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.

Interesting new scam "worry free purchase"

Ordered something online and this is on they list this...

It has a delete icon, but do it, and it re-appears.

Update: They credited the £11.99 - yay!

Seems a third party service.

Seems mandatory.

So ordered the goods, and then emailed (seller, and supplier of 3rd party service) and said under various UK distance selling directives I wish to cancel the "worry-free purchase" service as I am more than happy with my purchase to be covered by UK statutory provisions, which seem to cover all they cover on that service.

We'll see if I get a refund or I have to claw back on card.

Extra irony, their "worry-free" purchase service is causing me "worry" I would not have on any normal purchase.

OK this has worried me...

NFC reader and alarm/door entry system

A long time ago I made a door entry and alarm system. Actually my first was approx 1989 using a mag head from a Sony walkman on a block of wood on the door and a wire wrap 6502. My latest attempt a few years ago is a lot more sophisticated.

It is good, indeed, I would say it is very good. It has a lot of off line working built in but backed by internet management/control system, so designed for power and internet failure, for hours, or even days.

The NFC door control uses AES on DESFire cards, so no plain text even on RF, and challenge both ways, so super secure. It even has different keys for each card. But it scales to any number of cards, with different access levels encoded in the card so as to work off line if needed (for a configurable time).

Like I say, it is good, and we use it, and a hack spare uses it (maybe two) and several small offices.

But it is tricky to sell.

Insurance and alarm companies have stuff tied up

Perhaps the biggest issue is that insurance companies and alarm companies have some industry standards and something of a private club. Yes, we could join, I am sure, but only if I wanted to be come an alarm company. Open source stuff is not going to get in to the club no matter how good it is. This is a shame as proper (Galaxy) alarm systems can be crap by comparison, as we know because we had one, installed by a certified installer, and were robbed!

My understanding is that one of the rules (I heard from an installer) was you can't have some external indication of armed or not. This ment staff did not understand they failed to arm. It beeps in various incomprehensible ways, and shows stuff on the keypad (which you cannot read from outside when using the fob to arm), so they assumed armed when not.

My system can show such, but we go for subtle - internal lights go off when armed. I mean you would turn off anyway, but staff can tell instantly that the lobby light not going off means not alarmed. The light switch does not allow manual turn off. Simple steps but has meant that on the odd occasion of not arming (e.g. fire exit open) staff knew. This is what caused the problem on Galaxy.

I also allow a forced alarm for such cases as a last resort - where the open fire exit becomes a sensor - someone closing it would set off the alarm. This means I can set forced alarm on timer, and be alarmed if staff have missed the problem somehow and still have a working alarm (all PIRs, etc). The Galaxy, when it does not arm, does not arm, end of story. It is a compromise I suspect an official system would not allow.

So basically you need to check (and record the call) insurance are happy with no proper alarm system, etc. Seems many are, and may not even charge more, but having it on record should mean you are covered.

Monitoring

Another issue is monitoring of the alarm. We had that once at an office, and it was such a pain. And one time when we did not know then code word, they said the police would be called. The police did not turn up so I was stuck there for 4 hours on a Sunday waiting for police. Also police won't come if you have too many false alarms.

My system monitors, but messages people, several people, like me, people with access to the CCTV who can confirm it is a false alarm, and if not call the police explaining they can see the burglary in progress on CCTV. That will, I expect, get a way better response than an alarm company calling.

Also much easier to integrate to external systems - staff in office logging for fire list, etc.

Locks

Another issue is locks, and the typical internal door lock is a mag lock, which is really easy to defeat. I have found much better locks and would recommend using them - Abloy locks. These work without the alarm and use a proper euro profile lock, and can be set to open from inside regardless, but also have a load of sensors (key used, handle used, lock in/out, etc).

Opening from inside also avoids the messy "break glass" and "exit button" you typically need.

So my system has to handle everything from a simple maglock and exit button, to the Abloy with something like 5 inputs - which it does nicely now.

It costs more, but in the end it is worth it.

Professional kit

With all of the above, an alarm or door entry system can work, with insurance confirming OK, etc.

But the kit is not as professional, or is it.

When I started I had single sided copper clad boards milled and hand soldered. I have moved on to proper PCBs made in China. I have moved on through a load of connector types to WAGO PCB connectors which are just simple to use for an installer. I have added per input/output LED status on the PCB.

But still, the case is a messy 3D print on my printer. Well, now we moved on finally with high resolution, smooth, clean, 3D resin prints from China.

The wiring and connector to the NFC reader was also a concern, but ironically the leads I got made in China for Faikin boards are perfect for this, and again, professional, so making it all easy to install and just more professional.

I finally feel like I have stuff that is professional looking.

The NFC sensor on a door. It looks proper now.

I have even now designed one for a 1 gang UK pattress box.

So now I plan to list these boards and cases on Tindie soon. The NFC reader is ideal for a hobbyist working on any NFC stuff.

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.

Trying 0201

I decided to take the step to move some of my PCB designs to using 0201 components.

This is basically accepting that I do not even try to solder these things now. A few years ago I started milling boards and hand soldering 0805, and then 0603. I can just manage 0402 if I am very careful. But no way I could do 0201s. These days I design boards and have them made and assembled and shipped. 

It seems JLCPCB can do 0201, so why not?

What's an 0201

Components have various size designations, sizes liked 0805, 0603, 0402, 0201, 01005 are used for standard chip type resistors and capacitors. An 0402 is 0.04" by 0.02" which is 1mm by 0.5mm. An 0201 is 0.6mm by 0.3mm which is tiny.

This picture gives you an idea - a ball point pen shown for stale (a banana would not fit), and the diagonal square things (LEDs) are 1mm by 1mm. You can see ten 0201 resistors and an 0201 capacitor.

So yes, grains of sand. The 01005 things (not doing those yet) are like dust, and there are some that are smaller!

Pros and cons

With 0402 it is possible to run a track under it, i.e. between the two pads, but with 0201, not so much. That said, I rarely ever do a track under an 0402 anyway. Sometimes larger components.

Obviously some components have to be bigger, and you end up with this crazy mix for capacitors - but that has always been the case - larger caps, higher voltages, mean physically bigger caps. But resistors are less of a problem usually - yes sometimes you need bigger ones, but mostly they can be 0201s.

The main advantage is the space saving - my PCBs are often nice and small, so this is handy.

Now, I know my colleagues doing PCB design also need 0201 caps for decoupling as they need to be physically small and close to components. Thankfully I am not doing stuff that high speed with my ESP32 modules, well, yet.

So far they are working - in that JLC seem more than capable of placing 0201.

Footprint

KiCAD has standard footprints, but interestingly I found this fun article, so trying their suggestions. Some test boards to make sure no production issues - surprisingly JLC has not specific recommendations.