Print splitting

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philipy
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Print splitting

Post by philipy » Mon Dec 12, 2022 5:43 pm

Several weeks ago I printed the boiler complete with cylinders, slidebars etc, for my DeWinton. I printed exactly as I had hoped with no problems - until I realised that I had the diameter wrong (I had thickened the walls inside the original cylinder instead of outside, so that the o/a diameter was 3mm to small).
No problem - rescale the boiler and reattach the cylinder ,etc, assembly then reprint. This is where it all goes to pot. The boiler cylinder now refuses to print properly. It lays down a base layer and then creates a diagonal opening/split which slowly gets small er until it joins itself up and then carries on up, printing properly. I have tried it at least 6 times, using 4 different types of resin and even redrew the whole thing part way through this saga.
I'm as sure as I can be that the drawing is fine and the slicing doesn't have any problems that I can see. The only thing I can think of is that the settings are incorrect, but I'm using the same ones I've used since forever, and the same ones that printed fine the first time and that I've used for all the small parts I posted a few days ago.

I suspect that it may be to do with the suction created inside the print as it goes up and down, but how do I allow for that in the settings? Any suggestions?

Sketchup drawing
Screenshot 2022-12-12 17.18.39.png
Screenshot 2022-12-12 17.18.39.png (67.37 KiB) Viewed 3635 times
Chitubox slicer
Screenshot 2022-12-12 17.21.10.png
Screenshot 2022-12-12 17.21.10.png (115.21 KiB) Viewed 3635 times
Failed print number 7
DSC_0002.JPG
DSC_0002.JPG (415.25 KiB) Viewed 3635 times
Philip

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Re: Print splitting

Post by ge_rik » Mon Dec 12, 2022 7:54 pm

No idea, sorry. My only observation is that the summit of the missing chunk seems to coincide with the height of the bracket on the opposite side.
Could you print the boiler separately from the bracket and cylinders etc and then glue them together?

Rik
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Re: Print splitting

Post by philipy » Mon Dec 12, 2022 8:14 pm

I've been trying to avoid doing that because the motion needs to line up exactly, fore and aft, with the eccentrics on the axle under the footplate.

I suspect that it is coincidence because some of the other gaps s have been more to one side or the other. I think it is because the cylinder block is printing flat on the plate and has much more grip, so when it tries to lift it takes the easiest bit off.
Philip

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Re: Print splitting

Post by -steves- » Tue Dec 13, 2022 8:42 am

I am assuming you are using Chitubox for the slicer? If not, why not :lol: If so, add auto support and it will be on a raft which I have never had a print split, as normal, you may need to tilt the piece to achieve perfection and maybe add n some extra manual supports if need be.
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Re: Print splitting

Post by philipy » Tue Dec 13, 2022 9:03 am

Yes, using Chitu.

I dont want to use use a raft and supports underneath the body ( obviously need them under bits that stick out part way up). The reason I don't want them and also don't want to print at an angle is that it is printed upside down and the boiler top/chimney and the cylinder tops are printed as separate parts, also flat on the plate, to get perfectly flat mating surfaces to glue together.

For the record, I rarely use auto support. It tries to put way too many supports into locations that don't need them but then misses places that do, and I spend more time taking out the extraneous ones than it would have taken to do it manually in the first place.

The real issue is why the first one ( with my dimensional error) printed perfectly and 9 more ( I just actually counted them) got screwed up!

I have now modified the drawing to add a solid top to the cylinder, ( It was an open tube before), thickened the walls by another 0.5mm and added a fillet on the inside where the walls meet the new solid top. I'm hoping this will add sufficient rigidity to overcome the suction when it lifts. I'll try it later on, but I've got one of the flexible magnetic plates coming today and I want to put that on first. I'm a bit concerned that a flat 49mm circle, 2mm thick, won't want to come off the plate!
Philip

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Re: Print splitting

Post by Trevor Thompson » Wed Dec 14, 2022 3:04 pm

I know you want to print it flat on the plate. without a raft and without supports underneath the boiler shell.

However I think that is the problem!

Trevor

PS I think you are correct to worry about getting a 45 mm diameter 2mm thick plate off the bed in one piece.

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Re: Print splitting

Post by philipy » Wed Dec 14, 2022 5:47 pm

Trevor, I'd agree with you that I'm trying to do the impossible, if it had not worked the first time!

Having said that, I've just done it, with the revised drawing with complete flat top, on the bed.

As for getting it off the bed, working from a totally statistically valid sample of ONE, the spring s/s magnetic plate is absolutely the best thing since sliced bread. It really does work, even before I'd detached the s/s plate from the machine, the simple flexing as I removed it was enough to pop the print off cleanly.

If anyone is interested, this is the one I bought ( but it comes in different sizes to fit a range of different printers):

https://www.amazon.co.uk/BIGTREETECH-pr ... C76&sr=1-9
Philip

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Re: Print splitting

Post by philipy » Thu Dec 15, 2022 5:17 pm

Thought it might be of interest to show a print coming off the flexible plate. I have literally just flexed the plate and swmbo managed to grab a piccy as I did so.
IMG_3874.JPG
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Re: Print splitting

Post by Trevor Thompson » Fri Dec 16, 2022 10:18 am

That is impressive!

How are you getting on with resin printing in the temperatures we are experiencing? You must have it set up in a comfortably warm area!

Trevor

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Re: Print splitting

Post by philipy » Fri Dec 16, 2022 11:01 am

I have both printers set up in the small spare bedroom that I use as a workshop and general dumping ground. Atm, the radiator in there is off, but the door is open so it gets some warmth from general heating in the house, although that is also turned down significantly!
DSC_0002.JPG
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