Board holders

Started by trev, January 16, 2018, 01:20:26 PM

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trev

Hi

I am now on the look out for the best way to mount PCBs on the machine bed. I have found some magnetic blocks from Grove but the corner pieces do not have the dial that rotates and holds the board down. Am thinking they are probably not much use without the dial. Not sure if I can really fix them. I have an idea to make my own but if the magnets work well and I can come up with a solution then its quicker and easier for me just to buy those. Do pople use the magnets?

Any thoughts from folk?

Trev

spiyda

I guess my method is a bit unusual...
I have some aluminium blocks with magnets to hold them to the bed. ( similar to the original blocks)

In the blocks are some screw pins ( the sort used in the watch strap repair vice)

The pins screw up from underneath and align in holes in the pcb

so,  two blocks, one pin in each means I can use the method for all the boards I make.

The locating is dependent on the drilled hole positions rather than the edge of the board

I've not had a board come off yet.. 

Mike

Kapton tape

Something I've used for additional support, which would probably also work is 1" long x 1/4" dia magnets, with an M4 nut  or small disc magnet on top of the PCB.
Need to keep reasonably clear of components though as most are magnetic to some extent

alanambrose

I thought I replied, but it obviously didn't make it though the ether...

Mulling over 'optical breadboard' here with a grid of dowel pin / threaded holes. Poss using 1mm acrylic with cutouts to hold our regular 5cm and 10cm boards.

Do the boards actually need to be held down or just positioned in X/Y accurately?

A.

spiyda

I just rest the boards on a couple of pins and never had one come off yet...

the only issue I have had is that I have had a couple of bigger boards that were slightly warped,
but I doubt you will get that unless you use toner transfer.

In those rare cases, just added a weight at each corner to press out the warp.

The only issue with optical breadboard is that you won't be able to pick up holes already designed into the pcb for through hole parts.
you will have to put holes in the boards specifically at the pitch of the optical breadboard.
Two blocks with one pin in each get round that problem

I think in future what I may do for the boards I run most of is just use mdf or perspex, a new baseboard for each project
a couple of dowels and the board location is taken care of.
It will also allow multiple small boards that are already depanelled to be set up on one base board with one pair of fiducials

Perspex is brilliant for jigs, especially when you have a laser.



alanambrose

>>> The only issue with optical breadboard is that you won't be able to pick up holes already designed into the pcb for through hole parts.

Ah yes, I didn't explain v. well - was planning to cut 1mm acrylic with 5x5 and 10x10 cm squares to place the boards in, then hold that to the breadboard with button head machine screws in a couple of places to match up with the breadboard. We try to use, v. few through hole parts :) Would then need to only cut/put a new piece of acrylic on if we had (for us) odd-shaped boards or changed the board size. Yeah, would cut the acrylic with a laser.

Ah, I see, you're using the through holes and rest those on the standard RVxS pointy supports?

A.

alanambrose


spiyda

Quote from: alanambrose on February 06, 2018, 05:33:49 PM
BTW anyone noticed this before - my bed has a 1mm+ bow in it:


Both mine are flat as a pancake..   ( within 0.2mm )
but it shouldn't be an issue if you centre your boards approximately over the low point.
and I imagine there is some compensation from the "set board height" routine measuring at two points,
whether it averages or graduates, I don't know.

but I wouldn't worry about it.