Re: Which Mini CNC mill #mill


John Ferguson
 

I agree that height mapping would be a good thing, but I don't have it.  I hadn't thought of indicating my fixture after I install it but before I fly-cut level it.  I can't get to this for a week or two, because I'm building another shop setup, but when that's done, I'll show you what i have.

john

On 2/11/20 9:19 PM, CJD wrote:

I keep seeing this post about getting your bed flat.

I don’t even worry about it.

I get great results using the height mapping routine in candle.

You cannot trust within .05mm a flat bed.

When I height map there is almost always .5mm difference across a 10mm X 20mm piece of PCB.

It gets even worse when the pcb piece is bigger.

I don’t know how anyone can do this without height mapping.

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*From: *John Ferguson via Groups.Io <mailto:jferg977=aol.com@groups.io>
*Sent: *Monday, February 10, 2020 8:01 PM
*To: *pcbgcode@groups.io <mailto:pcbgcode@groups.io>
*Subject: *Re: [pcbgcode] Which Mini CNC mill #mill

how did you get your bed flat?

On 2/10/20 6:03 PM, Dan.Staver wrote:

I get good results using very thin double-sided sticky carpet tape to
hold the PCBs down for milling.
Dan Staver
Tave Tech Corp.
3130 Hollycrest Dr.
Colorado Springs, CO 80920
+1-719-359-5352 - office
+1-719-502-1675 - cell
tavetech - Skype
dan.staver@...
www.tavetech.com
W3QDO
On Feb 10, 2020, at 11:06 AM, John Ferguson via Groups.Io
<jferg977=aol.com@groups.io> wrote:
Maybe there should be a subject change. Have a look at the two
fixtures whose photos I've attached.
I make printed circuits which are about 2 inch by 3 inch. I found
that I couldn't get reliable trace widths unless the board was
absolutely level to the machine. So I started with an MDF fixture
bolted to the milling table and drilled and tapped in four places so
I could use nylon screws to hold the pcb down. Every time I do a new
setup, I mill the surface of the fixture with a fly-cutter to level
it.  This works 100% of the time. I've had no bad experience with
PCB's not being of constant thickness.
I had such good luck with the MDF board that I made a better one for
HDPE. I also made a jig to drill the holes in the pcb so they would
be sure to align with the ones in the fixture.
Frankly, I don't see how you could ever get reliable cuts without
leveling the surface the pcb is secured to while etching.
john
Attachments:
DSC07301.JPG: https://groups.io/g/pcbgcode/attachment/8053/0
pcb-etching-fixture&pcb-drill-jig.JPG:
https://groups.io/g/pcbgcode/attachment/8053/1

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