Since this is not a production job I would program a nonagressive cutting regime. I would find some material a little thick (1/2?). I would clamp on parallels so I could machine the entire periphery and face of the most precise features. I would then turn the block over and face the block to thickness and machine the rest of the features. thanks Stuart
On Sun, Jul 14, 2019 at 12:35 PM Gene Heskett <ghesk...@shentel.net> wrote: > On Sunday 14 July 2019 12:11:00 John Dammeyer wrote: > > > > -----Original Message----- > > > From: Gene Heskett [mailto:ghesk...@shentel.net] > > > Sent: July-14-19 8:26 AM > > > To: emc-users@lists.sourceforge.net > > > Subject: Re: [Emc-users] Work holding machining Techniques > > > > > > On Sunday 14 July 2019 09:46:02 andy pugh wrote: > > > > On Sun, 14 Jul 2019 at 14:43, Roland Jollivet > > > > <roland.jolli...@gmail.com> > > > > > > > > wrote: > > > > > Jogging up is better, backlash notwithstanding. > > > > > Use an accurate rod or the shank of an endmill, say 10mm > > > > > Jog upwards while you gently try to roll the rod under the > > > > > cutter > > > > > > > > Yes, I should have perhaps gone in to more detail of the > > > > touch-off. The way you describe is what I do when I want accuracy, > > > > I use some of my massive stock of broken end-mills as the > > > > reference. > > > > > > > > But for a skim cut to start a job, especually with the big shell > > > > mill, I often simply jog down until it starts to cut, and call > > > > that my surface (it soon will be) > > > > > > Another technique I've used, works well on the G0704 as its spindle > > > is well grounded, and when making a "box" of parts, is to plant a > > > small bit of pcb at some fixed and findable point on the jigging > > > with super glue, and run the machine to above it. The top of the > > > pcb is connected to the probe input, I start the spindle in reverse > > > so the contact is not destructive either to the copper or the tool, > > > go down to the probe trip, then back upwards at about 10% of the > > > down speed until the probe opens. This point is recorded as the > > > #<_tlo>, and that becomes z=0 for the rest of the time that tool is > > > in use. Unforch I've got to figure out a better way on the 6040 as > > > theres no way, with all the epoxy paint, and apparently ceramic > > > bearings in the spindle motor to assure a good ground on the tool. > > > So I've both a spindle mount probe and a contact pad/switch. Now my > > > problem is a solid mount for it... Due to the wires stiffness, and > > > its low weight it cannot be convinced to lay dead flat on the table. > > > Combine that with the lack of a grounded tool needing to have a > > > ground clipped onto the tool and a PITA is what it is ATM. But I'll > > > figure out something. > > > > > > Just saying there's more than one way to skin this cat. > > > > > > Cheers, Gene Heskett > > > -- > > > > For my CNC router I use the PCB with a very thin flexible wire > > soldered to it and to an input on the BoB. When I press the tool zero > > button on MACH3 it runs a customized macro I wrote that throws up a > > dialot telling me to put the ground clip onto the tool. It expects > > the tool tip to be within a specific distance of the PC board which I > > lay on top of the work I want as Z Zero. Once I've done that I click > > on OK and it goes down probing for contact with the PCB. After it's > > found that it adds the PCB thickness to the Z axis position and > > retracts to the Safe Z location. Then throws up another dialog > > telling me to remove the clip from the tool. Nothing runs until I > > click OK on that. > > > > John > > > That should do a good job too, just be aware that you should actually > measure the thickness of the pcb material to get that offset, I've had > it vary by over a thou over a 1" x 2" teeny board. First noticed when I > made micarta pallets to hold the pcb flat as I was carving a circuit. > The micarta was flat, but the etching was not as consistent as I would > have liked. There, the idea is to remove the copper, without digging > into the glass, which obviously is hell on the etching tool. Works best > actually when you have worn a small flat on the end of the tool. Or I > have drawn the end of the v-tip across a diamond plate at a slight angle > designed to make the cut wider by a thou or 2. The end will wear as it > cuts glass until it no longer cuts the glass but skids in it, while the > cutting edge still removes the copper. Tool is finished when you need > to 4-0 steel wool the board to remove the coppers burrs on side one so > side 2 will lay flat. > > I learned too, that you only drill a thru hole about 3/4 of the board > thick deep, then run the drill pattern from both sides so it meets > inside the board and doesn't drill thru, screwing up the pallets > flatness with a dulling carbide drill. That of course demands .001" > accuracy. I got that by planting a 1/16" brass contact just outside the > cutout in the pallet, calibrating where its center was at, per pallet > and offsetting the co-ords to fit. > > Slow work on a std mill, with its slow spindle limiting cutting speeds > and one of the reasons I bought the 6040 with it's 24k revs spindle. > Rapids are much faster too. Unforch. the bed is nowhere near flat enough > for that level of work, so I'm debating on how best to replace it with > something stronger and flatter. > > Cheers, Gene Heskett > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Addressee is the intended audience. If you are not the addressee then my consent is not given for you to read this email furthermore it is my wish you would close this without saving or reading, and cease and desist from saving or opening my private correspondence. 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