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He said, "It's much more accurate than I would expect." He's referring to how accurate it is based on how it is designed. And I disagree that it's not very ac

by swimfar 10y ago

He said, "It's much more accurate than I would expect." He's referring to how accurate it is based on how it is designed. And I disagree that it's not very accurate, given the use case. 0.4mm or 1/64" is way more accurate than almost anyone can do with traditional power tools. Sure, other more expensive machines have better precision. But how many people actually need that much? Even plywood is going to experience changes in length due to temperature/humidity greater than 0.001" (0.025mm). Solid wood (which I guess this machine isn't really designed to cut) is going to be even more.

DannyBee 10y ago
"And I disagree that it's not very accurate, given the use case. " What use case? "construction" is mentioned, but plywood guys and drywall guys can make cutouts and curves far faster and more accurately than this machine can cut. So seriously, what is the real use case other than "fun toy"? " 0.4mm or 1/64" is way more accurate than almost anyone can do with traditional power tools." This is just flat out false. With a simple track saw, i can easily get within 1/128th without even trying. Hell, i can do that with a circular saw and a straight edge without a track. You can get to within 0.005 pretty easily if you have bothered to tune your tools at all and don't beat them up. You can definitely get 0.005 if "traditional power tools" includes routers. Of course, if you go to hand tools, getting within 0.001 is utterly trivial with good hand planes. "But how many people actually need that much? " Wood certainly moves, but 0.005 is about being able to make nice fitting joinery repeatably. https://woodgears.ca/mortise/accuracy.html https://woodgears.ca/mortise/accuracy.html "With a mortise of 0.503", here's how the tenons fit: ... Realistically, the total range of latitude is about 0.005" for a good fit. And this is using spruce, which is a very forgiving soft wood. For mortise and tenon joints in hardwoods, accuracy is even more critical. "
- Yaggo 10y ago
  For a wood-cutting system supported by two chains and gravity, .4mm is surprisingly good tolerance. Sure, it is possible to get far more stricter tolerance with tradiotional power tools (for skilled person) but first you need to somehow draw a line to follow, a challenging task in itself for complex shapes. This tool can do CAD, a big benefit.
  - DannyBee 10y ago
    "For a wood-cutting system supported by two chains and gravity, .4mm is surprisingly good tolerance." Remember that this is jut the 'precision'. It says nothing about the repeatability. I have strong doubts it's repeatable to even that level. "but first you need to somehow draw a line to follow, a challenging task in itself for complex shapes" ???? It's really just not that hard. In the absolute worst case, you use graph paper and cut it out. Most of the time, you just use a protractor or a bow and cut it nearly perfect anyway. Given the tolerances pretty much restrict this to "construction work", you can get the same result quite easily. "This tool can do CAD, a big benefit." I'm also going to assume you've not used much cad/cam software, because for most people, it's infinitely faster for a one off to draw it by hand than it is to draw it in a cad program and generate gcode for it using cam software. People have enough trouble using sketchup, let alone something real :) The advantage for most people for CNC is the ability to repeatedly do the same thing. Unless you invest 100k in automated workflows, you aren't ever going to get to the point where it's simply "draw in cad, click button, have machine cut it". It's just never that simple, from workholding to what have you. Which is another reason why i think it's neat, but has no real use case.
    - Yaggo 10y ago
      You are right that the sweet spot for this tool (toy) is very narrow. Let's say I'm still surprised that you can rope-hang a router like that and get usable results, let alone ~millimeter accuracy :)
    - abakker 10y ago
      Thank you for these detailed responses. They track very well with my experience using a 4x8' CNCrouterparts machine. There are so many things acting against precision that I spent my first year of CNC ownership finding out what was really practical. Inlays on machines with >.005" accuracy don't work. Guitar necks do NOT fit. Puzzle joints don't glue up. The sources of problems are endless, even in a rigid machine: 1. spindle runout. 2. bit diameter changes (its is labeled at .25", but its really .246 3. climb vs conventional milling yields different characteristics in different materials. 4. bit deflection in certain cutting actions (plunge, tight corners, etc) 5. bit wear during the job. 6. dust removal / chip recutting 7. lost steps 8. dust in the ways of the machine 9. linear motion system misalignment. 10. workpiece slippage/hold down. 11. material not being flat/level (especially with cheap plywood, which often varies in thickness by >.005")(try making accurate box joints with that...)(also, it is never flat, it always has some twist/warp because of the way the plys are cut out of the tree). This machine seems to be a great thing, and I very well may build one for an outdoor plasma cutter, but, I find the accuracy claims very difficult to believe. All of these sources of precision loss will effect the end result.

by swimfar 10y ago

DannyBee 10y ago

"And I disagree that it's not very accurate, given the use case. " What use case? "construction" is mentioned, but plywood guys and drywall guys can make cutouts and curves far faster and more accurately than this machine can cut. So seriously, what is the real use case other than "fun toy"? " 0.4mm or 1/64" is way more accurate than almost anyone can do with traditional power tools." This is just flat out false. With a simple track saw, i can easily get within 1/128th without even trying. Hell, i can do that with a circular saw and a straight edge without a track. You can get to within 0.005 pretty easily if you have bothered to tune your tools at all and don't beat them up. You can definitely get 0.005 if "traditional power tools" includes routers. Of course, if you go to hand tools, getting within 0.001 is utterly trivial with good hand planes. "But how many people actually need that much? " Wood certainly moves, but 0.005 is about being able to make nice fitting joinery repeatably. https://woodgears.ca/mortise/accuracy.html https://woodgears.ca/mortise/accuracy.html "With a mortise of 0.503", here's how the tenons fit: ... Realistically, the total range of latitude is about 0.005" for a good fit. And this is using spruce, which is a very forgiving soft wood. For mortise and tenon joints in hardwoods, accuracy is even more critical. "

Yaggo 10y ago
For a wood-cutting system supported by two chains and gravity, .4mm is surprisingly good tolerance. Sure, it is possible to get far more stricter tolerance with tradiotional power tools (for skilled person) but first you need to somehow draw a line to follow, a challenging task in itself for complex shapes. This tool can do CAD, a big benefit.
- DannyBee 10y ago
  "For a wood-cutting system supported by two chains and gravity, .4mm is surprisingly good tolerance." Remember that this is jut the 'precision'. It says nothing about the repeatability. I have strong doubts it's repeatable to even that level. "but first you need to somehow draw a line to follow, a challenging task in itself for complex shapes" ???? It's really just not that hard. In the absolute worst case, you use graph paper and cut it out. Most of the time, you just use a protractor or a bow and cut it nearly perfect anyway. Given the tolerances pretty much restrict this to "construction work", you can get the same result quite easily. "This tool can do CAD, a big benefit." I'm also going to assume you've not used much cad/cam software, because for most people, it's infinitely faster for a one off to draw it by hand than it is to draw it in a cad program and generate gcode for it using cam software. People have enough trouble using sketchup, let alone something real :) The advantage for most people for CNC is the ability to repeatedly do the same thing. Unless you invest 100k in automated workflows, you aren't ever going to get to the point where it's simply "draw in cad, click button, have machine cut it". It's just never that simple, from workholding to what have you. Which is another reason why i think it's neat, but has no real use case.
  - Yaggo 10y ago
    You are right that the sweet spot for this tool (toy) is very narrow. Let's say I'm still surprised that you can rope-hang a router like that and get usable results, let alone ~millimeter accuracy :)
  - abakker 10y ago
    Thank you for these detailed responses. They track very well with my experience using a 4x8' CNCrouterparts machine. There are so many things acting against precision that I spent my first year of CNC ownership finding out what was really practical. Inlays on machines with >.005" accuracy don't work. Guitar necks do NOT fit. Puzzle joints don't glue up. The sources of problems are endless, even in a rigid machine: 1. spindle runout. 2. bit diameter changes (its is labeled at .25", but its really .246 3. climb vs conventional milling yields different characteristics in different materials. 4. bit deflection in certain cutting actions (plunge, tight corners, etc) 5. bit wear during the job. 6. dust removal / chip recutting 7. lost steps 8. dust in the ways of the machine 9. linear motion system misalignment. 10. workpiece slippage/hold down. 11. material not being flat/level (especially with cheap plywood, which often varies in thickness by >.005")(try making accurate box joints with that...)(also, it is never flat, it always has some twist/warp because of the way the plys are cut out of the tree). This machine seems to be a great thing, and I very well may build one for an outdoor plasma cutter, but, I find the accuracy claims very difficult to believe. All of these sources of precision loss will effect the end result.