Resolving bloom?

[Beanwood]

I haven’t seen a satisfactory answer anywhere for this yet I.e. not one I like) so open to the expertise here.
Occasionally when printing Petg I can get some bloom on the surface that was in contact with the plate. Likely a number of reasons for this- but how to cope after it has happened?
Small amounts of heat doesn’t seem to fix it. Is it possible to polish it out somehow? Don’t mind buying a tool if it’s going to resolve it but don’t want a polishing mop hanging around for no good reason.
Photo to illustrate but it doesn’t show the problem very clearly.

 

[iNf]

Can't recall ever seeing that on any petg I've printed. Do you use glue or something else on the build plate? Does it do it on different brands of filament? Have you tried different bed/nozzle temperatures?

 

[Beanwood]

It does happen
Using Bambu or other filaments- no glue just the texture plate..
Often caused when the print has stuck ‘too well’, or removed before fully cool.

Not worried about the cause- just how to deal with the aftermath.

 

[Screwdriver]

Have you tried wiping it with IPA?

 

[Dozzer]

do you know the moisture content of the filament? much above 20% and some colours react.
Had some orange PETG that would print fine even when filament box showed 50% humidity.
Same make & type, but bright green, anything over about 25% would leave a dull white patches all over the place, looks just like you have.
Cant say it will fix your issue, but some filament/colours seem to be more sensitive to humidity than others.

Only ever used heat to improve surface, but PETG doesn't seem to work as well as PLA as it need much higher temp to reach its plastic stage again.
you could try silicon oil? or another type of polish, but the finish from the bed will not help.

 

[Beanwood]

Have you tried wiping it with IPA?

Yes, thanks- tried hot water with soap, IPA, neither made any difference. It seems to be the actual structure rather than a deposit on the structure if that makes sense.

 

[Beanwood]

do you know the moisture content of the filament? much above 20% and some colours react.
Had some orange PETG that would print fine even when filament box showed 50% humidity.
Same make & type, but bright green, anything over about 25% would leave a dull white patches all over the place, looks just like you have.
Cant say it will fix your issue, but some filament/colours seem to be more sensitive to humidity than others.

Only ever used heat to improve surface, but PETG doesn't seem to work as well as PLA as it need much higher temp to reach its plastic stage again.
you could try silicon oil? or another type of polish, but the finish from the bed will not help.

Thanks- I don’t THINK it’s moisture dependent- but I don’t know that for certain.
I have a couple that I can try things with, so will try some silicone oil, some extra heat, but also something slightly abrasive.

 

[Beanwood]

…and the prize goes to @Dozzer . Heat is the answer. A lot of it applied carefully using a heat gun to melt the surface but not distort the structure.
Example showing the difference:

 

[Screwdriver]

If it's a plastic effect, use flame rather than a heat gun. Much higher temperature for a shorter time less risk of melting, just don't burn it.

Textured finishes are particularly tricky when flame polishing but short bursts work incredibly well, almost like spray painting.

 

[Beanwood]

If it's a plastic effect, use flame rather than a heat gun. Much higher temperature for a shorter time less risk of melting, just don't burn it.

Textured finishes are particularly tricky when flame polishing but short bursts work incredibly well, almost like spray painting.

Ooooh - ok - that seems to makes sense - I shall have a practice with another one. (I am a bit of a 'dab hand' with the air gun as I use it very frequently to remove labels from plastic pipes.) All I have in 'flame' is a candle (Will be sooty I'd imagine) or a Superfire 2 that may melt it more quickly than the hot air gun flashed across - but certainly worth a go.

 

[Screwdriver]

I use one of those kitchen flame torches. Cheap and reliable. Bought several actually, noted on here somewhere.

Great for removing strings, even from delicate prints but you really have to waft it quite quickly.

Also good for lighting bonfires, forges, barbecues though I must confess, haven't done much actual cooking with it!

 

[Dozzer]

 

[Beanwood]

View attachment 536995

That is great thanks - I tend to use PETG more than PLA, and it’s (almost) always dried before use. This problem only occurs occasionally- and the remainder of the print is fine- just the bed interface is the issue.

 

[Kram]

View attachment 536995

What did you ask ai for that response?

Of the various (cheaply available) filaments, PETG is the least effected by moisture. PLA next, then ABS. TPU is the most hydroscopic , it needs to be kept at low humidity while printing or the quality suffers greatly.

 

[Dozzer]

What did you ask ai for that response?

Of the various (cheaply available) filaments, PETG is the least effected by moisture. PLA next, then ABS. TPU is the most hydroscopic , it needs to be kept at low humidity while printing or the quality suffers greatly.

Yes its a on line response but echoes my limited 3D printing experience, while not as extensive as others, i have found PETG to be the Biggest PITA with regards to moisture out of all the filaments i have use, not all but some colours (mainly green & blues) have been so sensitive i have throw a roll away.

 

[Kram]

That to me sounds a bit odd, but perhaps it is the pigment, not the filament itself, that is hydroscopic. Had you tried drying them, before throwing away?

 

[Dozzer]

That to me sounds a bit odd, but perhaps it is the pigment, not the filament itself, that is hydroscopic. Had you tried drying them, before throwing away?

Yep, have a dryer, and had the green Sunluat 60c for over 3 hrs and the dryer showing 23% and it still printed like crap, got lots of little bobbles on the surface and it was misting, surface blooming, oddly enough the Sunlu semi transparent green (think it has some polyprop in it) printed perfectly with the same settings.
Its a bit like white filament, some colours can be a bit challenging. white is a bugger as most whites are achieved with titanium dioxide and it wares tips out and can bit a bit more brittle/temp sensitive.
Still think that fact that we have mini plastic factories that can produce most shapes we want amazing. even if it can be a learning curve.

 

[Kram]

Yep, have a dryer, and had the green Sunluat 60c for over 3 hrs and the dryer showing 23%

If the drier is working properly it should not be at 23% after hours.
Are you trying to dry dessicant at the same time? That will greatly increase the amount of moisture in the drier, and prevent the filament from being dried.

Its always best to remove dessicant for drying and replace with fresh dry dessicant afterwards, when I do this I can get my filament down to 0% and it stays low for two months.