Forums

Gerbv

Started by Unknown August 16, 2018
Tim <tim@bugblat.invalid> wrote:
> On 17/08/2018 19:15, Theo Markettos wrote: > Sounds great. And only "from $21,995" :) Until I'm a millionaire I'll > keep getting semi-routed double sided boards from China...
Well, unless your boards are 1m x 60cm x 1 inch thick, I think our laser cutter might be a /little/ overkill :) There are small lower power laser cutters that do a few watts for a few hundred dollars, which might be suitable for cardboard. This sort of thing, though it might need a higher power version, and different software: https://www.ebay.com/itm/NEJE-DK-BL-1500mw-Laser-Engraver-Cutter-Engraving-Carving-Machine-Printer-350DPI/282292190327 Theo
On Saturday, August 18, 2018 at 8:13:19 AM UTC-4, Theo Markettos wrote:
> Well, unless your boards are 1m x 60cm x 1 inch thick, I think our laser > cutter might be a /little/ overkill :) > > There are small lower power laser cutters that do a few watts for a few > hundred dollars, which might be suitable for cardboard. This sort of thing...
https://mcuoneclipse.com/2017/08/13/getting-control-over-a-50-watt-co2-laser-cutter-from-china/
On 18.8.2018 &#1075;. 15:13, Theo Markettos wrote:
> Tim <tim@bugblat.invalid> wrote: >> On 17/08/2018 19:15, Theo Markettos wrote: >> Sounds great. And only "from $21,995" :) Until I'm a millionaire I'll >> keep getting semi-routed double sided boards from China... > > Well, unless your boards are 1m x 60cm x 1 inch thick, I think our laser > cutter might be a /little/ overkill :) > > There are small lower power laser cutters that do a few watts for a few > hundred dollars, which might be suitable for cardboard. This sort of thing, > though it might need a higher power version, and different software: > https://www.ebay.com/itm/NEJE-DK-BL-1500mw-Laser-Engraver-Cutter-Engraving-Carving-Machine-Printer-350DPI/282292190327 > > Theo >
Somewhat remotely related but while on a mechanical wave perhaps someone would weigh in as to how to weld PT100 leads to teflon wire. Soldering is not an option, they work around 300C and if they lose feedback etc. they could get to 400. Well at 400 the joint will not be the only victim but still. Any experiences? Dimiter ====================================================== Dimiter Popoff, TGI http://www.tgi-sci.com ====================================================== http://www.flickr.com/photos/didi_tgi/
On 08/18/18 18:22, Dimiter_Popoff wrote:


> > Somewhat remotely related but while on a mechanical wave perhaps > someone would weigh in as to how to weld PT100 leads to teflon > wire. Soldering is not an option, they work around 300C and if > they lose feedback etc. they could get to 400. Well at 400 the > joint will not be the only victim but still. > Any experiences? >
Do search on "pulse arc welder". Used for very thin wire welding, thermocouples etc... Chris
On 19.8.2018 &#1075;. 01:33, Chris wrote:
> On 08/18/18 18:22, Dimiter_Popoff wrote: > > >> >> Somewhat remotely related but while on a mechanical wave perhaps >> someone would weigh in as to how to weld PT100 leads to teflon >> wire. Soldering is not an option, they work around 300C and if >> they lose feedback etc. they could get to 400. Well at 400 the >> joint will not be the only victim but still. >> Any experiences? >> > > Do search on "pulse arc welder". Used for very thin wire welding, > thermocouples etc... > > > Chris >
Thanks, I think I get it how it is done now. Not sure I'll buy such a welder though, I only need a few welded for now.
On 08/19/18 11:09, Dimiter_Popoff wrote:

> > Thanks, I think I get it how it is done now. Not sure I'll buy > such a welder though, I only need a few welded for now.
I had a similar problem a year or so ago when rebuilding an old HP double oven frequency standard, where the heater element was probably nichrome, and which needed to be bonded to ptfe tinned copper wire. Thought the pulse arc welders very good, but as you imply, too expensive for a one of job. Eventually used a power supply to charge a large electrolytic and a tungsten probe in series with an iron cored choke to generate an arc on break. A few tries at various voltage levels got the job done as per a proper pulse arc welder... Chris
On 20.8.2018 &#1075;. 01:30, Chris wrote:
> On 08/19/18 11:09, Dimiter_Popoff wrote: > >> >> Thanks, I think I get it how it is done now. Not sure I'll buy >> such a welder though, I only need a few welded for now. > > I had a similar problem a year or so ago when rebuilding an old > HP double oven frequency standard, where the heater element was > probably nichrome, and which needed to be bonded to ptfe tinned > copper wire. Thought the pulse arc welders very good, but as you > imply, too expensive for a one of job. Eventually used a power > supply to charge a large electrolytic and a tungsten probe in > series with an iron cored choke to generate an arc on break. A > few tries at various voltage levels got the job done as per a > proper pulse arc welder... > > Chris >
Oh thanks, this is very encouraging. I think I can manage it somehow. The best part of it is that you did not use any inert gas? I have a handful of 4700 uF caps - some fast, some not - in a drawer here, might just do the job... I'll experiment around next few days. Please share any details you might remember - voltage, capacitance etc., I mean ballpark range. Dimiter
On 08/19/18 23:44, Dimiter_Popoff wrote:

> > Oh thanks, this is very encouraging. I think I can manage it somehow. > The best part of it is that you did not use any inert gas? > I have a handful of 4700 uF caps - some fast, some not - in a drawer > here, might just do the job... I'll experiment around next few days. > > Please share any details you might remember - voltage, capacitance > etc., I mean ballpark range. > > Dimiter >
It was all a bit of a hack, but it was using the stored energy in the choke, back emf, to generate the arc on break. The choke was an old C core item, about 4" square, 5 amp rating, fwir. Wires stripped off and tightly twisted together, trimmed level at the ends, then copper clip to the twists and a tungsten scriber for the electrode at the tip. Tried various approaches, but thinking back, used a psu in current limit mode to charge the inductor, then arc on break. It's possible to get a neat rounded weld without gas, but it is a bit hit and miss. As this was to be refoamed up, used a magnifier to make sure there was a good weld between the two metals. If you have one of the old 5v 100amp or more computer psus, you could try that with home made copper electrodes to crush spot weld the twisted wires at the ends, as an alternative method. Not everyone has a junk box with iron cored chokes these days, though a large 50Hz low voltage transformer secondary winding might get the job done. Just got to experiment :-)... Chris
On 20.8.2018 &#1075;. 03:12, Chris wrote:
> On 08/19/18 23:44, Dimiter_Popoff wrote: > >> >> Oh thanks, this is very encouraging. I think I can manage it somehow. >> The best part of it is that you did not use any inert gas? >> I have a handful of 4700 uF caps - some fast, some not - in a drawer >> here, might just do the job... I'll experiment around next few days. >> >> Please share any details you might remember - voltage, capacitance >> etc., I mean ballpark range. >> >> Dimiter >> > > It was all a bit of a hack, but it was using the stored energy > in the choke, back emf, to generate the arc on break. The choke > was an old C core item, about 4" square, 5 amp rating, fwir. > Wires stripped off and tightly twisted together, trimmed level > at the ends, then copper clip to the twists and a tungsten > scriber for the electrode at the tip. > > Tried various approaches, but thinking back, used a psu in > current limit mode to charge the inductor, then arc on break. > It's possible to get a neat rounded weld without gas, but it > is a bit hit and miss. As this was to be refoamed up, used a > magnifier to make sure there was a good weld between the two > metals. > > If you have one of the old 5v 100amp or more computer psus, you > could try that with home made copper electrodes to crush spot > weld the twisted wires at the ends, as an alternative method. > Not everyone has a junk box with iron cored chokes these days, > though a large 50Hz low voltage transformer secondary winding > might get the job done. Just got to experiment :-)... > > Chris
Thanks Chris, I'll try various hacks once I know it can be done. I'll figure out something. I don't have a choke similar enough to yours but I'll find something suitable somehow. The alternative method you suggest I could try using the transformer of an old microwave, replacing the HV secondary with 1-2 windings of thick cable, I know people do it - not sure how it will work on copper wires but well, it should melt them allright. Dimiter
On 08/20/18 10:58, Dimiter_Popoff wrote:

> > Thanks Chris, I'll try various hacks once I know it can be done. > I'll figure out something. I don't have a choke similar enough > to yours but I'll find something suitable somehow. > The alternative method you suggest I could try using the transformer > of an old microwave, replacing the HV secondary with 1-2 windings > of thick cable, I know people do it - not sure how it will work > on copper wires but well, it should melt them allright. > > Dimiter >
That might work well. Have a spotwelder in the workshop here, but a bit to clunky for fine wire work. I'm still considering buying one of the commercial pulse arc welders, but would look at those made for jewelery work, rather than those for thermocouples, where you put the twisted ends into a hole in the front panel. Afaics, the jewellery use a tungsten electrode, where the tip is withdrawn from the workpiece on contact. Then a hv supply starts an arc across the subsequent small gap, conducting and forms a plasma from the discharge of a capacitor. Seems a clever idea to me and could be useful in the lab here for other purposes as well. More fun to build one though, given the time :-). I did tried soldering, as the oven temp is only ~60 c, but failed miserably, even using acid flux... Chris