ferrite machining?
in [Design]
|
Prev: Heat effect on FR4?
Next: More PIC fun
From: BlindBaby on 12 Jun 2010 20:18 On Sat, 12 Jun 2010 16:32:43 -0700 (PDT), Bill Sloman <bill.sloman(a)ieee.org> wrote: >your deficiencies You haven't even read the thread. The deficiencies are all YOURS.
From: Grant on 12 Jun 2010 20:42 On Sat, 12 Jun 2010 08:09:45 -0700, Archimedes' Lever <OneBigLever(a)InfiniteSeries.Org> wrote: >On Sat, 12 Jun 2010 22:30:06 +1000, Grant <omg(a)grrr.id.au> wrote: > >>On Fri, 11 Jun 2010 20:20:54 -0700 (PDT), MooseFET <kensmith(a)rahul.net> wrote: >> >>>On Jun 12, 12:07 am, BlindBaby >>><BlindMelonChit...(a)wellnevergetthatonethealbumcover.org> wrote: >>>> On Fri, 11 Jun 2010 08:11:04 -0700, John Larkin >>>> >>>> >>>> >>>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> >On Fri, 11 Jun 2010 06:41:57 -0700 (PDT), MooseFET >>>> ><kensm...(a)rahul.net> wrote: >>>> >>>> >>On Jun 11, 8:42 pm, Yzordderrex <powersupply...(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. >>>> >>>> >>Grinding is the way to go. If you want to cut something that >>>> >>you would normally do with a lathe in metal, consider a tool >>>> >>post mounted grinder. Watch the temperature rise. >>>> >>>> >Maybe a dremel with a diamond wheel? >>>> >>>> >John >>>> >>>> After the grooves get ground (any cutting attempt will result in >>>> fracture), you need to cover the rod with transformer tape to insulate it >>>> from your primary wire. >>>> >>>> If you make an open ended core transformer, it will be pretty leaky >>>> unless you use a closed loop core arrangement. >>>> >>>> You would probably be better off with a pot core. >>>> >>>> I would use a dremel tool and grinding or cutting (abrasive cutting) >>>> disc attached. >>>> >>>> If you are making a large groove for a single layer of larger wire the >>>> grooves will allow the wire profile to sit a bit lower., >>>> >>>> If you are using fairly small primary wire, you do not need the grooves >>>> at all. >>>> >>>> Temperature rise? They are not magnets. There are no properties to >>>> lose via introduction of heat. >>> >>>The one partedness can be lost through the heat rise at the machined >>>point. They don't conduct heat well and neither does the grinder. >>>I stand by my suggestion that temperature rise be watched. >> >>I just spent some time with a high speed hobby drill, various grinding >>attachments and a then piece of ferrite, a figure eight buckle type they >>wind those mains filters on, the type with sprocket teeth on the coil >>former so the ferrite is one piece. >> >>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 sanders and other grinders a bit more gentle, most gentle (but slow) >>was the thin cutoff wheel when use with light pressure and kept moving >>to avoid localised heating. If I tried too hard to grind one spot, the >>ferrite would fracture from the hot spot, through several mm of ferrite. >> >>Machining ferrite is easy, with a little practice to develop a feel >>for what is easy, and stuff that is dangerous in the sense of risking >>fracturing the job. >> >>Diamond tools would need to be a lot finer than 150 grit to lessen the >>impact and give a smoother finish -- easy to control with light pressure >>and rips out the material quickly. >> >>Interesting stuff to play with. And try different tool speeds, the >>abrasion rate doesn't necessarily go up with speed. Odd? >> >>Grant. > > Ever seen a pot core pair with mirror polished mating faces? > They are abrasively finished. Sure, but with much finer stuff than I have here, unless I go to wet'n'dry emery paper. The exercise I tried last night was simply to get a feel for how the stuff reacts to 'hobby' working, and also to see how easy it is to fracture that stuff. Machining a fine groove is difficult because of the need to keep the tool moving to avoid creating a hot spot that will generate a fracture somewhat like scratching and tapping glass does. The stuff is very brittle but still easy to machine with lots of patience and a light touch. I've broken many transformer cores trying to recover them from busted PC power supplies -- haven't hit on a safe way to get them apart when the things have so well been vacuum with varnish or glued. One pair from maybe couple dozen attempts, but I wrecked the former -- found a transformer not well varnished that time. My interest in grinding ferrite stems from seeing an article on a high power transformer where the author ground the centre stem down to half diameter, instead of using a gapped core. I forget now just why this was considered better than an air gap. So many here prefer arguing instead of simple discovery ;) Suck it and see. Grant. -- http://bugs.id.au/
From: Grant on 12 Jun 2010 20:51 On Sat, 12 Jun 2010 09:29:32 -0700 (PDT), MooseFET <kensmith(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. 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. Grant. -- http://bugs.id.au/
From: Grant on 12 Jun 2010 21:05 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. -- http://bugs.id.au/
From: Archimedes' Lever on 12 Jun 2010 21:12
On Sun, 13 Jun 2010 10:42:12 +1000, Grant <omg(a)grrr.id.au> wrote: >Sure, but with much finer stuff than I have here, unless I go to >wet'n'dry emery paper. Jeweler's rouge from the hobby shop. It's a rock polishing tool. Pot cores are like rocks. Folks been doin' it that way for decades. Many decades. |