Post by Derek the Admin on Sept 13, 2017 3:20:03 GMT
We get a lot of questions about whether our machines can actually be rigid since we use an MDF frame. My argument has always been that rigidity is a function of both the material and its geometric configuration. I think our machines use the exact right balance that gives what I truly believe is the best cost/performance ratio in the industry. Theory aside, the proof is really in the pudding. I usually encourage people to go watch videos of our machines and the competing machines running and go with which one they think performs best. Given our sales trends I think that strategy is working well for us.
In particular though, I wanted to challenge what I viewed as a misconception about the Carve King versus the Shapeoko 3. I think that the Shapeoko 3's use of a really beefy rail (exceeding what is needed) has fed into a misconception that it must be the most rigid in the class. Ever the scientist, I sought not to disprove it, but to observe reality. I wanted to present some actual data to compare the two machines.
Here is a link to a Shapeoko 3 owner performing some tests. For the record, he performed this test some time ago and did not post it for the sake of comparing machines nor has he invited a comparison. He simply placed his results in the public domain and it was about the only semi-scientific data I could find on these measurements for the Shapeoko 3. As such, I'm using it as the basis for comparison.
timf.anansi-web.com/wp/shapeoko-3-some-tests-and-some-results/
The below tests are his results and do not represent anything official from Carbide 3D (the producers of the SO3). I can not guarantee the repeatability of his numbers. I should also note that his machine is modified. It appears to be modified for the better, but it's only fair to mention that this is not the stock configuration that they send out. I can not guarantee that their stock machine wouldn't perform better than what he measured. I doubt it, but I should mention that to be fair. C3D is welcome to publish numbers if they so desire. I challenge them to do so. From what I can tell, this gentleman used a pull force gauge pull the end mill with 10 pounds of force. I can't be sure that he pulled directly on the end mill, but I know of this gentleman from another forum and perceived him to be a very smart guy. This is the proper way to measure it, so I assume he did it that way.
He tested it with the motors on (to hold position), and pulled in the Y direction with the Z all the way retracted, in the Y direction with the Z all the way extended, and also did the same two tests pulling in the X direction. I measured it the same way. The Carve King's Z stage will be positioned roughly in the center of the gantry as this is it's weakest position. There is less deflection on a beam if the force is applied near its fixed end versus at the center, so this is the "worst case" measurement. I must also mention for full disclosure that the machine I'm measuring this on is made with King Starboard (a high end marine board brand). This is the "ST" version of Starboard which is stiffer than their conventional Starboard. It's elastic modulus, however, is not greater than medium density fiberboard. In other words, an MDF framed version of the Carve King would theoretically perform a little better than the numbers I will present below.
Deflection is measured at the end mill, given a 10 pound pull on the end mill. Just to be out of the way of the dial indicator, some of my pull forces were a little off axis. Even if the pull force is off say 10 or 15 degrees, the component of that force in that direction is still very very close to the force applied (google vector components for more information on this). I pulled a little harder than 10 lbs to compensate. My back of the envelope figuring shows that a 10.5 pound pull made 15 degrees off axis is about the same as a 10 lb pull purely along that axis, so I think these numbers are pretty accurate. 10 pounds is an arbitrary figure. I used it simply because the gentleman with the SO3 who did these tests used 10 pounds. In reality, these machines are making cuts much lighter than 10 pounds. Even working in something like 6061 aluminum making what seems to be a pretty good cut, you might only be applying 2 to 4 lbs of force. Sometimes it might even be less than a pound. The point is that for both machines, your cuts will likely be under 10 lbs and therefore experience substantially lower deflection than measured in these tests. Both machines do what they do fine. Let's turn to the results and see how the Carve King stacks up though.
Here's the general setup. The Carve King has a vise on it used to mount the magnetic base of the dial indicator.
imgur.com/hdecqeL
X direction, Z at full retract:
Carve King: .012"
His Shapeoko 3: .015"
imgur.com/jg1sg0T
X direction, Z at full extension: (Note that on this test I set the DI to 0 and pulled from the opposite direction causing the dial to spin counter-clockwise. This method was used because between the vise and the DI I had very little room to get the gauge in there. This method is just as valid).
Carve King: 0.013
His Shapeoko 3: .015"
imgur.com/EViZeBO
Y direction, Z at full retract:
Carve King: .025"
His Shapeoko 3: .025"
imgur.com/6z8sy4v
Y direction, Z at full extension: (note that deflection is lower in both machines with the Z raised higher. This stands to reason)
Carve King: 0.035"
His Shapeoko 3: .040"
imgur.com/7SIOCSH
These numbers are very close. The raw numbers show a tie in one test and the Carve King winning in the other three. In the one test I'm calling a tie, the reading on my dial indicator was actually closer to .024" instead of 0.025" but I was a little more off axis with the pull than I wanted to be (for the sake of getting both the DI and gauge in the pic) so I'll round up to the next thou in the interest of fairness. Because these differences are small and were not done using the exact same method, I'm not going to go beat the drum that this is an all out victory. Even though comparing my figures to his show the Carve King winning 3 and a tie on the 4th, the numbers are close and there is certainly measurement error contained in both tests so there could some changes either way. That said, I think this is a big showing for the Carve King. Next time you see some one on your Facebook, on a forum, etc, tell you that the SO3 is "more rigid", send them here and dispel that falsehood.
In particular though, I wanted to challenge what I viewed as a misconception about the Carve King versus the Shapeoko 3. I think that the Shapeoko 3's use of a really beefy rail (exceeding what is needed) has fed into a misconception that it must be the most rigid in the class. Ever the scientist, I sought not to disprove it, but to observe reality. I wanted to present some actual data to compare the two machines.
Here is a link to a Shapeoko 3 owner performing some tests. For the record, he performed this test some time ago and did not post it for the sake of comparing machines nor has he invited a comparison. He simply placed his results in the public domain and it was about the only semi-scientific data I could find on these measurements for the Shapeoko 3. As such, I'm using it as the basis for comparison.
timf.anansi-web.com/wp/shapeoko-3-some-tests-and-some-results/
The below tests are his results and do not represent anything official from Carbide 3D (the producers of the SO3). I can not guarantee the repeatability of his numbers. I should also note that his machine is modified. It appears to be modified for the better, but it's only fair to mention that this is not the stock configuration that they send out. I can not guarantee that their stock machine wouldn't perform better than what he measured. I doubt it, but I should mention that to be fair. C3D is welcome to publish numbers if they so desire. I challenge them to do so. From what I can tell, this gentleman used a pull force gauge pull the end mill with 10 pounds of force. I can't be sure that he pulled directly on the end mill, but I know of this gentleman from another forum and perceived him to be a very smart guy. This is the proper way to measure it, so I assume he did it that way.
He tested it with the motors on (to hold position), and pulled in the Y direction with the Z all the way retracted, in the Y direction with the Z all the way extended, and also did the same two tests pulling in the X direction. I measured it the same way. The Carve King's Z stage will be positioned roughly in the center of the gantry as this is it's weakest position. There is less deflection on a beam if the force is applied near its fixed end versus at the center, so this is the "worst case" measurement. I must also mention for full disclosure that the machine I'm measuring this on is made with King Starboard (a high end marine board brand). This is the "ST" version of Starboard which is stiffer than their conventional Starboard. It's elastic modulus, however, is not greater than medium density fiberboard. In other words, an MDF framed version of the Carve King would theoretically perform a little better than the numbers I will present below.
Deflection is measured at the end mill, given a 10 pound pull on the end mill. Just to be out of the way of the dial indicator, some of my pull forces were a little off axis. Even if the pull force is off say 10 or 15 degrees, the component of that force in that direction is still very very close to the force applied (google vector components for more information on this). I pulled a little harder than 10 lbs to compensate. My back of the envelope figuring shows that a 10.5 pound pull made 15 degrees off axis is about the same as a 10 lb pull purely along that axis, so I think these numbers are pretty accurate. 10 pounds is an arbitrary figure. I used it simply because the gentleman with the SO3 who did these tests used 10 pounds. In reality, these machines are making cuts much lighter than 10 pounds. Even working in something like 6061 aluminum making what seems to be a pretty good cut, you might only be applying 2 to 4 lbs of force. Sometimes it might even be less than a pound. The point is that for both machines, your cuts will likely be under 10 lbs and therefore experience substantially lower deflection than measured in these tests. Both machines do what they do fine. Let's turn to the results and see how the Carve King stacks up though.
Here's the general setup. The Carve King has a vise on it used to mount the magnetic base of the dial indicator.
imgur.com/hdecqeL
X direction, Z at full retract:
Carve King: .012"
His Shapeoko 3: .015"
imgur.com/jg1sg0T
X direction, Z at full extension: (Note that on this test I set the DI to 0 and pulled from the opposite direction causing the dial to spin counter-clockwise. This method was used because between the vise and the DI I had very little room to get the gauge in there. This method is just as valid).
Carve King: 0.013
His Shapeoko 3: .015"
imgur.com/EViZeBO
Y direction, Z at full retract:
Carve King: .025"
His Shapeoko 3: .025"
imgur.com/6z8sy4v
Y direction, Z at full extension: (note that deflection is lower in both machines with the Z raised higher. This stands to reason)
Carve King: 0.035"
His Shapeoko 3: .040"
imgur.com/7SIOCSH
These numbers are very close. The raw numbers show a tie in one test and the Carve King winning in the other three. In the one test I'm calling a tie, the reading on my dial indicator was actually closer to .024" instead of 0.025" but I was a little more off axis with the pull than I wanted to be (for the sake of getting both the DI and gauge in the pic) so I'll round up to the next thou in the interest of fairness. Because these differences are small and were not done using the exact same method, I'm not going to go beat the drum that this is an all out victory. Even though comparing my figures to his show the Carve King winning 3 and a tie on the 4th, the numbers are close and there is certainly measurement error contained in both tests so there could some changes either way. That said, I think this is a big showing for the Carve King. Next time you see some one on your Facebook, on a forum, etc, tell you that the SO3 is "more rigid", send them here and dispel that falsehood.
1mm DOC, full width in aluminum at +40 ipm? He he he.
