Comments on RepRap: Blog: Rethinking the Mk II heater nozzle...

The bottom hole wouldn't have to be as small as 0....

2006-10-19T14:44:41.996+01:00

The bottom hole wouldn't have to be as small as 0.5 mm. Only the wire would be. That would crimp the nozzle rather like a .22 caliber blank cartridge. I wonder, though, if you'd get a clean orifice that way. It's worth a try.

If I could use a 3 mm rod within the copper barrel to keep it from crumpling that would probably cut down the care with which you had to do the crimping.

The flaring mandrel was a great idea.I wonder if y...

2006-10-19T10:55:08.246+01:00

The flaring mandrel was a great idea.

I wonder if you might drill a blind 5/32 inch hole right next to your through hole, and maybe put a 0.5mm hole in the bottom once you get the properly-sized bit. You can then put a short length of filement into a fresh piece of tube to keep the drill chuck from crushing it, leave the stub end of the bit where the nozzle will ultimately be, and create your nozzle with a mandrel, too.

I'm guessing that would be both stronger and more precise than the crimping method.

Yeah, don't fancy spraying around solvents much.As...

2006-10-19T01:49:05.193+01:00

Yeah, don't fancy spraying around solvents much.

As to the cement model, it goes wrong the moment any plastic is deposited inside the cement body. Some non-conducting liner is needed.

Vik :v)

"What if we used 'plastic on an spray can'."How do...

2006-10-19T01:05:18.213+01:00

"What if we used 'plastic on an spray can'."

How do we recycle the product? how do we create it ourselves? how expensive is 'plastic on a spray can'? A big thing, to me at least, for the RepRap is its ability to recycle the items it creates (it's still more theory than practice at the moment, but it's certainly viable).

Okay let me try to do some late night out of the b...

2006-10-18T21:23:46.726+01:00

Okay let me try to do some late night out of the box thinking.

Bare with me wild ideas coming up.

The first question in my mind "Can we eliminate the heat source ?"

What if we used 'plastic on an spray can'. I don't know the English word
for it. But your use them for new-years party pranks.

If we had a plastic that became solid with the contact of air. Then
we only had to pure it out of the tube and we could eliminate the heat
source.

***How much of the heat is held by the plastic com...

2006-10-18T18:53:35.323+01:00

***How much of the heat is held by the plastic compared to the metal itself (I would guess the plastic has most of the heat once it gets up to temperature)***

Let's see. If I haven't dropped a decimal somewhere we have something just under 0.4 grammes of CAPA in the extruder barrel and 8.5 grammes of brass in the barrel itself. Figuring that the specific heat of metals tends to be about a tenth of that of organic materials it would appear that the energy inventory in the CAPA would be about half of the inventory of energy in the barrel.

The design I'm working on runs about 2.5 grammes so the barrel would have about half of the energy inventory of the CAPA in that case.

Of course, if you wrap the whole show up in something heavy there is no point in trying to make the barrel itself as light as possible.

How much thermal mass is there in the existing des...

2006-10-18T15:48:53.103+01:00

How much thermal mass is there in the existing design?

How much of the heat is held by the plastic compared to the metal itself (I would guess the plastic has most of the heat once it gets up to temperature)

It seems like your (Vic's) cement nozzle design would by far be the better solution if higher thermal mass is a good thing. It also seems such a solution would easily adapt to the copper pipe designs.

It is possible though that the increased thermal m...

2006-10-18T01:19:56.303+01:00

It is possible though that the increased thermal mass in the existing design smooths out temperature variations - that's where my guess takes me anyway. It'll be interesting to see how things pan out.

Vik :v)

BTW, once I had the parts to do the job it took me...

2006-10-17T18:42:09.013+01:00

BTW, once I had the parts to do the job it took me about 30 minutes to make it.

I spent several hours documenting what I did on the blog. :-p

***One thing that concerns me is the extrusion ori...

2006-10-17T18:41:00.060+01:00

***One thing that concerns me is the extrusion orifice... would enough pressure from the extruder itself cause the nozel to deform/uncrush?***

That concerns me, too. I'll let you know how that works out.

***how much force does it take to 'bend' the metal there?***

I put it a vise and crushed it.

I've been putting off trying to make a MKII, becau...

2006-10-17T15:48:02.373+01:00

I've been putting off trying to make a MKII, because of its complexity and my lack of proper tools, but this looks like something I could knock off in an afternoon!

One thing that concerns me is the extrusion orifice... would enough pressure from the extruder itself cause the nozel to deform/uncrush? how much force does it take to 'bend' the metal there?

Alternativley, I wonder if you could get a speed improvement on larger parts/areas with a wider/slit nozel instead of simply increasing the size of the hole.