The Lowspec spectrometer

[Paul Gerlach]

Printing the body in ASA can be challenging. Temperature differences will cause warping so keep out any draft or place a large cardboard box over your printer to keep the temperature more stable.
Don't use to much infill. I found that three shells and a 30% infill (full honeycomb). The more material you put into the model the larger the shrinkage forces.
I use AlfaOmnia for the body and lid. It's a carbon filled material that's stiff and very easy to print with little to no warping. Here's a body I printed on a Sidewinder X1 with a steel nozzle (0.5 mm) and 250 micron layer height.

 

[Gregj888]

Paul, thank you.  I dropped back to 30% infill and made a few other minor changes.  Now have a 2 day, 4 hour and 3 minute print...🙄

The print is underway, to be continued...

Update 2/25 @ 11:30 Pacific-  Well calling it a night, printer can keep working (I hope)- 14 hours in.   Paul, 0.4mm nozzle, 40mm/s print which is cut to 20 for a lot of operations and Cubic fill so ~52 hours.  Cura doesn't have honeycomb but does have a mix of hex and triangle.  For a one time print, 52 is OK if it makes it through.  adding to the earlier post to keep it in one place, hope that's OK?

 

Edited May 26, 2020 by Gregj888

[Paul Gerlach]

Print time for the body on mine Sidewinder X1 takes 30 hours (0.5 mm nozzle, 250 micron layer height, 3 shells, 30% infill full honeycomb, speed 60 mm/sec)...

[Valerio]

Hello Paul and everybody, first of all thanks for the great LOWSPEC 3 project I am starting to build. I am new to this forum but I read all the conversation and hope to be able to print everything and then add the optics (that seems pretty complex reading all the chat threads). Anyway, I just printed the lid and the main box (printer ENDER 3), and I see Paul has just updated the lid. Is it important to reprint it? If it's so I will of course print it again 🙂

Now I need to print all the other pieces... and then I will think to buy the optics
I am going to use this spectroscope with this setup:

Celestron C6 f/10 or f/6.3 (with reducer)

Main Camera ZWO ASI 294MC pro color

guide camera ZWO ASI 120 MM Mini mono

Do you think it is a good working setup ? Is it ok without changing anything in the original project (to have correct focus on both cameras?)
Thank you!

Valerio

 

[Paul Gerlach]

Hello Valerio! Welcome to the world of spectroscopy!
If you've printed the lid face up (according to the image it looks like it) then you're fine.

Although the 294MC pro colour is fine to start to get your feet wet, it's better (almost mandatory) to use a monochrome camera. Due to the bayer mask used in your colour camera you'll loose sensitivity and resolution.
I think the back focus is something in the order of 53 mm so no problem.

Nice looking prints! What material did you use?

regards,
Paul

[Merlin66]

Valerio,

Welcome on board. Good to see other LowSpec instruments being built. It has great potential and allows the amateur to get involved in spectroscopy and the science.

Look forward to seeing your results.

Stay safe.

 

[Valerio]

Hi Paul and Ken, thanks for your kind words I hope to be able to build it! I know it's not the best material but I am using PLA on an ENDER 3 printer. Never used other materials and not sure if this printer is suitable for this kind of project but I hope so! I hear there are heat expansion possible problems and IR transparency issues: how are they bad with this material?

Yes for a start I will use the cameras I presently use for my astrophotography, later, if everything works fine I will think of a mono camera

Valerio

Trento, Italy

[Gregj888]

Well the print is done.  ASA on an ENDER 3 pro... Turned out OK and with a little more work could probably get it the rest of the way, however...  If I reprint I'll use the Carbon reinforced PETG that Paul mentioned.

There are a couple of splits in the skin I attempted to patch with Acetone and dissolved ASA.  Edge also lifted slightly as can be seen in the central photo.  Tigar strips are from the ASA juice.  Sanding gives a pretty flat finish.  Thinking I might try vapor polishing. 

Back at it... some assembly now required 🙂

[Paul Gerlach]

22 hours ago, Valerio said:

Hi Paul and Ken, thanks for your kind words I hope to be able to build it! I know it's not the best material but I am using PLA on an ENDER 3 printer. Never used other materials and not sure if this printer is suitable for this kind of project but I hope so! I hear there are heat expansion possible problems and IR transparency issues: how are they bad with this material?

Yes for a start I will use the cameras I presently use for my astrophotography, later, if everything works fine I will think of a mono camera

Valerio

Trento, Italy

Well Valario, that's a very good question. No one, as far as I know, actually measured the spectral transparency of these materials. Besides the reported IR transparency of PLA it also has a low glass transition point (about 55-60 degrees Celsius) so leaving it in a hot observatory during the day is not a good idea.

[Paul Gerlach]

9 hours ago, Gregj888 said:

There are a couple of splits in the skin I attempted to patch with Acetone and dissolved ASA.  Edge also lifted slightly as can be seen in the central photo. 

ASA is a great material but still difficult to print relatively large objects with. The accumulated shrink forces can be large with those object. I've tried it on a magnetic flex plate only to discover that the whole plate bended of the magnetic surface.... I had better results on a glass plate.
I still use it for the smaller components of the LOWSPEC and Polycarbonate (PC-Max) for the threaded parts.

[Gregj888]

In reading earlier comments "around the web" thought ASA was the preferred material for the LOWSPEC.  Would not use it again on this printer anyway.  That said, most of the parts seem to fit or be close to a fit.  Not like the filament is a big part of the price...  Awesome project, thank you...

I had a similar experience and have been using glass.

Edited May 30, 2020 by Gregj888

[Paul Gerlach]

And while I'm messing about making a calibration unit, this comes along: LINK

Great work form the developers of the UVEX.

[Valerio]

Wow it's a great project! But I think I will stick to your design and maybe one day build the calibation unit as well 🙂

[Paul Gerlach]

I'm a bit envious 😉. They have a team and I'm still by my self despite some efforts to change that.
The French group already has a track record when it comes to spectroscopy. I tried to search for some collaboration on the German side, to no avail (Dutch and Belgium side same story). Though they each have great knowledge in this field, they often operate individually. It may be  a character trait...

[Fellside]

On 04/06/2020 at 12:41, Paul Gerlach said:

I'm a bit envious 😉. They have a team and I'm still by my self despite some efforts to change that.
The French group already has a track record when it comes to spectroscopy. I tried to search for some collaboration on the German side, to no avail (Dutch and Belgium side same story). Though they each have great knowledge in this field, they often operate individually. It may be  a character trait...

Hi Paul,

Have you tried to contact the UVEX group. I could not see any copyright notices on there site. They may be happy for you to use the Calibrex PCB and software. It would be a shortcut to getting a LowSpec calibration unit.

I have loaded there software into a Arduino Nano. It works as it should from a Voyager Dragscript. I beleave Prism is mentioned and shown in there Vids.

Regards

Graham

 

[Fellside]

On 27/05/2020 at 22:51, Gregj888 said:

GregJ888

What Slicer are you using to generate support like that?

Graham

[Gregj888]

On 08/06/2020 at 02:40, Fellside said:

GregJ888

What Slicer are you using to generate support like that?

Graham

Cura 4.1,  turn off "supports" and under "Experimental" enable "Tree supports". 

A little update...  All the parts are printed.  Didn't have as many of the optical parts as I had hoped so got them on order (surplus shed )  and those should be here soon.  Magnets hot here yesterday and other hardware the day before.

New to this forum, but those that know me know I can't leave anything alone...  Made one tiny change on the grub screws (set screws in the US) and changed them to "Dog point". 

Having a terrible time with the threads on the grating holder cap and front cover.  Part of it is due to the size changes with ASA, plus the simply ASA on ASA which doesn't seem to slide well.  Will print the cap with PetG (I don't have any Polycarbonate).  I may just make one out of Aluminum and call it good if the PetG doesn't work any better.  I did make a container out of PETG and it seems to slide better with the ASA...so there is hope,  If I were to suggest a change it would be to a courser thread, 1.5-2mm... or simply a push on with o-ring and groove.  Not a complaint, just brain storming.    As it is I've used a T2 adapter as a thread chaser, and have it so I can assemble it once anyway.

Again, great project!!!

[Fellside]

Greg,

Thanks for the information. I did find them hidden in Experimental. At the moment I am going with the normal support.

I wonder if it would be a good idea to just make a hole in the cover and print a separate thread insert to take the Grating holder cap. That way you could print the cover fairly fast and the Grating thread insert slow with the optimum setting for thread printing. Insert would then be glued in later.

At the moment I am having a problem with PETG carbon. Every where it says it sticks to every bed surface to well. But after a successful test print I cant get it to stick. It just drag's around and forms a ball around the nozzle.😬

Many Thanks

Graham

[Paul Gerlach]

16 hours ago, Gregj888 said:

As it is I've used a T2 adapter as a thread chaser, and have it so I can assemble it once anyway.

Printing these fine threads is always challenging. I too use metal T2 threads to 'clean' the printed threads.
I don't have any experience with Cura as I use Simplify3D but it's a powerful slicer.
I print the threads at a resolution of 100 micron (0.1 mm). In Simplify3D I can instruct the slicer to use that resolution for the threaded part and a resolution of 0.2 mm for the remaining part of the print.
Calibrating the extruder is crucial. You don't want to much plastic being pushed out when you are printing something as delicate as threads as the tolerances are pretty tight.

[Paul Gerlach]

15 hours ago, Fellside said:

At the moment I am having a problem with PETG carbon. Every where it says it sticks to every bed surface to well. But after a successful test print I cant get it to stick. It just drag's around and forms a ball around the nozzle.

I think your nozzle is set to high. You'll have to bring it down a bit. Also make sure the filament is dry.
I've used different brands of carbon filled PETG with mixed success. The best filament so far in my opinion is Alfaomnia.

[Fellside]

15 minutes ago, Paul Gerlach said:

Printing these fine threads is always challenging. I too use metal T2 threads to 'clean' the printed threads.
I don't have any experience with Cura as I use Simplify3D but it's a powerful slicer.
I print the threads at a resolution of 100 micron (0.1 mm). In Simplify3D I can instruct the slicer to use that resolution for the threaded part and a resolution of 0.2 mm for the remaining part of the print.
Calibrating the extruder is crucial. You don't want to much plastic being pushed out when you are printing something as delicate as threads as the tolerances are pretty tight.

Hi Paul,

I'm pretty much a beginner using Cura. So there may be an option to print different areas at different settings. I will have a look. Printing the cover at 0.1mm would take a while

PETG carbon was new and straight out of a sealed bag. I will have another try today.

Question. Is the Lowspec 3 Fusion 360 whole model on Thingiverse file automatically kept up to date as updates are applied?

Graham

[Paul Gerlach]

42 minutes ago, Fellside said:

Question. Is the Lowspec 3 Fusion 360 whole model on Thingiverse file automatically kept up to date as updates are applied?

Hm, no. Sorry. I can upload a new version but that one is not as 'clean'. I've recently made some changes to other parts e.g. the guide lens holder and I have to make changes to the manual to reflect them.
But if it helps I can upload it here for you.

Paul
 

[Fellside]

Paul,

No its ok. I thought is might be updated when ever you uploaded a new part or modification.

Graham

 

[Valerio]

Hi Paul,

I almost finished to print all the smaller pieces. I see from your last post there is an upgrade for the guide lens holder: is it already on thingiverse or do you plan to update it soon?
Found almost all the hardware parts, can you tell me if this Micrometer is ok ? https://www.thorlabs.com/thorproduct.cfm?partnumber=148-801ST

I will now order the optical parts from Thorlabs. Question: for a starter, is it ok to order just the 300 l/mm grating? You list also the 1800 l/mm, but will this spec work also with 600 l/mm? Is it a good compromise between the two (in terms of low res spectra and cost/usability)? I think they all work with the lenses you list in the Optical parts, right?

Thank you!

Valerio
 

[Paul Gerlach]

Hi Valerio,

That looks okay. But I can buy several for that price.... Have a look at this.
You need the SR4 model. Mabe their German branch will ship to Italy. If not I can order it as I'm planning to order a few anyway. With shipping cost you still save some money.

The 600 l/mm grating would be a great compromise indeed. In fact anything from 1800 l/mm downward will work. The LOWSPEC (@ 300 l/mm) struggles with getting the whole visual spectrum into proper focus anyway (especially when operated faster than f/10) and if you want to do some higher resolution you'll have to work at f/10 and use a 30 x 30 mm grating in order avoid lost of efficiency. The 25 x 25 mm grating at 1800 l/mm is just a bit to small.

Regards,

Paul