add that the settings posted by Smithy in post linked below are great for improving tolerance.

Here it is:

 

 

 

they are a bit slow though, and there are a lot of retractions causing stringing in prints, and perhaps this can be tweeked.

 

I'll check out the engeneering settings posted by gr5 and hope they are better.

 

Thanks.

 

[Smithy 1,144]

Basically there is no more need to use these settings, because Cura has now included the Engineering settings when you have an S3 or S5. The settings I posted sometimes ago or the GR5 settings were the "Beta" version of the now included settings.

[Smithy 1,144]

Ok, just have seen you are using an UM3 and unfortunately the engineering intent settings are not available for the UM3. But there is no much difference between mine or gr5 settings and the Cura engineering profile. I still use this settings on my UM3 and I am happy with it.

 

And the slowness is one of the key points to dimensional accuracy, so don't print too fast.