Garden Railway Forum

I'm having a problem with trying to resin print some 20mm diam wheels for my Wickham trolley.
the wheel shape is unusual and very specific and although my drawing isn't perfect, I'm fairly satisfied. I've had at least half a dozen attempts at printing it with varying degrees of success, ranging from 'disaster' to 'Oh no, not again!'
I've got to the stage where I'm improving things worse each time I tweak it so before I waste any more time and resin I wondered if anyone has any ideas?

This is what I've got from the front and it looks good if I do say so myself, even down to the minute fixing bolts and nuts.





Hooowever...from the side, you can see that the raft isn't sticking to the plate properly at the edges and the wheels itself is trying to pull off the supports. I think it must be to do with the slicer support settings. I've just thickened the raft to 2mm and increased the support sizes to try to get it to hold better, but the most recent one has the raft stuck to the plate and the wheel ripped apart horizontally.

Have you tried printing them without any support? That's how I did all my resin wheels without any issues, however, I found them very brittle and had a few break when just putting axles in them, not sure how they would fair under any load or much use, but they would look good

-steves- wrote: ↑Tue Mar 23, 2021 11:19 am Have you tried printing them without any support? That's how I did all my resin wheels without any issues, however, I found them very brittle and had a few break when just putting axles in them, not sure how they would fair under any load or much use, but they would look good

No I haven't tried no supports, never thought of it tbh, but it's worth a try.

I've always been suspicious of the idea of resin printed wheels as well, but when I saw Jerry Irwins load test on his printed link couplings I thought it worth having a go, so I asked him what resin he was using and this is it.

The Wickham trolley won't get a huge amount of use and certainly won't be pulling heavy loads, so it's good starting test, IF I can get them to print!

Thanks Steve, printing them flat on the plate worked a treat, although I still have no idea why I was having so much trouble with supports.
I did half a dozen whilst I was at it, bearing in mind your comment about breaking them.

philipy wrote: ↑Wed Mar 24, 2021 10:08 am Thanks Steve, printing them flat on the plate worked a treat, although I still have no idea why I was having so much trouble with supports.
I did half a dozen whilst I was at it, bearing in mind your comment about breaking them.

Well they do look considerably better don't they Glad it worked for you too, I have never tried wheels with supports so couldn't comment on whether mine would do it too?

Sorry to be a bit late coming to this - I have been sidelined by making kitchen cabinets!

I might be able to add something to the issue. I have had problems with large flat areas preferring to stick to the bottom of the machine rather than the build plate. For example a person printed on its back. Half way through the build there is a large area being subjected to uv at one moment - and that preferred to stay on the tank bottom when the arm rises. I think that is what might have been happening with the wheels. The suction of the flat area overcoming the strength of the supports.

I found 2 ways to prevent it.

Firstly printing at an angle - say 30 degrees making the flat area at the bottom of the tank much smaller and the supports can hold it.

Secondly using more thicker supports to increase the strength of the support system.

Printing without any supports of course solved it in the same way.

Trevor

If larger flat things are things are sticking to the base rather than the build plate then it "could" be that your build plate a a gnat's cock too close or even too far from the base. I had to lift mine by the smallest amount possible and it's never happened since. The only issue I get now is that a large flat thin prints generally warp during the drying process, I have not overcome this problem yet, even by letting them dry more naturally

Thanks both.
Trevor , yes I agree, I've had the same problem with things preferring to stick to the botom of the tank. I did up th supports to the heavy type and increased contact area and depth, but that didn;t really help. Printing at an angle would probably solve it as you say, but being wheels I wanted the backs flat obviously, and horizontal seemed the best way to print to achieve that.

I've also been trying to print the sides to my gearbox with limited success. They are 110x20x2mm thick and by angling it I could just squeeze it in. First time I printed one on supports, flat to the plate and got all sorts of warping issues. 2nd time I adjusted the raft and supports to give a bit more clearance but it peeled off the supports. I've just finished printing the two of them on edge, they are mirror images and printed side by side at the same time yet one of them has printed with thin spots verging on holes. They have both developed a slight curve whilst drying but I'm hopeful that leaving them pressed flat until I actally need them might cure that and once they are held by the spacers they should be ok.

As for the closeness to the plate, I suppose it could be that but I only checked the levels and zero set it the day before yesterday.

Edited to add that now they have set properly, under a weight, the bows seem to have gone. I also think I may know the answer to the thin spots. As I said, I printed them side by side close together to be able to get the length diagonally in the vat, plus the frame spacers in the triangular gap left at one side. I suspect that the viscosity of the resin prevented it from flowing back properly into the gaps between the elements between layers, because the defects are all at the plate edges and everything looks ok further up the print
I'll redo them in a day or so, but I'm waiting for some screws to arrive to assemble what I've done first, in case I need any mods.