If your work can easily do without surfacing, do without if you want.
To be technically correct and don’t want to loose any thickness of your base that you would otherwise use as a spoilboard, I think glue down an oversized piece of MDF, let it dry, then surface the MDF as needed. Then if the spoilboard starts seeming to thin, just glue a new MDF sheet on top, resurface if needed. That way you always have some sacrificial spoil board available. … Just a thought (stolen from other forums …grin…)
My spoil board is screwed down to the plywood table, so no worries there.
The plus on surfacing the table frame (2x4’s) rather than the actual MDF spoilboard is that whenever I need to change out to a new spoilboard, I just unscrew the old, screw in the new one and it will still be level because I’ve levelled the frame, not the spoilboard, and ontop of that it only took me a couple hours compared to 40 that was predicted by Estlcam
John, I’m excited to see if that worked for you. On my (smaller) low rider, I cut a bunch of 2mm holes in the spoil board (about 1/4" diameter, IIRC) and used digital calipers to measure the actual depth I got at various places around the machine. I posted it here somewhere and it was interesting. I wonder what you’d get with a test like that. I would consider anything under 1mm to be good, and anything under 0.1mm to be perfect.
I’ll try that some time on the weekend I reckon. It would be interesting to see. I don’t think it would be perfect, as for one thing, there were a couple places where the bit didn’t quite touch the 2x4’s when I was surfacing them, but only a couple spots. Ultimate for me would be to be able to add 0.4 to my DOC and have all the pieces go right through on the whole sheet.
Depending on the results I get, I might do another pass to try and get to those parts that didn’t get touched last time
0.4mm on an entire 4’x8’ sheet is very very good.
The sheet is going to sit on the highest parts, so if there is a bump where you didn’t get, but it’s only 1/8 of the 2x4, then you can knock that part down with a chisel, even.
On big, big hand tool workbenches. The kinds made from solid lumber, there is enough movement that they need to be flattened a few times. When you remove some material, the internal stress of kiln dried lumber will release, and change the shape a little. That, plus the moisture content changes with the seasons. If the process to flatten it is easy enough though, and you have a decent way of measuring it, then you’ll probably have a lot more credibility on how often to flatten than any of them in a year or so.
Yeah I never said it was gonna happen lol.
No no, you lost me there. The part that didn’t get flattened was too low when the bit went over it. So to try and get it as perfect as possible, I would need to do another full run, maybe 1mm lower to see if the lower parts will even out with the rest. It was 2 spots that were lower if I remember right, half way up the long side, on the right hand side of the table. At a guess, probably about a 500x500mm square area.
Glad it is sorted. Sorry to hear about the router.
Marlin firmware also has an manual mesh bed leveling feature. It is really simple to use and only requires a cheap dial indicator and a mount for the indicator. I use it on my 3d printer and it helps a lot in some circumstances.
It might not be enabled in the MPCNC/LR firmware build. But it is an option to consider.
Got it down to 2 hours, upped the speed to 30mm/s, and I’m pretty sure I can go faster. While all this was happening, I finally got around to upgrading the mpcnc with the burly parts. I think I was the second or third to finish printing them… I blame the weather. ?
Really shows how not flat the table is though.
https://t.co/d8EN2iA6dV <<<— Speaker warning!! Turn them down.
Here you can see how not flat my “flat” torsion box framed table is. Not sure how much the room has moved though. The last 8-ish feet of the room actually overhangs the outside wall of the barn’s basement floor. I know the barn moves seasonally.
Had the vac running the whole time, even though the above picture shows a bunch of dust on the board, all this was sucked up, there’s about 6 inches of mdf dust in the bucket. There’s none in the shop vac bucket, and the vac’s filter didn’t clog, so not too much made it past the dust deputy.
The surfaced surface isn’t that flat though. Once I started running the job I noticed the carriage has a slight tilt to it. Looking at the table, the side closest to the flag in back sits lower than the other side. Not sure why, it sits flat plastic to plastic when the steppers are deenergized.
Looks good @Barry. A couple hours isn’t that bad at all.
@Jeffeb3 I just got a chance to do some holes into my spoilboard to see how level it is and it seems the biggest difference is 0.5mm spanning across the whole 8x4 sheet. I drilled 9 holes @ 2mm depth, spaced evenly and I’ll try to illustrate it bellow.
2.19 2.25 2.36
1.86 1.87 2.05
1.89 1.86 2.12
So I’m going to leave it at that. That should be more than level enough for what I do. I just thought I’d share my results
2.05mm ±0.19mm! That is great!
That is a very good result. Thank you for sharing this.
The front left side is especially flat, huh? That’s still a 2’x4’ area.
Yeah. I’m pretty happy with those results. I’m thinking of writing these numbers and keep it handy close to the LR2. It would be an easy reference if I need to mill something smaller, then I can decide which part of the 8x4 area I would use, being the flattest.
Thanks for your suggestion to actually flatten the frame instead of the spoilboard. Now when I change spoilboards I don’t have to worry about getting it flat.
I’m kinda late here, but I used a 1" bit running about 45mm/s, 1200mm x 750mm took me a little over 1 hour to mill down 2mm.
8-O
Why not simply add some shims between the frame and spoil board to take up the areras that are affected the most and then run a surfacing bit over all.
