Question about duel X Axis drives

[Bobby783]

JAZZCNC

Last year when I decided I wanted to build a CNC Machine I knee jerked and went for the fasted option to get going, which to me at that time was a chinese kit which comprised the following

2pcs SBR16 - 350mm linear rail
2pcs SBR16 - 1000mm linear rail
2pcs SBR16 - 1500mm linear rail
12pcs SBR16UU block
1pc* SFU1605 - 350mm ballscrew with ball nut* *(BK12/BF12 end machined)
1pc* SFU1605 - 1000mm ballscrew with ball nut*(BK12/BF12 end machined)
2pcs SFU1605- 1500mm ballscrew with ball nut* (BK12/BF12 end machined)
4pcs BK/BF12 Support
4pcs 6.35*10mm coupling
4pcs Nut housing

4 Nema 23 motors
4 cheap Motor Drivers
1 Mach3 Break out Board (Parallel interface) this has now been replaced with a Chinese USB breakout board. The red one in the images attached.
So i still intend to build a ter with this kit to use as a learning tool but will want to build a more quality version in the near future whit bigger motors capable of cutting aluminium. High Speed cutting is not a priority for me

[JAZZCNC]

So i still intend to build a ter with this kit to use as a learning tool but will want to build a more quality version in the near future whit bigger motors capable of cutting aluminium. High Speed cutting is not a priority for me

Ok well first thing to clear up is cutting speed.? A common mistake made by new users is to think they can cut at any speed which suits them.! When In reality, to cut correctly so get a good finish and decent tool life the speed you cut at is determined by several parameters like the Material type, tool material #flutes dia & length, depth of cut.

This is where people go wrong and become disheartened because these kits won't allow the required feeds. I'm telling you this now so hopefully, you don't get pissed off and give up.

This kit just isn't suitable for a router, simple as that. The rails are ok but the rest will just cripple the machine.

I will need more details of the motors and drives and PSU to be 100% but I'm pretty sure looking at the pic that they are TB based drives and probably max out at 36V.
Worse still is the PSU looks like it's 24V which would fit because if you ran TB based drive at 36v you'll blow them up in minutes, so they leave a healthy safety margin.
Knowing these kits the motors will be High inductance motors which without getting too deep means they require more volts to get the same RPM as low inductance motors. Not good when you only have 24v to start with.
Steppers require volts to achieve higher RPM and still have any torque left. 24v will be crippling to all but small steppers. This leads on to the ball-screws.?

The 5mm pitch is too slow for a router which is compounded further by the low stepper RPM. For instance, a proper sized motor, drive, psu combo using 50V will safely allow around 1000rpm which connected to a 5mm pitchball-screw gives a max Rapid feed rate of 5000mm/min. To give some idea of proper feeds this is on the low sides for cutting even MDF correctly.
You also need to realize that at 5000mm/min the motors are close to the point of running out of torque so only really run at this speed for rapid positional moves not cutting underload. A safe Max cutting feed would be 4000mm/min which depending on MDF and cutter etc is likely to burn edges or give a poor finish.

The point to this is that your electronics and ball-screw combo if running at 24V will be lucky if let you run at half this speed so you'll be lucky if can cut at 2000mm/min.
Now here's where it really gets daft.!! . . . . . You won't be able to cut MDF or other soft materials that require speed but if you build it strong you will be able to cut Aluminium as you'll rarely cut much above 1500mm/min.

My advice is to sell the KIT and start again. OR Just sell the Electronics start with decent electrics and build a nice strong frame to give self half a chance then replace the ball-screws at later date with a higher pitch. You'll only need to replace the ball-screw as all the bearings etc can be reused.
If you take my advice you will save your self a lot of frustration and some money at the same time.