Need some help getting started

[ranchak]

I stumbled onto this site and another by accident, but you guys have me interested in building a machine. This is the other site:

http://techreport.com/forums/viewtopic.php?p=360821

I don't know what I am going to use it for yet, but I'll figure that out as I go. But this does pose a question, how big should I build my machine? I was thinking somewhere around a 3'x3' table. Is this too big? I am building my own drivers and controller from the 4 axis site. I am planning on using Mach3 and Eagle software (I will be making some PCBs for personal use).

I bought these motors on eBay. I will use them for my x and y axis. I will find something for my z-axis. I think I would like to be done with this project sometime before Christmas if all goes well. I guess I have a thousand more questions, but for now I guess any input would be appreciated. Thanks, Ron

[ahren]

FYI, I sell a set of parts that are perfect for a leadscrew driven 3x3 table off of my website, www.cncrouterparts.com. I'm currently working on a complete machine plan built from 8020 aluminum extrusion and the parts I sell. If you're interested, I'd be happy to help you with your machine.

Best regards,

Ahren Johnson
www.cncrouterparts.com

[ranchak]

Hi Ahren, I would appreciate your help. My biggest question or decision at this time is whether to use linear rails with trucks or round linear rails with bearings. I like the idea of the round rails with the support/mounting bracket, but that may be overkill. I guess my next decision is the table size. I have been watching eBay and I think I will go with a table with of 32-36" depending on what I can get on eBay. I'm in the process of building my breakout board and stepper boards. I am using the layouts from the 4 axis page. Thanks, Ron

[ahren]

Ron,
Bearings are a big decision. I would definitely go with linear rails and trucks over the round bearings, unless you can support the round rails, which is always a pain. Otherwise you'll be dealing with deflection issues, and at 3' of table, you'll definitely run into this. I'm working on a inexpensive bearing system (that I'll be selling on my site) that uses a piece of 1/4" x 4" cold rolled steel and a set of skate bearings combined with 8020, but it isn't finished yet. Ebay has some good deals on THK, NSK and IKO rails pretty regularly -- I'd go with these.

Also, mods -- should this thread be moved somewhere else, like the DIY router forum? We probably shouldn't be muddying up the FAQ section. Ron, feel free to keep asking questions -- this forum is a great place to get help!

Ahren
www.cncrouterparts.com

[ranchak]

Ahren, how do we move this post to another forum? I originally was going to build my table out of 80/20 aluminum, but I'm thinking about maybe using steel rectangular tubing. The only downfall I can see other than the weight is that I don't know how straight and true the tubing will be. There may be a tolerance problem with the rail sitting on top of the tube and the surface of the tube not being true. Maybe I better stick with the 80/20 plan. I found some bearings on eBay that I'm going to bid on. That will determine the size of my table. I need to come up with some ideas of what I am going to do with this machine once it's completed. It would be a shame if all it did was collect dust and parts of other projects (I have a table saw for that!).

[ahren]

Ron,
Don't worry about moving the thread -- the moderators can do that. I was just trying to alert them to the fact that they might want to.

As for steel vs 8020, you'll find that steel tube really isn't that square, since it is folded and then welded. The other thing is that it's tough to adjust your design, and you'll have to do some machining. 8020 is pricier, but has some advantages in that it's relatively straight, you can mount bearing rails directly to it with the appropriate t-nuts, and you use the t-slots to slide your screw bearings and drive screw together, as seen here:

http://www.cncrouterparts.com/parts.html

And don't worry about finding things for your machine to do! There are always signs, and parts for your next machine .

Ahren
www.cncrouterparts.com

[ranchak]

Ahren, what software do you use to design your projects? Thanks, Ron

[ahren]

I use Solidworks 2007 for my projects -- it's what I use at my "real" job as a mechanical engineer also. Pricey, but very powerful. I have tried Alibre designs, and it seems fairly capable for a lower price. And for quick mock-ups or amateur designs, Google Sketchup is fairly impressive (and free!).

[ranchak]

I'm thinking about going with a 2 lead screw design, something similar to this:

http://www.k2cnc.com/DuportalPro343A...annel=Pictures

I know that it requires an additional motor and ball screw, but it seams like there could be a few advantages to it. Do you use another driver board (2 for the x-axis) and parallel the x-axis input to both boards? Is there anything wrong with using a longer y-axis than x-axis? It seems like the industry standard is the x-axis is always the same or longer than the y-axis.

I plan on starting on the framework this week, but I need to figure out my dimensions. I've been waiting to see what I can get off of eBay, but I think I'm going to go with a 36" x 48" layout.