Prints resolution/distortion in area of supports and surfaces facing platform

I appear to be having an issue with print surface distortion/resolution in areas where there is support density and on surfaces that face the platform during printing. These areas have substantial waviness and tend to become stretched/oblong-ated towards the platform
. Other surfaces keep there tolerances perfectly.

Variables I’ve tested:
-full raft vs mini raft, no differnece
-printing with surface parallel to the platform vs at an angle, no difference (the large flat surface of the cylinder actually printed a bit cleaner parallel but the distortion of the elbow fitting printed worse along it’s curved surface when parallel to the platform, but neither is adequate)

-using GreyV4 FLGPGR04 resin(brand new with new tank) in a 3B+ printer(newest firmware as of a couple weeks ago).
-Using preform for setup; 50um layers, IPA postprocessing and post cure

What size support attachments are you using for the point where the support touches the print object?

This is inherent in the technology. The pieces print upside down, with the supports printing first. The first layer of the piece to be cured is very thin and flexible and so when it is pushed down into the resin it bows up slightly towards the built plate between the more solid supports. The next layer cures the resin in the slight hollow between the bowed up first layer and the tank surface. Hence there is an uneven surface on any printed parallel to the build plate.

This certainly can’t be the case. People print more delicate, thin sections with supports near by, and have great resolution and maintain tolerance…

For the cylinder on the left I used .5 and the right I used .35

Thank you. I have a Form 3 and am not familiar with the differences between this and the 3B+. The problems in your photos were a significant issue with the Form 3 too. A recent release of PreForm has helped significantly in my experience. The shape of the touchpoints has changed with 0.30mm size settings. The build plate surface of the model is not perfect but it is a lot better. Unfortunately, I have a major print run underway for the next few weeks but if you want to message me and can send the file then I am more than happy to look at it in PreForm. No problem if you don’t want to send the file though. Once the current print run is done then I can print your part and see what happens. Robert.

Thanks for the response Robert.

I think the 3+ was supposed to have taken care of some of the issues you mentioned with the 3, by way of software and some mechanical improvements. The “B” designation just means that it will accept/recognize the formlabs biocompatible resins for medical uses.

I can send you the STL file for the cylindrical part to see how it prints for you- much appreciated. PM sent.

The file came through. Thanks. I will keep you posted on progress.

The print runs were completed for the other job. This enabled me to get back to Tray Riser model for you. Here is the set up in PreForm:

Here is the print, starting with the top and side views with raft still attached and then the bottom and side views with raft removed:

Tray riser side elevation with raft

Tray riser side elevation without raft


Thank you Robert!
It looks very similar to my model, theres notable difference in the edge quality of the platform vs opposite side… I guess it’s not possible to maintain the same level of tolerance for the platform surfaces unfortunately.

You’re welcome. This version was printed without any tilting from the horizontal plane. I will repeat the print with longer supports and with a slight angle. The key take-away from this print, in addition to the very important observation that you have made, is that fewer supports can be used compared to the PreForms auto-generated supports.

I also pointed this problem out to the support people. Their response was just that this is the way it is. Which really doesn’t make sense to me. If im looking to prototype and maintain dimension on all planes, edges, etc, printing can’t do it?..

That seems like a cop out to me… maybe a design flaw?

It is true, and I’ve explained the reason to you, but you rejected it.

It is worth noting that almost all Formlabs sample parts are printed directly on the build plate to avoid this problem. Though it means that vertical holes can’t be included because they would lead to failures due to cupping.

Your description of the reason is spot on, I just couldn’t believe that it was the same problem I was facing and manifesting to such a noticeable degree.

So does this mean that you essentially can’t print prototype models and maintain tolerances in XYZ? Perhaps due to the use of a flexible membrane instead of a rigid glass surface for the print interface? If this is the case it certainly leaves the printer kind of useless…

How do I get around the problem of printing on the platform and the variability that introduces to my tolerances in the Z direction?

Set Supports → Raft Type to “None”

Set Supports → Advance Settings → Z-Compression Correction to 0 mm

and go from there.

You will have to make an airway between any hole in the face on the build plate and the curved outside face, other wise you will have problems with cupping.

1 Like