3D Printers?

[PeterW]

.... wall/floor/ceiling thickness matters more than infill. I use 1.6-2mm (especially if I need to tap holes) and then 40% infill or so (unless I really need it to be fully dense).

Peter

[CedricTheBrave]

jumping on this thread what are peoples thoughts on the Creality CR-10S Pro V2?

looks like it ticks all my boxes 

[vlaiv]

2 minutes ago, CedricTheBrave said:

jumping on this thread what are peoples thoughts on the Creality CR-10S Pro V2?

looks like it ticks all my boxes 

I was looking at that line of printers prior to Ender 3 series and it was my favorite.

Then I realized that there is no much difference in print quality between series - only print volume size and price.

Depends really on how large things you want to print and I can't think anything that can't be printed out of multiple parts in Ender 3 print volume that I would want to print.

[DaveS]

Waiting for my printer to arrive. Was supposed to be today. The reel of PLA turned up, but then about the same time I got the "Your delivery has been delayed" message from Amazon, for maybe Mon or Tue. So, your guess:

This year?

Next year? 

Sometime?

Never?

[Mognet]

1 hour ago, CedricTheBrave said:

jumping on this thread what are peoples thoughts on the Creality CR-10S Pro V2?

looks like it ticks all my boxes 

I can't say much about the Pro V2 part, but I do have a CR-10S and it's a nice machine. The only advantage that I know it has over the Ender 3 is print volume. Most of the other parts are interchangeable with the Ender 3. Only time I've used the full size of the print bed was for printing visor frames as I could get four on at once. Haven't needed to print anything tall yet. As @vlaiv says, it depends on how large you need to print

[CedricTheBrave]

ordered a CR10s Pro V2 in the end!!

you can never be too big

 

 

[AlexK]

On 31/12/2020 at 13:56, tooth_dr said:

Can ask what is the main concern over threads?

Yes, it's printable and even works and looks just fine. But there are unavoidable FDM deposition errors which making the thread's precision not only uneven but also "polarized". In a nutshell, that means zillions of hot spots on the plastic threads' surface which will be eventually removed by the use with mating metal thread(s), but may leave weakened spots and damaged layers (delaminating as threads geometry obviously weakening layers adhesion periodically) with unpredictable reaction to the stress in the plastic part which will grow with use (and time if done in the biodegrading PLA). Add to that the stress from metal thermal expansion/contraction and you will see why I would never use it for an EP filter holder, for example, as it's used too often and may be exposed to elements. But a more permanent adapter should be OK for several years. Then just print it again.

Edited January 5, 2021 by AlexK

[AlexK]

On 02/01/2021 at 09:15, vlaiv said:

Also question - how does one overcome "fear of plastic parts"? I mean, when it comes to telescopes - I guess we have heard, read and experienced many times that plastic parts are low quality parts. This has become somewhat of a norm in the way we think about things - you know "Plastic focuser? Pass that one ..."

I believe that FDM is an order of magnitude more precise process compared to the mass-production inject-molding (IM) used in the typical production of "cheap plastic telescope focusers".
Also, you have much more control over its design, so you can overbuild parts on purpose if concerned, which is a no-no for the mass production shaving each cent they are investing into the product cutting corners everywhere. For example, there is a well known fact that IM forms (molds) are aging (deteriorating) really fast, so some later batches of mass-prod. plastic parts might be on the very edge of mechanical tolerances creating horrible experience for unfortunate late batches buyers. I saw one Astroscan telescope tube (two parts IM form required to manufacture it) with one half visually smaller on the UTA end than the other due to that. It's a miracle they've managed to get the secondary collimating with the front glass at an angle.
With the FDM process it depends on your new spool of plastic only. So if the pilot print doesn't mate, just adjust for that and reprint. That's only cents over the "budget", while new IM forms might be hundreds of thousands.

Edited January 5, 2021 by AlexK

[PeterW]

Properly done injection molding can achieve micron level accuracy, just ask Lego. Of course not everyone is as experienced and there are a range of common defects. That said FDM has similar common issues with print lines, overhangs and the elephants foot, ringing marks, anisotropic properties. From testing length accuracy of FDM multi axial bars is typically 0.1mm. I was using PLA so warping wasn’t an issue. For snug fits I leave a 0.6mm ish gap and add bits of duct tape to tune the snugness. I also regularly test print small pieces of parts to tune critical dimensions for the specifics of my printer and settings etc.

 

Peter

Edited January 5, 2021 by PeterW
Correction

[Chriske]

In the past I've printed a few telescopes. The first one was a 10" Dob, the second was small Kutter, next a Cass, in fact a Gregorian, and the last one I've built is a large Bino-Kutter. There are all posted on this forum.
Many people looking at these scope during open door do frown, making remarks, questioning the stability, strength, etc of these printed scopes.
After explaining and have a closer look, almost all visitors do agree these 'plastic' telescope will work.
All the printed scopes I made so fare are not 100% fully printed of course. There's always a metal frame(aluminium) to start with. That 'frame' makes the base on which I start adding printed parts. I never allow a printed part to support the scope. I also never allow printed parts ending up stressed, meaning, not one single parts will have to deal with tension. That is my golden rule.
Respect that rule, and you can build whatever you possibly can think of.
These scopes I made, it's always a well thought over concept, a combination of different materials, ending up with a very sturdy telescope.
And there are two more rules you need to take into account :

1- N-e-v-e-r draw/print slim-line parts. Slim-line parts look very nice, but that's all you can say about them.
2- Using a telescope in the heat of the sun, ALWAYS print your parts pristine white, even PLA..!

[vlaiv]

2 hours ago, Chriske said:

In the past I've printed a few telescopes.

I've seen some of yours beautiful focusers in one thread when I was searching to see what people have done with 3d printing.

I realized that I need a 3d printer when my list of ideas of what could be 3d printed reached about 10 items. I should have made a list back then as I've forgotten some of them now, but new ideas often spring to mind.

Latest one, one that I'm concerned with in terms of strength and durability is M90 to ID96 adapter. That is quite a big part (tolerance issues due to shrinking when cooling), will be load bearing and is easiest to print in orientation the least suitable for load bearing.

It is supposed to carry focuser + everything that is attached to focuser on my Skywatcher Evostar 102 F/10 achromat to replace stock focuser.

Another thing that I would love to print but have concerns if it will work - is small helical focuser. I have this idea of building small telescopes out of "scrap optics" - like used up / broken binoculars or similar. I don't see issues with 3d printing lens cell which will then be mounted in aluminum tube. I want to print the rest of the scope - including EP holder and focuser.

Here I'm worrying about smoothness and tolerances. Smoothness can be achieved with sanding things down, but I'm not sure how sand down very fine detail properly - like straight and helical slots and pin that rides those.

[DaveS]

Well my printer turned up and I'm working my way through the destructions putting it together.

[DaveS]

After many backtracks due to my miserable coordination I finally got the wretched thing built. Will deal with bed leveling and software installation tomorrow when a few more brain cells might be present and correct.

[AlexK]

16 hours ago, Chriske said:

...
A. I never allow a printed part to support the scope.
B. I also never allow printed parts ending up stressed, meaning, not one single parts will have to deal with tension.
1- N-e-v-e-r draw/print slim-line parts. Slim-line parts look very nice, but that's all you can say about them.
2- Using a telescope in the heat of the sun, ALWAYS print your parts pristine white, even PLA..!

(in blue - my marks for the reference)
A. I have no problems with that. Properly designed and printed ABS parts can support the weight of a car! I saw plenty of projects for my Subaru Forester, like making adaptors to foreign suspention.
B. Stretching is the same. You just need to adjust your design for the possible stretch/flex distance at the projected load. Quite contrary, that's the important property of plastic parts which you can harness to minimize the number of metal parts (often fasteners) in your design.
1. Slim parts have their place in certain designs as soon as they are not for any serious load bearing. E.g. dust covers. But in fact you will be surprised how strong a 4x0.1mm layers plate printed in CF-nylon! I have printed a "credit card" sized piece with cut-out micro tools in trivial PETG, and had a hard time tearing out these tools (with dedicated tearing ponts holding them in the card's shape) by hands, had to resort to the wire cutter.
2. Never print anything in PLA except temporary pilot designs, temporary fixers (like shims), and toys. It melts in the Sun in summer and in the well heated car in winter, even from trivial friction, and also became brittle after a couple of years of exposure to elements, especially if handled a lot (from biodegradation of the material).

Just from my personal experience.

 

Edited January 6, 2021 by AlexK

[DaveS]

"Sun"?

"Summer"?

What are they? unfamiliar this far north.

And my car in winter is still like an ice box without the heating on. And I'm only on the south west coast, not even north north.

[PeterW]

OK, name the materials that can withstand >100C. Nylon and PETG are little better than PLA. I’ve been using PVDF, but that’s for very special applications. 
if you’re not printing PLA I hope you are very careful to fit extracts to avoid breathing my the fumes.

Peter

[DaveS]

ABS I know needs fume extraction, but does PETG or Nylon? Where my printer is going I could construct a fume cupboard.

And how many telescopes are useable above 100C?

[vlaiv]

2 minutes ago, PeterW said:

OK, name the materials that can withstand >100C. Nylon and PETG are little better than PLA. I’ve been using PVDF, but that’s for very special applications. 
if you’re not printing PLA I hope you are very careful to fit extracts to avoid breathing my the fumes.

Peter

According to this:

https://www.simplify3d.com/support/materials-guide/properties-table/

HIPS, PC and PP are only one with service temps above 100°C. I would add ABS/ASA and Nylon as well as high temp resistant materials. Don't really think it would be easy to encounter 90°C+ in everyday use (unless submerged in boiling water or something like that).

On that list, PC and PETG look like very decent materials with good properties.

I'm not sure how much coefficient of thermal expansion is applicable. I watched one video on dimensional accuracy of 3d prints and person in video measured 0.5% size reduction on material that is declared as 0.4%.

Supposedly, it was some sort of enhanced material - not sure which one - was it ABS or PLA - in any case, I thought that such small dimensional change is not consistent with above linked table.

For example PLA has 68µm/m/°C.

It is printed at 190-220°C and let's assume that room temperature is 20°C so that is roughly 200°C of difference.

68µm * 200 = 13.6mm = 1.36% - about three times more than above quoted value and PLA has one of smallest coefficients of thermal expansion.

How come that there is such mismatch?

 

[pete_l]

8 minutes ago, DaveS said:

And how many telescopes are useable above 100C?

Something that is worth consideration is differential expansion.

When you have a metal - metal connection, both parts will expand in the heat or contract in the cold by roughly the same amount, since they will be made from the same type of metal - aluminium, probably.

However, when one part is metal and the other is plastic they might be a good fit at room temperature, but what about when they are 30°C hotter in an observatory during a summer day, or 30°C below room temperature in the night sky in winter. Will they get loose? Will they tighten so much that the plastic cracks? Will the cycling over time cause fractures?
I would not like to have £££££'s worth of delicate equipment suspended above a concrete floor just by something like that.

[AlexK]

Drastic temperature changes are indeed a bummer. I had a trivial 1.25" adaptor, converting my tele-lens to 70x300 frac, exposed to -10C for ~30 min and then could not use it, as eyepieces simply can't fit.
Threaded adaptors will suffer even more as the thread pitch will change, and possibly unevenly. However, it looks like if parts are mated that's less of an immediate problem, though that might depend on the actual topology of the part, e.g. a dense uniform infill might cause weird shell deformations. I can imagine a design with flanges being pulled far enough to break the threaded shell off.

One of the solutions would be to avoid any infill and print enough top (or bottom) surfaces where it's threaded.
By the way, that's the proper way of printing solids. The 100% infill I saw mentioned above might be (depending on the "AI" of your slicer) printing very slow and possibly with unpleasant artifacts. So just divide your part's height by the layer thickness and set that many tops in the slicer instead. I'm often using that to print only some top or/and bottom portion of the part solid, and the rest with some infill (in fact 20% is the highest infill I ever use as anything more seem to have no value for the rigidity or anything), usually, that's ether a slim geometry or a thread/bayonet I want to reinforce a bit.

Oh, and regarding the PLA in the car: 
I had a sophisticated GPS holder built of PLA and some screws installed high above the driver side vent. On one winter trip through Yosemite (to a remote uber-dark "B0" observing site in Nevada) with the heater cranked well up, I've reached some road fork and glanced the map again... but the GPS was gone! I've immediately pulled to the shoulder as I was afraid it might end up under pedals, jumped out and down but couldn't find anything on the floor. Then found the holder and GPS hanging under the vent with all four holder consoles graciously bent down 180 degrees. I.o.w. it's not really melted, but softened enough to give up under a rather minimal load.

Edited January 6, 2021 by AlexK

[PeterW]

Most polymers have much larger thermal expansion than metals. Not special the 3D printing.

I made a sun finder in black PLA (just printed in the material I had to hand)... it bubbled away nicely...! 
 

Peter

[Chriske]

What about this test I did years ago now. Different materials. nGen, ABS, PLA.
FYI the white ring is PLA. All these rings are very thin and hollow. Diameter about 150mm.
These rings hung for a almost a full year in my garden in full sun all day long. During that year there was even a heatwave..!
On each ring a weight of 1kg.
Winner of this 'contest'.  White PLA.
Don't believe it : just try it for yourself.
Do not print PLA objects to be used in your car, not even white PLA. That will not work. It's a completely different story.

I have different objects in my garden, all printed in PLA-white. Yet again a new project will be installed in my garden next week. A set of covers is ready to be installed on top of thin aluminium poles around our garden. Purpose is to screw insulators in these covers. These insulators will lead electric wires around are garden. These covers, again printed in PLA...  WHITE PLA...! No other colour will survive the backing heat of the sun.

 

Because there was hardly deformation I filled the bottles up to 1 litre instead of 0.5 litre

And at the end of the summer  the white ring hardly deformed. To be clear, when removing the weight it jumped almost back to it's original shape. The other three did not...!
And yes I know, when I would have chosen white ABS and white nGen the result would have been different. But I wanted to make a point here : To be safe, use white filament for outside projects.

[Chriske]

This is one of my many projects printed in white PLA.
As I said before there are some metal parts involved in this binocular, as in all my other projects.
Length of this bino about 1.2m.
Pay attention to the special tripod...😁

[PeterW]

Do you have any details of that binocular?? Nice “analog” tripod!

Peter

[Chriske]

Yep...😉