Sturdy and Fast all Steel CNC , my first build

[ImanGH]

Hi dear
I want to design and then building a industrial CNC. the aim of design is milling Aluminum and moving axis must have
2500mm X axis - 2000mm Y axis and 600mm Z axis.
for this condition i start to design a cnc machine. this is a initial design and i have must better my design.


I have some question. please answer me.
1- because X and Y axis is long I used rotary bull nut. for this condition I design a rotary bull nut mechanism. is it important to use Super-precision angular contact ball bearings: High-speed for example 7015 or typical angular contact in good for this mechanism. It's notice that MY cnc machine is used for milling AL and i want to build it.
2-if the rotary speed of Spindle motor is 6000 rpm how design my cnc that vibration of this is minimum. how simulation I do in software? for example Harmonic response? and what the condition of analysis?
3- because i want to build this what's the important notice in design and assembly of the part?
Thank's

[routercnc]

Hi Iman,

Best to start a new build thread for your design questions.

Have you built a cnc machine before, or have other building experience? 2500x2000x600 is a very large machine, especially for machining aluminium. Machining aluminium requires a stiff machine and having 600mm Z travel makes that very difficult, especially with a single gantry and large overhang.

1- I've not used rotating ballnut design but the stiffness of the axis is dependent on the AC bearing stiffness/quality so it will be a factor.

2- The simplest analysis to perform is to work out the stiffness at the collet in the X Y Z directions. The axes have to be locked in some way to stop them sliding when you do the analysis. 10-20 N/um (Newtons per micrometer) would be considered a very stiff / commercial machine. You need to apply 1N at the collet and get the software to work out the displacement. I don't think what you have drawn will come anywhere near that value.

3- Design and assembly. Make sure it can be built in a particular order so you can access the bolts as you build it. It is easy to design a set of parts which can't be put together especially if bearing blocks are near each other for Y and Z axes. Also, make sure you have slotted holes and adjustment in multiple planes. Assume the stock you buy will not be flat or straight or free from twist (although aluminium ecocast / tooling plate should be pretty good).

To give you some idea of commercial machines, here is the Mori Seki. Look through the pdf file and note the travel (way less than your dimensions), and note the weight.




pdf:
pm0uk13-nmv5080-pdf-data.zip


Also have a look at this thread :
http://www.mycncuk.com/threads/9809-...zed-CNC-router

[Boyan Silyavski]

Hi dear
I want to design and then building a industrial CNC. the aim of design is milling Aluminum and moving axis must have
2500mm X axis - 2000mm Y axis and 600mm Z axis.
for this condition i start to design a cnc machine. this is a initial design and i have must better my design.


I have some question. please answer me.
1- because X and Y axis is long I used rotary bull nut. for this condition I design a rotary bull nut mechanism. is it important to use Super-precision angular contact ball bearings: High-speed for example 7015 or typical angular contact in good for this mechanism. It's notice that MY cnc machine is used for milling AL and i want to build it.
2-if the rotary speed of Spindle motor is 6000 rpm how design my cnc that vibration of this is minimum. how simulation I do in software? for example Harmonic response? and what the condition of analysis?
3- because i want to build this what's the important notice in design and assembly of the part?
Thank's

i will not lie to you. If you have mechanical questions how to make 600mm Z axis strong and this is your first build, better contract me or sb from forum to design you the machine. You will make mistakes, that's reality. It takes much more planning to make a perfect machine, and to tell you the truth common sense is much more better than simulation software

So either make your own build log where people help you for free, or contract sb to design you the machine, at the end it would be much cheaper, as every mistake there is very costly.

[CharlesJenkinson]

It's a dead giveaway - that email was meant for his wife, ..."Hi dear". But it was sent here by mistake.

Honestly, my wife would just say, build it with whatever x axis you want Love, you know best 😉

[jono5axe]

Awesome thread, thanks, and thanks again.

Regarding the epoxy self leveling mounts for the linear rail, I would be very interested to learn about how the epoxy mounts stood up over time in respect to hardness?

I am a bit worried that it may not be hard enough to put up with the loads over an extended time (in a production shop router), as the bearing area under the linear rails is not huge. So my question is really hoping that you can tell me that it is all still good after the machine has been in service for a good while?

I am thinking about this in terms of (on my own coming build) whether to add additives to the epoxy to increase hardness, or alternatively, I may just use the epoxy for producing a level datum surface but then install a machined flat (i.e. 100mm x 10mm milled m/steel) on top of the hardened epoxy. I should mention that my build is planned as a production shop router at 2.5m x 2.5m bed, 30mm rails, 5kw spindle, gantry assembly approx 120kg.

Any feedback on the epoxy hardness issue would be very much appreciated.

Regards, Jono

[Boyan Silyavski]

Awesome thread, thanks, and thanks again.

Regarding the epoxy self leveling mounts for the linear rail, I would be very interested to learn about how the epoxy mounts stood up over time in respect to hardness?

I am a bit worried that it may not be hard enough to put up with the loads over an extended time (in a production shop router), as the bearing area under the linear rails is not huge. So my question is really hoping that you can tell me that it is all still good after the machine has been in service for a good while?

I am thinking about this in terms of (on my own coming build) whether to add additives to the epoxy to increase hardness, or alternatively, I may just use the epoxy for producing a level datum surface but then install a machined flat (i.e. 100mm x 10mm milled m/steel) on top of the hardened epoxy. I should mention that my build is planned as a production shop router at 2.5m x 2.5m bed, 30mm rails, 5kw spindle, gantry assembly approx 120kg.

Any feedback on the epoxy hardness issue would be very much appreciated.

Regards, Jono

No problem at all with the epoxy for the moment. Its hard enough. Similar machine but 2600x1300/ look my signature/ is working nicely in my garage at 50C in the summer.

But if you are to do ~1meter machine, better use aluminum bolted to the frame and pay a machine shop to surface it. you will avoid experiments and mess.

If i was to do it again i would have ordered cast aluminum plate say 20mm thick to 40mm wide from my aluminum supplier/ they cut to any size/ . Then using a straight edge and epoxy putty i would have fitted and shimmed it there. Then drill and bolt it to frame. Then fit Hiwin on top.

hence the straight edge is most important instrument for precise build.

[ImanGH]

HI Boyan.
is it possible to use this machine for milling and engraving stone? is it have enough stiffness?
Thank's

[Boyan Silyavski]

HI Boyan.
is it possible to use this machine for milling and engraving stone? is it have enough stiffness?
Thank's

Yes. I received that question also on youtube. if i can mill in steel 1mm deep with Z fully extended, i dont see a reason not to be used for stone engraving. In fact i was just to purchase a couple of diamond bits so i try and see how well that goes.

I will make a video about that. Meanwhile enjoy how it cuts aluminum like cheese with mirror like finish. Still dont have more videos as i am busy but will make more

[ImanGH]

Excuse me Boyan. I have doubt about this subject.
i see the hardness of some stone and metal in https://www.tf.uni-kiel.de/matwis/am...ed/t8_4_2.html
for example the hardness of Al is 25 Vickers hardness and the hardness of granite is 850 Vickers hardness. now we see that the hardness of some stone much more than Al and Fe.
now if we milling and engraving stone, then the force in chassis is much more rather than milling Al. what's your opinion about this subject?
thank's