Hi
I would like to have a moderated sticky post where all suggested configurations are placed in the first message. We have the https://docs.duet3d.com/User_manual/Machine_configuration/Configuration_CNC but it is not really updated and does not mentions configurations that needs to be done for a working CNC.

None trivial things I have noticed that needs to be configured for a Cartesian CNC in Duet Wifi firmware 3.4.6:

M203 RRF has a default minimum movement speed of 0.5mm/sec. This is way to high. I crashed my CNC while trying to drill a hole. Very BAD. A warning should appear in the DWC when it replaces speeds lower than 0.5mm/s for 0.5mm/s.
M350 Interpolation should not be used. The lowest speed limit for Interpolation to always work good is to high for my CNC it created wobbly lines while turning a cone.
M669 Segmentation is good to have if you need to stop the motion in a predictable manner.

Looking forward to learn more things that should be configured.

Thanks
//P

@T3P3Tony This thread can of course be joined to the very similar sticky thread about configs and macros. I didn’t want to high jack that thread.

I think the best way is to make the first message moderated/“ wiki like” so that all relevant info is mentioned first. The rest of the conversation can be suggestions and discussions.

@o_lampe my bad! I thought you criticized something I wrote about segmentation.

@o_lampe I think there are examples macros available. It’s no problems to program pauses for ramp up/down in macros.

Hi
I would like to have a moderated sticky post where all suggested configurations are placed in the first message. We have the https://docs.duet3d.com/User_manual/Machine_configuration/Configuration_CNC but it is not really updated and does not mentions configurations that needs to be done for a working CNC.

None trivial things I have noticed that needs to be configured for a Cartesian CNC in Duet Wifi firmware 3.4.6:

M203 RRF has a default minimum movement speed of 0.5mm/sec. This is way to high. I crashed my CNC while trying to drill a hole. Very BAD. A warning should appear in the DWC when it replaces speeds lower than 0.5mm/s for 0.5mm/s.
M350 Interpolation should not be used. The lowest speed limit for Interpolation to always work good is to high for my CNC it created wobbly lines while turning a cone.
M669 Segmentation is good to have if you need to stop the motion in a predictable manner.

Looking forward to learn more things that should be configured.

Thanks
//P

The point is that the mounting arrangement is not good. Just because it is done doesn't mean its good and life time of a bearing is not until it ceases to function or exist as a ball bearing. I know that 100N is in the high tension for most people and 2000 RPM is the upper speed for many steppers. Slower speed and repeated short back and forth motion can be really bad for bearings since the grease has problems forming a good film inside it at lower speeds.

Here is what happens if you do as I told you earlier and center the load between the ball bearings. All else the same. You can run with much harder tension and lower friction. That reduces ringing since the extra load due to the accelerated mass is smaller compared to the tension in the cord. This should be extra important for you since you have a very long thin free cord and hence a relatively elastic setup.

Loading a deep grove ball bearing axially is not that bad since it distribute the load on all included balls.

Depends on how fast you want to drive the system. If you go slow it can be open. Your Z is going slow.

//P

Congratulations! Looks really nice.

Just as a quick calculation of the life time of a high quality motor bearing mounted as you have it and a 200N load sideways. This means 100N cord tension @2000RPM.

//P

I want more videos Perhaps have rolling side supports instead of fixed ones.

I don't get any notifications as well.

@dc42:

Yes motors can be that bad, some are better than others. Even full steps can vary in size by up to 5%. Changing to 0.9deg motors helped me a lot, but didn't completely solve it.

Good to know

I also have issues with how all drive pulleys are attached to the motors. This is a common fault on almost all machines. The front bearings of the motors are not designed to take up torque and that is how they are mounted now. To be 100% correct you should have bearings above and under the pulley and a somewhat flexible shaft to the motor. That can be simplified on almost all machines to the front bearing of the motor and a bearing above the pulley. Technical that constitutes an overrefined system but should be ok. On your machine I would go for a separate bearing above and under since the pulley is to high. Benefit is higher belt tension with less resistance.

An issue that might create ripples would be if your pulley is not fitting 100% to the shaft and rocks in the direction of the load. My guess is that it would be less repeating but it could still be the fault.

//P