8020 Aluminum 48*96 table

[norby16]

Hey guys, I'm about to start ordering some aluminum extrusions out of the 80/20 stuff for my table.

My table is gonna be pretty big, a little bigger than 48x96 so I'm wondering what kinda extrudes I should go with. The 1" scale ones would work perfect...

I plan on going 2"x4" for gantry.
2"x2" for the table top structure.
1"x2" for particle board / T slot table support
And 2"x2"'s for about 6 legs.

I don't want to use anything other than the extrudes for this project. What do you guys think? Will this hold?

[cheetahcnc]

Tha 80/20 is really nice stuff, they even offer discounted lengths and parts on ebay. The one inch is pretty light. They offer a Deflection Calculator which gives specific info on their products with length and weight variables. My current router uses the 2x4 (72" long) on the gantry, and 2x2 for the table surface supports. I think this a little on the light side, but am able to machine wood and plastics accurately and quickly. I've been thinking about using the 1x3 (3 vertical) on 4" centers, for the MDF table support, but it seems a little light according to the Deflection Calculator.

[norby16]

Thanks for the re-assuring words cheetah. I downloaded that calculator, pretty nifty stuff. I've just placed an order for these aluminum extrusions along with some 20mm heavy duty rails and blocks. Aside rack and pinion and gear reduction I have almost everything placed on order. I want this thing to be soundly built so I've decided against the skate type slides and will have Hiwin rails guiding my X, and Y... I'll try to find my camera and document the whole building process once I get started. I don't even know how much this entire setup has set me back but I will back track and make a complete bill of materials.

The router will probably be up and running in the beginning of next year, nice upgrade for the business. Just wonder how long it will take to pay for itself

To close with a question:
Speaking of and not knowing anything of racks, pinions and gear reduction belts. What would you recommend? I have no clue ( aside that I don't want an expensive planetary gearbox ) regarding how large the gear reducing circle should be, number of teeth it needs , etc...

[EidenC]

What do you plan on using for Motors and Controllers (Size/Type/Brand)?

I am looking at building a machine around the same size and am unsure of what size range motors it would require. Just want to make sure I can afford the parts before I start.

Chris

[norby16]

Hey Eiden,
My motors are in route from a Canadian company I found on Ebay - MotionTek. If you goto http://motiontek.ca/Retrofitkit.html and take a look at KIT1200XYZ I ordered that but swapped out a NEMA34 with a NEMA23 311oz for my Z axis mount. The X and Y will be NEMA34's at 1200 oz. I've been told that these motors should be powerful enough to move the large sized machine. Lotta weight.

That kit and a controller box ready to go has been shipped to me today so it will probably arrive in Chicago by the end of the month...

Originally I was happy to find in-expensive motor kits all over the place but after presenting the application to the supplier they said I need to go stronger.

As far as the damage report goes I will back track on the paperwork once I have everything I need in my warehouse. I'm guessing it will be around 5-7k once the whole project is complete.

Initially I started building this trying to go cheap as possible, but now I've come to realize that spending a bit more and having a professionally built router ( but without the professional price tag ) will be worth it.

Body made of 1"1" aluminum extrusions
Linear slides HIWIN for both X and Y (Originally wanted to save money and build skates . Once I put the block on my Hiwin rail the quality of rigidity could be considered medical)
And Electrical will be the kit stated above

End result = Amateur router hopefully to be on par with such as K2CNC, EZ Router, dare I say... Shopsabre

_______________________
Advice from one noob to another

[norby16]

I keep trying to figure this out.

Do we need gear reduction? It only complicates the design... How do I know what sizes to get? Can anyone recommend anything? Or do I have to figure this out once I attach the motors to the pinion?

Also, anyone know where I could get some stainless steel or aluminum plates? I'm looking for 2 pcs 113" x 2 " x .25 ( or so for holes and threading ). And 1 pc. 60" x 4" x .25 ( or so for holes and threading ). I will be using these to mount onto the aluminum extrusions and mount rails onto these...

Thanks!

[cheetahcnc]

My three axis router uses 4 NEMA 34 triple stacked 500-600 in oz steppers, (2) on the Y, moving the X gantry. The X and Y use about .800 pitch diameter spur gear pinned to the 3/8" shaft, no belts or gearboxes. When jogging Y slow, I can't stop it by hand. It is a very strong combo. I have had the rapids up to 1200 ipm, but run at 650 to 850 to keep from occasionally loosing steps. It can easily cut at 120 ipm with a 3/8 solid carbide downshear. It will even cut 3/4" in one pass in particle board or cherry, a little rough for a PC7518, but just to smoke the tires a bit. Look into the motor specs as high current, low inductance is better for high speed torque and low current high inductance is better for low speed torque. Usually the same motor size is offered in different inductance/current ratings for different applications. A gearbox or belt drive, when underdriven, will increase output torque and required motor speed for a set ipm movement.

[cheetahcnc]

Also, anyone know where I could get some stainless steel or aluminum plates?

I would stay away from the stainless if your intend to bolt up to raw aluminum, as there is an electro chemical reaction which occurs between the two. Another plus with the aluminum is that it is much easier to machine, just go a little thicker.

[norby16]

Thanks for the feedback cheetah. Never knew you can't slide aluminum against stainless steel... Electrosta... err What happens?

Also your saying you don't have a gear setup for your cnc? Just a spur gear on the motor shaft? What kinda motion movements do you get? 1/32"? 1/64"?

One idea I thought of is instead of having a belt between the gears/ why not just have the small spur gear directly against the larger gear - kinda like a watch. And then have THAT whole setup run along the rack. Cut some U shaped holes for adjustment and bolt everything in once firmly touching the rack. No belts/ springs for pressure and all that nonsense...

In another note:
Motiontek called me today saying that TSA needs a certificate (aka 400 dollars) for the setup to cross the border from Canada. In other words they want money so I'm gonna get my kit un-assembled I guess I was there first order of a completely built kit...

[cheetahcnc]

Yes, just a .8" pitch spur gear mounted on the motor shaft, running directly on the rack gear. Resolution on the controller is in the 0.0003" area, but as far as actual accuracy, probably around 0.003" adding up backlash, motor shaft movement, and multiple deflection points. The 200 step/rev steppers are microstepped to 2000 steps/rev. The slower the running feed speed the finer the resolution for movement.

[norby16]

Now is this something that can be achieved with any motor? Or is "micro stepping" a custom option that comes with some motors... I ask because EVERYWHERE I hear and see planetary gear boxes, gear reduction setups and so on. Take a look at the pix at EZ router for example. Personally 0.003" accuracy is more than enough for my demands.

Originally I wanted to just attach a spur gear on the motor and run that along a rack / plain and simple but once I got into the cnc world everyone has all these crazy designs. I guess they increase precision and power since less distance is covered with same amount of force = more power and less distance per step or whatever.

Conclusively I'm glad that its something I can always upgrade if need be. I will get a side plate to mount the motor on for my x and y and see what happens when it comes to motion. Not that hard to take off if I have to...

Also I will lay down aluminum for the x rails to be mounted on and y axis also... Rather spend the few bucks more and labor and not regret it... Heres a question though, should I go with Unpolished ( Mill ) or precision ground aluminum? Any bad experience with unpolished? I will get it over at Mcmaster-Carr

Will stop in soon, thanks for the helpful replies cheetah

[nikbrewer]

Im building a 63 x 34 out of the 80/20. i am using the 15 series, 1.5" x 3" for everything. Got 10 sticks at 65" on ebay for about 300$. well worth it. the 10 series is just not thich enough if you are trying to match the accuracy and quality of a shop bot, or other low end commercial CNC