80/20 Aluminum Design Verification

**ttjarrett** · 9th April 2009, 12:01 AM

Hi All,

I think I should start by introducing myself. My name is Toby, and I was invited to this wonderful forum from CNCZone by Greg. I'd like to thank Greg very much for the invite over here, asI have already seen some of the highest quality builds (Rod's Morphy for example) that I'm sure there are on the net! I have yet to seek out some pics of Greg's machine on here, but I'm sure it's a work of art as well!

The reason I initially contacted Greg on CNCZone was for some design verification. I have recently completed an all MDF router (which I might start another thread on) and am now already in the process of designing an all aluminum (plate and 80/20 extrusion) machine. At this stage this design is more theoretical than anything else, as I do not have the cash to begin building yet, but I would still like some advice on a couple of elements of the machine. Hopefully Greg, and the rest of you knowledgeable chaps, will be able to help me out.

The aluminum machine is going have a working envelope of around 600mm x 800mm x 150mm, and I am intending to use direct driven ball screw throughout, some beefy square linear rails and carriages, and two steppers enslaved on the X Axis (to completely eliminate racking). I have tentatively designed the tool holder, but have yet to decide what it will actually be holding. An air cooled spindle would be nice! As for electronics, all I'm thinking at the moment is Geckos.

The Gantry and Z Axis of my design, like many that have come before, are predominantly made of aluminum plate. The first piece of advice I need from you guys is, do you think 12mm plate would be robust enough for these jobs? In my mind I can't see 12mm of plate deflecting a great deal, but reality may be a different story!

The second aspect of my design that I am not too sure about is the linear carriages on my Z Axis. As you can see in the pictures, I have decided to only go with two carriages for linear z motion, rather than four. Do you guys think that this will present problems? The carriages are 109mm long, giving quite a bit if support to the front z plate, but is this enough? The reason I have gone with this idea is purely because two carriages would cost less that four!

All of your advice on these matters, and anything else that sticks out on my design would be much appreciated!

Thanks

Toby

Mind the part colours on the pictures, they are purely to differentiate all the parts from each other. The aluminum plate (obviously) is mid-grey.

Also, I haven't added the Y Axis ball screw or stepper yet. That will come shortly!

**rodm** · 9th April 2009, 05:28 AM

Hi Toby,

Welcome to the Ubeaut CNC threads.

It is obvious you already know a great deal about constructing a machine so you are well on the way.

Single 109mm trucks will be fine. As for the 12mm plate it can be strengthened by adding additional plates at right angles. If you take your Z axis design and then attach say 50 by 5mm strips to the edges of the 12mm plate then you not only strenghten the main plate you also provide some dust protection to the rails and ballscrews. I only used 10mm plate with 50mm strengtheners and I cannot get any deflection at all. Same with gantry sides just stack additional plates or design a strenghtening rib to take out the flex.

Not sure if you need dual screws on X with a Y of only 600mm but that is your choice and it will certainly take out racking if you do.

By all means start a thread on your MDF machine as there is a lot of interest in lower cost machines. For some reason people are reluctant to show their MDF machines but I think they are a valuable entry into the CNC world.

I like your drawings and wish I had the discipline to do the same. Yes Greg's machine is a ripper and there are also other builds done or in progress that are in the same class. I am sure to forget some so I won't nominate any except to say there are a few dragging their feet on their builds

I can say that now I have finshed mine.

Thanks for taking the time and effort to share your journey.

**crocky** · 9th April 2009, 12:24 PM

Hi Toby,

Sounds very much like mine

You can have a good read about the full machine here http://www.cnczone.com/forums/showthread.php?t=35996

You will be right with the Gecko's, wished I had done them first!

The ballscrew for the Y-axis, put it behind the supporting plane. Mine is where I think yours will be going and it is a pain to keep clean. The ideal position would be to the back of the spreaders

and not near any or much dust...

**twistedfuse** · 9th April 2009, 03:26 PM

Hi toby, good to have you aboard. As they say the more there are...the more dust that flys.

Just following what bob said, mine is where i think yours will be going too and i agree with bob in putting it away from the dust (although it does get everywhere).The other option since you have two smaller extrusions in your design is you can leave it there (between the spreaders) and find ways to prevent as much dust as possible. Add a 3mm aluminum sheet or thicker across the back of the gantry spreaders and it will prevent it coming in the back and if you go thicker adds strength to the design. Also for the front you can do the same but have the nut mount go through a cutout and then add brushes to this cutout to make it sealed a little more... plus personally it looks cool.

See mad vac cnc machine. It doesn't have brushes but it has the same idea.

http://www.oneoceankayaks.com/madvac/madvac_index.htm

These are just ideas and i'm sure you'll end up with more ideas and suggestions, so add what you want. You are definitely well on your way, and the extrusion is great stuff. Wished my first machine was built with that stuff. Look forward to following another post.

Daniel

**PsychoPig7** · 9th April 2009, 04:58 PM

Hi Toby
Sounds quite similar to the machine I have just 'completed'???
have a look at my post www.woodworkforums.ubeaut.com.au/showthread.php?t=84835
I used 10mm plate and it is literally as solid as a rock.
If you want more pics let me know.
Cheers
Noel

**stevejw** · 9th April 2009, 05:29 PM

Hi Toby,
Welcome to the forum, as a newbie myself I can tell you you are in the right place to get good advice and see some high quality builds.

I am just starting mine after changing my mind several times since joining here. The guys here are all very helpful and love to look at the work of others and help with suggestions.

You can check out my humble efforts so far here

https://www.woodworkforums.com/f170/cnc-gantry-stevejw-92096

Look forward to more design drawings and pics as go along.

Cheers
Steve

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