3D printing two flywheel patterns, one resin, one PLA.

[A7er]

I decided that instead of reprinting my conrod pattern I would repair the pattern and print something else. That something else is the flywheel for the engine I am working on, it has two. I sliced the STL file in Cura5 for the Ender3, duplicated the pattern half to give me the two sides, and set it printing. Estimated time for the print was six hours-ish at 0.2 layer height. I also loaded the STL into Prusa slicer, just one half, and hollowed it out and added drain holes and supports. This file was then saved as a new STL and loaded into Photon workshop. Prusa slicer can't produce a sliced file for the Anycubic resin printers as yet. In Photon workshop I duplicated the STL file and sliced it for the resin printer. I then set the resin printer going. Estimated print time was six hours. I checked on the progress of both printers now and then. The Ender3 was not having a good time, I think the bed might be warping. I didn't worry too much about that as I am used to repairing the bottom of my prints where bed problems have caused partial failure. The resin printer was happily chugging away, but I couldn't see anything until the parts cleared the resin tray some time after starting. The flywheel halves were looking very good. When the resin print had finished I could then see that the print was not good at all. The halves had printed, but there was a fair bit of distortion in both of them. I put the printer build plate including flywheels into a large container of water in the wash and cure machine and set the wash process for ten minutes. I the removed the water vat and set the cure time for two minutes for both sides. The Ender3 had also finished by now and the prints were a lot better than I had thought they would be. I am including three photo's of the flywheels showing the distortion on the resin flywheel which occured in two places, and the almost perfect PLA flywheels. I have taped the two halves together for sanding and filling. I wll cast one flywheel from each of the prints to compare them.

[BillTodd]

Have you got an image or photo of the supported resin stl?

I'm wondering about that drain hole,  and if it is enough.

Bill

[A7er]

Hi Bill
There are 7 drain holes in each half, but they are only 4mm dia. I should have made them 6mm. The holes are at the top and bottom of the outer face of the rim, the top and bottom of the mating faces and a few more to make sure. The flywheel is 110mm dia and the wall thickness after hollowing is 2mm. The two halves were printed at a slight angle so that the outer faces didn't have too many supports. I does seem to me that it might be a build up of resin, I am not sure. All the "odd" areas have now been filled and sanded and the flywheel is almost ready for casting. I would like to paint it but I am unsure about using the acrylic primer I have because of the distortion on the conrod I printed a few days ago. The conrod was never right after that and I had to discard it. I have seen Myfordboy use household emusion paint, I have some magnolia I could try! The PLA flywheel halves are almost filled and sanded, thet came out very well. I haven't filled the drain holes in the resin prints yet as there still seems to some water lurking. I will leave them in my conservatory for a day. I might try a casting before next weekend, the conrod too. Both castings will be with greensand.

[BillTodd]

I'm wondering why the distortion is inwards , which suggests a suction cup effect - the drain holes should really be called vents as they are there to let air into the voids to prevent a suction cup.


If you send me the stl , I'll try to print one 

Vill

[A7er]

Thank you for that very kind offer Bill, I'll take you up on it. The file is on a different computer, this computer is far too slow for cad work. How do I send you the file? A private message via this forum?
Lee
I did another print of some different parts today. Two halves of a part for casting. This time I decided to print it flat, but raised from the bed 5mm. I then altered the cad drawing to add some thickness to the face that would have the supports, I added six times 0.05mm, 0.3mm, and made it slightly wider than the part. This has given me a roughish face that I can now sand down to the correct line. The other part was a small name plate. Lettering 2.5mm high extruded 1mm with 8 deg of draft. A lovely printout that proves the name plate is far too small to cast easily, especially if I cast in brass. I am altering the name plate to make it a bit larger.

[BillTodd]

Email sent via forum

[BillTodd]

Thanks Lee,

I'm printing it now.

[BillTodd]

First attempt failed completely. Broke away from supports (I had reduced their size to print a miniature and hadn't noticed how small they were on screen)

Once more with feeling....

[A7er]

Bill, I feel your pain. 

[A7er]

Today I cast the flywheel pattern that I had made with the Anycubic mono 4k resin printer. The first attempt failed because I hadn't melted enough aluminium (the aluminium is from a Renault car wheel). The second attempt is probably usable after machining and fettling. I had told myself NOT to make the flywheel oval shaped spokes with the smaller of the diameters facing out, as in the picture. Sorry about the poor description. I think it would be easier to extract the pattern from the sand if the larger diameter was facing out, less spoke being extracted from the sand, I think. I have left the gating and pouring basin on to show the setup. The aluminium in the centre feeder should be higher, I miscalculated the amount of metal to melt, again! There was enough, and that's what counts.
The photos aren't high-res.

[BillTodd]

That looks very good to me ,8-)

( My grandfather was a 'forman moulder'  ,  for Paxman's here in Colchester,  so there's iron in the blood ;-))

[A7er]

Thanks Bill,
I will try casting the conrod tomorrow. I have two patterns, one pla the other resin. That means I can cast them both at once.
Retired carpenter here, I have sawdust in my blood.
Lee

[Zephyrin]

this cast flywheel looks pretty good, congratulations !

[A7er]

Thanks, I hope to make a better job of it next time.
Lee

[BillTodd]

Second print came out better:

I changed to Anycubic Basic black after using Elegoo ABSlike resin (the abs like is quite soft)


I haven't spent too much (any) time cleaning this up . Hence the dribble of resin/IPA coming out the vent holes. Chitubox creates plugs for the vents but I didn't bother to print them.

The back is fairly flat , a quick rub on a sheet of wet 'n' dry on the flat of the desk seem to hit most of the area .

The edges are pretty good , some support marks - I was none too careful ripping them off. If you want even sharper edges then , you could put (model) a 1-2mm ridge around the edge that can be filed/sanded off once cured.


I hollowed out the model and used a grid infill just to support the front face. I added quite a few extra supports after the previous failure .

supported model here :-  https://drive.google.com/file/d/1TtY3gSDmZGM_5t7BsXoEelgA1dTQwkWs/view?usp=sharing