The bed temp starts out turned off and goes up in increments until it is 100% then it stays on until the print is done. I haven’t tried a draft shield yet.
1 Like
OK there is a little joy in Mudville tonight. (if you understand this reference then you are old like me)
I watched a vid were this guy shows how he makes the “brim” part of the CAD model and not added by Cura, for parts that absolutely have to be flat. You could add a brim in Cura if you wanted.
So I tried it by adding an 8mm wide layer (the default width of a brim in Cura) to the outside of the CAD model, two layers thick (one might be enough but maybe not) plus a skirt. When printed it looks like a brim but is part of the printed part. The part was absolutely flat on the bottom. Possibly the width of the flat area on the part, it was basically a ring, was to narrow to get good adhesion.
The down side is that the “brim” part of the printed piece has to be cut off and cleaned up it doesn’t peal off like a real brim. A small price to pay for a flat bottom. On top of that it was really stuck to the bed, even when it was cooled off there was no lack of adhesion. Normally instead of using a scraper to get under the print and prying it off, which peals the glue up, (danger Will Robinson another PSA is approaching) I use a small brass hammer to lightly rap the side of the print and pop the part off leaving the glue layer intact but not his time, it had to be pried off and not easily. I suppose it works like something half way between a brim and a raft.
If someone was printing something square-ish which can be a problem with curling at the corners then you could just add large-ish circular layers around the corners and have the same effect.
2 Likes
Sort of successful then!
When I had things that wouldn’t come off the bed, I’d put the bed with the piece on it in the freezer for 30 min.
1 Like
To me if I completely understand what you are saying, is the model is not dead flat? Thingiverse is full of not flat models often remixes. Something to be careful of. I offen as a matter of course depress a model 0.2-.5 below the bed. effectively eliminating not flat bottoms.
1 Like
I removed it with a scraper but it was stuck down fairly well.
This is a model I drew up in CAD, it was flat, it just didn’t stay flat when it printed.
I did change the roll of filament as the previous one ran out but it was the same brand and type just a different colour. Maybe blue sticks better then black. I did see that wet nylon doesn’t stick to the bed very well is that the same with PLA?
I do think that the narrow base on this part contributed to it curling up and the wider base of the last print stopped it. The brim couldn’t keep it from curling.
I will do some more test prints and post results…eventually.
1 Like
Heck ya. OK. this 20 character limit is annoying.
1 Like
Personally wet filament sucks. In my experiences wet nylon is unusable it is a train wreck. Wet pla isn’t anywhere near as bad.
For the best results you need to dry it however. I sometimes use wet pla for a test print if I am in a hurry. The rolls I don’t really like I don’t treat well either, they are the ones left out often.
1 Like
I just finished printing some test parts and like usual it didn’t go as it should have.
All the print where:
.5 wall line width (new)
125% initial line width
4 wall lines
20% infill
210 print temp.
5" x .4" x .25" thick
The first one was printed with a bed temp. of 70C and 65C with a brim
The second was printed with a bed temp. of 60C and 50C with a brim
The third was also printed with a bed temp. of 60C and 50C and no brim
I picked this shape because a long narrow part has a tendency to curl up at the ends and lift off of the bed.
All of them had an excellent finish and none of them lifted or curled up from the bed.
Very annoying. some of them should have failed but all of them where stuck onto the bed and I had to use the scrapper to pry them off.
Both the filaments I used earlier and the current one are 3D Printing Canada Value PLA, the only difference is the colour, the first ones that cause me so much trouble with curling where black and these ones are blue. Generally this filament has been very good as far as finish goes, prints nice but like most straight PLA it is brittle.
The only conclusion I can get out of the empirical data is that blue filament sticks better then black. 
1 Like
blue might print at a different temperature than black have you done any temperature towers on these?
1 Like
I don’t see why they would print at different temps., they are the same brand and type of filament only the colour is different. I haven’t printed a tower, I haven’t had any real problems before this so I didn’t see the need.
I was just being tongue in cheek about the colours, I really have no idea why the one spool didn’t stick and the other did stick very well. Possibly the black roll had some moisture in it, if the would even cause this problem but they are both stored in the same box with a lot of desiccant.
One of life’s great mysteries.
1 Like
I have found some colours to be different. Pigment heavy sometimes take a different setting than less pigments. Glows are completely different in my experience as well.
1 Like
I agree, I will reg print white and pastels -10 deg cooler that Blues, Blacks and heavy colours.
1 Like
At a guess and I am assuming, that that roll of filament had moisture in it and that was the problem. I can’t test it because I ran out.
I did a print yesterday with a different brand of PLA filament and I really had to fight with it to get it off of the bed. Never had one stick that well before.
1 Like
Is this you?
1 Like
Not me sorry. That is very cool but it wouldn’t be much good on a lathe. The stress on it could/might blow it apart. Even large cast iron bodied chucks have speed limits on them because they will blow apart if run to fast.
2 Likes
So you have not tried leaving the bed temperature the same for the whole print? PLA has less expansion/contraction due to temperature changes than say PETG, but using PETG as an example, once the bed has cooled down after the print finishes, it pops off by itself as the temperature drops to room temp on the way down. This usually happens somewhere in the middle of the temp range.
With PLA, my experience is if the temperature at the bed were to cycle or change by the amount you are dropping it, I would have lost the adhesion starting at the edges. I sometimes bump the second and above layers up 5 deg c to allow for the fluctuation in temp so that I give myself a little dreadband to allow the 1st layer to contract to the size it was layed down at. If it were to contract beyond this point, the separation begins. Albeit raising the temp above the 1st layer temp should cause the PLA to expand and thereby losing adhesion, it’s easier to lose heat than to gain heat.
This works most of the time when I have lifting/adhesion issues. When I don’t, I keep the bed at the same temp all the way to the end and protected by a draft shield.
Also, I find the adhesion issue becomes more of a risk when the print time gets longer.
1 Like
I have only had trouble with that one role of filament, other roles have been fine.
2 Likes