Printing Tips/help


#1

Hi,

Any suggestions on how to get a perfect print for a file like this? I find that i can’t get it as nice as I think the printer can handle. The mounting bosses did not come out so well, I’m not getting a shape that I’d consider good enough.

I want to try printing straight from the build plate, in theory that should offer a very good print finish.

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#2

I would definitely try to print it flat on the platform with the cavity pointing up (like the lower image). I would only need to support the openings.

You should also consider that the first few layers are heavily compressed, so you should add some additional thickness to the bottom (your top cover as it were).

My printer compresses the bottom layers by about 0.6-0.7mm, yours may be different. Print a small cube of a known dimension directly on the late, and then measure the height to see how much you need to adjust your model by.

You may also have to sand the surface once you printed it, as it will probably have the marks on it that are on your build plate., but that should only be minor.


#3

In PreForm 3.0, there’s an option to do this scaling w/o modifying your model. You still need to know the correct adjustment value for your printer. You can find the details on this page:

https://support.formlabs.com/s/article/Advanced-Support-Structure-Settings

In the section titled “Adjusting the Z-compression correction”.


#4

With the Preform screenshot you show, the bosses might come out better if you add some support to them. Minimal as it is, the walls have a path of support all the way up in the screenshot, but the bosses don’t have as much as they need.

If you do print it flat on Form 2, you’ll probably need to add some vent holes just off the biggest flat surface to avoid cupping, and maybe a chamfer to aid in removal. That could work well with very little support material except for the wall holes.

In my opinion/educated guess, you’d actually be best off with the cavity facing the build platform at a moderate angle - maybe a 30 degree tilt on X and Y - with plenty of supports, but most supports on the inside surface. That would leave you with a lot of support marks on the inside, but very few on the outside, and you might also find an overall improvement from the supports generally stiffening the part as it prints.


#5

When I referred to scaling the bottom part to account for the compression I meant use the original CAD program or something similar to add additional thickness only to the bottom part. Not scale the the whole model.


#6

When I referred to scaling the bottom part to account for the compression I meant use the original CAD program or something similar to add additional thickness only to the bottom part. Not scale the the whole model.

Exactly. I’m saying we added that feature to PreForm in 3.0.0.


#7

Hi,

Thanks for the feedback.

I ran the build plate print flat with no supports, and got the quality I was expecting. Very pleased about that. However, it appears that my print somehow shrunk, in comparison to the file.

Any suggestions on where the shrinkage or scaled down print may have come from?

I am not running the preform 3 software since I could not get figure out how to get my form 1+ to connect to it. On the older version there is a section “z-compression correction” set to 0.75 - is this automatic input correct? And does it automatically apply to a build plate print?

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#8

Sorry, I missed that we were talking about a 1+. No, 2.20.0 is the last version with 1+ support.


#9

Here is a comparison of the shrinkage in case it helps.


#10

Sorry, I also missed that this was on a Form1+, and I should have noticed it from the first screenshot.

Anyway, in some circumstances, resin shrinks when it cures, and in my experience it’s a stronger effect for objects built on the build platform. In this case, I think your best bet would be to try scaling your model proportionately to the shrinkage you measure, and just print it otherwise the same way again. The shrinkage factor on your next print should be close enough to the shrinkage factor on this print that you wind up much closer to if not exactly at your desired dimensions.


#11

I just seems strange because the shrinkage seems only to affect the width on one side, and not proportionally across the entire print.

I have double checked the file and the width is short by about 5.66mm, whereas all aspects of the print are only off by about 0.30mm or less.

Also, the mounting bosses seem not to be impacted by this shrinkage, which is strange.

If i compensate for this drift, do I adjust only the width without changing anything else? If I scale it as a whole unit, then all other dimensions will change, which I would not want.

Any other suggestions on what could be the problem?


#12

That 5.66mm small is on a dimension that should be?

If that dimension was say 100mm then approx 6% shrinkage in the x/y plane seems very large.

Is the box tapered after printing (larger at the point it touches the build platform and then significantly smaller at the end furthest away from the build plate, that effect should only show after leaving the print for a while after printing or on postcure.if it is in fact shrinkage rather than either the optics or the model being to incorrect dimensions


#13

Attached is an image of the disparity. Pink is bad, Green is good.

Is it possible for the optics to be off like this? I think that might be the best explanation but I am not too sure about the possibilities.


#14

No taper, it seems to be the perfect print that I want. Just turned out to be too short on one side.


#15

Note, the print that it is being compared to was printed diagonally, and with supports. The problem for that print is that it is very rough, and not usable for my purpose. The higher quality print which is the one I prefer, was printed right off the build plate, cavity towards the resin thank, and base towards platform.

Not sure why the overall dimensions would be more accurate on the diagonal print, and not the vertical.


#16


#17

I had a similar isue with my Form 1+, over a period of time it started enalrging the front to back dimension, so my prints would come out wider or longer in one direction. That was not normally sen when printing the model at an angle, but once you laid it flat, it was there.

In Preform you can tweak the the printer so it can account for this in percentage. Print a square piece of known dimensions (preferably as large as your print surface. it only need to be a few mm in height, then measure it to see how much you are off by, then figure out what percentage you have to shrink or enlarge the dimensions by.

Open Preform, and fine tune the X/Y scale:

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#18

I think this might be what I am looking for, thanks for the feedback and will give it a try. Quick question: will this adjustment do the opposite, i.e. produce inaccurate diagonal prints? Or is it the case that the diagonal prints are already compromised, I just haven’t noticed.


#19

I’m pretty sure that the discrepancy is there, but because you’re printing it diagonally, the error is compounded in both directions


#20

So at this moment, I accounted for the discrepancy by editing the actual file, looks like i got the perfect fit. I will try the software option soon.

For this print I decided to go high resolution just to see what would come of it, and a few items have presented themselves.

a. Warping in one corner
b. A gash in the side wall (one big one and one small one)

Any easy tips on how to avoid this sort of thing?

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