So I’m having a great time learning on my lowrider v2. It’s a full sheet table using the kit from Ryan. I am doing some cutting in cedar, and notice that the amount of play in the gantry (X axis in this case) is significant from the belt. If I clamp down sides so movement is only from the belt and I push left and right there is a lot of play. (I need to get a dial indicator, but easily 1mm+ in each direction without a lot of force.). How rigid can these GT2 belts make that part of the gantry? Am I too loose, or am I at the limits of what a GT2 belt can do? You can see this demonstrated in this cut, as the bit moves through varying density (the rings of the cedar tree are much harder than than the wood between them)
The cut looks jagged because of the play in the gantry that happens as the bit transitions from harder to softer wood it seems. I just don’t want to over tighten it. My expectations might just be unrealistic though, so looking for input.
To cut aluminum with an 1/8" endmill there is about 1.5kg force on the tip of the endmill (wood is far less). You can grab the machine and shake and flex all sorts of stuff but that doesn’t mean much.
You wood cut seems to be more likely a software/cam issue, or perhaps your tension bolts are through the roof tight.
Your whole machine from a few angle in pictures tells me more that extreme zoom videos.
There is the overall table. It’s not a gcode/software issue. The same code cuts different depending on the board. A brand new bit does better and as it dulls it gets worse. It shows the play in the gantry.
If a lateral force on the bit of about 1kg moves the bit by 1mm from where it’s supposed to be I don’t understand how that doesn’t mean much. That give is what causes that jagged cut. You can see how when it hits the stiffer resistance of the ring in the wood grain it stops moving across the x axis ubtil the pressure overcomes the harder grain and then it jumps back to where it is supposed to be. And it does it over and over.
I’m.workinf through where there is give in the gantry and right now the biggest source I can find is the belt (on mine). I’ve used belts for 3d printers and laser cutters where there is no lateral load in comparison bit this is my first gt2 belt pushing significant force in comparison. I don’t know how tight the belt is ideally and how much of the give in the belt I can remove.
The arc you are having issues with is very large and subtle. How did you generate it, what is your gcode like, do you have arcs enabled in CAM, What control board and step rate are you using?
That shows the wear in the bit. As I said it will move but as a bit dulls the forces get too high. Me and Kevin went back and forth testing some bits. He can do aluminum cuts for hours on end with the cheap import single flutes, I only get 45 minutes with them in MDF and they are garbage after that. The other ones I use go for 6 hours or so of cutting time. A dull bit is literally just getting dragged through the wood.
I doubt you have a force of only 1kg if it is moving your whole machine 1mm. A dull bit is going to be way worse. Look at how ragged the “cuts” are. If they are not clean and sharp your endmill is dead.
This is 10mm belt with fiber reinforcing, the belt is not stretching. It is rated very high. The GT2 6mm is rated at 1-5lbf install so that is a good place to start.
So there is definitely play with the belt. Doesn’t mean the belt is stretching, it can be from the zap straps securing it to the gantry at each end. I can see movement at the end of the belt when pushing a bit on the gantry with a finger. That’s where my tension question came in. Maybe I need to change how the belt ends are fastened. I believe I did them as your instructions showed.
Just a random thought, have you checked the tightness of the stepper pulleys? Could one of them be loose on the stepper shaft? Are all of the center assembly bearings touching the pipe and firmly attached to the center assembly? Also, can you upload some more pictures like the center assembly and side views showing how the belts are attached.
Is that both sides? One side should be pulled tight against the printed corner, that should eliminate half the cable tie flex (if there is any). I would also check you pulley, good suggestion.
What endmill are you using? Can I see a picture of the endmill and a good shot of the bad cut. And some gcode or you cut specs.
Also, what’s your DOC and feed rate? Maybe you are trying to push it too hard in Cedar (with the varying densities). Have you tried your gcode in just some pine board to see what it does? That will help figure things out.
I’ve cut up to 40" diameter circles in 3/4" cabinet grade plywood on my full sheet LR2 with a 3mm DOC and 15mm/s Feed Rate using a 1/4" upcut 2 flute end mill and the LR2 produces perfect circles every time. The machine is capable of this kind of accuracy but each build is different. I’m still experimenting with mine to see what the limits of DOC and Feed Rate are for plywood. Each material is different so you have to experiment with each to see what you can do. At the bottom of the Milling Basics page is a calculator that will help you get starting numbers and you can go from there.
It is both sides ya. I will change that, but the belts may be too short now for that so I probably have to order more from you.
I’d like to be able to remove all play from the ends of the belt.
Also, the end mill is from you. 2 flute 1/8 upcut. But it wore out fast on the cedar. I’m using a 1 flute I got from you now and so far so good but after 30 minutes of cutting it’s already noticable the change in cut not as clean.
Thanks for the feedback Jeff. I am pushing the machine. I’m figuring out the limits of it for my needs. For a full sheet machine I want to be able to cut at a reasonable speed that has a good chip loading to make the bits last a lot longer and get more done. It’s not gcode. With a brand new bit it cuts it just fine. But this experience showed me on my machine that there was a lot of play there that removing it would allow me to cut a little faster. Rigidity is key so anywhere I can remove play and add rigidity is a good thing. This pic is with the blade dulling a bit already.
So my question for the thread is about how tight people are making the belts and how much play they have.
