NordicCNC's build log

[pippin88]

Regarding spindle, I didn't realise it was an ATC spindle, which are a lot longer. Clamping high up may not be appropriate (though with a decent tolerance clamp I doubt you'd be crushing the spindle). The point is the longer the clamping area (or the further apart the clamping points) the better.

Yes, that's what I meant about the ribs. You don't need 15mm thick plate, even 5mm would be fine. The stiffness comes from the dimension in the direction of the force.

You should also add stiffening ribs to the carriage .

[NordicCnc]

Regarding spindle, I didn't realise it was an ATC spindle, which are a lot longer. Clamping high up may not be appropriate (though with a decent tolerance clamp I doubt you'd be crushing the spindle). The point is the longer the clamping area (or the further apart the clamping points) the better.

Yes, that's what I meant about the ribs. You don't need 15mm thick plate, even 5mm would be fine. The stiffness comes from the dimension in the direction of the force.

You should also add stiffening ribs to the carriage .

Machines only as strong as its weakest point. Currently what is keeping the back of your Z axis still? Its those carriages, which are attached via a 90 degree but-joint. So I'd say those two or so screws are the weakest point! That's why I created the side plates on my Z axis to give some support to the joints.

Thanks both of you pippin and Andy! I took your advice and now I've added 10mm aluminium ribs bolted to the front plate. I've also added 10mm side plates that are bolted to the rear plate, motor bracket and top bearing plate.



New total weights did not change much, while I think I have added quite a bit of stiffness!

Z-axis moving weight: 26.8kg -> 26.4kg
Z-axis total weight: 39.7kg -> 42.4kg



I am now debating, should I do something of the following things:

1. Remove the spacer plates used for the linear rails completely and add machining (on both the rear and front plate)? This would reduce weight (maybe 3-4kg?) and fewer parts needed. More machining though.



2. Move the spacers from the rear plate to the front plate. Linear rails would then go directly on the rear plate. Shorter spacers would be added behind the guide carriages and the front plate. This would increase the Z-axis moving weight by like 1kg, but reduce total weight by 1kg. I would gain some stiffness on the front plate, but lose some on the rear plate. Not sure where the weak point is and where the spacers are needed the most.

[JAZZCNC]

Ok well first, the ribs on the front plate add virtually nothing but weight because the plate is fastened directly to the bearings with no overhang, it's also short and strong so very little vibrations come from that area.

Regards the plates on the sides then these would help, however, I have a better suggestion. If you look at the pic and at the other machines I've built I always put a cover over the Z-axis. This isn't just to protect from debris it's also structural as it does the same job those plates. You don't need a 10mm plate, I use 3mm for the covers and it's more than strong enough.

The spindle mounting area is limited to the lower area (see the pic, it's the silver area, the black is drawbar cylinders.) However, they are steel and would easily handle another clamp.

Regards putting the spacer plates on the front plate to save weight then I wouldn't do that either because of your shifting weight to the wrong area.
To be honest I wouldn't use spacer plates as it lowers precision and makes it complicated.

Regards Motor brake then I can't answer that because I don't know those motors, but servos are not like steppers where they have a shaft sticking out the back, mostly because this is often used for the encoder.

How the motor handles the weight will depend on usage, but if you plan on doing 3D type work with lots of short moves with high acceleration then I think they 180W motors will struggle with the inertia and you'll get some following errors. Because again servos are unlike steppers where if they lose the position you visually see the lost steps, instead the encoders along with the drives close the loop and catch back up so will always return to exact same place when stopped provided they don't go outside of parameters set in the drives.

However, what you get is a following error which if it stays within following error parameters can trick people into thinking they don't have a problem because if they do a type of work which is mostly 2D the Z-axis isn't whizzing up & down so it gets missed.

[NordicCnc]

Ok well first, the ribs on the front plate add virtually nothing but weight because the plate is fastened directly to the bearings with no overhang, it's also short and strong so very little vibrations come from that area.

Regards the plates on the sides then these would help, however, I have a better suggestion. If you look at the pic and at the other machines I've built I always put a cover over the Z-axis. This isn't just to protect from debris it's also structural as it does the same job those plates. You don't need a 10mm plate, I use 3mm for the covers and it's more than strong enough.

The spindle mounting area is limited to the lower area (see the pic, it's the silver area, the black is drawbar cylinders.) However, they are steel and would easily handle another clamp.

Regards putting the spacer plates on the front plate to save weight then I wouldn't do that either because of your shifting weight to the wrong area.
To be honest I wouldn't use spacer plates as it lowers precision and makes it complicated.

Regards Motor brake then I can't answer that because I don't know those motors, but servos are not like steppers where they have a shaft sticking out the back, mostly because this is often used for the encoder.

How the motor handles the weight will depend on usage, but if you plan on doing 3D type work with lots of short moves with high acceleration then I think they 180W motors will struggle with the inertia and you'll get some following errors. Because again servos are unlike steppers where if they lose the position you visually see the lost steps, instead the encoders along with the drives close the loop and catch back up so will always return to exact same place when stopped provided they don't go outside of parameters set in the drives.

However, what you get is a following error which if it stays within following error parameters can trick people into thinking they don't have a problem because if they do a type of work which is mostly 2D the Z-axis isn't whizzing up & down so it gets missed.

Thanks for your advice. I think you forgot to add a picture though?

I will reply back once you have added, as I think things will make more sense to me then.

Skickat från min SM-A530F via Tapatalk

[JAZZCNC]

Thanks for your advice. I think you forgot to add a picture though?

I will reply back once you have added, as I think things will make more sense to me then.

Skickat från min SM-A530F via Tapatalk

No didn't forget the forum is playing silly buggers again and won't let me upload the pic. I'll try again later.

[NordicCnc]

No didn't forget the forum is playing silly buggers again and won't let me upload the pic. I'll try again later.

Thanks man!

Skickat från min SM-A530F via Tapatalk

[phill05]

Here's where I throw a spanner in the works.

This is from my own way of working I think you are going way overboard with the construction of the Z axis adding more and more to it.

I made a Z axis 510mm high x 220mm wide using 12mm backing plate with cut outs to ease the weight on the Y axis with 20mm Hywin rails direct on the plate no packers and carriages direct on the spindle plate, I made a rotating ball nut and fixed 1605 screw which helps to have the very minimum of overhang and adds to the strength of the design.


It carries a German 2.2kw water cooled spindle, (I know not as heavy as yours) I do not get any drop of the Z when powered off weather this is down to the 2 to 1 reduction to the nut I am not sure but it works very well, it has cut wood, plastics, aluminium, steel plate and stone with no problems whatsoever.

Recently I setup a 4th axis to cut 2 1/2D designs around the edges of 150mm disks again works really well.
I am currently designing another machine with extended Y axis to be able to have a 4th axis running down the length of the X axis, and be able to cut around 300mm dia disks and have no problem using the same kind of design in fact I am going to use a rotating ball nut on the X & Y axis as well it is more compact and so smooth compared to turning screws.


Phill

[NordicCnc]

Ok well first, the ribs on the front plate add virtually nothing but weight because the plate is fastened directly to the bearings with no overhang, it's also short and strong so very little vibrations come from that area.

Regards the plates on the sides then these would help, however, I have a better suggestion. If you look at the pic and at the other machines I've built I always put a cover over the Z-axis. This isn't just to protect from debris it's also structural as it does the same job those plates. You don't need a 10mm plate, I use 3mm for the covers and it's more than strong enough.

The spindle mounting area is limited to the lower area (see the pic, it's the silver area, the black is drawbar cylinders.) However, they are steel and would easily handle another clamp.

Regards putting the spacer plates on the front plate to save weight then I wouldn't do that either because of your shifting weight to the wrong area.
To be honest I wouldn't use spacer plates as it lowers precision and makes it complicated.

Regards Motor brake then I can't answer that because I don't know those motors, but servos are not like steppers where they have a shaft sticking out the back, mostly because this is often used for the encoder.

How the motor handles the weight will depend on usage, but if you plan on doing 3D type work with lots of short moves with high acceleration then I think they 180W motors will struggle with the inertia and you'll get some following errors. Because again servos are unlike steppers where if they lose the position you visually see the lost steps, instead the encoders along with the drives close the loop and catch back up so will always return to exact same place when stopped provided they don't go outside of parameters set in the drives.

However, what you get is a following error which if it stays within following error parameters can trick people into thinking they don't have a problem because if they do a type of work which is mostly 2D the Z-axis isn't whizzing up & down so it gets missed.

JAZZ, I think the way you have installed the pneumatic actuators and the Z-axis cover design is great! The whole machine design is phenomenal.. I hope you don't me taking ideas and copying some features from it?

I've removed my spacer plates now and added a machining to both the rear and the front plate to make room for the bearing and ball screw nut housing. This reduced the overhang by 15mm! It also reduced the total weight a few kg's. Thanks for the tip!

[JAZZCNC]

JAZZ, I think the way you have installed the pneumatic actuators and the Z-axis cover design is great! The whole machine design is phenomenal.. I hope you don't me taking ideas and copying some features from it?

No don't mind at all , go for it.! . . . Thou bare in mind some of these pictures are not of the finished article, the covers, for instance, are still missing some fastenings and slot covers, etc but hopefully show what I've been saying.

[NordicCnc]

No don't mind at all , go for it.! . . . Thou bare in mind some of these pictures are not of the finished article, the covers, for instance, are still missing some fastenings and slot covers, etc but hopefully show what I've been saying.

Great and you have explained it very well!

By the way I have now decided that I will not use the 180W JMC servo motors that I bought in advance. I've come to realize that they are holding me back by limiting the weight of he machine. It was an expensive learning lesson but now I know that I should always wait with buying any components until the design is completed.

I've contacted the supplier and they might be willing to accept a return and I would pay a little more to get the 400W JMC servo motors in change (https://www.aliexpress.com/item/4000067490526.html). In case they don't accept the return for some reason then I have already found another use case for them, so that problem is solved - no money lost. If I then still buy the 400W JMC's, I don't know, I will have to check what you and the others here think. I saw that delta servo's were recommended as well and it was also mentioned that larger than 400W would probably be good?

Anyway the motor power issue is now out of the way and I have the money to spend on new and way more powerful motors!

So now having solved the motor power issue, do I still keep the Z-axis weight as low as possible or should I start trying to beef it up? The covers I will design to be structural, taking ideas from your machines JAZZ. The Z-axis front plate I am not so sure if I can improve much since it is already very stiff. Perhaps the Z-axis design is good as light weight and I can just stop worrying if the motor power will be enough to handle the heavy ATC spindle!