First resin print failure

It had to happen, for some reason a print did not release.

This is another area where FDM and resin are very different. With FDM it keeps going and you end up with a lot of spaghetti and goo. With resin the print keeps moving up but the failed layer stays on the release film, and just gets re-cured as the print go - you end up with one aggregate layer.

So, poor out the resin (need funnel and filter) in to a bottle. Remove stuck layer, that was easy. And ready to go.

Well, not quite, for some reason it kept saying foreign material detected. I cleaned out the tray, both sides, and started again and OK. In fact, it seems once can remove failed print layer with a fingernail (in a glove) without pouring out resin even.

I have noticed a scratch on the film though, so have more coming and will have he fun of replacing the file. That may be a job for tomorrow.

I have no idea why it did not release. The print was the same as previous.

Update: sorted release film, seemed good, but had another failure - which highlights a feature of resin. With FDM a failed item would wreck the whole print, the spaghetti sticks to the nozzle, and you end up with a total failed print. With resin, one can have a partial failure, like this.

Prototype 3D

This is why I got the printer...

One of the challenges with any engineering is that no matter how much to check the design, some issue are only noticed when you finally make the actual item, and have it in your hands. This is even more true for 3D models.

I can order 3D prints from China, with a turnaround of around a week. I could print designs on my FDM printer, but not the same - especially small details like the interlocking lips on the case designs (those on the right of the image are for a Faikin). The precision needed for these is not possible on FDM.

But even simple things can catch out out. The white 1 gang back box cover on the left took a week, and on arrival I see the problems - not just the square corners that do not match the back box I have, positioning nipples in the ring are wrong so the back does not lock in the right place, and the back of the ring is 0.5mm thinner which shows on the actual print. Now I can prototype I can test with a turn around of half an hour. I can get the designs right, and then order some from China. I have white resin coming soon as well.

What is fun is that having spotted the errors in the white 1 gang plate, I fixed the design, and printed a prototype for this post. I have just checked and my fix is not correct - I see why now, and have another fix to prototype.

As you can see this saves a lot of time, and some money.

Getting the hang of it (3D resin)

I am getting the hang of it. I am sticking with the washer washable resin for now. It will be an extra step of messy to use the standard resin, and I don't have any spray bottles of isopropyl alcohol left at the moment.

The Mercury washing/curing machine was somehow jamming the stirrer, which is why it did not seem to work. It is OK now, and does a good job cleaning - which makes it much easier. It also seems I can clean with isopropyl alcohol, which dries quickly before curing and will be the same for standard resin.

I did manage to spill resin all over the machine, which was annoying, and some is still leaking out of the bottom days later! I am, however, very reluctant to dismantle it. It is working fine.

I have the air purifier now, which links in to the back of the printer with a hose, and keeps the odour down. Again, standard resin may be a different matter.

So far the printing side is click and print with no problems. The model supports are indeed a lot simpler than for FDM - just needing the smallest contact. Basically it looks like bridging is much cleaner on resin printing just needing an anchor each end where as on FDM the bridge will sag. With resin it is upside-down.

The detail is impressive. The fact that the resolution of FDM is the same as resin hides the ability for resin to produce detail that is impossible for FDM. The extruded filament on FDM has a shape and per layer texture and minimum size that make the detail impossible. The teeth on this model highlight this nicely.

Moving from FDM to resin 3D

I have done 3D printing for a long time, since the days of 3D printers being kits and burning out stepper motor drivers.

My latest 3D printer was Lulzbot Workhorse, and it is pretty good. The Bamboo ones are, as I understand it, way more impressive than that even.

But this is FDM - using reels of filament, melted and deposited. It works well. But there is another whole 3D printing world with resin printing.

My new printer is an Elegoo Saturn 4 Ultra 16K - a resin printer.

Print size

Downside number 1 is the print size, way smaller. FDM can do all sorts of large sizes, my Lulzbot is 279x279x284mm which is quite big.

The resin printer is 211.68 × 118.37 × 220 mm. The reason is the print bed has an LCD or some such that prints a layer at a time. Where as the FDM has X/Y/Z motors and is limited only by physical size. Bigger LCDs are expensive. Longer bits of metal to make a larger FDM printer are less so. 

Resolution

Upside number 1 is resolution, and this is where it gets crazy. FDM is good, but resin printers are crazy. For Z axis the Lulzbot can go down to 50µm, but the Elegoo starts at that, and can, AFAIK go down to 20µm or perhaps lower. As for X/Y, both do well, with Lulzbot down to 10µm, but the filament is a 0.5mm (500µm) nozzle. The resin can print down to pixel at 14x19µm.

The result is resin printing sharp points and groves, and features really well where FDM is 0.5mm nozzle limited, and printing with way lower layer size. This allows sharp and exact features for resin printing.

Also the print is per layer textured, the layer has a bulge in centre of filament track. Not so with resin. Vertically resin is smooth and clean. So even at same 50µm layer, resin printing is way cleaner.

Level surfaces

Another difference I was amazed to see for resin was the top edge flat surface of a print was level, exactly level, I mean shiny level and smooth. FDM has ridges and texture. The bottom not so different as both print against a base plate and tend to be as smooth as that plate.

Levelling for the start of print is important and the resin printer seems better.

Print speed

This is more of an interesting one - FDM prints depend on time to trace the print layer by layer. So more detail in any layer takes longer. Adding support takes longer.

With resin a layer takes a number of seconds, end of story - no matter what.

So a biggie is if I have a small thing to print, for FDM, if I print 5 (assuming they fit on build area) is 5x longer, or worse. For resin it is same time as same height. Uses more resin but not more time.

Similarly the complexity of a design, the detail, the supports, all matter for FDM print time, but no issue for resin.

All that matters for resin is height and layer thickness. I.e. how many layers. It is a very different way to consider complexity.

Smell

The resin printing has a smell, but very minor. I have an air filter on order, but to be honest I am not sure I need that.

Sound

Resin printing is way quieter. I like this. Really way better.

Sticky

With FDM, print finish, take off bed, done.

With resin, messier. I am working on the best way to handle this, but you remove print, it drips, take to tub for cleaning (or maybe tap for water cleaned resin), put in curing for a few minutes, remove from bed. It is more work, and more chance of stuff dripping. More chance of "mess".

Changing material means pouring resin back from tray, cleaning and new resin, maybe changing fluid for cleaning (water/alcohol), way more hassle than a filament change on FDM.

So yes, a bit more, but working on it - not sure it is a lot more hassle in the long run. The results are amazing.

Prototype

The main reason for this is prototype designs - I can order bulk resin prints from China, but they take a week. This allows way quicker design refining before ordering, and quick one-off prints.

That alone makes it worthwhile.

Ordering 3D prints

I have a 3D printer, it is pretty good, but I decided to try ordering some 3D prints from JLC.

Price

The most obvious issue is price, and actually, it is good. I have 2 part 3D printed cases for my Faikin boards for $0.47, but the postage is actually more, making $1.52 delivered, (£1.13+VAT). This is actually pretty good.

Quality

This is perhaps more important - could I have printed myself better - well NO, really NO! The quality is amazing. Resin prints are always good compared to FDM, and these are post processed with sanding.

The precision is also amazing. These designs are made with exact edges, no margins. I thought this was a good test. Well they fit smoothly, and just stick, but not very firmly. This means the dimensions of the print are, well, pretty damn exact to tiny fractions of a millimetre.

The result is quite impressive.

Improvements

My case design are auto generated from the PCB, so as to make sure they fit exactly. I have now done a load of work to tweak these, adding 0.1mm more to the edges that lock and a tiny angle to snap to place. So will be trying those. Will be interesting to see if I can make it a tighter locking edge now.

But, for now, a tiny spot of glue makes a nice case, so selling these on Tindie.