[flyboy52a]

My goal is to construct a machine that is capable of cutting out foam blocks to form the plugs for aircraft parts. I would like to be able to work on an area of 7' X 5' X 4'. This type of volume would be sufficient to produce molds for engine cowlings and leading edge D-tubes (in sections). I was inspired by what I saw at http://www.grabercars.com/content/view/67/2/. However, I feel that while the design is promising, it can be improved much upon.

My CNC expierence is limited to a 3 axis machine equiped with stepper motors. I have been reading what I could online and I feel I have formed a good idea of what the machine will look like. My main problem is there is too much information to digest. If anyone has any helpful advice or pointers, it will be much appreciated.

Description
The CNC is to be constructed out of 8020 Aluminum extrusion when at all possible. I have considered welding steel tube, but the 8020 leaves more flexibility.

The X axis is mounted on 8020 rails secured to the floor of my garage. The gantry rides on THK rails and the motion is to be provided by a ball screw on either side. Similarly the Y and Z azis are to move on a gantry constructed from 8020 and slide on THK rails with the motion provided by a ball screw.

What I am stumpped with is how to construct the swivel head. I have looked at dougherty drives, DoughtyDrive Products, but am a little put off by the price tag. Besides, I rather build one myself. I am considering constructing a head from Harmonic Drives off ebay, but I have no expierence with them or the servos they are usually powered by. Further more I have been using a milwalkee router and it is much larger then any other swivel head that I have seen. That brings up the question of a spindle.

Does anyone have any good swivel head ideas/ plans Sould I use servos or steppers. Finally would I need to get a fancy spindle for the head or can I get by on my hardware store router?

I have considered the CAM and CAD issue and can afford a good program. I also am looking at flash cam for the controller. Any assistance is much appreciated, I just need some direction.

[oneturboneeded]

Ill be watching close. I just started my build for about the same reason. Im building a cozy and want to make most of the parts and jigs with it but ultimately im going to build the molds to my own design twin. My machine will be 12'x5.5'x2.5'.

[flyboy52a]

No replies yet. I am getting the feeling that this is going to become quite an RnD project. Right now I am thinking of purchasing either a Sherline or a Taig mini mill to turn out parts for the bigger machine. They come CNC ready and will be neaded for the other machine. With out much guidence I am sure I will have to make a few attempts at the oversized contraption.

The cozy is a good looking aircraft. I am looking a modifying an RV-4 with a diesel engine and a fast back. Good luck with your build.

[awerby]

Have you priced out the 7'+ ballscrews for the long axis? You'd need something pretty beefy to avoid whip. Dual slaved rack-and-pinion motors might work just about as well, for a lot less money. Since you'll be cutting foam, you'll want to be able to go fast. Here's a link for them: CNCRouterParts

A small rotary table (or two) might work for the tilting/swiveling motion of the fourth and fifth axes. Sherline makes a good one: CNC-ready Rotary Table that's ready to add a 23-frame stepper to. They do have a tiny amount of backlash, which only comes into play when you're changing directions, but you'll never notice it if you're just cutting foam.

I'm a Sherline and Taig dealer, so I can get you a discount on all thieir stuff, including mills and accessories.

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[oneturboneeded]

One way to do it (the way i plan) is use harmonic drives. I'm going to build mine as a 3 axis to cut out the parts for my 5 axis. All my 3 axis drive parts will be plate n spacer built. I would also suggest going rack n pinion. There is less ware and can go faster. I'm going to use 3 to 1 reduction because my gantry is 280 lbs. and im using 960oz inch nema 34.

On my cozy im going unconventional on the motor and using a rotary. I would like to do a diesel conversion when smartplugs start production. good luck on your project.

[flyboy52a]

I like the idea of the rack and pinion. I am slightly concerned about the accuracy of such a system. But for the price it seems to be worth a shot. I have one some research and am shying away from the BC drives. The money is high for something I am unsure of. Instead I have been considering an epicycloid gear system. If what I have read is accurate they are very competive to the BC drives in their abilities. Below are a few links that I found. When I get back to my workshop I plan to make a test one out of wood. Hopefully some time in the next year I will purchase a Sherline will and knock out a working metal version. Here are the links...

Hypocycloid News Information

Gear geometry and applied theory - Google Books

http://diyhpl.us/~bryan/papers2/On%2...y%20center.pdf

Hypocycloid Gear Reduction

Ellipse -- from Wolfram MathWorld

It may take a bit, but I think the fun will be in the testing

[Joe S.]

Ballscrew whip can be negated to near zero at any speed you like by simply not turning the screw. Put the ballnut in the center of a timing sprocket and belt drive it with a motor, yes you will need to capture it between some thrust bearings, but woo hoo no whip and you can drive it fast too, no special bearings on the ends either.:banana:

[jharvey407]

I like the idea of the rack and pinion. I am slightly concerned about the accuracy of such a system. But for the price it seems to be worth a shot.

I recently built a R&P router out of 80/20 extrusions. The cutting area is 36" x 52".I used the rack from Moore Gear, and the drive from CNC router parts. I drive the router using 425 oz. steppers from Keling Inc.

I can achieve rapids as high as 1000 ipm. I usually use a rapid of 500 ipm and do most of my cutting at 240 ipm. I cut wood, MDF, plywood, plastic and acrylic, etc.

The R&P system is fast and accurate. I can find no measurable backlash.

I would recommend the R&P for any machine.

J

[flyboy52a]

I think the R&P is the way to go. The big question is how the BC head is going to shape up. That will determine the shape of my gantry. I hope to begin the R&D of the head when I get back home in a month. I have made a CAD drawing of a 2 stage epicycloidal gear with a 100:1 reduction. With little info on DIY BC heads I am mostly shooting in the dark. When I make something of value I will post the plans onto this thread.

Does anyone know where I can find the plastic "chain" that is used to run wires inside. I have seen it on many CNC machines and it works very well to keep wires tidy especially with the longer travels.

[jharvey407]

I think the R&P is the way to go. The big question is how the BC head is going to shape up. That will determine the shape of my gantry. I hope to begin the R&D of the head when I get back home in a month. I have made a CAD drawing of a 2 stage epicycloidal gear with a 100:1 reduction. With little info on DIY BC heads I am mostly shooting in the dark. When I make something of value I will post the plans onto this thread.

Does anyone know where I can find the plastic "chain" that is used to run wires inside. I have seen it on many CNC machines and it works very well to keep wires tidy especially with the longer travels.

The cable chain can be found at McMaster Carr.

I am interested in seeing your BC head. I am planning on building one as well. I'll pass on any information that I find on the subject.

[flyboy52a]

At the moment I only have my test gear drawn. I don't even know if it will work as I would like it to. I will try to add a pic of it in this post within the next few days. While I have rough drawings of what I would like the final product to be, there is no sense making CAD drawings until I learn what I must from the test gear reducer. Compact, simple to produce and with near zero backlash. Thats how others advertise similar designs.

Thank you for the Mcmastercarr heads up.

[Doctor Bombeii]

Hello, I joined this forum to find out how to acquire the same type of machine that flyboy is building, but maybe a little larger. Either way, if someone could source a functioning machine or kit, then I definitely want to talk business.

this picture is from a company who outsources work to Contactscale.com


These last pics are what I need, just not as flashy



If anyone can help with any info on supplying me a kit or building this for me, please PM me. thanks

[jharvey407]

Hello, I joined this forum to find out how to acquire the same type of machine that flyboy is building, but maybe a little larger. Either way, if someone could source a functioning machine or kit, then I definitely want to talk business.

These last pics are what I need, just not as flashy. If anyone can help with any info on supplying me a kit or building this for me, please PM me. thanks

Do you need a 5 axis machine? The machine that you posted pics of doesn't look like a 5 axis machine, just a very large 3 axis. Unless I'm missing something.

[Doctor Bombeii]

Do you need a 5 axis machine? The machine that you posted pics of doesn't look like a 5 axis machine, just a very large 3 axis. Unless I'm missing something.

This is true. I guess that's what I need then. This company reproduces auto body panels in carbon fiber and that's what I'm seeking to do.

For more info: http://www.cnczone.com/forums/cnc_wi...ml#post1030365

[jharvey407]

This is true. I guess that's what I need then. This company reproduces auto body panels in carbon fiber and that's what I'm seeking to do.

For more info: http://www.cnczone.com/forums/cnc_wi...ml#post1030365

I'm familiar with the type of work you are looking to do.

A 3 axis machine will be very useful, but a 5 axis machine will allow greater versatility.

I would build a 3 axis machine like the one in the pictures you posted, but with long term plans of adding the BC head for 5 axis milling later.

[jharvey407]

My CNC expierence is limited to a 3 axis machine equiped with stepper motors. I have been reading what I could online and I feel I have formed a good idea of what the machine will look like. My main problem is there is too much information to digest. If anyone has any helpful advice or pointers, it will be much appreciated.

Do you have a 3 axis machine now?

Have you thought about slicing your large plugs to be machined in layers, like this?

[jharvey407]

Here is some inspiration for you. These are pics of 5 axis heads that I have collected. I hope this helps with your design. Take a look at the first one, it's very interesting.

[flyboy52a]

I am sorry I have not been on here for a bit. I have purchased a taig mill to start making parts for my machine. Right now I need to finish a sailplane project that I am working on to make room in my shop. Building an airplane is a series of 5 minute projects, none of which take less then 1 hour to complete. I hope to get my BC head started by the end of January, but the forecast is not looking good.

[Ncrazyballa]

Im looking to do the same thing, but im making a smaller version 4x4x4. Instead of cutting milling the whole part in one block, i will divide it in sections and mill each individual section. Then when i have all pieces milled out of foam i will glue them together to make the whole piece/plug.

This one is a homebuilt one probably something OP was thinking of building
[ame=http://www.youtube.com/watch?v=nITLI_WcnuM&list=UUcJmNXm7EUDd9zwRqLv08nA&index=6&feature=plcp]Homemade 5 axis CNC - YouTube[/ame]

[flyboy52a]

The previous post is exactly what I would like to create. It looks to me like he used Dougherty drives. I was looking for a cheaper alternative. I guess it is only cheaper if you don't value your time.