I was more going on the lower melting point, tensile strength and hardness all of which can make cutting it with a high speed router bit quite tricky as chips will melt and go stringy very easily compared to it’s higher melting point, harder cousin. I have found that it saws very easily, laser cuts very well (with suitable fume extraction) and water jets nicely. Perhaps with water or air jet coolants it will also cut well on a router machine?
Honestly I think you guys are making too big of a deal about this. They are 3 dollar cutting boards. I got them because I figured the torque requirements to machine it are low so it would be a good initial test.
For me it’s more about understanding which materials we can cut and how to cut them effectively.
I am keen to see the cheese experiments, particularly the workholding, I suspect some of the more Brie like cheese may need freezing before machining…
Would need to find food grade end mills if you want to eat the cheese. Not sure how well stainless steel would work for that. I know you can water jet cheese.
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What are you going to call this thing once it’s done?
A Modkita? Something else?
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So at 10k RPM plunging into oak with a 1/8th in single flute end mill the ODrive is maxing at 7.43A. I have it current limited to 20A so there seems to be quite a bit of head room.
Already got the hashtag going lol. The VESC is still working great with zero tuning but limited to manual app computer control.
Really really impressed on the performance, even without running a fan. Marv from KERN asked me to do some high power high rpm tests, after this Z is done we’ll push it!
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It was 1/4 in. Very nice graphs.
Sensorless Read Velocity is the electrical velocity (Ve).
RPM = Ve * ( 60 / ( PolePairs * 2 * pi ) )
This motor has two pole pairs so:
60 / ( 2 * 2 * pi ) = 4.7746
thus:
RPM = 4.7746 * Ve
I am curious how you are deriving the watts.
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Yup - I screwed that up - thanks:
Power is calculated from speed and torque. Torque is calculated from measured current and motor’s torque constant. Force is calculated from torque increase when cutting and endmill diameter. Do you want the spreadsheet?
I am already converting the Ve to RPM in the data as SensorlessRPM. I mostly included the Ve because that is what I have to send to the ODrive as the set point. This allows me to see how close to the set point the motor is actually running at.
I figured that is how you were calculating the power. Just wanted to make sure you were not basing it on the voltage.
Maybe add (log and display?) torque and power too (spindle/power supply usage)?
Also displaying cutting force in “real time” would help the operator determine when and how to adjust cutting parameters to optimize performance.
Material removal rate, in conjunction with cutting power, enables calculation of material K Factors which are useful for speeds and feeds calculations. Having accurate K Factors would greatly increase the utility of those calculators.
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A live monitoring program that listens to the arduino output will have to handle those conversions. Among other things the Arduino does not know the cutter diameter.
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Except torque and power - right?
My general thought is if a PC running at multiple GHz can do the calculation with the data the arduino is already outputting then there is no point for the 20Mhz arduino to do the calculation. The arduino is there to spit out the raw data. The only reason I am doing the Ve to RPM conversion right now is because it is needed for tuning the ODrive’s PID parameters and I do not have a GUI written. The less the arduino does the faster it can refresh the data. The faster it is refreshing the faster it can react to the ODrive going into an error state.
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So good news is the isolator works perfectly.
Bad news is that for some reason if I have the ODrive start up in sensorless mode, it is immediately spinning at 400Ve (~1900 RPM). This appears to be hard coded for some reason even though I can run at 150Ve and have no issues. This means I have to put it into sensorless mode only when actually spinning up the spindle, wait for it to get to 400Ve and then adjust from the 400Ve to the speed I want.
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Finding these things is what testing is for
Why do you prefer sensorless mode?
I don’t. Long story but basically this motor produces so much Back EMF that the current waveform is a sawtooth instead of sinusoidal. This confuses the ODrive and probably confused the VESC. The ODrive developer has an idea of how to deal with this by doing a “harmonic feedfoward” in the current control. In the meantime sensorless works fine.
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