Adventures in the third dimension

Winander
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Re: Adventures in the third dimension

Postby Winander » Mon Feb 22, 2021 12:48 pm

kelly wrote:If you find his pace a bit too fast, then you may try to slow the video down using the YouTube controls.


Kelly, Paul,

Also try using captions/subtitles. They're automatically generated but are pretty accurate.
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Paul Willis
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Re: Adventures in the third dimension

Postby Paul Willis » Mon Feb 22, 2021 7:44 pm

Winander wrote:
kelly wrote:If you find his pace a bit too fast, then you may try to slow the video down using the YouTube controls.


Kelly, Paul,

Also try using captions/subtitles. They're automatically generated but are pretty accurate.


Thank you both. I've just tried the subtitles, and they are pretty effective. I'm still going back and forth, but not as often as I was at the outset. Whether that is the subtitles, or whether it is an increasing familiarity with the basic controls in the program, I don't know. I'll ascribe it to the subtitles...

It's working though. The latest lessons cover a lineside relay box:

3D relay cabinet.png


And a gas bottle:

3D Gas bottle.png


More importantly, they aren't just "objects", I do actually understand how they are put together.

If I have more time later, I might just rattle through another lesson.

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Paul
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kelly
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Re: Adventures in the third dimension

Postby kelly » Mon Feb 22, 2021 8:17 pm

Winander wrote:
kelly wrote:If you find his pace a bit too fast, then you may try to slow the video down using the YouTube controls.


Kelly, Paul,

Also try using captions/subtitles. They're automatically generated but are pretty accurate.


The reason I didn't suggest that is the auto generated nature of them can struggle with some videos, so very much a hit or miss affair.
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barhamd
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Re: Adventures in the third dimension

Postby barhamd » Tue Feb 23, 2021 12:21 am

I know this is 16mm not 4mm but I thought you might like my tortoise stove..
IMG_8459a.jpg


The printer even managed the 'Slow but sure combustion' text.

IMG_8423a.jpg


On the 4mm front here was my attempt at a GER chimney.

J17-chimney-IMG_8550a.jpg
J17-chimney-IMG_8550a.jpg (149.13 KiB) Viewed 1705 times


The chimney was printed on a Phrozen Sonic Mini 4K.

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Paul Willis
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Re: Adventures in the third dimension

Postby Paul Willis » Tue Feb 23, 2021 6:39 am

barhamd wrote:On the 4mm front here was my attempt at a GER chimney.

J17-chimney-IMG_8550a.jpg

The chimney was printed on a Phrozen Sonic Mini 4K.


Thanks David. I was thinking about chimneys as a use case yesterday...

We've all had that situation where the diameter of the smokebox doesn't quite match the diameter of the flange at the base of the chimney. It usually results in a little cursing, a lot of filing, and a flooding with solder.

Speaking hypothetically, as I haven't tried this yet, it should be possible to measure the diameter of the smokebox to a fair degree of accuracy, then use that to make the cut-out at the base of the printed chimney. That could result in a perfect match with no gaps.

What I next have a need for such I thing, I'll have to remember this post...

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Paul
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Adventures in the third dimension - what's in the box?

Postby Paul Willis » Sat Mar 06, 2021 10:36 pm

It's been a couple of weeks since I last posted an update on my exploration of 3D printing.

I still haven't set up the printer :-)

I have, however been very busy learning Fusion 360 to know how to use it when I do. As I commented elsewhere, it's a bad workman who blames his tools, and I need to know how to use the "tools" in the form of the software before making my own new and interesting form of mistakes.

I've reached Lesson 10 in the series that I mentioned in a previous post. It's motivating to be doing design that is relevant to railway modelling - I'm currently learning how to create arched window frames of the type that you would find in an engine shed. I'm making a lot of mistakes, such as drawing bricks on the wrong side of walls, but I'm probably learning more from finding out what I did wrong and how to put it right than I would do from simply following instructions and never having anything go wrong.

However, I thought that I'd better mention something else about the Elegoo printers, in case Amazon have another one of their "flash sales" and someone fancies taking advantage. After all, I saved nearly 20% off the price of mine when I bought it.

When I unpacked the box, I was surprised to find this:

IMG_7634.JPG


And inside was this:

IMG_7635.JPG


Apart from the necessary power leads, it really does include a "start-up" set of tools - rubber gloves, mask for use when handling resin, jug for pouring resin, a USB stick to transfer design files to the machine, and a couple of scrapers for removing the prints when they have finished. I've learned that bit already! All this will save you a few quid - I had a £5.99 plastic razor blade scrapper on the way to me at the same time as they had been recommended.

Also included was effectively a further 15 quid discount:

IMG_7633.JPG


A proper set of Xuron shears, intended for removing sprues from prints, but in reality going straight in my toolbox :-)

Now back to that online learning...

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Paul
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Guy Rixon
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Re: Adventures in the third dimension

Postby Guy Rixon » Thu Mar 11, 2021 12:51 pm

I've just changed the FEP film on my Mars Pro for the first time. It's both easier and harder than I expected: easier, because the tensioning is less of a problem than I expected; and harder, because the official instructions leave out some information. I set down some detail here so that nobody else need make the mistakes I made last night.

First, tensioning: it's important to get the film properly taut, otherwise it deflects too much and prints go wrong in the middle of the bed (so I'm told). On the Mars Pro, the film is clamped between two pressed-metal frames with 24 screws and that assembly is then put into the cast-metal surround of the resin tank with 10 more screws. It looks like one has to get the tension right with the frames and film on the bench, before mounting in the tank and this is hard. I spent ages pulling at the film with one hand, holding the frame with the other and tightening screws with the hypothetical third hand. All wasted, because this is not the stage where the tension is set.

What needs doing is tightening up the screws evenly and properly tight, because the eventual tension will be high and much clamping force is needed. When the frame is screwed into the tank, the film is stretched like a drum head across the lip of the channel in which the frame sits and it's the torque on the frame-securing screws that sets the film tension.

The frame needs to sink into the channel by most of a millimetre from the position where it first sits with the film resting on the lip of the tank. This make things tricky, because the screws are a millimetre shorter than they really need to be. Once the first screw is engaged, the frame tilts and the others won't reach their tapped holes in the frame. Therefore it's important to tighten down the screws in stages, and on alternate sides of the frame a little like fitting a cylinder head. Each time a screw is tightened the frame sinks a little more into the channel and all the other screws loosen.

People claim that the tension can be checked by the note that the film plays when tapped. That's a great idea, but what the on-line information doesn't explain is that it's consistency of the note that matters, not the absolute pitch. I got my film to play as near as possible the same note when tapped next to each screw. I couldn't get as high a note next to the screws in the middle of the short sides of the tank, so I assume that the tension there is less and printing at the ends of the bed will be less reliable. The design possibly needs two screws in the middle of each short side. The torque on the screws was "as much as I can get with an Allen key without hurting my fingers too much"; and I have weak, sensitive fingers.

Second, the big mistake I made last night: not removing the protectors from the FEP. The films are shipped with clear-plastic protectors --- like screen protectors on a 'phone --- and these have to come off before fitting. If they are left in place then all the prints stick to the film like excrement to a bed covering, the protectors not being as smooth as the film proper. Elegoo's instruction video doesn't mention this. There's a protector on both sides of each FEP sheet.

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Paul Willis
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Re: Adventures in the third dimension

Postby Paul Willis » Thu Mar 11, 2021 5:38 pm

Guy Rixon wrote:Therefore it's important to tighten down the screws in stages, and on alternate sides of the frame a little like fitting a cylinder head.


Best bit of advice here. Just because it makes me smile.

I wonder if I should go to the garage and get out the smallest of my torque wrenches when I first need to do the job...

More seriously, as a question: what were the indications that you had that the FEP needed changing?

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Paul
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Guy Rixon
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Re: Adventures in the third dimension

Postby Guy Rixon » Thu Mar 11, 2021 7:20 pm

The old film had picked up a few scratches, so I was getting ready to change it, just in case they were affecting the print quality. Then I had a failed print stick very firmly to the film and in removing it things got a bit wrecked.

Essentially, every time something sticks to the film instead of the build plate it degrades the film. As it degrades, it gets less slick and things are more likely to stick. After a dozen or so print-failures it goes to blazes rather quickly.

davidatkinson
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Re: Adventures in the third dimension

Postby davidatkinson » Thu Mar 11, 2021 9:07 pm

It’s not unknown for a small hole to appear in the FEP film, you’ll know this has happened as resin will ooze out. If it does take care when you remove the vat, some of the resin may have cured between the FEP and the screen, thus take care it’s very easy to pull the screen out accidentally.

If this does happen all’s not lost a new screen is £26 and less than 10 minutes to fit.

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Guy Rixon
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Re: Adventures in the third dimension

Postby Guy Rixon » Fri Mar 12, 2021 12:05 pm

Another factino that may help specifically with the Mars Pro and its particular design of build plate: wide things stick better than narrow things.

The print that prompted the refilming was a batch of wagon brake-levers, printed on supports with skates. The base layers came out about 30 mm long by perhaps 8 mm wide, and most of them fell away into the Pit of Doom, even with the new film. I closed up the arrangement in Chitubox so that the skates were contiguous and they then printed properly.

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Paul Willis
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Re: Adventures in the third dimension

Postby Paul Willis » Fri Mar 12, 2021 9:39 pm

Thanks Guy - couple of really useful bits of information there.

I'm still waiting to set mine up. I'm mulling over plans on how to rearrange the study to accommodate all the bits and pieces that I want to have access to, without constantly unboxing and boxing them. Ho hum!

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Paul
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Winander
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Re: Adventures in the third dimension

Postby Winander » Sat Mar 13, 2021 4:14 pm

Guy,

With regard to the brake cylinders you have just posted on your 'The LNWR brown train' thread, how does the quality of the home produced print compare to, say, the most practical material from Shapeways? Also I am surprised that you need to print platform - i.e. the 'sheet' that the support framework is connected too; what's the reasoning behind that?

The results do look really good.

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Guy Rixon
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Re: Adventures in the third dimension

Postby Guy Rixon » Sat Mar 13, 2021 4:44 pm

Richard,

visually, the print quality from my Mars Pro printer (the same one that Paul is setting up) is comparable to Shapeways SFDP on the fine detail and somewhat better on flat surfaces. In the high-resolution version of the photo I posted today I can see a ridged pattern on the flat tops of the vacuum cylinders, but it's invisible to my unaided eye and in the low-res photo as posted.

The practical limit on thin wires is about equal to what Shapeways will accept at ~0.5 mm thickness. When the home prints are cured, the parts are more fragile than Shapeways resin. This makes sanding away the support nubs a bit fraught.

The platform is just the conjoined skates at the build-platform end of each support. If I had fewer supports it wouldn't be a contiguous sheet. In the brake-cylinder batch, the undercut on the edge of each skate (added by Chitubox, to help one get a scraper in to detach it from the build plate) leaves grooves across the platform and the combined print has snapped at one of these groove, separating the batch into four and two useable assemblies.

As I mentioned in my previous post, if there is a narrow platform or too few skates, the chance of the print detaching from the build plate gets too high (this may not hold true for all resin printers of this general type).

For these brake thingies, which are each bound together by fragments of the middle bearers, I could print directly on the build plate, without supports and skates. I decided not to do this, firstly because of the risk of things dropping off and secondly because of the risk of breaking the prints when getting them off the build plate. Usually, if they stick at all, they stick very firmly; brutality with the metal scraper is needed to remove them.

Winander
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Re: Adventures in the third dimension

Postby Winander » Sat Mar 13, 2021 6:37 pm

Thanks very much Guy, extremely useful information.
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