You can post a link to a google photos or youtube, or probably imgur.
Did you mistakenly get the ziptie around the screw in there? You are not having issues with the other 4 ziptie connections?
That’s possible. When I had it first installed, no, as I added that part after. But when I replaced them I did not take that piece off so it’s very possible. I will need to check that tomorrow. Good thought.
I was thinking about that too. That is possible. I was planning on making a mark on the actual stator shaft to check that but the quick check I couldn’t see it today. I lock tighted it on yesterday just before I tested it and that may have set by now and possibly solidified that? If it was just me seeing it I would have assumed I was mistaken but two of us saw it clearly. But we would not have been able to see if the shaft itself was turning. This will frustrate me if I can’t produce repeatedly. I hate unknown variables. Lol
Something like this might help:
I have no idea how they attach.
superglue.
Uhh, all I’m seeing is slack in the belt. I had more than that when I cut a 40ish inch diameter circle in plywood and mdf. Circles came out perfect except for the part where I didn’t start far enough over, so the mdf has a small flat from the edge. The end mill started and ended at the same location. I think you’re chasing squirrels that don’t matter.
I agree with Barry. I have also cut multiple circles from 12” diameter up to 40” and they have all be perfect on my full sheet LR2.
Also, earlier in the thread you said you were running your 611 at full speed. I wonder if you are running it too fast, creating dust and not chips and burning the bit out faster then it should be? I don’t run my 611 over 3.5 generally and I’m usually at 3. I’ve done 9mm doc with a single flute up cut 1/8” en mill running at 15mm/s in 1/2” MDF and it has just chewed through it without any loss of steps or any issues - end cut returns right back to the start point. Running the router too fast will literally smoke the bit way before it should because of the dust you create. Dust doesn’t evacuate heat anywhere near as efficiently as chips do. You could also try to evacuate the dust with a vacuum or air blowing into the channel - that might help with bit longevity.
I know you are looking at the flex in the system (and I will check mine when I get home to see how it compares) but since a new bit cuts well in the cedar it seems like the bits are dulling really quickly and that is compounding the problem - dull but will significantly increase the drag and the force that the machine has to overcome. Slowing down the router is kinda counterintuitive but it might help - I had to do that with mine and it really helped.
This may not be the case - but could some of the flex you are seeing be coming from your X Axis rails? What are you using? I have .120” Stainless Steel (304L). It’s probably overkill in the wall thickness but it’s what my local metal yard had in the drops pile.
I think that needs the shaft on the back of the stepper to be longer than mine. I was thinking of just hotmelting a toothpick to the pulley as an indicator. But the play I found after clamping the belt was the far smaller of the two, so I agree with Ryan. Leave that, at least for now, and focus on the belt mounting.
They matter in my cuts. With MDF being conservative, not much, but with cedar you could see just how much out it was. When the router would plunge to start a cut, it would drop in nicely. Was at 3mm/s. Then when it started the horizontal slot, the force would push the bit sideways from where it was supposed to be. So in the end where tabs were and the z axis plunges you could see about 1mm depth of the bit into the piece. For these pieces I needed to cut for someone it didn’t matter, but it showed me there was flex, and that is when I did a little testing and found what I feel is either something wrong with my setup, or an opportunity for improvement.
It’s interesting that slack only appears from the side with the zip tie. I have to check if it went around the bolt. Previously I had them so tight to get rid of the slack it was hard to move the 611 plate along the x axis from the tension. Up until the ziptie actually snapped.
In the cedar I had to, or the steppers would skip badly and totally destroy the cut. I’d rather be at 1 and moving faster to get a proper chip loading. MDF is really easy to cut. Cedar is pretty hard on bits because of the silica and oils in the wood. Also greatly varying density and knots. But the tradeoff is you destroy bits much faster for sure.
I have so far only tested flex in the x axis, which would not be able to flex the x rails as the forces are straight down the tube. I actually have the same rails as you. They are only $60cdn for a 20’ length at our local metal market for some reason.
So, the videos I just did the force was applied by my thumb while my hand was holding the x tube. However, when I was actually measuring, it was a load applied to the gantry without anchoring to the x tube. So the flex could come from all avenues combined. The connection of the horizontal and vertical tubes flexing etc.
What was clear was that the clamping method of the belt reduced the majority of it. Now I need to confirm that my zip tie doesn’t go around the bolt since I replaced the one that snapped. That would definitely introduce flex. If not, then I want to design a new piece that allows proper clamping.
In the cedar I had to, or the steppers would skip badly and totally destroy the cut. I’d rather be at 1 and moving faster to get a proper chip loading. MDF is really easy to cut. Cedar is pretty hard on bits because of the silica and oils in the wood. Also greatly varying density and knots. But the tradeoff is you destroy bits much faster for sure.
I have so far only tested flex in the x axis, which would not be able to flex the x rails as the forces are straight down the tube. I actually have the same rails as you. They are only $60cdn for a 20’ length at our local metal market for some reason.
So, the videos I just did the force was applied by my thumb while my hand was holding the x tube. However, when I was actually measuring, it was a load applied to the gantry without anchoring to the x tube. So the flex could come from all avenues combined. The connection of the horizontal and vertical tubes flexing etc.
What was clear was that the clamping method of the belt reduced the majority of it. Now I need to confirm that my zip tie doesn’t go around the bolt since I replaced the one that snapped. That would definitely introduce flex. If not, then I want to design a new piece that allows proper clamping. In CNC, anytime you increase rigidity and remove any play it’s a positive move imho. 
So maybe a wider shot and use your scale to show us where you are pulling and the forces needed to cause that.
You keep coming back to cedar, if you think it is that much different that all the woods we use, lets do all the tests in MDF. I cut in MDF mostly so this is my best place to help. Wasting cedar is heartbreaking
MDF is more dense by far and full of glue, I know we disagree on this but lets stick to MDF as a test, since Cedar is variable (knots) and expensive, MDF is not. I also disagree on your philosophy on speed, Faster/deeper. “proper chipload” All bits have a range, obviously we are on the lowest end every time as compared to a half million dollar CNC. Chip load can be increased by moving faster (bad for us) or cutting deeper. Slow RPM, 8mm/s feedrate, increase depth until you get inaccuracies, in MDF, 6mm DOC max, 1-3 on the 611 speed, Single flute, slotting is how I cut with amazing accuracy. So why don’t we start there. Make some test cuts using my recipe in a “known” material.
At the same time you are out getting MDF maybe a handful of 40lb zip ties so we are all on the same page. You are convinced it is the zipties, you are the only one using what you have. At this point we need to match every spec we can to eliminate as many variables. So $1 on the spec’d cable ties will help.
I’ll make up a longer video showing what I’m doing as soon as I get the chance.
I am using the zip ties from your store. Are those not the same zip ties you are using?
I’m very happy to do what I can to reproduce any tests with repeatability. Once satisfied there is something to my results then perhaps someone else would be willing to measure theirs if they have a dial indicator and scale that would work.
I still have to out some of it back together as I was putting on new y plates milled from aluminum. I still have to reattach the y belts and just printed some new brackets to attach to the y plate to hold the LCD and mini Rambo.
The aluminum plate stopped the flex.by the skateboard wheels. May not matter but they look good and it was some machining experience on my friends Tormach CNC mill.
Added a bunch of tapped mount holes for any potential total future use as I can’t just screw into it like I could with MDF.
Dude! That’s cool looking! I like the threaded holes, good idea!
Ok, so there are some caveats and differences for my test:
- I’m using LR1, with 6mm belt. I haven’t upgraded yet.
- My zip ties are sloppy. I have decent tension on the belt, which I think keeps them all the way stretched, but each side is over 1/2" wide. I just haven’t bothered since it’s working fine.
- I’m using the weight of a full bottle of oil, which weighs 1309g according to my kitchen scale, but I am not pulling directly, it’s connected via fishing wire, and draped over a piece of PVC to reduce friction on the plywood.
So here’s what I did:
- I tied the end of a piece of fishing line to the 1.3kg weight, and the other end to the roller closest to the weight, on the motor side.
- I turned on the machine, to make the X, Y, and Z axes all held in place by the motors.
- I set up my dial indicator (I didn’t rezero it) on one of the other rollers on the other side. I took a picture of the indicator, it was at +0.005". The gantry was most of the way away from the weight, probably a foot from the far side.
- I hung the weight off the side, and I did my best to make sure the PVC wasn’t holding up the weight with friction by twisting it a little.
- I looked at the dial indicator, and took another pic, and it was at -0.004".
So, it looks to me like it moved 0.009" towards the weight (I would be very shocked if it moved away :)). The Internet says that is 0.23mm for 1.3kg.
Other thoughts about it:
1kg seems like it’s really not an accurate representation of the load. This is definitely a worst case scenario. I would expect this much load momentarily if dug too deep or something, but not in normal milling and definitely not on a finish pass (which is where you get accuracy).
My zip ties are definitely not as tight as they could be. I couldn’t tell where the distortion was, but I bet it came from the far zip tie.
I am not sure what the reaction would be if I used a smaller or larger weight.
And finally:
There’s no authority on this, a lot of people have made replacement belt holders for the MPCNC zip ties. It’s a common gripe. Some people love them and others hate them. I’m sure if you make a part that just pulls directly on the belt, and includes adjustable tension, some people will use it. I want to be clear that I’m not trying to keep you from doing that.
You posted some pretty crazy numbers earlier (30mm/s with a 1/4" bit and 10mmDOC or something). This machine compares favorably to the next highest expense set of machines, but there are far better machines out there, with associated $$$$$. You shouldn’t compare the LR to a $10k machine or a $2k machine with 1/10th the cutting volume. If you want repeatable parts, and bit longevity, then you need to be more realistic with your CAM. If you want high accuracy, then you need to do a finishing pass with almost no load on the bit.
Here is my photo album, Sorry for the messy shop. Please don’t study the pictures and point out how much stuff I have in there :D. I promise none of the stuff was touching the experiment.
Thanks. I’m lucky to have a friend with a very expensive since CNC mill as a hobby toy that I have access to and he helps make parts. My 611 plate is now aluminum also. I did think to add threaded holes to it sadly. (Made that first) so I’ll have to take it off at some point and do some more work. Also want to thread all the holes so there would be nothing extruding on the bottom of the plate if so cut bolts to length. I’m really happy with the y plates so far.
I’ll reply further a little later but just throwing up these two videos quickly until I get the kids down and can reply.
Having the gantry that high will give the Z pipes a lot more torque on the ZX corner, which will make it easier for that whole Gantry to tip.
Put another way, if the gantry were lower, the ZX corners would be able to resist the torque from that pull more. Can you test with the Z lower?
The magnet base is probably heavy enough to just sit on the table. The needle will move with almost no force. The magnet base is just so you don’t ruin everything if you bump it (or to stay still on a vibrating surface).
Those aluminum plates are really awesome.