ferrite machining?
in [Design]
|
Prev: Heat effect on FR4?
Next: More PIC fun
From: John Ferrell on 13 Jun 2010 10:31 On Sat, 12 Jun 2010 13:43:58 -0700, Archimedes' Lever <OneBigLever(a)InfiniteSeries.Org> wrote: >On Sat, 12 Jun 2010 15:59:17 -0400, John Ferrell ><jferrell13(a)triad.rr.com> wrote: > >> the tiny >>abrasive disk that shatters every time you use one hand held. > > The fibrous "concrete saw" type disc works better. "dado" two together >for wider cuts. If it is small enough to do the job it is a better choice. I don't throw the away until they are dime size! John Ferrell W8CCW
From: MooseFET on 13 Jun 2010 10:35 On Jun 13, 1:40 am, John Fields <jfie...(a)austininstruments.com> wrote: > On Sat, 12 Jun 2010 09:20:37 -0700 (PDT), MooseFET > > > > <kensm...(a)rahul.net> wrote: > >On Jun 12, 11:48 am, BlindBaby > ><BlindMelonChit...(a)wellnevergetthatonethealbumcover.org> wrote: > >> On Fri, 11 Jun 2010 20:24:34 -0700 (PDT), MooseFET <kensm...(a)rahul.net> > >> wrote: > > >> >On Jun 12, 1:33 am, Bill Sloman <bill.slo...(a)ieee.org> wrote: > >> >[...] > >> >> Wrong. Permeability drops with rising temperature, and leakage flux > >> >> rises. Ferrite cores don't have to get very hot before they become > >> >> magnetically insignificant. Read the relevant data sheets for the > >> >> material used to make your core on the manufactuere's web site. > > >> >This has nothing to do with the reason to watch the temperature rise. > >> >It is just plain a mechanical issue. The material is brittle and a > >> >bad > >> >conductor of heat. > > >> And grinding it doesn't hurt it at all. It got heated when it got > >> made. It is a sintered, stamped, baked manufacturing process. > > >All sintered things are brittle. Watch the temperature. > > --- > I don't believe that's right, since at least some (if not most) > sintered metallic parts retain the mechanical properties of their > parent metals or alloys. The cores I have experience with are metal oxides not metals. They are brittle.
From: MooseFET on 13 Jun 2010 10:37 On Jun 13, 1:21 am, BlindBaby <BlindMelonChit...(a)wellnevergetthatonethealbumcover.org> wrote: > On Sat, 12 Jun 2010 09:29:32 -0700 (PDT), MooseFET <kensm...(a)rahul.net> > wrote: > > >On Jun 12, 8:30 pm, Grant <o...(a)grrr.id.au> wrote: > >> On Fri, 11 Jun 2010 20:20:54 -0700 (PDT), MooseFET <kensm...(a)rahul.net> wrote: > >[...] > >> Anyway, 150 grit diamond tool rips into the stuff, black dust everywhere, > >> easy to fracture pieces off, very harsh if one applies too much pressure. > > >The problem is mostly the local temperature rise. If you are careful, > >you > >can cut an O-ring groove into a rod core to seal the place where it > >goes > >through a wall. Fine work can be done but when making any sort of a > >groove a lot of care is needed. > > Your brain is on overkill, and you can't even get that right. I stand by my warning. What you claim doesn't matter because I know I will be shown to be correct.
From: John Ferrell on 13 Jun 2010 10:38 On Sun, 13 Jun 2010 11:05:06 +1000, Grant <omg(a)grrr.id.au> wrote: >On Sat, 12 Jun 2010 15:59:17 -0400, John Ferrell <jferrell13(a)triad.rr.com> wrote: > >>On Fri, 11 Jun 2010 05:42:19 -0700 (PDT), Yzordderrex >><powersupplyguy(a)netzero.net> wrote: >> >>>Does anyone know of ferrrite can be turned on a lathe? >>> >>>I have a short 1" long by 1" dia. rod ( i know, i know, a personal >>>problem) and I would like to have a grove machined into it to accept a >>>few turns of wire. there will then be a bobbin slipped over that with >>>the secondary on it. >>> >>>I suppose this might be done with some type of grinder as well. >>> >>>Just curious to know what machining options are available for ferrite. >>> >>>regards, >>>Bob >>I made a simple fixture to hold a Dremel tool on the toolpost of my >>Jet 9X20 Metal lathe. Most of the 9X20's seem to have the same >>castings so there are a lot of them around. The cutting tool for this >>job would be the same as what I use for e-clips on rod stock: the tiny >>abrasive disk that shatters every time you use one hand held. > >The 22mm red and black ones? I break them not in use, but in careless >handling of the tool! Only had high speed thingy for a few weeks, it's >been great. > >> It will >>last a while in this application. As for the tool post mount, think >>about a piece of angle, wood block & wood screws and hose clamps. >>light cuts don't need to be super rigid. A well positioned vacuum >>cleaner (use duct tape!) will save a lot on clean up. > >Yes, I need to arrange some dust vacuum here, but it's more difficult >for handheld -- I'm dreaming up some sort of blower + vacuum arrangement >that could help direct the dust to a vacuum. Or maybe a high volume, >low vacuum fan and duct arrangement so some sort of filter; like I've >seen in some photos of handheld machining. > >The 150 grit diamond tool tips in the cheapy abrasive sets seem too >harsh for ferrite, they jar and shatter, but diamond does cut the >stuff quite well. So I imagine finer grit diamond tools would be >good to try. > >The miniature thin cutting off wheels are much slower cutting ferrite, >but very little vibration if you properly mount and dress them before >use. > >Grant. I prefer abrasives whenever possible for cutting. They simply costy a lot less. I sometimes need a special dust collector for a project. It does not have to be fancy. Think shoe box with perf board duct taped to to the top, vacuum cleaner hose in the side with a rag for a seal. All vacuum cleaners need to move a lot of air for cooling. John Ferrell W8CCW
From: MooseFET on 13 Jun 2010 10:41
On Jun 13, 8:51 am, Grant <o...(a)grrr.id.au> wrote: > On Sat, 12 Jun 2010 09:29:32 -0700 (PDT), MooseFET <kensm...(a)rahul.net> wrote: > >On Jun 12, 8:30 pm, Grant <o...(a)grrr.id.au> wrote: > >> On Fri, 11 Jun 2010 20:20:54 -0700 (PDT), MooseFET <kensm...(a)rahul.net> wrote: > >[...] > >> Anyway, 150 grit diamond tool rips into the stuff, black dust everywhere, > >> easy to fracture pieces off, very harsh if one applies too much pressure. > > >The problem is mostly the local temperature rise. If you are careful, > >you > >can cut an O-ring groove into a rod core to seal the place where it > >goes > >through a wall. Fine work can be done but when making any sort of a > >groove a lot of care is needed. > > Yes, I discovered that last night, localised heating trying to get a > narrow cut will easily start a fracture, there's no great pressure or > vibration evident to cause the fracture, it's the localised heat. > Obvious, when one works with the material. Need to keep the tool > moving to distribute the heat loading. If you want accurate machining of a groove, you need a small grinder mounted to a lathe. Doing it by hand is ok if you just need to make a small notch or the like. > And the generated heat is very localised, I was holding the ferrite > in my hand, and the stuff did not warm up after being ground. > > Ferrite not a good heat conductor. I've also fractured ferrites by > heating with a hot air gun trying to soften the varnish and/or glue > to separate and recover transformer parts. same story, localised > heat will fracture ferrite material. I have used a heat gun to get glue off cores. I think the trick is to have a big heat gun so that the whole core is warmed up. |