My new build (keepin' it simple)

[jkarisny]

So I have been working on a design for this new router project. I really want to keep it as simple as I can, and looking clean (obviously not as important).

I hope to use this to cut wood, some light alum, and plastics.

Details: Frame made from 1" square tubing x .065(16 ga.) wall welded together. 64" x 50"


I will be using the 3 axis Nema 23 kit from CNCrouterparts.com, as well as their rack and pinion drive assembly on x/y.

I also plan on using a Porter Cable 6902 router for my spindle with the Super PID speed controller.

Here are a few pictures of the frame so far, I still need to add bearings under the rails and on the inside of the rails of x/y to keep it all in place. As well as supports under the frame.

And not sure about my z-axis yet. Anyone have ideas?

[zool]

For your Z-axis, take a look at a MechMate.

MechMate CNC Router - Build your own with our detailed plans

[CNC Lurker]

Details: Frame made from 1" square tubing x .065(16 ga.) wall welded together. 64" x 50"

I hate to say this, but 1" square tubing for that span is too weak and you can expect deflection.

[jkarisny]

The frame is far from complete as I said. I still have yet to weld on the braces under the frame rails.
When properly supported, I can add up to 36 lbs. on top without deflection. I will not even be close to that weight when its complete.

[zool]

When I was designing my machine of 3030 extruded aluminum, calculations showed a deflection of 2/1000-inch in the center of the 83-inch side rail, when that rail was supported on each end, and the weight was evenly distributed along the length, and not counting the support given by the cross-rails that intersected to the 83-inch rail perpendicularly. [These calculations represented the worse case scenario.]

Adding a leg in the middle of the 83-inch rail dropped the deflection to 1/10,000-inch in the identical circumstances.

An easy way to achieve over-kill.

[harryn]

The frame is far from complete as I said. I still have yet to weld on the braces under the frame rails.
When properly supported, I can add up to 36 lbs. on top without deflection. I will not even be close to that weight when its complete.

Hi, before you imagine that to be true, just keep a few things in mind. I did some hand held experiments with more or less the same router on a 2x4, and it took about 80 lbs of force on the router to do cutting at very reasonable speeds.

You will need at least 2 in depth to have any chance with that large of unit. Test it yourself the easy way. Go to a hardware store that has 20 ft sections of pipe, and start shaking some from one end. Keep going larger until you find one that does not shake a lot, just from its own weight. I found this to be around 2 inch.

[jkarisny]

Hi, before you imagine that to be true, just keep a few things in mind. I did some hand held experiments with more or less the same router on a 2x4, and it took about 80 lbs of force on the router to do cutting at very reasonable speeds.

You will need at least 2 in depth to have any chance with that large of unit. Test it yourself the easy way. Go to a hardware store that has 20 ft sections of pipe, and start shaking some from one end. Keep going larger until you find one that does not shake a lot, just from its own weight. I found this to be around 2 inch.

Black pipe from Lowes or H.D is quite a bit different than steel square tubing.

I realize I will get some deflection, but I'm not planning on building medical equipment with this tool.

On the longer sections of the frame, there will be supports every 1o inches to support the weight. And also, there will be 1/2" angle iron used to stiffen up the 1" square tube on the y axis.

Hopefully I can get it completed this weekend.

Thank you all for your feedback.....stay tuned!

[zool]

I respectfully suggest you read this article and put pencil to paper before picking up your welder.

Second moment of area - Wikipedia, the free encyclopedia

"The second moment of area, also known as the area moment of inertia, moment of inertia of plane area, or second moment of inertia is a property of a cross section that can be used to predict the resistance of beams to bending and deflection, around an axis that lies in the cross-sectional plane. The deflection of a beam under load depends not only on the load, but also on the geometry of the beam's cross-section. This is why beams with higher area moments of inertia, such as I-beams (properly denoted as: wide-flange beams), are so often seen in building construction as opposed to other beams with the same area."

If you don't want to do the math, make an appointment with a structural engineer and spend $100 to have him do the calculations and provide you with advice. It will be money well spent.

[jkarisny]

I respectfully suggest you read this article and put pencil to paper before picking up your welder.

Second moment of area - Wikipedia, the free encyclopedia

"The second moment of area, also known as the area moment of inertia, moment of inertia of plane area, or second moment of inertia is a property of a cross section that can be used to predict the resistance of beams to bending and deflection, around an axis that lies in the cross-sectional plane. The deflection of a beam under load depends not only on the load, but also on the geometry of the beam's cross-section. This is why beams with higher area moments of inertia, such as I-beams (properly denoted as: wide-flange beams), are so often seen in building construction as opposed to other beams with the same area."

If you don't want to do the math, make an appointment with a structural engineer and spend $100 to have him do the calculations and provide you with advice. It will be money well spent.

Just curious as to how many people have designed their own cnc router and consulted with a structural engineer?

[zool]

I did.

It was well worth the $150 I spent. Not only did some issues get clarified, but she showed me how to do simple calculations myself.

Her help made me much more confident of what I was doing and what to expect.

Knowledge is power.

You might be thinking that this will slow you down, however, in the long run you will save times and money, and in the end have a better machine that does better work. Constantly fussing with a machine to obtain acceptable output is not what any of us like.

We are all just trying to make your build as successful and painless as possible.

We have all got our own encyclopedias of errors if you'd like to borrow them.

[zool]

On the longer sections of the frame, there will be supports every 1o inches to support the weight. And also, there will be 1/2" angle iron used to stiffen up the 1" square tube on the y axis.

I respectfully suggest instead of adding the rigidity on, the rigidity be built in by using larger tubing.

Using larger tubing will means less welding [save time] and less distortion of tubing [a more accurate machine].

[CNC Lurker]

Just curious as to how many people have designed their own cnc router and consulted with a structural engineer?

From your previous posts, it sounds like like you are new to CNC building. No biggie, we've all been there (I'm still relatively new to it). Others here are just trying to help you out and you are getting defensive with this constructive criticism.

Build it however you want, it's your time and your money, but if you don't want any input just say so.