Has anyone 3d printed a bahnitov mask

[melsmore]

Hi, SWMBO gave me a surprise Prusa I3 Pro W DIY 3d printer kit for Christmas, which we have built. One of the A4988 stepper motor controllers is NAFF, but a replacement should arrive soon.

I was thinking of printing a bahnitov mask for my TS80APO. Has anyone done this?

Should I use ABS or PLA?

I have installed Blender, any one else using this?

[angryowl]

I printed a Bahtinov mask for my 11" RASA using this design. It is fully customisable in OpenScad and can split into four parts for larger scopes.

Printed mine in black PLA and works beautifully with the scope.

[melsmore]

Thanks AngryOwl - at least I know it isn't a silly idea. I was just starting on the tutorials for Blender at the moment - it seems a very complex, all inclusive bit of software. I'll go and look at OpenScad before I go any further.

[Mognet]

I tried printing https://www.thingiverse.com/thing:160391 for my camera as one of my early objects. As I haven't seen a decently clear sky since it hasn't seen any use yet.

I have Blender and I've experimented with creating basic 3D objects, but I'm not entirely convinced on using it to create printable models. It is powerful, but seems better suited as a 3D art tool. I've tried a couple of others. OpenSCAD is good if you can wrap your head around programmatic descriptions of objects. FreeCAD is a visual design tool and seems ok, and there are a several online tools, like SketchUp and TinkerCad that can be used for object creation.

As for the ABS vs PLA question, go for PLA. My girlfriend has worked with a 3D printing company that uses ABS, and says that it stinks of burning plastic during printing. PLA has a much nicer smell, and (according to Wikipedia) is also more environmentally friendly being plant based, biodegradable and recyclable.

[Gina]

ABS doesn't just smell horrible, the fumes are bad for you.  I use a fume cabinet with extractor fan and ducting to outdoors, on my main 3D printer for printing ABS.  PLA won't hurt you I gather but it's more susceptible to heat and degrades faster in daylight (UV).  It's also more brittle.

[melsmore]

Thanks for the replies everyone. I've just ordered a spool of  PLA. The replacement A4988 arrived today and I tried my first prints, with mixed results. Blocked the extruder once, and the best test "cube" print was stringier than a Shreadedwheat ? Some way to go before printing bahnitov mask, let alone a clock ? 

[ejp1684]

I use a cheap Prusa I3 printer, and found that the best results come when using a speed of 30mm/s. Yes it's very slow, but I get good results.

Eric.

[melsmore]

9 minutes ago, ejp1684 said:

I use a cheap Prusa I3 printer, and found that the best results come when using a speed of 30mm/s. Yes it's very slow, but I get good results.

Eric.

Thanks, will try that. I've only used it on "standard" so far. What temperature do you use for the bed and extruder?

[jbrazio]

I’ve built and printed a couple of Bahtinov masks. If this is your first print it will not be easy due to the narrow slits on a 80mm scope.

Please stop using ABS, nowadays there are other materials with the same properties and they will not kill you, think PETG.

Using PLA for astronomy is OK just remember it doesn’t like sun exposure nor high ambient temperatures.

[jbrazio]

It depends on brand of material but usually PLA is 190C with bed between 45-60C (depends on the size of the piece and external drafts, more temp the more mm^2 the object occupies). If you have a lot of stringing lower the nozzle temp before trying to increase retraction over 1mm.

[Mognet]

1 hour ago, melsmore said:

Thanks for the replies everyone. I've just ordered a spool of  PLA. The replacement A4988 arrived today and I tried my first prints, with mixed results. Blocked the extruder once, and the best test "cube" print was stringier than a Shreadedwheat ? Some way to go before printing bahnitov mask, let alone a clock ? 

There could be several causes to the stringy Shredded Wheat effect. First thing to check as it's been assembled from the kit is the tension in the belts. If that's not tight enough it will look like my example photo here where one of the belts wasn't right (both loose belt tension and loose wheel on the stepper motor in this instance) and the slop in one axis caused irregular printing, with the infill (the criss-cross internal strengthening structure) showing through.

Next thing to check is the print quality selected for the model. If you've passed an .STL file through a slicer like Cura or Slic3r there will be options for that ranging from extra coarse to extra fine (or similar). I print at fine and leave the speed at the default 40mm/s. I used to have a couple of examples of coarse and draft quality prints, but they fell apart with handling.

If it's stringing during travels (where it's not supposed to be laying down filament) then you are probably printing at too high a temperature. This can be adjusted in the slicer programme too. With mine I get stringing at 210C, but when I reduce to 200C most of it has gone. As @jbrazio says, 190C is probably where to aim. The PLA I use has a listed temperature range of 180C to 210C. Can't say anything about bed temperature as mine doesn't have a heated bed.

There's further help on https://www.simplify3d.com/support/print-quality-troubleshooting/

[ejp1684]

10 hours ago, melsmore said:

Thanks, will try that. I've only used it on "standard" so far. What temperature do you use for the bed and extruder?

For the bed temperature 40 for the first layer and 30 for the remainder. Extruder 210. I also wind up the flow rate from 100 to 120 for the first layer, then 110 for the rest. The extruder temp would be considered by many to be too high, but it produces good results for me. 3D printing is a bit of a dark art. I played around for ages to get good results so now I stick with what works for me. Best of luck!

Eric.

[Gina]

Temperature sensors are usually thermistors which are not very accurate and the temperature reading may be well out.  Trial and error is needed to get 3D printers working properly.

[jbrazio]

Actually NTC are accurate enough for the task here, what maybe happening is that the value lookup table used by Marlin to correlate the temperature with the ADC reading is not the optimal one for the type of Thermistor in use, this will make temperatures to be off (in some cases by 20, 30C) from the actual running temperature. If you have a DMM with a temperature probe is easy to validate if Marlin is setup correctly (within the error margin of the DMM, probe error, etc).