Spoilboards! My wife just loves the fascinating discussions I can offer with cnc stuff.
I’ve used foam board in the past on other cnc builds and it’s worked okay. Everything is a trade off. But never as a spoil board on a cnc this big.
So, we will give this a try. Relatively cheap and of course super lightweight compared to mdf. Its use is to be all destroyed but does look pretty when new.
I still may lateral back to mdf but I just really hate the stuff.
Oh, as far as the actual hold downs I’ll be trying something new that I’ve thought about for a while. Plastic airgun nails.
The plywood under the foam board is made up of three sheets of 1/4 inch plywood and was meant to be replaced as needed. My plan is that the foam board will take up the majority of the dig ins, the plywood under will slowly get filled with plastic nails (after a ton of cutting) and then a new foam board will be put in. But we will see how it all goes.
Frank Howarth uses those plastic nails and a special nail gun. There were some topics about it a few years ago. I don’t remember if you can use them in a regular nail gun or not.
The build looks nice. I bet the nails will work great.
The only issue I see is it is really easy to mess up your Z height. Secure it down too tight and the board gets a big couple of bows in it.
Very good point. After setting up the foam this evening I was looking at it and thinking that the composite nails would have to be very long if I was holding down 3/4" stock for signs and parts too. I may just lateral over to old MDF. We’ll see. The tinkering is part of the fun.
Yep - all my milling to date has been with a foam board clamped at both ends of the table, and it does warp significantly.
I have thought about printing oversized washers and screwing it down every 300mm or so, but what am I gaining really? Once I get through the stage where every second attempt at making the thing go ends up crashing through the spoil board, I’m sure mdf will be fine for me as it is for everyone else in the world!
Well, the more I thought about it the more the foam spoil board wasn’t doing it for me. While running through the hardware store this morning I saw these painted 1/2” MDF strips for about $8 each. I need one more, was estimating the cut area when there.
The cost was about the same as a full sheet but this gives the advantage of being able to replace some of the strips. AND it doesn’t weigh so much that I need help to get it home.
Well, I wanted to try some boat panel cuts with the LR3. While I’ve built many cnc machines this is by far the biggest. And I wanted to see how the puzzle joints scaled up. As discussed those joints may not be the best or easiest way to go but I personally really like them for a variety of reasons.
Still working out the bugs with the new machine but we’re getting there!
