How to print without raft ? (Preform 2.20 + Form1+)

[rkagerer]

If I understand correctly you want to print a part directly on the base on a Form 1+ but still have Preform generate a support lattice (without any raft).

I don’t think that’s supported. As you identified, when the Form 1+ is selected as your printer Preform does not show the “On Build Platform” option. Your problem is summed up by this picture:

The different printers have slightly different support generation algorithms and my guess is Formlabs didn’t want to backport the new feature to the older algorithm (or perhaps they didn’t feel confident the smaller footprint of direct-on-base supports would provide enough surface area on the Form 1+ for reliable adhesion).

However, if you’re really intent on doing this, you can exploit a “bug” in older versions of Preform that allows you to swap resin and printer profiles while leaving the existing support structure intact.

Workaround

When you open a .form file in Preform version 2.13.1 or below, it blindly maintains whatever printer and resin were previously selected. I was able to:

1. Generate mini-supports in version 2.20 using a Form 2 profile
2. Save the result as a .form file
3. Launch Preform 2.13.1 and select a Form 1+ profile
4. Open the .form file, without regenerating the lattice

Here’s the result:

Unfortunately 2.13.1 is no longer available on the Older PreForm releases page (right now 2.16.0 seems the earliest one there). I had a copy lying around, and uploaded it here if you want to experiment: PreForm 2.13.1 for Windows

Limitations

Be forewarned the method is imperfect.

I noticed the file sometimes gets loaded missing the mini-rafts at the bottom of the on-base supports:

I couldn’t figure out a rhyme or reason. If it happens, I suggest you close Preform and keep trying again until it comes in correctly (at one point during testing it took me half a dozen attempts).

Also keep in mind you have to select the Form 1+ printer before opening the file. If you try to change the profile afterward, Preform will force you to clear the support structure and start again:

Version 2.13.1 is old, and doesn’t support some resin types. It also can’t open .form files that were saved under the latest versions.

Finally, and most important, I’m not sure how much mileage you’ll get taking a lattice designed for the Form 2 and printing it on the Form 1+.

Here’s some discussion from around the time they fixed the bug: Option to keep supports intact when changing printer/resin in Preform

Pay attention to this comment from @mgarrity:

@mgarrity

Although the supports for the two printers look similar, there are actually some important differences. Because of the differences in the way the two printers perform the peel, I don’t think we could really qualify Form 1+ supports on a Form 2, or vice versa. Sorry about that.

The details of the support generation is tuned to the printer type and trying to use supports generated for a different printer type really really likely to get you into trouble.

Until the “Import Touchpoints” feature was available, the trick above was the only way you could change resins without having to redo all your touchpoints. Starting with version 2.14.0 they introduced the option to maintain the existing touchpoints, and made it so Preform always forces you to regenerate the support structure:

As far as I know there’s no way to generate a Form 1+ tuned lattice with mini-rafts.

The hack I described is worth a shot, but I still expect you’d get more reliable results just printing on traditional rafts (or using different software, such as Formware, to create the supports as part of your STL model).