Best way to remove support bumps?

Hey everyone, I noticed that after removing supports that the area around the supports would always be bumpy. For some prints, this is fine for they are barely noticeable. For most of my other prints, they are not only noticeable, but messing up the way parts are supposed to connect to one another.

I guess my question is: are there ways to reduce the amount of surface warping from supports? Also are there tools that you would recommend to help finish prints (Like sandpaper, sanding sponges, and what brands, etc.)?

First of all- I try to identify the critical mating surfaces and orient the parts so that no supports connect to those surfaces.
Or- I will allow supports on a mating surface if the part is such that I can easily plane the surface flat to a correct dimension.
I use sandpaper rated for WET uses, because you can literally wash it off and get a much longer life out of it.
I also like the newer sandpapers that are not on paper- but on a sheet of thin silicone rubber.

Small jeweler’s files work well on the more brittle resins like Clear and Grey- not so well on tough or durable.

And an xacto knife with a blade that has a positive CURVE to its edge is good because you can get the curved edge in contact with the support nub without touching the part elsewhere.

beyond that- a lot of this can be solved in MODELING. design your parts around the fact that they will have supports… I will cut a part into several pieces to enable me to hide support errors where they will not be an issue…and then glue the parts together after printing.
Or alter a design to make an area slightly proud to enable me to plane the support area to correct shape after printing,

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It’s something that will always be an issue with this type of printing. The best way to deal with it is adjusting your part orientation and possibly even splitting the object into more parts so that you can orient things in a way that you can place supports in areas that won’t cause problems or are easier to clean up.

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Thanks for the replies @Zachary_Brackin & @Sculptingman. Cutting the parts isn’t really something we can do at the moment due to the small scale of our project. I think the support bumps aren’t as big of an issue as we previously thought. We really just needed to work on minimizing supports and the clean up practices, so all is good there.

Another issue I noticed this morning (and I’ll probably make a new thread for this) is that my prints have been printing at the wrong sizes. For example, a 1/8 in square on both fusion 360 and the preform software would end up printing .02 inches smaller or bigger. Have you guys ever experienced something like this?

I’m going to check some of my previous prints to see if the same errors occurred before I make a new post, but again, thanks for the replies.

Preform actually changes the scale of parts on export slightly to try and compensate for the shrinkage rates of differing resins, and even differing layer thicknesses… ( part of why you have to select the correct resin in Preform before sending the print to the printer. ) but there are just too many variables to juggle for true dimensional accuracy. A change in ambient temperature or humidity during the course of a print can affect the dimensions of a part and is a significant component of warpage issues. Some resins are worse than others at tolerances.

And Formlabs states plainly that if dimensional accuracy is paramount, then you should print at the thickest layer height.- this is the most reliable for a couple of reasons… First, if each layer printed is dimensionally correct plus or minus 0.0003%- then 500 layers will have less cumulative error than 2,000 layers.
And, because a 0.1 layer part will print Much faster… and so there will be less change in ambient conditions affecting the curing and shrinkage of the resin.

Another trick is to make sure that parts that must fit to one another are Printed Together in the same build.

And, of course- you will find that certain orientations can minimize dimensional changes in the axis that is the most critical.

there are white papers Formlabs have published that discuss tolerances you should build into various parts for various levels of fitment, and they are worth a read.