Micro Burner

I will shortly have a need for a Micro Burner ... for working very fine rods of glass.

Reading a brochure from Ernst Leitz, I found this 'Mikrobrenner' illustrated:

My curiosity aroused ... I let Google translate the German text into English:

MichaelG.

.

Edited By Michael Gilligan on 23/08/2017 00:22:06

That's OK, but 'abkneifen' means to pinch or nip off, not pierce. Obviously a hypodermic needle's already pierced, and to do so again, for example by a side hole to admit air, wouldn't really be easy.

Thanks for that, Mick ... I did wonder about "pierced and abraded"

... "nipped-off and cleaned-up" would make more sense; although I do note that the illustration shows an angled tip, which just looks like a short hypodermic needle.

The biggest puzzle for me is the [apparently non-existent] air-inlet.

Perhaps I'm just preconditioned by their starting with a Bunsen Burner stand, but, without any air mixing I don't see how it can produce a clean flame.

MichaelG.

Could "abraded" mean to file the side wall of the needle to create an air inlet. It could also mean filing the point of the needle as hypodermics have slanted points.

Mick

I think if you look at an enlargement of the Bunsen stand, you will see, or at least I can, just above the rubber tubing, below the needle, what looks like air inlet ports ( dark shaded ) spaced at what I reckon are about 90* around the circumference which will give the clean flame.

George.

I think I would leave the standard bunsen closed then use a Dremel to notch the side of the needle. Turn up a small sleeve that is a firm fit over the needle and just slide that up and down to adjust the flame.

I think the hose might melt - use silicone rubber.

I have some difficulty in seeing how an air inlet can be created.

In a bunsen burner, the jet is used to restrict the flow of gas and to create a jet of gas which sucks air into the airhole.

Without re-jetting the burner, the flow will be restricted by the needle, not the jet, Therefore the pressure lower down in the needle will be above atmospheric, and not below: therefore gas would escape via the 'airhole', rather than air coming in.

Maybe with a very small fast flame, it will burn efficiently without an airhole?

NB could be best to use a dispensing needle (not sharp and cut straight across the end), not a hypodermic needle, unless the taper of the needle end is beneficial in terms of mixing air into the gas - would abrading/reshaping the tip help?

Edited By Martin Whittle on 23/08/2017 08:48:04

I suppose if the bit that fits in the rubber tube had say a 0.5mm hole and the needle were 2mm as the text suggests then you would get the same effect as you do with the jet and air hole on a full size bunsen.

I'd agree with that.

My own impression is that:

i) Google's algorithm looked for an existing translation first before trying to do it itself, and found one, and

ii) whoever wrote the original was guessing, and hadn't actually made the equipment.

Mind you, I ain't done it neither - but what I'd suggest is using the needle tube from an inkjet-cartridge refilling syringe (or suchlike) as the mixing/burner tube, with part of a fine hypodermic needle as the jet. Then make a sleeve with an airhole to fit over the burner tube. I think there'd be a fair bit of watchmaker-fine engineering to do to fit this lot together, with a number of different possible solutions, but in principle it's a miniaturised Bunsen.

A Google search for micro bunsen produces a few options, but most look a bit too big or otherwise iffy for a 2mm flame.

Edited By Mick B1 on 23/08/2017 09:38:42

What about making it like this. needle fixed into lower brass section that has the smallest hole you can drill ( enlarge if needed) Top ring rotates to open and close hole in side of needle.

You could even thread the lower section say M4 and have a screw in jet which would make it easier to put a pointed end on it

Edited By JasonB on 23/08/2017 09:35:20

You can get assorted hypodermic needles without a bevel cut and blunt ended needles too. Example of the former would be a spinal needle for the latter some form of tiny trochar/cannula or if larger then a sprule needle. Much more expensive as tend to be sold in units rather than boxes of 100 and less easily accessed for the hobbyist. Easiest place to pick up hypodrrmic needles.. either local vet (unless he thinks your a 'user' or just pop down to local agri feed/general supplies merchant who sells them in small numbers.

I'd experiment with a filed notch for air flow (or better a fine point highspeed bur) but it's going to weaken the walls of a very fine needle which might be best reinforced by sleeving with another which could then be used to adjust that airflow if counter-notched.

Edir... I see others posted similar principles. But lookign again at the original pic... back then hypodermic needles has steel hubs. You can still get them like that and that's what;s wedged into the rubber? tubing. Then one drills the airvent into the needle hub which it pretty solid

Edited By pgk pgk on 23/08/2017 09:42:55

The jet would need to be very small, and also much smaller than the needle diameter for the air hole to work. I cannot see an air hole near the lower end of a needle working.

Incidentally I re-jetted a bunsen burner to work using a 37mBar regulator supply from a propane cylinder a while ago. I recall I drilled the jet probably around 0.5mm diameter for a 'regular' size bunsen: a micro burner will need something a lot smaller.

Dispensing syringes are available from **LINK** in sizes from 0.15mm to 1.7mm (but packs of 50). The plastic sleeved end might not appreciate getting too hot, but this may not be an issue since the flame is small.

With repect to shaping the tip: if a hypodermic needle were reground with a taper on both sides instead of one, what would this do in terms of oxygenation of the flame, while at least keeping the flame symmetrical?

Edited By Martin Whittle on 23/08/2017 10:32:40

Could always take the jewlers option and have a small hose off the side that you can blow through to intensify the flame. This would force the air in rather than hoping it will be drawn in.

Or for about £3 on e-bay you can buy the small "pen" size torches that have a flame about 2-3mm wide. Refil with lighter gas.

Yes, there are these:-

http://www.diy.com/departments/gosystem-torch-kit/182311_BQ.prd?tab=reviews

though they're dearer than 3 quid.

I've had one for a year or two and after a lot of problems at first (see the product reviews) it's reasonably reliable now, but doesn't deliver enough heat for what I originally wanted it for - bluing titanium.

This was the type I was thinking of.

Thanks for all the replies

The "design" [such as it is] comes from the most credible of sources; the manual for a Leitz Micromanipulator.

Its purpose is to facilitate the 'second operation" work required to produce Micropipettes and Microinstruments like these:

.

The glass is drawn out in another device, and finished in the microburner.

The quantity of heat required will be very small, and the flame needs to be gentle.

I was surprised by the apparent crudity of the design, but if it's good enough for Leitz, it can't be far off.

MichaelG.

.

P.S. ... I am still considering options: I have heard of platinum strip heaters being used for similar work [powered like a Weller soldering gun]

.

I have those, and similar, Jason ... but I think they are probably too big and too fierce for the job.

[bet you never thought you would hear them described like that]

... see my previous post

MichaelG.

.

Edit: Your earlier illustration looks very promising, and it would be reasonably simple to adapt the blunt 'dispensing needles' that are widely available.

I recently bought some of these for another job: http://www.ebay.co.uk/itm/12pcs-1-5-13Gauge-Silver-Stainless-Steel-Glue-Dispensing-Blunt-Needle/122325619604 ... They are also available in smaller diameters.

Edited By Michael Gilligan on 23/08/2017 12:39:13

Seeing how fine the glass is in those pics i would agree that the pen torch would just result in a blob. Infact I wonder if just a soft flame would be adequate to heat such fine things to red heat.

J

PS good job you got your eyes done!

Messing around as a child I used hypo needles, large for bum injections, on a camping gaz stove. Very difficult to get a small enough gas flow with that to avoid blowing out the flame but it would burn with a yellow 'no air' type Bunsen flame. I thins Jason had the best idea with the jeweller's trick of a blowpipe. I suggest a good gas valve be made first.