Also wondering about part strength. Spent many years in plastic molding industry, and things made that had a "knit line" where the plastic came together when molding were not allowed, due to part strength issuses from knit lines. Knit lines usually due to low mold temp, low fill volume or bad venting of the mold. 3D printed parts seem to be made from many layers of knit lines?

That is exactly what they are made of.

An insulated and heated build chamber really helps keep the previous layer warm and improves the bond of the knit lines. It also minimizes warpage.

The acetone vapor chamber is extremely dangerous. Vapor clould explosions have incredible force. Even if you are outside, this is very dangerous!!!

 

Yep.

The acetone vapor chamber is extremely dangerous. Vapor clould explosions have incredible force. Even if you are outside, this is very dangerous!!!

So is etching with chemicals, or carving a turkey with a sharp knife, but people manage to do it safely. Hyperbole does not make something true, if you do something like this around an open flame or uncovered then maybe you would have a point.

As for strength, plastic is not meant to be a load bearing material. These parts don't delaminate unless the process is flawed.

 

Also wondering about part strength. Spent many years in plastic molding industry, and things made that had a "knit line" where the plastic came together when molding were not allowed, due to part strength issuses from knit lines. Knit lines usually due to low mold temp, low fill volume or bad venting of the mold. 3D printed parts seem to be made from many layers of knit lines?

I did extensive testing of 3d printed part strength when i was last working on my prosthetic hand project (still in the works but currently dormant). Long story short, parts printed by filament extrusion type printers are as you suspect; a big pile of "knit lines." Or as i say a big pile of "got hot and smooshed together." They aren't very strong, with "strong" being relative of course. They are strongest in one axis, and weak in the other two. ABS prints can be made stronger by applying acetone, which to some degree chemically "welds" the layers together with a better bond than simply getting hot and smooshed together, but still nowhere near as strong as the same part made by injection molding. I had some very good results printing very small parts, very hot, very fast, in nylon, so that i was printing a layer of molten liquid nylon on top of a fresh layer of still-molten still-liquid nylon. But while those parts were incredibly strong, they were unacceptable in terms of Aesthetics and dimensional tolerance. I abandoned the idea of extrusion 3d printing a viable prosthetic. For an enclosure it would probably be fine as long as you don't expect it to be drop-proof and you don't need to drill any holes in it.

 

Yep.



So is etching with chemicals, or carving a turkey with a sharp knife, but people manage to do it safely. Hyperbole does not make something true, if you do something like this around an open flame or uncovered then maybe you would have a point.

Are you serious? Hyperbole? Does covered vs uncovered make a difference with a crock pot (I can smell my stew cooking). Your analogies are used by people who drive drunk. I cannot believe I am saying this, "your chance of dying or causing significant damage to a home by carving a turkey is non-existant". However, deep-frying a turkey is done everyday yet people manage to end up in the emergency room or burning down their house. In fact they do it so often that doctors and insurance companies advise against it. Now, you are suggesting replacing the peanut oil with acetone and saying it is reasonably safe if you know what you are doing? Well, I e worked in the chemical industry long enough to let you know that "chemical familiarity" is a real thing. People get used to working with hazardous materials and their fear and concern slowly deminishes with frequent contact. You initially say, "only do it outside". Then, after a few dozen projects, you want to finish a new project but it is raining out side - so you do it in the garage. Or, you pull your part out and forget to out the lid back on. Or the dog runs past and knocks the card table over, or... You the maintenance team just gets so used to working with hazardous solvents that they ask guys to crawl into machines with solvent vapor still present and (almost) asphyxiate or poison the guy that pulls the short straw (or the temp employee) - sound familiar?

 

Look, we ARE not going there here. Understand?

The process exists, and has been done safely, much like a lot of different things in the world that could go wrong if not done with respect. You may not respect it or me, but it has been done.

Jpanhalt, would you like me to split the other stuff off the thread, since it seems to have gang aglay? We can pick up the short comings of 3D printing there.

 

@Bill, I'd just leave it as a single thread. I think 3D printing will be common place in a few years, and these concerns, while real, will have been resolved. Remember our first dot-matrix printers? It didn't take long to get from them to inkjets and lasers.

 

Look, we ARE not going there here. Understand?

The process exists, and has been done safely, much like a lot of different things in the world that could go wrong if not done with respect. You may not respect it or me, but it has been done.

For the rest of the world...
fuses, cord restraints, proper grounding techniques and many other electrical safety standards all exist just in case something goes wrong and apparently can be ignored if "done with respect", but I DON'T recommended it.

Just like I don't recommend making an acetone vapor chamber in a crock pot.

 

Without knowing how it is done. A decision based on facts. And 3 wire extension cords are an option, not a requirement.

Very well, I'll keep the 3D subjects here, but I am too depressed to engage in adversarial posting. If a question comes up I'll try to answer it.

As to the strength issue, the boxes I have printed (personal experience, not just opinion) compare very favorably with their store bought counterparts. I have even smashed a few to test the flawed units to destruction, they do no delaminate in the slightest. 3D printing tries to save on plastic by using filler on thick areas, but this is an option. Even so, the strength compares favorably to a solid chunk of plastic.

One of the big pluses is no machining, you include the holes and various mounts as part of the original drawing and you can mount the stuff as quickly as it is finished printing. If you screw up it machines well also.

 

Sorry you guys, I didn't mean for my questions to degrade this thread. They were meant to answer questions I had on 3D printing of parts. Again, I'm sorry for even bringing it up.

 

One of the big pluses is no machining, you include the holes and various mounts as part of the original drawing and you can mount the stuff as quickly as it is finished printing. If you screw up it machines well also.

As kind of the opposite of machining, can the printers be used to ADD to an existing box, assuming the box is a compatible plastic? For example, I have noticed that the fit of two-part boxes (like lid to box) is often relatively poor compared to Hammond boxes. On the other hand, a commercial box may not have the stand-offs, partitions, or other details you want. It might be better to start with a commercial box and modify it.

To be even more specific, assume you want to mount an LCD above the top surface of a box, but you need lips on both sides to protect it. Can the 3D printer be used to add the lips? My concern is not so much that the two plastics won't stick to each other, but that the extruded box will deform too much as the printed plastic is welded to it.

John

 

Can you print the LCD as an add-on feature and glue it on after? Proper dimensions and drawing is critical.

 

As kind of the opposite of machining, can the printers be used to ADD to an existing box, assuming the box is a compatible plastic? For example, I have noticed that the fit of two-part boxes (like lid to box) is often relatively poor compared to Hammond boxes. On the other hand, a commercial box may not have the stand-offs, partitions, or other details you want. It might be better to start with a commercial box and modify it.

To be even more specific, assume you want to mount an LCD above the top surface of a box, but you need lips on both sides to protect it. Can the 3D printer be used to add the lips? My concern is not so much that the two plastics won't stick to each other, but that the extruded box will deform too much as the printed plastic is welded to it.

John

"Can you add to an existing box..." Yes but not directly. If you are printing in ABS, parts can be "welded" together with acetone. You print the "addition" you want, not on top of the existing box, but as a standalone part and then weld it on. The bond is fairly good.

 

Maybe not suitable this time, but cheap for small one-off projects around the shop I have a sample of the square plastic containers from $1 Store, these are hermetically sealed and use a series of snap clips around the lid if access has to be made for batteries etc.
Come in various sizes.
Max.

 

@stantor ABS pipe cement is also pretty good. It is a bit more aggressive than acetone alone and has dissolved polymer in it. ABS is not code in many locales, so it may be hard to find. As an alternative, I have made my own using small chips of plastic of the same type and color.
@MaxHeadRoom I got some very nice, cheap boxes from China last year. Copies of some common NA brands, but fairly well made.

John

 

I have used superglue with the battery buckets (see Completed Projects forum) with good result. My experience with tolerance is +/- 10 mils is typical, usually a bit tighter. I have made new lids for commercial boxes, they are usually better than the cheap stuff I replaced them with.

I learned Sketch Up, a CAD program, from the ground up. It is easy to use, but there are lots of things I have not figured out, and there are much better CAD programs out there. Making sphere's and curved surfaces remains a challenge, for example. Anything which generates a .stl (stereo lithography) file will work. Typically we run this file through a program called KISSlicer, which generates the G-Codes the machine itself uses.

Sketch UP has a bug involving text, which is unfortunate. Maybe later revisions will fix it.

 

I agree on Sketch Up. It is quite useful and intuitive. When I last used it a few years ago, dimensioning and particularly editing were not as easy as with other CAD programs I have used. Surface mates were also awkward, but there was a download that made doing them quite easy. Maybe both of those issues have been addressed. Google has done a good job with that program.

I had SolidWorks through the university here. Never got very good at it. The context sensitive icons, what I call jumping icons, were the worst part for me. Once I found the icon I needed, then the rest wasn't bad. I have also used Ashlar-Vellum's products and still have its Graphite (aka Drawing Board) on my PC. Although, it is woefully outdated, it still works fine and is my turn-to for anything 2D.

John

 

Sketchup is no longer offered by google; they've handed it off to someone else. I like sketchup and have been able to train myself to use it almost proficiently. But as I find myself doing more and more mechanical designs outside of the hobbyist realm, I am growing out of it. I need something geared more toward the professional, and I need to take some 3D modelling classes. That is coming up; as soon as my current project is done, my employer is sending me out to learn the big guns.

 

, I am growing out of it. I need something geared more toward the professional, and I need to take some 3D modelling classes.

SolidWorks seems the one of choice out there.
Most of the engineering companies I deal with seem to use/prefer it.
Max.

 

I'm using Freecad. It is both for Linux and Windows. It has a steep learning curve, and you need to think outside the box. I never got the hang of SolidWorks or Autodesks Autocad.

 

My wireless remote leveler project is done. I have even found a source for the MXD2020EL accelerometer from Memsic (DigiKey @ $6.99 ea. FOB USA).

I now need a box to put it in. The GLCD display is 2-1/2" X 1-3/4", and the entire electronics can fit under that display. A box that is 3X4 plus battery space would be plenty big. The display needs +5V.

Nice boxes that have built-in battery compartments for 2XAA or 1X9V batteries are readily available. The problem is that my current need is about 0.08A, when you consider the display and the XBEE wireless. So, I have thought of using two lithium-ion 18650 batteries.

I cannot find any electronic enclosures that have built-in boxes for Li-ion batteries. Any suggestions? (As a last resort, I have located a box with a compartment for 4XAA batteries.)

John

How about 5 x 3
http://www.mpja.com/512in-X-299in-X...Instrument-Box-Encloser/productinfo/17548 BX/