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Messin' With Resin - 3D printed track

Martin Wynne

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Many thanks for the comments. All in all a pleasing result for a first effort.

The pong wasn't quite as bad as I feared, although it is very pervasive and still strong in that room this morning. I had the window wide open and a big fan blowing out through it as an extractor. A more engineered version of an extractor fan is on the cards.

The unsung hero of the evening, and not even mentioned in the instructions, is the plastic hook thingy to hold the build plate at 45 degrees while it drips the worst off. The print took 19 minutes and I left it dripping afterwards for about 20 minutes. All that time with the lid on and the air filter doing its stuff. I don't know how much effect the filter had, but the pong in the room got significantly worse later while cleaning up.

I then transferred the build plate quickly to the washer. With the holder at its lowest setting it required 1.5 litres of IPA (half the full capacity of the tub) to cover the plate. After finally realising that the washer won't start without the lid on (!) I gave it 5 minutes machine washing. Then a further 0.5 litres of IPA in an ice cream tub for brush washing (with a Lidl no.12 flat watercolour brush, other brushes are available). With intricate detailed parts I imagine thorough cleaning with a fine brush is important to reveal the full detail.

After which the print peeled away from the build plate quite easily with minimal persuasion from the scraper. Finally I put it in the basket for another 5 minutes machine washing, although whether that made any difference I don't know. I ideally you need a second tub with clean IPA for a final wash -- I will look at getting one.

Then a blast with the air gun which I use for removing dust when scanning negatives (other hairdryers are available) to dry it off. Finally back into the machine for curing. The turntable is a fiddly thing to engage the two studs. I supported the print on a small glass jar to put it more central within the UV lighting. I gave it 2 minutes as suggested, but it was still quite soft and flexible when removed. It has since hardened noticeably on the window cill this morning, so I may give it longer next time.

I didn't want to put the used resin back in with the new, so I found a black polypropylene container for it until next time. I couldn't find any information about a suitable container for it, but so far there has been no reaction with the polypropylene. I used a plastic funnel to support the disposable filter supplied -- bad move as it made one more thing to clean up afterwards. In future I shall use the disposable filter unaided (10 supplied).

The messiest job is cleaning up the resin tank. I wiped it out as clean as possible with kitchen roll, and then dunked it in the ice cream tub for brush washing. Obviously any smears of resin left on the film will harden and interfere with future prints, so it's important to get it completely clean. In case there is any resin left on it, I have stored it in the dark until next time (actually in the box the toolkit came in). There is a pouring lip in one corner of the tank, but clearly it was designed by a left-handed person because for me it seems to be in the wrong corner.

I've learned for next time that you need lots of clear bench space for putting things down, several old biscuit-tin lids ready to put them on, a big roll of kitchen towels, and a big tie-handle plastic bag to put the used ones in. The whole process seems a bit environmentally suspect, but we are not planning to make chairs on an industrial scale.

All in all a lot to learn, and it's a bit unpleasant to work with. Unlike using the Bibo FDM printer, which is a laid-back breeze in comparison, with a pleasant smell reminding me of childhood jam-making and blackberrying on summer afternoons long ago. The Elegoo reminds me only of my A-level Chemistry exam. :)

cheers,

Martin.
 
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Martin,

If you are going to use the printer fairly regularly, then you can leave the resin in the tank on the machine and cover it over to stop anything dropping into it. It saves all the hassle of decanting the resin somewhere and cleaning out the tank. You just need to give the resin a bit of a stir before use using a plastic utensil - I use a bit of 3mm styrene sheet although I've got a plastic scraper somewhere which came with my original printer but I can't find it. :) I now only empty the resin tank when I have to clean the FEP, change the FEP or change the resin.

Jim.
 
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Charles Orr

Member
Location
Leicester UK
Hi Martin,
My printer and wash/cure unit have been delivered and tomorrow I shall make use of all the good advice posted here to set it up ready to try it out.
I only have one track file at the moment which I think somebody posted some time ago. It's half a dozen sleepers with chairs.
I would be very grateful if you or any one else could let me have some stl files of chairs/sleepers etc to try out and experiment with print settings.
I'm modelling in 4-SF.
I can make a dropbox upload link available if necessary. (You don't need dropbox to use it.)
Many thanks.

Charles
 
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Martin Wynne

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West of the Severn UK
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Please do not send requests for help direct to me via email.

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And the verdict is?

I used the bog-standard default slicing settings for the Mars 2P in the Chitubox software. I was tempted to try changing things for finer detail, but decided to leave that until I know what I'm doing. :) In the event the result was very good, so it was probably a wise decision.

The end 2 chairs in each row failed to print. I got only the support pyramids with no chair on top. But the 3rd chair from the end in each row printed perfectly, and all chairs in between.

* This suggests that the UV illumination is not even, and drops off suddenly at each end of the build area. This probably means that only the middle 80mm square area of the build area can be used for fine-detail models. This may be on my machine only of course (Mars 2P).

* edit: see next post.

I found the missing bits of half-printed chair lurking in the resin, partly stuck to the FEP film, but easily removed. This surely affects the idea of leaving the resin in the tank unfiltered for next time? They would clearly impede the first layer of the next print. So if doing that, it would be important to check that the previous print was fully formed with nothing missing.

I set the dimensions in Templot to match Exactoscale code 75 steel rail, and it worked out very well. The chairs can be threaded onto the rail without difficulty (much easier than threading Exactoscale moulded chairs), but then hold the rail vertical (as intended) with no wobble or play. As you can see in the photos, there is no infill below the key (this is an option in Templot), so that the rail is held entirely by the key against the rail web as on the prototype, and not by means of the rail foot:

index.php


index.php


The plug under the base of the chair gives it a lot more "heft" than other 4mm chairs (if you can use such a word for such a tiny thing) so that there is no distortion and the chair sits flat after threading (unlike Exactoscale chairs).

Dimensionally there has been about 1-1.5% shrinkage. I don't know where in the process this occurs, but I suspect in curing. The finished sizes are:

chair length: 4.79mm. Prototype 14.5" = 4.83mm (Exactoscale 5.08mm, noticeably larger than scale alongside these).

chair width: 2.64mm. Prototype 8" = 2.67mm (Exactoscale 2.79mm, noticeably larger than scale alongside these).

plug length: 4.12mm. Design 12.5" = 4.17mm.

plug width: 1.97mm. Design 6" = 2.00mm.

Some allowance for the shrinkage may need to be included in the files. On the other hand, the shrinkage on the plug is maybe welcome to ensure a clearance in the sockets. But we don't want too much because they will be setting the gauge. Some final tweaking of the dimensions is likely to be needed.

I'm attaching the .ctb file below for Charles and anyone who wants to try repeating my antics in an Elegoo. But you won't be able to make any actual use of the chairs until we have some timbers with matching sockets.

(This file is ready to use on the printer, it is already sliced and ready to go -- just save it onto a USB stick.)

p.s. I'm using the "ABS-like" Elegoo resin. Results with the standard resin may differ. Colour grey, results with other colours may differ.

cheers,

Martin.
 

Attachments

  • _32_chairs_s1_exacto_rail.ctb
    1.5 MB · Views: 19
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Martin Wynne

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Please do not send requests for help direct to me via email.

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I've been thinking a bit more about the missing chairs.

As the build plate lifts, some fresh resin must get sucked in under it. Anything very delicate near the edge may get dislodged by the incoming tide. Such as the first bottom layer of the chair plug, which is only 2 thou thick. This would suggest there is an area about 20mm wide all around the build area which can't be used for fine detail.

The solution would be for the underside of the chair plug not to be flat, but deeper in the centre, so that the area increases gradually as new layers are added. And maybe change the lift speed.

I can see there is going to be a lot of tweaking and trial and error needed to reach a final working design.

Martin.
 
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I found the missing bits of half-printed chair lurking in the resin, partly stuck to the FEP film, but easily removed. This surely affects the idea of leaving the resin in the tank unfiltered for next time? They would clearly impede the first layer of the next print. So if doing that, it would be important to check that the previous print was fully formed with nothing missing.

Martin,

You have to check out your prints to make sure everything is there if you leave the resin in the tank. You can double check that the FEP is clean by gently scraping a plastic scraper along the FEP to check for stuck on bits when stirring the resin to mix it up in the tank. If you can feel anything, then you can empty the resin out through a filter to catch any loose bits then clean the FEP.

There's also a facility on my Phrozen Sonic Mini to clean the VAT. This illuminates the LED array for a period with no build plate involved, and it forms a thin sheet across the whole print area which includes any bits left on the FEP. You can then remove this thin sheet along with all the left over bits. I find it a bit fiddly to get under the edge of this film to lift it out of the tank with the resin still in but I'm getting there, using a bit of thick styrene as a tool. I'm assuming that the film should be removed leaving the resin in the tank otherwise, if you have to pour the resin out before removing the film, why bother using the facility in the first place. :) It's a new thing to me and I'm still finding out about it.

Jim.
 
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Last edited:

Martin Wynne

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West of the Severn UK
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Please do not send requests for help direct to me via email.

Post your questions on the forum where everyone can see them and add helpful replies.
I would be very grateful if you or any one else could let me have some stl files of chairs/sleepers etc to try out and experiment with print settings.
I'm modelling in 4-SF.

Hi Charles,

See my previous post for the CTB file of the chairs with plugs, ready for printing.

Here's an STL file which you might like to try. 8 sleepers in 4-SF / 00-SF with S1 chairs for Exactoscale/C&L rail:

stl_for_charles.png


The offset webbing is to indicate which side is MS. it is 1mm square.

I have never printed this, so I've no idea if it is any good. :)

p.s. ignore the message in Chitubox that it is too small. Every single thing I've tried has been allegedly "too small".


cheers,

Martin.
 

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  • exacto_rail_8_sleepers_4_sf.stl
    2 MB · Views: 17
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Charles Orr

Member
Location
Leicester UK
Hi Martin,
I've set the printer up and the first print is excellent. I've attached some photos below.
I'm very pleased with the quality.

20210318_155654.jpg20210318_155705.jpg20210318_155422.jpg20210318_155510.jpg20210318_155607.jpg
I'll have a go at the stl file tomorrow.

Charles
 
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Martin Wynne

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Please do not send requests for help direct to me via email.

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Hi Martin,
I've set the printer up and the first print is excellent. I've attached some photos below.
I'm very pleased with the quality.

View attachment 643View attachment 644View attachment 645View attachment 646View attachment 648

Charles
Hi Charles,

Those look great! I'm glad you're pleased. :)

Did you get all 32 chairs, or lose some at the ends of the strip?

Your close-up photography is better than mine, and for the first time I can see the square tops and random angle on the chair screw heads. Well on two of them anyway:

charles_chair.jpg


I notice that you've lost one corner of the chair base. That happened to me in handling, too. I will look to thicken it up a fraction. It's prototypical for an occasional chair, but not too many.

I can also see some layering from the slicer on the side of the base. I set the standard 0.05mm Z layers in Chitubox, which matches the X-Y pixel resolution for the UV image. It's possible to go finer for the layers only, some tweaking experiments are called for. On the other hand, the layers will probably vanish under the paint. The chairs are infuriatingly difficult to photograph unpainted, even though the raw resin seems quite a dense grey.

I've been working for the last couple of days on getting a direct STL export from Templot, instead of needing to convert from DXF. It's now beginning to look promising, after a rubbish start.

Thanks for posting your results.

cheers,

Martin.
 
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Charles Orr

Member
Location
Leicester UK
Hi Martin,
Yes, 4 chairs at each end of the strip were missing.
Direct export from Templot would be fantastic. I'll keep everthing crossed . :)
I'm going to have a proper play tomorrow.
I've also got to get my head around the slicer settings.
Is it possible you could tell me the settings you actually used?
A photo of the relevant page in Chitubox would be fine.

Charles
 
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Martin Wynne

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Please do not send requests for help direct to me via email.

Post your questions on the forum where everyone can see them and add helpful replies.
Hi Martin,
Yes, 4 chairs at each end of the strip were missing.
Direct export from Templot would be fantastic. I'll keep everything crossed . :)
I'm going to have a proper play tomorrow.
I've also got to get my head around the slicer settings.
Is it possible you could tell me the settings you actually used?
A photo of the relevant page in Chitubox would be fine.

Charles

Hi Charles,

The missing end chairs are so repeatable and predictable that it looks to be something in the machine or software rather than just happenstance on the day. Something to investigate or find a work around for. I have already changed the bottom of the plug to be thicker in the centre -- there will be a clearance in the sockets anyway.

Did you empty and filter your resin tank? If not bear in mind that the missing chair bits will be still in the resin, to cause problems with the next print.

In the end I didn't change any Chitubox settings, I used the preset defaults for the Mars 2 Pro:

chitu_elegoo1.png


chitu_elegoo2.png


The settings are under the Print tab:

chitu_elegoo3.png


and can be changed as required.

This is utter simplicity compared with the dozens of settings and options for filament-printing. Ideally we would set finer layers for the chairs only, and not the whole thing, to save time. But that option doesn't seem to be available.

But given the results with the default settings above, there doesn't seem much reason to change them. Obviously layer height and exposure time are inter-dependent, so it would be easy to mess it up. :)

cheers,

Martin.
 
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Charles Orr

Member
Location
Leicester UK
Hi Martin,
Yes I need to filter the remaining resin.
I've got one of these arriving tomorrow, so no need to faff about with paper filters and intermediate pots.


I subscribe to a number of YouTube channels that offer advice on setting the Chitubox settings.

But, as you say, when the prints are this good there seems little point in changing them.

Charles
 
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Martin Wynne

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Location
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Please do not send requests for help direct to me via email.

Post your questions on the forum where everyone can see them and add helpful replies.
Hi Martin,
Interesting, your default settings are not quite the same as mine.
This is the latest version of Chitubox - 1.8.1
View attachment 662

Hi Charles,

That's interesting. Did that version of Chitubox come on your USB stick or have you upgraded since? I saw that there was an upgrade available, but decided to leave it until I had got going with the software actually supplied with the machine. The settings in there correspond to those in the printed manual (which is also the same on the latest download of the manual).

However, there is a spreadsheet available online which corresponds to your later settings, and has different settings for different resins and colours:

https://www.elegoo.com/blogs/3d-printing/elegoo-printers-resin-setting-sheet


mars2p_rec_settings.png


The significant change is the longer 2.5 second exposure time, and slower speeds. The only way to find out which works best is to try it and see on the same print. The longer exposure may make a stronger print with no effect on detail, or it may cause each layer to flash into the next, losing some of the finer detail. I don't know what difference the speed of movement makes to the print quality. But the overall printing time will be increased on the later settings.

p.s. did you notice on the box the resin came in, that "red" and "maroon" seem to have got swapped over? And also that "grey" is spelled like that in the UK way? (And above). On everything else in the IT world it is spelled "gray". Hmm.

cheers,

Martin.
 
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Loaded up your chair Chitubox project, scaled it ro S (119%) and saved it to suit my Phrozen Sonic Mini 4X and the Phrozen ABS-like Grey and had a print.

TemplotChairs-01.jpg


All chairs printed


TemplotChairs-02.jpg


A bit closer showing the layering at 0.05mm height. The print had a scoosh of Halford's Grey Primer to make it photograph better. I think I would try it at 0.03mm to see what the improvement might be. Anti-aliasing had been applied - setting "4" in Chitubox. But you don't actually notice the layering when viewed by eye.

TemplotChairs-03.jpg


And the chairs fit SSMRS Code 87 rail very well. :)

Have you got the original chair .STL without the plug and the single heavy support so that I could experiment with other methods of setting the chairs out for printing?

Jim.
 
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