PCB holding for thru holes

[yugami]

My first CNC project is going to be for automating the drilling of holes in pcb boards.

Looking at the number of posts in other areas I figure this is something other forum members have worked on in the past. How do you clamp the pcb to the work table (figuring a basic CNC router) and how do you gap the pcb from the table so that the bit does not mar the table?

A basic solution would be to have a sacrificial board of some sort (mdf or whatever) to take the damage. This is what I currently use when doing the boards by hand.

For thicker boards I'm envisioning a clamp type system that holds the edges only. I've seen something like this in the past but google is not being kind to me today.

Has anyone played with this problem?

[widgitmaster]

Because milling & drilling PC boards does not use a lot of lateral force, light clamping ia sll that's required.
Are you doing a production run of the same boards? If yes, then make a fixture by cutting a pocket the exact size as the boards, and as deep as they are thick. then a thin rectangular frame that is larger than the boards by 1/4" all around, and with an inside the same shape as the boards but 1/32 smaller!
Then drill holes for a few small screws to use the frame to clamp the entire board in the pocket! all low profile!
If you have a lot of boards, make two or more pockets with clamping frames!

Now every board will go to the exact same place for a fresh start of the program!

Save the fixture for future runs of that board!

Hope this helps!
Eric

[yugami]

The plan is to be upto doing a production run, but also to simplify R&D.

Finish a test board design, output the CAM info.... You get the picture.

Your idea works well for R&D as well as I tend to stick to only a couple board sizes during prototyping (to simplify what I need to have laying around).

[pminmo]

If your requirment incudes fine traces and isolation, you board has to be flat. Doublesided carpet tape helps. It's about the thinest DS tape there is.

[Torchhead]

Find the T-Slot material in strips (Woodcrafters, PennState,ect).
Mount slot material top and bottom of expected cut area to the table with screws. Use 1/4 X 20 hex head bolts to slide in the t-slots and make hold down arms with multiple holes to allow adjustment. The top if the slots ar at 1/2 in so Use 1/2"MDF in the center as spoil board. Stick it down with agressive double sided tape and use aluminum strips on the MDF to form a 90 deg fence. You can fashion sliding hold-downs that can be used to clamp along the borders of the material for drilling.

As stated if you intend to mill the runs, the board has to be perfectly level OR you need to design a floating cutting head with an adjustable nose piece to control cut depth and deal with unlevel material.

[yugami]

I'll probably chemically etch the boards, I have a setup that doesn't take much time for that.

How long does it take to mill a board if one where to go that route? (I know theres probably a huge number of factors) Figure small 60oz/in motors, 4"x4" being the typical max size.

[Geof]

Do you have a small vise with removable jaws? Make yourself some aluminum dovetail jaws like in the picture. For drilling perfect flatness is not needed and you do not need to grip enormously tight. The PCB is rigid enough to bridge a gap of an inch or so between the jaws so you can grip different sizes. With aluminum it does not matter if you run the drilling through. And releasing and tightening a vise is a whole lot quicker than double-sided tape or multiple hold down screws or clamps for production work, or R and D for the matter.

[JRoque]

Hello. To drill the PCB, nearly any holding system will do as suggested here. My first few boards were drilled and milled simply by placing the PCB on top of a MDF board and screwing it down at 4 corners. As Phil suggests, if you mill the fine traces needed for some of today's packages, you need a stable and flat surface. I now use a fixture I made with a .125" piece of stainless steel, 14"x14" so it takes a whole 12"x12" copper clad. I takes a while to adjust that surface so it's flat, after it's been removed from the machine. But once that's set you can remove the PCB knowing the next one (or the flip side if double sided) will be flat too. Using this system, I've milled the 0.007" space between the traces of an MS10 package (LT1991) with good results.

JR

[Madan Chachra]

The below problem is metioned &suggest me m\c's for bulk production of PCB's....

Originally Posted by yugami My first CNC project is going to be for automating the drilling of holes in pcb boards. Looking at the number of posts in other areas I figure this is something other forum members have worked on in the past. How do you clamp the pcb to the work table (figuring a basic CNC router) and how do you gap the pcb from the table so that the bit does not mar the table? A basic solution would be to have a sacrificial board of some sort (mdf or whatever) to take the damage. This is what I currently use when doing the boards by hand. For thicker boards I'm envisioning a clamp type system that holds the edges only. I've seen something like this in the past but google is not being kind to me today. Has anyone played with this problem?