qidi printer having problems with larger prints...larger print considerations?

I was here in december (man time flies) and got some great advice and manage to churn out a few cool 3d prints (namely some tiles for a board game called catan) worked great! Though I realized something strange then (got busy and haven't picked it up till now) that the larger prints of the borders for the board game were curling up bad on the corners and getting caught on the extruder.

Okay so fastforward to now...I tried to build my first 3d model and print it. it is a simple pinhole camera box based on a design of a checkbook box one I built. So here is the screenshot of the model:

Attachment 8676


So i thought it would be a simple print but it is pretty large and I have done 3 attempts:

attempt 1: I used the same settings I have for all my catan tiles 60degre print bed, 195c pla temp and slow speeds. no raft. It curled the corners up and twisted the main thing but it did 'print' though the bottom had divits in it (the part thats on the print bed). Also the left corner curled way up and i stopped it as it was printing the first wall on the bottom piece there (the top part). Are there more considerations with larger prints? Print speeds are slow still and I have the shells set to 3, roof and floor thickness to .90mm and the layer and infill heights to .20mm

I read around on the internet and saw maybe the print bed was not evenly heated and too cold and so I upped the temp to 64c .... no curling but the second print failed because I must of whacked the print bed out of alignment left side printed right side started to drag into print bed so I stopped it right away. Releveled.

Then a few other prints it just was a gunky mess...and not sticking any part down. Thought it was a glue stick issue so i tried more of that and that didnt help really...

Trying one where i am using a raft, that seems to be okay but its curling up on the corner and the edge (the raft) and i dont have much space from raft edge to edge of the other thing. plus the floors it slaying down are divited looking too...not stringy but not its normal greatness.

so stopping this latest print and coming to here the forums to ask what else I should look at? I built the model with tinker cad and its about 150+mm by 88mm by 60mm high. Not sure what the important factors to look at and try here. I am guessing the curling is a cooling issue but then I think the latest build with the raft and all that is because my print bed temp is still 64 c and its *too* hot?


So some pics of the first print and the most recent one im cancling too thats at 195c extruder, print bed 64c....
travel speed 150mm/s z-axis travel speed 23mm/s minimum layer duration 4.0s

and the rest of the settings here:
shells 3 roof floor thickness .90mm layer height .20mm
Speeds first layer 15, first layer raft 15mm/s infill 45mm/s outlines 20mm/s, raft 45mm/s raft base 25 mm/s
infill 20%
infill layer height .20mm

Attachment 8677

Attachment 8679
Attachment 8680

oh and another of the currently failing attempt.... Attachment 8681

Another recent thread I Talked about rounding corners. If those outside corners don't have to be square, round them off, I've had vast improvements in print quality with rounded corners vs square. Also consider adding a dime-quarter sized disc (about 1 layer thick) to each corner, this will give each corner more surface area to adhere, and if it does start to lift, the disc will lift before the corner. Also, reconsider your adhesive. Try something else.

Dunno about your print settings though, not my forte, but the gurus may have suggestions for temp adjustments.

thanks for the input, I think the dime sized disc I replaced with a Raft... i discovered a few things:

I think with my PLA printing I want the first few layers much warmer than the higher layers. I discovered the acrylic covers on the printer keep heat in and I want this and the door and the top, so the first layer is warm and adheres...with rafting too.

Secondly the manufacturer of the printer (Chinese) mentioned something bout NOT having the covers for PLA which i would agree for when it should be cooler so the corners of the higher layers don't warp up. I will try some temp control.

Secondly I scaled the model down and printed it, printed GREAT. just too small...I think part of the issue is that over the large area of the model the print bed is not 100% level... though I am having a hell of a time leveling it. The paper between the nozzle on left right front back middle is not cutting it and my printer has only three screws one in back and two in front...I am doing the paper and trying to use a cheapo level from the hardware store.

I don't know how anyone prints these models that are slightly larger... 3d printing is interesting, what works for one model might not work for another.

So I think its a first layer heating problem and then a level problem. I read on simplify3d (a software package I do not have) that provides lots of options for first layer and active cooling fan on during other layers not first etc etc.. even says it has a leveling something or other built in (im guessing id have to have the pc running it USB to the printer right now using SD card) but yah...maybe this package would help with some of these issues.

This is some pretty extreme curling for PLA.

I would suggest upping your print temperature a little bit. I print PLA at 215.

I use 65C for layer 1 bed temp.
30C after layer one.

Are you wiping your blue tape with rubbing alcohol before you print? That makes a huge difference to me.

As always, make sure your bed is very level or you will have issues.

If none of the above help, you might have a low/high spot in you bed - I do. Try moving your print to a different area of the bed and the issue may go away. Impact from a high or low spot can be reduced if you upgrade to a glass bed.

So what does the rubbing alcohol do? And actually I have been using the glue stick, which I scrape off the bed after a print and relevel. Though I was suspicious of my leveling procedure and I am going to be getting a feeler gauge today to better level the bed with (making sure there is a .15mm gap) This will surely tell me if I have a low high spot in the bed. Never thought about glass was just using what came with. I thought that was way to hot for PLA I should post the smaller version of what im trying to print and how it came out. It came out really well minus a few layers on the side in spots that was bumpy. How do you control the bed temp after the first layers? Makerbot desktop doesn't give you that option and I was afraid to get it i had to flash the rom on my 3dprinter (Which I read was not trivial and could resulted in a bricked unit)

Quote:

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Originally Posted by JohnnyV

This is some pretty extreme curling for PLA.

I would suggest upping your print temperature a little bit. I print PLA at 215.

I use 65C for layer 1 bed temp.
30C after layer one.

Are you wiping your blue tape with rubbing alcohol before you print? That makes a huge difference to me.

As always, make sure your bed is very level or you will have issues.

If none of the above help, you might have a low/high spot in you bed - I do. Try moving your print to a different area of the bed and the issue may go away. Impact from a high or low spot can be reduced if you upgrade to a glass bed.

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Quote:

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Originally Posted by codejoy

So what does the rubbing alcohol do? And actually I have been using the glue stick, which I scrape off the bed after a print and relevel.

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I think it just acts as a de-greaser to remove dirt, oil, grease, etc that is on the surface of the tape. In the picture it looked like you were using painters tape, which is why I suggested it. I've never used glue stick myself, so not sure how they compare.

Quote:

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Originally Posted by codejoy

How do you control the bed temp after the first layers?

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I use Simplify 3D - its very easy in the temperature settings window to control temp with layer height. I've never used Makerware, but I can't believe they wouldn't have this feature. Take a spin on Google and see if you can find the answer. You shouldn't need to reflash.

Thank you JohnnyV that is good, I am going to seriously consider Simplify3D. I did also think perhaps my extrusion was off and I did hear a clicking noise in the the extrusion motor (though material was being extruded) it didn't sound right and I saw an online video saying those gears on that motor can get clogged so I took it off to clean it and didn't find really clogged teeth but that gear is loose, is this supposed to have some give or is it supposed to be tight? I am guessing tight... this is the picture of the gear. I am sure this isn't helping things. I did get some feeler gauges to re-level my bed and blue painters tape, I am going to also probably get simplify3d so I can go hotter on the first few layers and control my (yet to be attached) active cooling fan after the first few layers too. Very excited I think I can pull this off...fingers crossed. Though guessing this gear should really be tight to start with?


Attachment 8751

I want to tighten it up but I am not sure if it should be a bit loose?

If I'm not too late to throw in my 2-cents' worth:
If your extruder is clicking, then 1). your nozzle is too close to the previous layer and is blocking the filament from extruding, or, 2) you're trying to push filament out faster than the melted filament can leave the nozzle (check the calibration of the extruder rate). Yeah, the gear set screw has to be tight.
FYI, I print big and small prints with (American-made) PLA on glass, with the nozzle (.4mm) at 185-195 C. (depending on filament color), and bed temp. at 40 C. I use Aqua Net Extra Super Hold Hairspray (the best my local Dollar Store carries). I print without a brim on small prints-less than 50mm x 50mm, and a 2mm brim on larger prints. I have a small fan blowing on the extruder housing (Prusa i3) and no fan blowing on the bed. If my print is small, I may reduce the nozzle temp 5-8 dergrees. NO PROBLEMS.
That's about all I have to say....


Wes