For 2-sided and other kinds of milling I’m looking for an edge finder type of device so I can reliably set the edge for the flip. For some reason I’m having trouble figuring out what kind of device I need and in what size. Can anyone make a suggestion?
Starret makes an edge finder with a .25" shaft that we use with a .25" collet. The problem is that Amazon only had it in a set of three for $50 (and the other two had larger shafts). You might be able to find that individual edge finder separately through a different vendor.
For what it’s worth, I’m working on Carbide Motion 2 right now. One of the additions will be ability to zero exactly on the centerline of the table where the dowel pins are so you can flip from that point.
We’re running our first batch of vises to get them to the anodizer right now and then we’ll start on the flip jigs, which (with Carbide Motion 2) will make the two-side machining process much easier.
Awesome! Thanks for the response.
Question, how do you run the spindle when jogging?
I’ve always found that edge finders are more trouble than they are worth, unless you are doing high-precision work. They only locate x-y coordinates, not z. You then need to repeat the process to locate z with your tool.
I typically just put the first tool of a job into the collet chuck and use that to locate x, y, and z. Take a thin strip of paper, place it between your workpiece and the tool. VERY carefully jog the tool up to the workpiece. When the paper catches between the tool and workpiece, you’ve got it located within a few thousands of an inch (plus the radius of the tool). Make sure you rotate the tool a little to make sure you got it on the outer diameter. Repeat for the other axes. When finished, just start the job. You don’t have to change out the tool. It’s a much faster way to locate IMHO.
I think I need to add that to the GUI.
Also, I checked in the shop and the edge finder was Brown and Sharpe, not Starrets.
I found a more affordable edge finder with a 1/4" shank:
I think I will order one…
great find! I ended up getting the single 250 piece here: http://www.ebay.com/itm/EDGE-FINDER-1-4-OR-3-8-OR-1-2-SHANK-MICRO-FISHER-USA-1-4-SHANK-FOR-SHERLINE-/131467128809?pt=LH_DefaultDomain_0&hash=item1e9c0d2fe9
Though I haven’t used it! The suggestion to just use a bit is good.
If I understand well, one has to find the edges with the proper collet and edge finder (e.g 1/4 or 1/2 inch) then replace the collet in order to insert the tool (e.g 1/8 inch).
The collet change preserves sufficient positioning accuracy.
Is that right ?
Mechanical edge finders are awesome. They are accurate, reliable, and repeatable. I would never run a hard tool up against my work piece from the side. Even with paper in between, you can damage both the tool and material. After you have snapped a few expensive carbide cutters you will also come to the same conclusion. You might get away with it using wood or plastic as they are softer and more forgiving. You are also not capturing total run out which a rotating edge finder does. Now… I do use either a thin piece of cellophane or paper to touch off the z-axis. Tools can withstand pressure along their long axis without issue. Just be gentle…
The rub here is that Carbide Motion will not let you turn on the spindle when manually jogging the machine. Which makes using an edge finder impossible. Unfortunately, I just bought one. Has anyone found a workaround to get the spindle going while jogging? Any help would be greatly appreciated.
I’ve been toying with an idea for an optical edge finder. When my Nomad arrives I will have to prototype it and see if it makes sense.
Take a laser and a photosensor, as a pair and mount them. Now put another photosensor some distance from the pair. When a laser hits an edge, the diffraction goes through the roof. This should be exploitable for an edge finder.
The ratio of the near photosensor to the far photosensor pickup could be used as a detector. How well this works remains to be seen, I know it works from other uses - I can find edges - but I don’t know how well I can make it work reliably (accurate/precise) for 0.001".
@Sean: I tried using an edge finder once or twice, but it was a bit of a bear and I just went back to using a tool + a thin brass sheet. The sheet is a lot thicker than paper (.41mm), so it meant there was less chance for me to fat finger the tool crashing into my stock (move by .1 mm increments, two at a time - even if CarbideMotion recognizes a double press on both key presses it still won’t crash - then see if I can fit the brass sheet in, etc.)
But to answer your question, my workaround was I downloaded a g-code sender (almost positive it was https://github.com/gerritv/Grbl-Panel ). I’d:
- Start Carbide Motion
- Let it home
- Set 0 for all axes
- Quit CarbideMotion
- Start up the g-code sender (grbl-panel)
- Note coordinates
- use grbl-panel to unlock and then turn on spindle
- use edge finder + grbl-panel to find edges
- Note new coordinates at edges
- quit grbl-panel, start up CarbideMotion again, use offset information (results from step 9 minus results from step 6) to correctly zero the machine on the stock.
My main issues with the edge finder were that the edge finder I found was really long ( http://littlemachineshop.com/products/product_view.php?ProductID=1961 ) and it seemed like because of that there was more (significant) runout at the tip. Also, again, I’ve never used the thing before, so I couldn’t tell if I had “found the edge” when I heard it start thumping quietly or when it clacked out to the side, and in any case, it didn’t seem within .01 mm repeatable when the thumping or clack happened anyway. But I could have been using it wrong.
Thanks for the detailed response kjl! I think that anything near 0.01mm (0.0004") would be pretty accurate given the overall nature of the Nomad. I am not expecting it to beat 0.001" on any dimension. It would be nice to minimize error as much as possible and resulting offset seams when doing two sided machining. I am hoping the edge finder works for me. I will test it on a real Bridgeport knee mill to see how repeatable the mechanics are and post my findings back here.
Jorge from support also sent me this nugget of info:
From Carbide Motion screen/interface, hit the “m” key. This brings up an MDI screen where you can input g-code commands and get the spindle turning. From there you can return to the jog screen and the spindle will stay on at the RPM you set. Just hit “m” again to go back and M5 to stop.
Thanks to Jorge for getting me this answer!
There are videos showing proper operations and just how accurate/precise (repeatable) they can be (using a Bridgeport) - 0.001" or less. One of the videos SHOWS AND PROVES THAT RUNOUT IS NOT AN ISSUE with edge finder that is spun during use.
Remember that the Nomad isn’t reliably repeatable below 0.001" (0.0254 mm).
C3D is now selling a high quality American made edge finder.
I would love to see that feature in the carbide motion too. It would be easier than manually typing G-Code.
has someone linked to this post yet?