Ok so, my Dragon’s Lair project, every single piece I did in MDF came out exactly to scale, and all the pieces went together amazingly. Fits like a glove so far, and I’ll be posting updated photos there later.
Today I wanted to be brave, and I grabbed a sheet of cabinet grade birch. I put it on the table, and let the machine rip. Using the same settings that I used on my MDF, only… This time, almost nothing was ‘accurate’. Everything was off by a few mm’s, and some things were even ‘oblong’ or ‘skewed’. Before we go into a long discussion about this, here’s the ‘theories’ I have in my mind, and if I’m missing something please chime in.
1 - I think maybe I shoulda put a new sharp bit in, since I had just cut 3 full sheets of MDF, and MDF is known to be hard on a bit.
2 - I think maybe it was running a little fast for a ‘hardwood’ like Birch. I used the same settings that were so successful with my MDF cuts. 6mm DOC, 10mm/s X&Y, 8mm/s Z. No lead in. Which I wanna try in the future.
3 - I had noticed that some of my tubes weren’t even touching the bearings. I tightened things up a bit, but didn’t notice any obvious binding. Belts are all still the same tension.
Does hardwoods like Birch work the LR2 harder than MDF? I Primarily work with MDF, but as I said, I stepped out of my comfort zone. I cut a nice little stool out of 3/4" plywood, was my first real cut actually, and it came out flawlessly. BUT, was also a fresh bit too.
Mdf is pretty hard material. It doesn’t have the same variance as read wood, but birch ply is pretty consistent if you average out the layers.
I also think it is hard to really have consistent cuts and not be nearly dead on with tolerances. If your finish looks about the same as the mdf, then it was probably pretty good settings.
I would be more suspicious of the fact this is a new day, and maybe your startup procedures aren’t giving you consistencies.
For example if you started the machine out of square today, but got it right yesterday. Or maybe one end skipped a step while you were setting it up. Can you think of something like that to explain it?
Honestly… Yes lol I get in a hurry alot and hell, I coulda screwed up something in CAD/CAM too… I also messed up my first start, by not zero’ing out the machine and had to stop it really quick and start over. I’m notorious for that kinda stuff tho. You probably nailed it with ‘maybe your startup procedures aren’t giving you consistencies’ part knowing me.
I was using a spiral upcut 1/4" and it was really tearing out the top like it does when the bit gets dull, that’s why I thought maybe that coulda been dragging the machine down and maybe getting it outta whack.
I was going to guess starting off out of square as well… I don’t have a LowRider, but on my MPCNC I know I would have one day where it was perfect, then the next day things were off by just enough… I solved my issues (well at least that one) with dual end-stops to help with auto-squaring, but my understanding is that’s not available on the LR…
That is very possible… I honestly can’t remember if I pulled it back to the hard stops before starting the 2nd time. Lesson here, take your time, slow down, start right.
So I removed the 1/4" 2 Flute Spiral upcut bit today just to look at it. It’s black… Like toast that got left in the toaster oven too long… By about 4 hours… All jokes aside, you know that color metal gets when you heat it up to just about the temp that it melts at, then let it cool down? Yea my bit looked like that. So I think alot of my inaccuracies could have been the fault of a dull bit. Anyone ever had any experience with dull bits throwing the cuts outta whack?
Side note, I cut 3 full sheets of 3/4" MDF with that same bit. I think it was dead in the water before it ever hit the birch. Just sucks I wasted a $66 sheet of wood. Live and learn. New bits every time you try to cut something expensive lmao
Ah, damn I actually dialed my router’s RPM’s UP… I didn’t know I shoulda slowed it down. I do know ALOT of the time, the bit sounded like it was struggling in the birch, that’s why I assumed it was just dull.
Well, it might be dull, but maybe not. If it has a lot of glue or pitch on it, it will cut like it’s dull.
I find router bits, and table/miter/band saw blades will usually cut like they’re new after I clean them. I picked up some sort of “Bit and Blade” cleaner on sale (at Woodcraft, I think) a few years ago, but there’s a bunch of different ways to clean em’.
I’m always running much higher RPM than the feeds and speeds charts and calculators say I should be. My personal approach is to run the highest RPM that doesn’t produce any burning smell or visible burning on the wood. It works for me, but it isn’t “Right”. I think I had to dial the 611 back to 2 or 3 to stop the burning smell on the cabinet grade birch. Baltic birch seems to tolerate much higher RPM. I have no idea why.
Crazy isn’t it? For now, I think I’m going to stick with my MDF. My stool came out so nicely cut from a 4’x4’ project panel (regular plywood from HD I think?) But that was WAY before I moved my speeds up for MDF. I think then I was running the ‘conservative’ settings from the build pages. So alot coulda went into factor. I didn’t start square, possibly. I was running to fast. Dull/Dirty bit. But I never did notice any burning smell. But quite a few times the bit was screaming pretty good haha
It would dramatically increase the load. Because the bit is pushing more than cutting, the material can work harden, and the flex can cause it to grab more bite at once. If that leads to just a few skipped steps, then it will be out of square from then on.
Bingo! I was hoping you’d chime in, and with this very answer. I cleaned up my shop a bit today because I got a bigger vac, and dust collection system installed, and when I cleaned out the vacuum port of my 611 plate, it had long spiraled wood strings all inside it from the birch. Also, it was wrapped around the bit when I took it out.
Just glad that I didn’t mess my machine up, or worse, burn down my shop. The bit was clearly burnt. Had gotten really hot and wasn’t silver any more, it was that really shiny black and blue color. Like metal that’s been welded but unfinished haha
I think however, from now on out, after 3 sheets of MDF, I’ll do a bit change. For safe measure. Especially before attempting any ‘real’ wood cutting.
Note: It was screaming in some parts during the cut as well. I think during the full depth finishing passes mostly. I would have stopped it and changed it then, but when I hit Pause on Repetier, it didn’t have any effect on the machine. Is there a way to pause & lift the machine during a cut? Would definitely be useful info to have.
The pause takes a moment to have an effect. The pause causes RH to stop sending commands to Marlin, but Marlin has a few already stored. If they are long commands (A straight line might be one single command), then it may travel for a long time before stopping. It’s not so obvious in 3D printing, because the commands are so short.
Then you can raise the tool, stop the router, and bring the tool back down with RH controls, or the LCD. I am not 100% sure it would do the right thing if you didn’t bring it back down to exactly the right spot though. So you might lift it by 20mm, and then drop it back by 20mm, being careful about it. If you change the bit midway, then you’ll need to figure out how to make it be the same depth.