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Mad Professor
13-03-2012, 07:59 PM
Good day all.

I am now starting to look at moving away from my DIY Built MDF & Plywood CNC Router/Mill.
It has been ok for small job's, and my pcb's, but I now want to move on to slighty bigger jobs, and also would like to start milling things like alu.

I have been looking on web sites, google, etc, at how other pepole have made there own z-axis.

Here is what I have come up with so far.


http://www.mad-professor.co.uk/Misc/Z-Axis Isometric View.jpg
If you wish to view my design I have the SolidWorks files here: Click Me (http://www.mad-professor.co.uk/Misc/CNC Z-Axis Design.zip) <1.2Mb.

I am not very good with SolidWorks, but I get there in the end, so the files might be some what messy.

I am looking to have it made from 20mm thick alu.
Will be using a TR16x4 leadscrew.

Any advice you can give me is grate.

Thanks for your time.

Best Regards.

wiatroda
13-03-2012, 08:03 PM
If that was me, I would try to use supported rails- you will gain extra stiffness and increase on travel (because you won't need support blocks anymore) . Otherwise looks OK

JunkieHobbo
13-03-2012, 08:34 PM
I am newbie at this CNC design/build area but most of the advice that I have seen has been along the lines of "Use Supported Rail".

Currently working on a Project aswell and from my investigation, Profile Rails are the way to go, then again I could me wrong.

HTH

wiatroda
13-03-2012, 08:39 PM
It is beneficial for additional rigidity to add extra mounting screws between joining screws of rail and supporting part- in middle, between two screws at the back of the rail

JAZZCNC
13-03-2012, 09:04 PM
If you have to use the unsupported rail then yes it's ok and just about the only way you can do it.!! . . . BUT it will struggle with Ali.!

If you can use supported rail then you would be best advised to change things around.! Put the rails on the front plate and the bearings on the rear plate.

This will give you maximum strength because the rail supports the front plate but more so because the distance from cutter to bearings is proportional to the Z axis extension. Less extension more support.
The way you have it now the distance from the bearings to the cutter tip is always the same no matter the Z axis extension and therefore the amount the front plate can or will flex is always the same.
When cutting hard materials like Ali this extension is very impotant to finish quality.!

Edit: On reflection if you have to use the unsupported you could still swap the rails/bearings and gain by reducing the extension. There will be slight strength gain to the front plate because you'd have to put braces top and bottom to clamp the round rails which will help slightly but you will always have the negative of unsupported rails potential to bend and flex.!! . . . . Hence why supported is better.!

JAZZCNC
13-03-2012, 09:08 PM
Profile Rails are the way to go, then again I could me wrong.HTH

Your not wrong they are far superior it's just the price becomes prohibitive to most DIY users.!!

Mad Professor
14-03-2012, 03:50 PM
Thanks for your feedback.

So what you are saying is that my design is no good, and will not be upto the job.

I was hoping to reuse the unsupported rails, and bearing blocks that I already have.

What sized supported rails would you recommend?

Thanks for your time.

Jonathan
14-03-2012, 04:32 PM
What sized supported rails would you recommend?

Might get away with 16mm, but I'd say minimum 20mm rails.

As it is the design will be much better than what you have made from plywood, but it has the potential to be significantly better with the changes already mentioned. Though it would be nice to use profile rails I don't think it's worth the money for this size machine as you will still be able to cut aluminium perfectly well with SBR20 rails on Z (as I do), just not quite as fast as with profile rails.

JAZZCNC
14-03-2012, 04:39 PM
Thanks for your feedback.

So what you are saying is that my design is no good, and will not be upto the job.

I was hoping to reuse the unsupported rails, and bearing blocks that I already have.

What sized supported rails would you recommend?

Thanks for your time.

Not saying it's no good but it's not the best it could be and with a few changes could be made stronger.

Supported rail is far better.!. . BUT. . If you have them then just change the design so the rails are on the front plate and bearings on the rear.

You won't gain the extra support to front plate supported rails give but to be honest this is minor and secondery to the gain from less cutter flex thru the proposional extension not acting like constant length spring board which is what your design allows. The 20mm plate will be strong anyway so IMO with these changes you'll be ok.

If you do go with supported then 16 or 20mm will be fine.

JAZZCNC
14-03-2012, 05:02 PM
Ermmm I've just down loaded your drawing and can see that your using 12mm round rail.!! . . . This would concern me and would seriously consider selling and upgrading to supported rail.

It's a lot of work and expensive aluminium to potentially waste and I'm confident to say it will significantly reduce your depths and feed rate in aluminium..:sad:

So times it's less painfull and expensive to cut your loss's and start a fresh.! . . . If you have a fully working Z axis now why not sell it complete to someone who doesn't need the strength or abilty to cut harder materials. Then treat your self to supported rails and ballscrew from china.? . . . Think you'll be surprised how cheap you can build a great Z axis for with supported rails and ballscrews.!!

Mad Professor
20-03-2012, 05:47 PM
I am trying to keep the footprint of my cnc unit as small as possible, as I don't have a garage or big workshop to put it.

As for your feedback, are you thinking something more along the lines of this?
http://www.mad-professor.co.uk/Misc/Z-Axis Isometric View 2.jpg

This was done quickly, and I know that I will have to adjust the spacing so that I am not covering over bolt holes etc.

Thanks again for your time.

Best Regards.

JAZZCNC
20-03-2012, 09:07 PM
Yes thats it's regards bearings and rails thou you don't need to have the motor going up & down with the Z axis if you don't want.!
So long as your motor can handle the heavier weight then it will work ok but it can be done so the motor and screw stays on the Backplate reducing the amount of weight the motor as to move.
Does mean the back plate has to be the same or just longer length than the screw with a plate at the top for the motor to mount to. Depending on length Could also mean notching the front plate at the top to miss the motor/plate.? but like I say this depends on front plate length but if does need it then it's at the top which you don't use and will be minor and of very little detriment strength wise.!

Mad Professor
31-03-2012, 06:51 PM
Thanks for all your advice.

I now have another design.
http://www.mad-professor.co.uk/Misc/Z-Axis Isometric View 5.jpg

What do we think about this one?

Thanks for your time.

Best Regards.

JAZZCNC
31-03-2012, 07:34 PM
Thanks for all your advice.

I now have another design.


BINGO!!

If you want to push it a step further and increase it's versatilty thru gearing along with abilty to handle resonance better then think about using timing belts.? Thats how I build most of my Z axis.
Here's a few pics of the one built for micheal marrino's machine, Micheal designed it mostly for his machine with slight guidance from me.

Mad Professor
03-04-2012, 08:20 PM
Thanks again for your time and feedback.

I now hope for this to be my last design.
http://www.mad-professor.co.uk/Misc/Z-Axis%20Isometric%20View%206.jpg

I am using 752 Drivers, 3Nm stepper motors, and TR16x4 Leadscrews.

Best Regards.

JAZZCNC
03-04-2012, 09:07 PM
Absolutely spot on that my friend. . :thumsup:

Jonathan
03-04-2012, 09:15 PM
Absolutely spot on that my friend. . :thumsup:

Yeah, sending the drawing and images of mine saved a lot of discussion.

Now to make it...

JAZZCNC
03-04-2012, 09:25 PM
Yeah, sending the drawing and images of mine saved a lot of discussion.

Now to make it...

Well stop bragging and get on with it then. .:playful:

Rogue
23-08-2012, 12:46 AM
BINGO!!
Here's a few pics of the one built for micheal marrino's machine, Micheal designed it mostly for his machine with slight guidance from me.
http://www.mycncuk.com/forums/attachments/diy-machine-building/5605d1333215046-z-axis-design-advice-imag0247.jpg


Well blow me down with a feather.

I missed this the first time round (hence resurrecting the thread!) but that's almost exactly the X/Z setup I wanted to use (as in pulleys, orientation of steppers etc) though with profile rail and a fixed gantry..

Was there a build thread on this? Any idea how it's been working out? Any design pitfalls to avoid?

jamie aust
06-04-2013, 10:37 AM
Thanks again for your time and feedback.

I now hope for this to be my last design.
http://www.mad-professor.co.uk/Misc/Z-Axis%20Isometric%20View%206.jpg

I am using 752 Drivers, 3Nm stepper motors, and TR16x4 Leadscrews.

Best Regards.

Hello Mad Professor, thankyou for your email, can you post the dimensions of your z-axis please, as I would like to build one like you have.

With thanks

jamie

Mad Professor
06-04-2013, 11:16 AM
The above was made from 20mm thick alu, 20mm Support Rails, SBR20 Bearings.

The main front part is 150x420mm.

There have been a few small design changes since the above.

The main two things is I quickly moved away from the TR16x4 Leadscrews, and upgraded to 1605 Ballscrew.

And added extra support for the stepper motor.

I am also no longer using a 1020w wood router for my spindle, but have now upgraded to a 2.2kw water cooled spindle.

Jamie Aust: Do you have access to any cad programs?

jamie aust
06-04-2013, 11:38 AM
What sort of problems did you get with Trapezoidal screws, as I was going to use them on all axis 16mm.
As much as I would like ballscrew, it just want work with my budget just now.
Im looking at x=1200mm, y=900mm, z=300mm ( I may drop each axis down by 100mm )
nema23 motors x 4, tb6560 drivers x 4 (stand alone drivers) and PSU ( upgrade to G450 soon )
Cad software I have is Autocad, google sketchup and draftsight.
From all the reading I have done on Z-axis, I think yours will work best for me.
jamie

Mad Professor
06-04-2013, 12:00 PM
Maybe I should of reworded it a little better.
I did not move away from the Trapezoidal screws due to a problem as such.
Just that a 1605 ballscrew with custom machined ends & ballnut, inc postage from Chai was cheaper then I was expecting.

One thing I would say is stay clear of the tb6560, I think I was one of the 1st on this forum to play about with them drivers, and it was nothing but hassle.
I do know some people that I using the newer tb6560 boards without a problem.
But nothing beats having good drivers.
I am / was using LeadShine 752 Drivers, but I am in a middle of a upgrading with NDA (http://en.wikipedia.org/wiki/Non-disclosure_agreement) steppers & drivers.

Just waiting for some more funds, and soon my current cnc router will no longer be classed as a desktop unit, going to need a better shed. :hysterical: