New Dual Lead Screw 3 Axis Cnc Router Build

[Lydra]

Hello Guys,

I'm a industrial designer in Turkey working for a wood & decoration company in Izmir, here is my 3 axis cnc project. im going to start to build this in this month. trying to solve some detail in cad... and prepare for industrial cnc machining for aluminium plates.
in 2008 i built another 3 axis cnc router, but it was trully worsth machine that i build.. here is some example in 2008,




here is new design 3 axis cnc router bom;

15mm aluminium plate for chasis of gantry and supports,
16mm ball screws for all axis,
20mm lineer bearing for all axis,
nema23 stepper with reducer (include)

for all machine dimension is; 1200x1600x805
working area is 1000x700x150

Renders;









Cad Scren Shots;
























Im looking for your advice, and critics... it is really importand for me... also can anyone make it stress and deformation test in solid works? this machine modelled in rhinoceros 5 as a nurbs and solid data file,
im going to share this model for free when i done with it.

Thanks and best regards...

Halil Orbay Okyay

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[alan_3301]

why the gearboxes? Seems unnecessary, and will decrease your max speed. Yes, resolution will increase, but not accuracy.
(assuming cheap rolled ballscrew)

[Lydra]

Alan, gear boxs are work with aluminium and hard metal.. that's why chasis of the cnc is supported everywhere.. and im still worry about rijity..

i will handle it, maybe i really don't need gear box, reducing the speed.

[pippin88]

If using steppers do not use gear or belt reduction. Drive 1:1.

What's the spacing on your linear bearing carriages?

I strongly suggest 10mm or 16mm pitch (lead) for the ballscrews (standard Chinese ones are 5mm pitch)

[Lydra]

yeah.. turly right but here is my goal,

Nema23 Stepper screw holes are not fit well on gantry and chasis of cnc... i need to move a bit.. is there any other way to move my motor axis? with out any reducer or gear box?

i though that, Dia 16mm, 10mm pitch.. that's why i used gear box... standart gear box rate is 1/5

could anyone tell me about gantry moment specification on this project? is it ok?

[pippin88]

It looks like you have couplings from the gearbox to screws? Just remove the gearbox.
You can use belts with a 1:1 ratio.

Your gantry, like most, is the weaker point in your design. Read many of the good threads on here about gantry design. dmalicky has made some great posts.
A good starting point: http://www.cnczone.com/forums/diy-cn...cad-posts.html

[Lydra]

Hey, I really apperiacated your link.. i have read all. Thanks pippin..

here is my next question is about Z axis design..

There is 2 different type Z axis Design.. with metric dimension.
one of these ballscrew nut is moving with lineer trucks at center..

other design lineer rails is supporting my spindable plate but ballscrew nuts it is not stay center of lineer trucks at up position.. (blue one)

Do you have any idea which i should to go? with reason..



working with: 20mm Rail trucks, 1605 ballscrew and nuts. also BK15 BF15 ends.

Thanks For advice and helping..

Orbay,

[MadeInTheShed]

I would go with the first one. Has more clearance around the cutting tool if you need to drop it down inside something (motor mount plate not going to get in the way). You also keep the gantry lower by 50mm whilst retaining the amount of Z movement.
If you use the second one, you may run into trouble mounting the linear bearings back to back unless you offset them, but then you need a wider Z Carriage, which limits your travel in the Y (across the gantry)

As far as being more rigid, I doubt it would make much difference

[Lydra]

totally right..

im going for first Z axis type.. for less weight and mounting the rail blocks..

here is my gantry design.. any suggest you guys can tell to me?







at bridge; 45x90mm aluminium extrusion.
at base: 90x90 aluminium extrusion.
with 20mm lineer rail and truck.
1605 ballscrew and nut.


Thanks and best regards.

[louieatienza]

I vote for the second design. It gives more overall strength every position. With the first design the spindle collet is in a worst case scenario in relation to the attachment of the lower bearing block to the plate, regardless of position. I would only advocate the first design if your z travel is relatively short. For longer z travel. I recommend design 2. Also for design 2 the lobg saddle plate is unnecessary if you mount the stepper to the carriage.

[Lydra]

Hi, in those days, im searcing about compact laminant chasis for my gantry design..

but i have never work with that material before..
Does anyone have any idea about compact laminate? especially assembly, rigity, humidity?

Thanks and Best Regards.

Here is the example of what i'm talking about.





Best Regards.

[Lydra]

I need to some changes.. as you can see all system has returned rack and pinion system..
also gantry design is changed..

Pictures below,

first design is,



after this design,



after this



and this...







finally this..

[alan_3301]

Unless you can mount your gear racks perfectly parallel with your linear rail, I would have some sort of spring tensioning system.
Even if you can mount them perfectly parallel, I would have some sort of micro adjustment mechanism. The difference between backlash and binding is very small.

What size are those pinions? They look very large. You will need those gearboxes now. Likely not necessary for the Z though. what is the pitch of the ballscrew?

[Lydra]

hi Alan..

ı changed design.. I'm going to use ballscrew to all axis.. 1605 and max travel 950mm

here is some render shots..

[ger21]

1610 ballscrews are a better choice.

[alan_3301]

I agree 1610 would be better.
That would give you 0.05mm full step resolution, which is right in line with c7 lead accuracy.
Any finer pitch would limit your rapid speed, without any increase in accuracy.

oops:

as well as cut your torque in half at all speeds

I meant that your torque would be less because of faster spinning stepper, but you would have twice the torque (minus motor speed torque loss) due to the finer screw lead.

[Lydra]

Hello guys..

Here is i show a connection between two types of aluminium extrusion..
In my design it is going to assembly face to face..

any other idea assembly two different types aluminium extrusion like that?

Thanks.

[pippin88]

Your design has reasonable stiffness in the long axis along the table, but suffers in the gantry axis. This is a common problem with many designs.

Plates for the gantry risers are not that stiff.

[hub]

Hello guys..

Here is i show a connection between two types of aluminium extrusion..
In my design it is going to assembly face to face..

any other idea assembly two different types aluminium extrusion like that?

Thanks.

That's not very rigid.. I use these:

[Lydra]

Here is what i did last month...

firstly i changed all design, because of money..

now i'm going to buy electronics.
could you guys can give any suggestion for 3 axis cnc kit?

Step motor size?
Step motor driver?
power supply?
spindle?













Thanks,