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xy size compensation for EM 2 pro
#1
Im using the printer to create accurate engineering models. Its well known that models are 0.1 mm bigger (ish) per layer due to light scatter exposing the outer edges making outer edges larger and holes smaller. So to compensate people have written tools to erode the image. Nothing works on EM 2 pro!.. even tried Z-suit slicer that comes with this feature, but mot supported on the pro 2. Anybody else having the same issues or have a work around?.
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#2
(12-13-2020, 12:11 PM)hardcak Wrote: Im using the printer to create accurate engineering models. Its well known that models are 0.1 mm bigger (ish) per layer due to light scatter exposing the outer edges making outer edges larger and holes smaller. So to compensate people have written tools to erode the image. Nothing works on EM 2 pro!.. even tried Z-suit slicer that comes with this feature, but mot supported on the pro 2. Anybody else having the same issues or have a work around?.

For what it's worth, the latest version of Chitubox supports compensation.
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#3
(12-13-2020, 12:11 PM)hardcak Wrote: Im using the printer to create accurate engineering models. Its well known that models are 0.1 mm bigger (ish) per layer due to light scatter exposing the outer edges making outer edges larger and holes smaller. So to compensate people have written tools to erode the image. Nothing works on EM 2 pro!.. even tried Z-suit slicer that comes with this feature, but mot supported on the pro 2. Anybody else having the same issues or have a work around?.

I'm only just getting started, so I won't be of much help, but my most recent print was almost spot on on X and Y, but WAY short on Z. Not sure if that is the Z axis, my settings, my resin, my model configuration  and orientation or some combination of the above.
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#4
These are hobbyist class printers built to meet a specific (low) price point--given that they work pretty good I calculated the percent of error and rescale my models as required, including modeling horizontal through holes as ellipses dimension-ed as needed and drilled/reamed to final size if necessary...
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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#5
I printed this last evening using a 50/50 mix of Siraya Tenacious and some cheap LAFVIN Standard Gray "ABS-like" resin:

[Image: 5mmStepBlockAnal-01.jpg]

It's a 20 x 20 x 25 mm step block with (5) 5 mm steps. Here's an analysis of the dimensions both before and after final curing:

[Image: 5mmStepBlockAnal-00.jpg]

As you can see, post final curing (it grew a bit), the maximum error was-1.20% at the height of the 3rd step.The block is as square in all planes as my 3" Starrett machinist's square can reveal. It has a 0.35 mm or so "elephant foot", easily removed with a triangle scraper or file.

For a $344  hobbyist level machine ($200 for the printer and $144 for the Z-axis mast upgrade) I cannot/will not complain about that level of accuracy. FWIW I suspect the Jackson mast has a whole lot to do with these results.

My next step is to clamp it in a vise and whack it with a 16 oz. ball peen to see how it stands up--I'll post photos once that's done...
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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#6
OK, the destructive test:

I clamped it rather firmly into my small bench vise ("upside down" at the third step):
[Image: StepBlockSmash-00.jpg]

Then whacked it (one good sharp blow) with a 16 oz. ball peen:
[Image: StepBlockSmash-01.jpg]

It held up pretty good for a 3-D printed thingy (you can see the indentations from the vise jaw):
[Image: StepBlockSmash-02.jpg]

Again, a 50/50mix of Tenacious and some cheap gray crap.

Seems like good mix, now I need to print some sort of real component...
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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#7
@cliffyk

nice to see your printed stairway-model - i have do the same - other model but same idea.
I have a EMPro2 and can not became correct results. I have a model with round cylinders with stairway on the innerside.
First level is 3,07mm and should 3,1mm - that okay i think so - but the next level is 8.08 mm instead of 8,5mm!

I have test these problem several times - send to elegoo support and they print it with the same problem - after that i don't hear anything fromt he support.
I have send the CAD-Model which is still accurate and the print-file - and also they have sliced by its own and still same problem.
Looks like is probem for the printer-firmware if the print circles and have different levels of z-axis!?
Undecided
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#8
(02-20-2021, 12:01 PM)cliffyk Wrote: As you can see, post final curing (it grew a bit), 
I have to admit, I am very surprised to see that it grew in cure. 

My experience has been with wax injection and metal veramic molds and those both shrink - although both of those go from a molten state to solid.

If I can come up with a way to check Z travel, I want to check repeatability. Given that the Z axis goes up and down a boatload of times, if there were a following error, it could quickly compound itself.
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#9
Most materials shrink when they cool¹--however the final cure of this stuff is not a cooling process but rather further polymerization.

-------------------------------------------------
¹ - There are low-melting point fusible alloys containing bismuth. iridium and the like that expand when they solidify--or shrink at frst then grow sometime after.
-cliff knight-
[Image: 816-20120803-wide800.jpg]
paladinmicro.com
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#10
(02-22-2021, 09:21 AM)cliffyk Wrote: Most materials shrink when they cool¹--however the final cure of this stuff is not a cooling process but rather further polymerization.

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¹ - There are low-melting point fusible alloys containing bismuth. iridium and the like that expand when they solidify--or shrink at frst then grow sometime  after.
I have worked with this stuff quite a bit and it is dimensionally stable - zero shrink when it cures - so I was surprised that these polymers grow. Typical materials shrink or stay stable, except things affected by humidity so this is a bit of a paradigm shift for me.
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