NordicCNC's build log

[NordicCnc]

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.
Attachment 27525

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.
Attachment 27526

Phill

Hello, looks good! Interesting with the rotating ball nut. I understand it so that you have placed the fixed bearing on the spindle plate and then the other ball screw end is lose. Does it stick up in the air or what does it look like when the Z-axis is fully retracted?

Anyway I have to say that your advice is quite contradicting compared to the advice I have received from others. I am not saying you are wrong but I try to stay open minded!

[phill05]

Hello, looks good! Interesting with the rotating ball nut. I understand it so that you have placed the fixed bearing on the spindle plate and then the other ball screw end is lose. Does it stick up in the air or what does it look like when the Z-axis is fully retracted?

Anyway I have to say that your advice is quite contradicting compared to the advice I have received from others. I am not saying you are wrong but I try to stay open minded!

I did say I was throwing a spanner in the works, I know it's not a conventional way of making this and yes contradicting to what has gone before but it works and works really well it is compact, less weight, and the machine cuts very well, just wanted to give you an idea of what works without going to far.

The screw is bolted tight to bottom of spindle plate (no bearing) and screw goes up with plate, attached is an image when I first put it together.


Phill

[NordicCnc]

I did say I was throwing a spanner in the works, I know it's not a conventional way of making this and yes contradicting to what has gone before but it works and works really well it is compact, less weight, and the machine cuts very well, just wanted to give you an idea of what works without going to far.

The screw is bolted tight to bottom of spindle plate (no bearing) and screw goes up with plate, attached is an image when I first put it together.


Phill

Oh my! You have quite some Z-axis travel height there. I can see that the screw will be sticking out in the air when Z-axis is fully retracted (at the top end position). I think you rarely use that Z-height or are you doing some custom jobs?

Looks like the gantry clearance is around 100-120mm, am I right? It would also be interesting seeing a video of its performance in aluminium/steel!

You have definitely given me something to consider, thanks for that.

[JAZZCNC]

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.

You can't be serious.? You are using a rotating ball-nut on the Z-axis and you think he's going overboard with things.!

That design with the screw sticking up 400-500mm above the z-axis when at the top is just a crazy, pointless design and overly complicated for its application. Rotating ball-nuts are great on longer axis but for a Z-axis they will make no difference because the screw is so short that whipping or inertia don't factor into the equation which is the only reason to use a rotating nut, even with servo's which spin much faster than steppers.

Also regards your intended design with the L-shape Gantry that is all mixed up as well. Your design wastes Gantry clearance height because using the middle slot on the profile and misses the whole point of the "L" design. The point being the L shape is so most of the cutting forces are directed into the horizontal piece placed at the bottom where forces are highest.

[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.
Attachment 27530 Attachment 27531 Attachment 27532

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!

[BobTSkutter]

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.
Attachment 27525

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.
Attachment 27526

Phill

hello, i would really like to know how you made that rotating ball nut. It looks like a flanged ball nut sandwiched in a pillow block bearing housing with a pulley holding it together. please can you share some pictures.

thanks
bob

[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!

[NordicCnc]

Short update on the Z-axis design! You might notice that the design is heavily influenced by JAZZCNC's build's (e.g. the cover and L-shape gantry), although still very different and definitely no where near his quality!

Modifications:

1. Based on feedback I have now removed the stiffening ribs from the front plate. The reason is that since the front plate is directly mounted to the X-axis bearings with literally no overhang, the stiffening ribs would add nothing but weight. Instead a 3mm aluminium sheet is bent and welded, forming a cover that is structural while also protecting the components and cables from chips.
2. Removed the linear rail spacer plates and added machining to both the rear and front plate, to make room for the BK12/BF12 bearings and the 1605 ball screw.
3. 180W servo motors are no longer a constraint. Now I am thinking about getting Delta 400W servo motors. On the Z-axis I plan to use one with brake: https://www.aliexpress.com/item/3267...23d152a8ZJcwMZ. On the X- and Y-axis I plan to use ones without brakes: https://www.aliexpress.com/item/32671356516.html?spm. All axis with still be geared 2:1, to limit the ball screw maximum speed to 1500rpm.
4. Modified the top bearing plate to account for BK15/BK15 bearings and 2010 ball screw on the X-axis (in design process).
5. Preliminary positioning of proximity switches. The X-axis will only need one, but for the Z-axis I might need 2 if I can't find a location which I can use for both homing/top limit switch as well as bottom limit switch.
6. New Z-axis weights are 45kg (total) and 25kg (moving).

Here is the Z-axis mounted on the draft X-axis design, made with 120x80 Item profiles (I will post a more detailed X-axis design description later):

[Clive S]

Preliminary positioning of proximity switches. The X-axis will only need one, but for the Z-axis I might need 2 if I can't find a location which I can use for both homing/top limit switch as well as bottom limit switch.

Its not easy or practical to put a bottom limit switch on the Z axis as the tool lengths will all vary .