How do I get circles on small interior holes to adhere to the bed?

2

I’m using a RepRap printer, PLA (Hatchbox 1.75 mm), SketchUp, and Slic3r. The heated bed is covered with a blue polyester sticker. When I print small holes (1 to 1.5 mm radius), slicer software considers the holes outside edges for the first layer and prints them before the internal first layer. The problem is, unlike the actual outer edges, the holes have no brim and the small first layer circles stick to the extruder rather than the bed. The rest of the first layer print sticks and the print eventually recovers with slight defects depending on where the lifted circles end up. If I could print the first layer circles after the surrounding first layer was printed, this wouldn’t be an issue. I’ve tried different bed and extrusion temperatures. All four holes in different locations do the same. First layer is 0.3 mm thick. Second layer is 0.2 mm thick.

Perry Webb

Posted 2019-04-16T21:12:54.427

Reputation: 961

Could you add an image of the print and of the sliced first layer? – 0scar – 2019-04-16T21:51:30.233

I don't have a picture right now. – Perry Webb – 2019-04-17T00:09:28.197

I'm considering making the first layer solid across the holes, then punching through the single layer. – Perry Webb – 2019-04-17T00:18:58.120

I had a similar issue and I had trying masking tape or glue to try and help and they didn't make a difference. I then tried a 3D print build surface. This has helped and I no longer have the issue. Have a search and see if you can find one which will fit your current build plate. – JackU – 2019-04-17T09:42:18.970

try to print the first layer 0.2mm – Fernando Baltazar – 2019-04-17T18:49:41.323

Putting a 0.2 mm layer across the hole bottoms so that the slice didn’t put small circles on the first layer worked. Large circles on the first layer weren’t an issue. This worked because they were through holes that could be located from the top and they were holes for screws that could easily penetrate the thin layer. The layer was too thin to keep the screws from turning and feeding into the attached part, but served to keep the screws from falling out of the hole. It would be difficult to locate holes that weren’t through holes using this method. – Perry Webb – 2019-04-17T23:45:23.087

@PerryWebb I've done so many times (because this gives a better aesthetic first layer), to find those holes look at the design and push with you fingers over the surface where a hole should be, the 0.2 mm layer will dent, while the rest won't. – 0scar – 2019-05-23T06:14:14.883

Answers

1

I would use a very slow print speed for the first layer, something like 20mm/s or less.

This will make your first layer so slow you will be tempted to bite the steel rods.

If you were using Cura (I don’t know if Slic3r has a similar feature) you can change this parameter only for those areas where you have these small holes: with the Custom Supports plugin you can specify a different print speed for a specific area

Cusa custom support print speed setting

Roberto Lo Giacco

Posted 2019-04-16T21:12:54.427

Reputation: 307

1

are you using hairspray or tape to help with bed adhesion? If not that might help.

Also try printing the first layer slower or try adjusting the bed level offset so you are squishing the first layer down a bit more.

Jayson

Posted 2019-04-16T21:12:54.427

Reputation: 161

The z offset is close enough that the extruder slightly marks printed surfaces if moving across them. – Perry Webb – 2019-04-17T00:16:01.683

how much the first layer measure? if your first layer should be 0.3mm and this measures 0.38 so your Z offset is incorrect. and this parameter is not enough to adhere the filament with a nozzle 0.4 – Fernando Baltazar – 2019-04-17T18:53:05.100

0

Print at 5% of the print speed, and ramp up cooling to 100%. This should give the plastic time to shrink and adhere to the bed. If not then use a raft.

user77232

Posted 2019-04-16T21:12:54.427

Reputation: 2 090

0

You didn't say what type of bed you have, but I'm guessing glass. Do you have a BuildTak or comparable generic surface you could clip on and use? I've never had adhesion problems like this with my Ender 3, which came with a BuildTak clone; PLA just sticks, with no brim, no glue, no hairspray, etc.

R.. GitHub STOP HELPING ICE

Posted 2019-04-16T21:12:54.427

Reputation: 5 311

There is a tape sheet over the glass. – Perry Webb – 2019-05-17T08:59:34.177

@PerryWebb Maybe you should add that to your question by [edit]. What kind of tape? Painters tape or Kapton tape? I use 3DLAC on glass, never fails. – 0scar – 2019-05-17T12:27:02.120

Given how little trouble I've ever had with adhesion compared to how much folks seem to have with tape, glue, hairspray, etc. on glass, I think there's got to be a huge difference in the effectiveness of BuildTak/clones vs these methods... – R.. GitHub STOP HELPING ICE – 2019-05-17T17:36:47.560