Thread: New to CNC
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28-08-2019 #4
Bobby think I'm probably too late saying this as you say ordered and cannot believe none of the other experienced builders haven't piped up.!
The parts you have shown are all wrong for the machine your wanting to build.
5mm pitch screws are too slow for cutting wood and larger machine. This is made worse by the cheap motors and drives probably combined with low voltage psu.
To cut woods correctly so your getting good finish and tool wear you'll need feedrates higher than what 5mm pitch screws and those electrics will allow.
Let me explain little better why.
If those motors/ drives and psu are what i think they are then you'll be limited on the usable rpm the motors can produce.
Cheap motors often have high inductance rating, inductance affects the speed that can produced for a given voltage before torque drops away. So if you have low voltage psu coupled with high inductance motors the motors stall low down the rpm range.
This combined with high pitch screw affects the feeds you can achieve.
To give some idea of how slow I'm going to guess a few details based on experience.
So lets say using 36v psu with inductance around 12mh which is typical for cheap nasty motors, then you'll be lucky to reach 900rpm before motors run out of usable torque and stall.
Given 5mm pitch then your maximum velocity will be 5 × 900 =4500mm/min.
Not that bad you may be thinking, but it gets worse because the drives are analog and highly likely to be affected by resonance which affects motors causing them stall even lower down rpm range.
Then factor in other power robbing affects like missalignments etc and you'll be down in the 3500mm/min area. In reality you'll leave a safety margin when tuning motors so your realistic max velocity will be 3000mm/min.
Now this is maximum velocity or rapid speed which can't really be used for cutting because your very close to maximum torque and extra forces cutting requires will stall motors.
In real world use you'll be limited to maximum cutting feed of around 2500mm/min which isn't any where near fast enough to cut woods.
For a router you really need 10mm pitch running motors at least with 60vdc and ideally with digital drives to help massively with resonance. Or at least with good analog drives.
Know it's like shutting gate after horse bolted but it's biggest mistake often made by new cnc builders rushing out buying parts before knowing whats required to give a good setup.
Sent from my SM-T580 using Tapatalk-use common sense, if you lack it, there is no software to help that.
Email: [email protected]
Web site: www.jazzcnc.co.uk
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