Author Topic: Cutting PCBs  (Read 14729 times)

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Offline akisTopic starter

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Cutting PCBs
« on: November 18, 2013, 10:58:19 am »
Currently I use a tile cutter to cut PCBs. My PCBs have photo resist and a protective film on both sides. The cutter has a platform and a guide rule to allow me to cut to quite precise widths. The quality of the cut is good, but there is a bit of munching of the copper and the plastic film. There is also a lot of dust and noise generated. I could insert a tray full of water under the tile cutter, as it is meant to cut tiles wet, but as I have it on my desk I have not done so yet (fears of spillages) plus I am not sure if the wet blade would produce a cleaner cut. And it still makes a lot of noise.

I have looked at guillotines as the best way to cut the board cleanly, without cracking on either side, and without reaping out the protective film. Both heavy duty paper cutters and metal shears seem to work on the same principle. There is a flat straight edge at the bottom and a curved blade at the top. The moving blade is slightly curved  so that the angle of cutting always remains the same. Metal shears have the thickest and strongest blades.

As I have never used the guillotines to cut the PCB would like to ask:

1) how is the PCB prevented from flipping during the cut since the (thick) blade is pushing it down?
2) If using metal shears, how would you keep the PCB steady while cutting, so as to cut in a straight line?
3) The blade stretches the cut-out part of the PCB while cutting: does that make that piece unusable? For example if I wanted to cut a large PCB into two equal pieces, would the blade deform/crack one of the pieces?

Edit: 4) Some heavy duty paper guillotines, for example with capacity of 400 sheets of 80 gsm paper, have a completely horizontal blade, not angled. Do you think these would be able to cut through 1.0 or 1.5mm of PCB board, both the cheaper type and fibreglass without cracking?

Thanks
« Last Edit: November 18, 2013, 11:07:00 am by akis »
 

Offline akisTopic starter

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Re: Cutting PCBs
« Reply #1 on: November 18, 2013, 11:59:12 am »
Replying to my own post: I took the plunge and bought a heavy duty A3 sized paper cutter with 400-500 sheet capacity as shown here: http://www.ebay.co.uk/itm/140926103196?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2648

Hopefully it will do the job!
 

Offline mcinque

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Re: Cutting PCBs
« Reply #2 on: November 18, 2013, 12:04:08 pm »
let me know if it works!  :D
 

Offline FrankBuss

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Re: Cutting PCBs
« Reply #3 on: November 18, 2013, 01:09:02 pm »
I use a metal shear, works well:

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Offline mcinque

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Re: Cutting PCBs
« Reply #4 on: November 18, 2013, 07:43:44 pm »
Oh, I bet it works well! But how much does it cost?
 

Offline sleemanj

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Re: Cutting PCBs
« Reply #5 on: November 18, 2013, 09:22:26 pm »
Guillotines work well for fibreglass substrate boards, hold board down to stop it moving.  I use an old school one (literally from an old school) similar to this
It can put a bit of a warp in the board but you just have to give the cut board a twist in the other direction to fix that.  Guillotines do not work for non fibrous substrates.


 A "hook knife" works best for those  (and also for fibreglass but it takes more work), such as
  score both sides with the tip (even for single sided, you must score both sides to get a clean cut), use the hook to rip along those scores to make it deeper, then just snap it.  These knifes also work well in the same way for cutting acrylic sheet.
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Offline FrankBuss

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Re: Cutting PCBs
« Reply #6 on: November 18, 2013, 09:54:37 pm »
Oh, I bet it works well! But how much does it cost?
I bought it for EUR 175 at eBay, a fair price for the quality. Cuts metal up to 6 mm as well. No more laborious sawing :)
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Offline akisTopic starter

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Re: Cutting PCBs
« Reply #7 on: November 18, 2013, 11:13:47 pm »
What is the longest cut you have made using the metal shears (without the board chipping or cracking) ?
 

Offline FrankBuss

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Re: Cutting PCBs
« Reply #8 on: November 19, 2013, 05:34:16 pm »
I just tried a longer board, one of my spare PCBs from my 4004 project, 1.4 uRulers long (25 cm) :



No crackings and only very small chippings near the cutting line, as far as I can see. An image of the cutting line with my (crappy) USB microscope camera:



It cuts even through plated vias :)
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Offline poorchava

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Re: Cutting PCBs
« Reply #9 on: November 20, 2013, 08:24:47 am »
For small pcbs on thin laminate (I prefer to use .8 or 1mm if I can) i use conpound action tin snips. They are bad for larger ones because they deform the edges. For larger PCBs:
-hacksaw
-break-away knife
-dremel
-router with serrated edge 6-flute endmill

Guillotine-style tools have a merit of not producing fiberglass dust in the process.
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Offline akisTopic starter

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Re: Cutting PCBs
« Reply #10 on: November 21, 2013, 07:07:45 pm »
Replying to my own post: I took the plunge and bought a heavy duty A3 sized paper cutter with 400-500 sheet capacity as shown here: http://www.ebay.co.uk/itm/140926103196?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2648

Hopefully it will do the job!

Machine arrived today and it is a monster, weighs like 25kgs. Unfortunately it cannot cut through a PCB either those all fibreglass or the softer mix of paper and fibreglass. The reason is that the blade descents horizontally and attempts to cut the PCB in one go all across its length, which is impossible, and there is no bottom blade, so there is nowhere for the PCB to go. I have improvised and added a thin metal plate under the PCB that goes right up to edge of the blade, to serve as a bottom blade, and I have managed to cut a couple of PCBs, with considerable pressure on the lever.

Considering that this machine will happily cut through a whole ream of printer paper ....
 

Offline strangelovemd12

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Re: Cutting PCBs
« Reply #11 on: November 21, 2013, 07:34:06 pm »
Considering that this machine will happily cut through a whole ream of printer paper ....
Have you tested that?

Maybe try biasing the metal plate so the the blade doesn't have to contact the entire board at once.  I imagine the straight down design helps prevent fanning when cutting paper.
Please hit my ignorance with a big stick.
 

Offline amiq

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Re: Cutting PCBs
« Reply #12 on: November 21, 2013, 07:36:11 pm »
I use a metal shear, works well:



Is that a Holzmann?
 

Offline FrankBuss

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Re: Cutting PCBs
« Reply #13 on: November 21, 2013, 07:57:03 pm »
I use a metal shear, works well:



Is that a Holzmann?
Yes, "Holzmann Hebelschere HS300".
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Offline akisTopic starter

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Re: Cutting PCBs
« Reply #14 on: November 22, 2013, 10:00:07 am »
Considering that this machine will happily cut through a whole ream of printer paper ....
Have you tested that?

Maybe try biasing the metal plate so the the blade doesn't have to contact the entire board at once.  I imagine the straight down design helps prevent fanning when cutting paper.

Yes it cuts paper like hot knife through butter!

You are right about the metal plate placed at an angle, but it is no easy feat to find such a plate. I currently use a metal plate (probably aluminium) that was attached to the bottom of a breadboard to provide ground, it is 1mm thick if that. Ideally I would want a steel plate, 2mm-4mm thick, with a very straight and sharp edge to play the role of the bottom blade.
 


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