3D Printed Quorn Tool & Cutter Grinder

[RotarySMP]

That rendering looks cool. Which CAD SW are you using?
Mark

[Joules]

Hot on the printer...



It doesn't photo well under artificial light, I have just started the clean up of this part so it looks worse than it actually is.



But I hope this gives some sense of scale.

Mark the software is Rhino, and it's using the artistic view.

[raynerd]

Great work. Can't wait to see it up and running - I'll stick my first parts order in 

[PekkaNF]

Grit on TCG....

My experience shows two approaches:
* Nothing covered. Keep dry and vacuum everything out before moving anything
* All covered/pressurized. Still needs to be vacuumed before shutting down pressure.

Rubber covers + non pressurized or any grease/coolant on ways: Worse than anything else.

Think of rubber cover over a bar. You move the cover and increase/decrease internal volume of the bellow = differential air pressure and that surely sucks the grit inside the area that was supposed to be protected. And it is hard to clean the area inside the bellow.

I was thinking of fitting plastic "scrapers" on ways and pressurizing a small plenum right behind of it. Needs some trial and error, plastic "washer" pops out if too tight fit to rod and if too loose, uses a lot of air and blows the dust/grit around.

I would not worry bout the grit on MK I model, just keep it dry and clean.

BTW. Grit is going to be embedded on the plastic and wear out the steel rods. May actually make nice laps.

Pekka

[Joules]

LOL bars are going to be perspex, so running it dry.  The initial thoughts here are 3D print different vacuum shields for the various grinding operations as printing is relatively quick I should be able to make custom hoods to enclose the work and wheel as much as possible and attach vacuum cleaner to reduce dust/grit MAYBE...

Having just checked the parts this morning, they have changed shape a little  !!!  My close fit isn't quite as close now, this could be temperature/humidity related, we shall see.  Sorry guys not expecting metal casting precision here, but perhaps good/enough for sharpening small items and cutters upto 6mm.  The challenge is getting something that works, it would be nice to see what this casting would be like printed in polycarbonate, but that is beyond the capability of my 3D printers.  Now when we have desktop metal printing   



Here you go Rob, if the rest of the project turns to crap this micrometer thimble will be worth the experimentation.  I have just applied Humbrol enamel with a toothpick, once it dries I can lightly rub down the surface and sharpen up the detail.  Little things like this make the printer soooooo  useful.

[awemawson]

That thimble has come out very nicely.

When you say things have changed size/shape have you a guesstimate what sort of percentage? As the medium is squirted out at melting point, presumably the whole body of a print will get quite warm during the process. As the plastics are poor heat conductors they will take a long time to come to a stable temperature in the core of the object which I assume will tend to set up stresses which will probably take quite a time to come to an equilibrium. Not important if printing a Yoda or a small precision object, but more so as the size and mass increase.

[Joules]

Andrew, this is the largest part I have printed, it does look like the internal structure has pulled the print out of line.  Not easy to say how much, I just made up some paper feeler gauges and its looking like 0.010""  has opened up at the thin fillet on top where the vertical part of the print joins.  When I finally come to welding these parts they will be clamped to a surface plate and tacked together, very much like tig welding.   Once I get the bars in I can measure from them, it's all good fun.

I have started the print for the other end support, once its finished I will give it 48hrs to stabilise and see what we have.  I tried to keep the wall thickness the same so if it is distorting due to internal stress, it may distort the same way, two wrongs making the best right I can hope for.

[RobWilson]

  looking good Joules 



Rob

[Joules]

29hrs printing see's the base castings complete.



Guess it might be Boxing day the bars go in.  The rear bar will be press fit and the front bar a sliding fit (in theory).  The micrometer thimble actually made a good gauge to test the 25mm Perspex bar.  It does vary a little, so I hope to manage the two bar fits from the 1m bar I have.  Otherwise doodling, the rest of the micrometer adjuster and working out a plan  .  Threads into PLA, not likely, might get away with it in Perspex though.  Will have to make some test parts and see how happy they are with 10lbs (4.5kg) load on them, otherwise its metal components in this area.

[nrml]

Slightly  .
Why not ABS-Polycarbonate blend instead of pure polycarbonate. It seems to be very highly rated by respected pioneers in the reprap movement. A tool grinder is not liklely to end up covered with oil and grease and the exposed areas could easily be given an appropriate protective coating.

[Joules]

No reason at all, my only concern PC/ABS mix, the ABS.  You're using it, admittedly in a blend, above ABS working temp.  Since ABS already stinks the place out off gassing, that is going to be worse at higher temperatures.  What happens to the ABS component at those higher temperatures ?   Bit like brass loosing its zinc, not sure I am happy getting a lower PC temp by burning off more ABS.

[BaronJ]

Seasons Greetings Joules,

Nice work.  Watching with interest.

Just a comment: You might find that the perspex bar is not truly round.

[Joules]

Cheers Baron, your spot on, but then my 3D prints aren't truly round in the bores 

I wonder if you can get ground and polished glass rod in 25 & 30mm diameter, would have to forget the spiral on 30mm glass, unless an angle grinder disk could put the groove in   

(no I am not being serious, but...)

[Joules]

Norman, much learning taking place.  I am just sat here  my head over why this part I just printed is undersize on only one surface.    Sorted, it was a combination of me cleaning up the inner surface on the thimble and the wheel being spot on.  I think I will reprint the wheel than my painted thimble.  (too much sherry and mince pies)

At the end of the day, it's printing what we get, see what the problems are and work round, wait for someone else to try and make a better job   


It's plastic, you can tweak it with a hair drier   

[Joules]

Today was finish off the micrometer handle and thimble assembly.  I had intended to use a pair of ball bearings as friction pads, but when I went looking for them I couldn't find any.  Right, another printed challenge.  My machine is only rated to 0.1mm layers, so what the hell.  I printed two friction pad/buttons at 0.05mm layer and they worked.  I wasn't sure how they would turn out, but they are good.  They have the profile on the top that the thimble has on its inner surface.  Maybe I could have increased the pad size by not just making them fit the cross hole and opening out the area over the hole.  But for now they work.



What I have found though, is when I assemble this and have no access to the spring once the threaded shaft is in.  I can't untension the spring to release the thimble, I can live with that as it's not going to fall apart any time soon.



The completed assembly.  I'm very pleased with how this worked out and can see me making more of these for things like microscope stages and other machine adjusters. I guess each one can be printed as a set of parts in just over an hour.

[awemawson]

...what....you didn't PRINT the spring ........

[Joules]

   BUGGER

[BaronJ]

Cheers Baron, your spot on, but then my 3D prints aren't truly round in the bores 

I wonder if you can get ground and polished glass rod in 25 & 30mm diameter, would have to forget the spiral on 30mm glass, unless an angle grinder disk could put the groove in   

(no I am not being serious, but...)

Actually you can !  I think Dow Corning or St Gobain do them.  They are used in the chemical/scientific and communications industry, though ground ceramic tube could be cheaper.

[Joules]

Now the Chaos gets really deep...



Converting these parts into printable models and incorporating more suitable bearing and clamping surfaces.  I will take a cue from the pointer casting with the taper hole, thats a good way to make locking parts with lots of contact area.  I'm thinking of going that route for all the split joints on these parts.  Another niggle for me, is a lack of knowledge in the use of the Quorn.  I'm not sure where parts are likely to collide if I add more material and the CAD model I am working from already has surfaces colliding, so I know the model is wrong in places.  LOTS to redraw 

I would really welcome links showing the Quorn in use and as many of the accessories as possible.

[sparky961]

Surely glass is easier to print than metal.... 

[Joules]

http://www.technologyreview.com/news/540926/3-d-printing-breaks-the-glass-barrier/

Perhaps I can add some ABS to bring the glass temperature down 

[DMIOM]

......


The completed assembly.  I'm very pleased with how this worked out and can see me making more of these for things like microscope stages and other machine adjusters. I guess each one can be printed as a set of parts in just over an hour.

Cracking work and the filled & cleaned markings look splendid

Dave

[Joules]

My thoughts are going back to bellows for the bars, having taken note of comments.  What if I centre drill and cross drill the bar ends beyond the castings, so the air has a path to equalise, then run silicon tube from a take off on each support casting to a filter box, or out of dusts way ?   How does that sound ?


I might even be able to print the bellows in Ninjaflex.

Well, as it turns out plenty of info on making paper bellows, it might be worth printing a couple of press tools that emboss the paper for folding the bellows.  Having the tools means I can remake bellows as and when.

[PekkaNF]

My thoughts are going back to bellows for the bars, having taken note of comments.  What if I centre drill and cross drill the bar ends beyond the castings, so the air has a path to equalise, then run silicon tube from a take off on each support casting to a filter box, or out of dusts way ?   How does that sound ?

Pressurizing a bellow inside is the most efficient way. Equalizing pressure trough filter will cause underpressure.

You could design the system with differential "piston rods" - the air would ideally move just inside the bellow...there will some real life limitations.

Or pressurize just a little - just ennough flow to compensate volume. Best to put orifice on feed, then bellows and plenum + sintered filter on exhaust, just to keep it under minimum pressure.

Pekka

[Joules]

Thanks Norman I have not put a cotter pin on the lever arm as that is clamping PLA to PLA. I expect the other areas to be cotter pins.



Todays printed part, I modified the boss, reducing its diameter so the part would print flat, it also will take a threaded insert.

I am wondering why the workhead centre is offset from the bar centre ?   As I really need to clamp the workhead support on both sides to counter any bending force, what impact will it have on the grind geometry having both centres inline ?


Thanks Pekka, might look at using a small computer fan to provide above ambient pressure, will look into that.