Linear motion

[Wez]

I am planning to build a CNC router, mainly for cutting balsa for my model planes but I also want to be able to cut harder wood and aluminum. For the moment I am looking for components to handle the linear motion and I found that there are many different approaches to this. I would want to have an overview of all different approaches (professional and non-proffessional) to be able to choose the most cost-efficient way to build my first CNC machine.

Andreas

[Ken_Shea]

Wez,
I have been following all the members efforts on this forum to build a CNC router and am amazed at the different methods to accomplish this and have come to this conclusion, When money is an issue (and it always is) there ain't no simple answer to your question.
It would be to your best advantage to read every post, look at every picture, decide what is the top dollar amount you want to spend and then just start building.
Some good advice I have read on this forum is start small, simple and cheap on your first attempt and build your next and larger machine better by what you have learned on the first project.
Ken

[Mr.Ed]

Wez,

Your story seems a bit like mine, except that my machine is allmost finished. I made it from scrap. That is, metal parts that anybody could find. I used no drawings / building plans. I went along on the idea of a router with a fixed carving object and moving spindle. A very basic principle. Anyway...

I allso want to cut balsa (among others) and my ultimate wish would be that i find a website where there is a download section with complete cuttingfiles of complete plane-sections. For instance, i download a design called "biplane", slide in a sheet of balsa or other lightweight material and carve out all the bits and pieces that only need to be pressed out of the sheet.

I know, that is a bit too much to ask and i really woke up after i have been building and reading the cnczone forum for weeks. It's all not that easy, but hey, i started off with such a wish and i'm nearly there. If i only could get me those files.

I have no real knowledge of (model)planes so it would take a lot of time to draw / design them. Why invent the wheel again when it has allready been done?

Anyway, good luck with your project. You'll get there.

Ed.

[balsaman]

Originally posted by Mr.Ed Wez, Your story seems a bit like mine, except that my machine is allmost finished. I made it from scrap. That is, metal parts that anybody could find. I used no drawings / building plans. I went along on the idea of a router with a fixed carving object and moving spindle. A very basic principle. Anyway... I allso want to cut balsa (among others) and my ultimate wish would be that i find a website where there is a download section with complete cuttingfiles of complete plane-sections. For instance, i download a design called "biplane", slide in a sheet of balsa or other lightweight material and carve out all the bits and pieces that only need to be pressed out of the sheet. I know, that is a bit too much to ask and i really woke up after i have been building and reading the cnczone forum for weeks. It's all not that easy, but hey, i started off with such a wish and i'm nearly there. If i only could get me those files. I have no real knowledge of (model)planes so it would take a lot of time to draw / design them. Why invent the wheel again when it has allready been done? Anyway, good luck with your project. You'll get there. Ed.

Ed,

No such thing of "cut" files out there for planes, but there are sites dedicated to free plans in DXF format for model airplanes. You would just need to add a tool path.

I will try and dig up one such site later this afternoon.

Eric

[Wez]

Ed,

I have been building RC-planes for about 1,5 years now and I have been helped a lot by a friend at the local RC-club ( http://www.narpes.fi/~portomrc/ The site is in swedish.. to see pictures, click on 'Bilder' in the left frame) . He has built about 60 planes, most of them scratch-built. I am on my 6:th (2nd scratch built). When I started making my own constructions I got the adwise to start simple and get ideas and learn from other designs (as with CNC machines) . Here is a link where you can find loads of drawings http://plans.rcmodell.hu/.

What kind of linear motion control do you use?
I have been thinking about using rods and bronze bearings. Ball bearings seems a bit expensive. For the moment I am looking for scrapped printerns to scavenge rods and bearings from.

I have already finnished the electrical design and made the PCB:s. My stepper motor driver should be able to control about 50V or 20 Ampere per channel (note the 'or', controlling 50V at 20A could give problems with cooling the transistors), but my power supply (an old PC-power supply) only provides 5V, 20 Ampere so I will not be able to use that big stepper motors.

Wez

[Mr.Ed]

Wez,

I made the linear motion with 16mm stainless steel pipes and small brass blocks that slide over it. It's not the most elegant method of doing it when i compare it with others. But it sure is one of the cheapest methods, and that was one of my goals.

I must be building a smaller CNC Router than yours because i tend to use steppers that run on 4 volts at 2Amps per phase. My electronics that came from NC-Step in Germany use chopping as well. I could run my steppers at 44V max at 2Amps. I have built the PCB's but have not tested them. It should do fine. The only doubt i have is if the steppers can do the job and move my solid steel, sheet-steel, stainless steel and brass construction. Fingers crossed !

I was a bit disapointed to see, when i mounted my Black&Decker spindle, that a part of the z-axis started bending when i moved it by hand. I have to make reinforcements i guess.

Anyway, thanks alot for the links. I'll pay them a visit.

Ed.

[cnczane]

Ed,

Re: Model Airplanes

One of my first "Oh my!" sites on the web was a guy making scale model airplanes out of beercan aluminum. He'd unroll the cans to get sheeting to cut his parts out of.

I contacted him to ask about the plans, and he said he just used old plans for balsa models, and I understood him to mean before 'die-cut' models came out.

In another instance, I ran across "card models" where designers print out color card stock on color printers and then cut and fold or form the card into scale model full-color models.

I seem to recall also an old fellow in Louisville, KY saying that "full-size airplane plans are still available" for things like Ryans and that era.

[cnczane]

Gosh durn it. THAT was supposed to be a pm. I'm afraid the thread was getting off-topic.

I guess I'm allus gunna be a Chip Sweeper!

[TopSpin80]

I am also interested in what to cheaply use for linear motion. as of now the plan is some drawer glides. I know they will end up with some slack in them, but I have found a set of really old ones that are free and have no slack. anyways, maybe I'll post a picture of what I am planning on building. for now the 3d gif model is on my website.

Ernie

http://tamug.tamu.edu/~egk9566/

[chuckknigh]

Which A&M campus do you attend? I live in Bonham, so the campuses in Richardson and Commerce are relatively close to me.

(Of course, I'm a UT grad, so I'm not supposed to be friendly to you. )

Machine's design looks great! How far along are you, in the construction?

-- Chuck Knight

[pminmo]

If your staying less than 3' on an axsis, drill rod is about as cheap as you can get. see the links on my page:
http://webpages.charter.net/pminmo/mycncpage.htm

[TopSpin80]

I'm at the A&M Galveston campus

Ernie