Rods "Spaceship" Scratch built Plasma Cutter build

rodw wrote: yeh a huge project to get that far. There is an insane amount of engineering behind the motor selection

true . But It does give you a whole new level of appreciation of what it really takes to design and build tools.
It's always hilarious to hear people who have never done anything intricate say " oh it can't be that hard."
And yes I have even said that myself in the past .( usually before I try to build something )

Are you driving the motors with higher amperage than they are defined?
Are you aware that you might drive them into magnetic nonliniarity, means you just force them to heat-up more.
Generaly with permanent magnets: Don't know the correct point, but pushing to much current into a magnet can demagnetize permanently. Fx.: Connecting a dc motor directly with a low impedance source with too high voltage... Killed on the first occasion..

Mike_Eitel wrote: Are you driving the motors with higher amperage than they are defined?
Are you aware that you might drive them into magnetic nonliniarity, means you just force them to heat-up more.
Generaly with permanent magnets: Don't know the correct point, but pushing to much current into a magnet can demagnetize permanently. Fx.: Connecting a dc motor directly with a low impedance source with too high voltage... Killed on the first occasion..

Yeh, thats OK. They are industrial quality motors, not a cheap and nasty Chinese stepper. The Nema 34's are rated for 7 amps and I don't drive them past 6 amps. But the voltage is pretty hot! Some other motors I looked at could be overdriven by their specs but their torque specs did not suit the application. I have some 2 amp Sanyo Denki Nema 24's which are amazing and I don't give them their full 2 amps either. They in particular are an amazing motor. I run them with a 3 amp driver with the same voltage and features. I did manage to drive them with acceleration of 8 m/sec/sec but I backed them off to 5 m/s/s to be the same as the NEMA34's

my1987toyota wrote:

rodw wrote: yeh a huge project to get that far. There is an insane amount of engineering behind the motor selection

true . But It does give you a whole new level of appreciation of what it really takes to design and build tools.
It's always hilarious to hear people who have never done anything intricate say " oh it can't be that hard."
And yes I have even said that myself in the past .( usually before I try to build something )

Yeh I designed and built this table fro scratch (about 5 to 8 times) and it took me 3 months to make the z axis in my spare time! But boy did I gain some confidence in machining after that!

I started playing with an engineer in the US who spent about 3 months building an engineering model and I scoped 100's of motors to validate the model before settling on what I used. He found a lot of errors in the published mathematical models so it was a hard slog for both of us! One day we might sell a table or controller package based on "the model" but I would not hold your breath. The Covid lockdown did not last long enough!

I'll be back here in a week to see the poor machine in pieces !
Those accelerations will dismantle everything.
I did push mine to 68m/m with 10m/s/s acc and it just started ripping the belts clean. It worked for about 5 minutes and was fun to watch a 500Kg machine walk all over the shop, but it did not last !

this was something I was thinking in the back of my head myself. with that much force on the acceleration it has to work hard on the connections. so finding a balance between crazy fast and not ripping things apart pushing things to hard is a fine line to define. i think the water sloshing around in the table is a good indicator to keep an eye on once things are down off the casters and on the ground starting off slow and working your way up to the brink might not be a bad idea it good to know you have the extra there if needed though

still fun to watch and impressive regardless