NordicCNC's build log

[NordicCnc]

Alright first actual design post with some pictures.

Z-axis design

- 3kW ATC spindle & Ø100mm spindle bracket. The spindle alone weights about 19kg according to the supplier (RattmMotors).



- 20x200x500mm aluminium rear plate, onto which spacers, BK12/BF12 bearings and motor bracket are mounted.
- 15x50x500mm aluminium spacers to make room for BK12/BF12 bearings and 1605 ballscrew. Linear rails are mounted to the spacers.
- 20x200x171mm aluminium top plate for HIWIN narrow guide carriages that goes on top of the gantry. Gantry ballscrew nut bracket will be mounted to the same plate.
- 20x200x240mm aluminium front plate, onto which the HIWIN narrow guide carriages and ballscrew nut bracket DSG16H are mounted.


- About 200mm gantry clearance
- 146mm overhang
- Spindle can be raised about 60mm above gantry
- 1605 ballscrew, 400m long with 25mm F-length end machining for BK12 fixed bearing to allow for pulley. Floating bearing in the other end.
- 20T HTD 5M pulley on the servomotor and 40T HTD 5M pulley on the ballscrew.
- 180W JMC servo motor.
- Motor bracket with oval holes to allow belt tensioning.



- Moving weight in Z-axis direction, about 26kg - still missing cables, water pipes, proximity switches etc
- Moving weight in X-axis (gantry) direction: 40kg - still missing cables, water pipes, proximity switches etc.



I am pretty happy with the total weight of the Z-axis. I don't think it'll go over 45-50kg with everything added.

I could still trim down the X-axis direction moving weight, by removing the linear rail spacers and adding machining to the front and rear plates. But I am thinking that I will need that stiffness which the 20mm plates gives me. Would it weaken the structure a lot by adding machining of 7x60mm along the middle of the plates, to allow room for the BK/BF bearings and ballscrew nut bracket?

[JAZZCNC]

- 3kW ATC spindle & Ø100mm spindle bracket. The spindle alone weights about 19kg according to the supplier (RattmMotors).

The spindle with Mount + BT30 Collet chuck weighs 19.5Kg. Don't forget if you are using dust extraction then you will need to retract the dust hood to allow access for tool change. This will mean adding pneumatic actuators and solenoid valves along with brackets etc and the dust hood its self.!... The weight creeps up fast.

Your estimate of 45-50Kg is about right. You will need a brake on the Z-axis motor to stop it dropping when not under power and i'm pretty sure your 180w motor won't handle the weight of ATC spindle.

[NordicCnc]

The spindle with Mount + BT30 Collet chuck weighs 19.5Kg. Don't forget if you are using dust extraction then you will need to retract the dust hood to allow access for tool change. This will mean adding pneumatic actuators and solenoid valves along with brackets etc and the dust hood its self.!... The weight creeps up fast.

I had not thought about retractable dust shoe. I need to investigate if I will need one!

Your estimate of 45-50Kg is about right. You will need a brake on the Z-axis motor to stop it dropping when not under power and i'm pretty sure your 180w motor won't handle the weight of ATC spindle.

The moving weight in the Z-axis direction is 25kg and the complete Z-axis will be around 50kg. 25kg will for sure drop when the Z-motor is not under power. Could I use stepper motor brakes on these servo motors?

In the one of the YouTube videos I linked to earlier, one guy is using the same servos and he told me that his Z-axis is around 20kg (I asked). This is only about 5kg lighter than mine and he said it works very well! His axis drops when not under power too.

Anyway as I mentioned earlier, I won't let the servos I have dictate the final design. I will buy new stronger ones if it turns out that they are too weak!