Need assiatnce to build a CNC machine

[gepeto]

Hi all,

I'm totally new to building CNC machines. I would like to build a table capable of handling (routing using a regular router ) at least 3/4" plywood with a size of at least 36" x 48" (or near that size).

Because I don't have proper tools to process metal (I work mostly with wood) I was thinking to buy some components already built. I saw these actuators on ebay:

http://cgi.ebay.com/ws/eBayISAPI.dll..._promot_widget

I have four questions:

1. Has anybody here used them?

2. Do you think they can handle the work I want?

3. In the picture it shows for the X axis to use two of them. How can I drive both of them to be sure they remain in sync (using two steppers one might skip)?

4. A frame of plywood built around these actuators will be strong enough?

I would appreciate your help.

Adrian

[Mcgyver]

they look like a home brew by the vendor, not that that is a bad thing, but you've got to rely on his claims of accuracy (ie will they bind), quality of materials etc. bronze bushed bearings and the acme screw and nut are basic, but again might work for you. the main thing i'd be worried about is you will get fair bit of flex with 7/8 shafting over 48". This starts you down the path of figuring loads, beams and deflections - not impossible for us amateur engineers, google beamboy, its a free calculator.

to your last question re frame, that would depend on your design. my preferance would be metal but there are many machines here built in wood. There is good thread in here somewhere on torsion box design - you can search for it.

In a general sense, I encourage you do spend a lot of time reading and designing before buying. That link you presented may be a quality effort, but its no fleabay pennies on the dollar deal - it;s fully priced so don't spend $600 until you know your design.

[ViperTX]

I would avoid using those actuators....the distance you're covering is pretty large....and you'll get alot of sag with shafts that are only supported at the ends.

I would look at using linear rails that you could mount on 80/20 extrusions for the x-axis and the y-axis. Then I would look at the z-axis that cnconabudget.com has.

You can cut 80/20 extrusions on your woodworking equipment using a sled and a TCG blade on your table saw.

This will give you a more robust system that you'll be happy with.

[gepeto]

Thanks for the comments.

they look like a home brew by the vendor, not that that is a bad thing, but you've got to rely on his claims of accuracy (ie will they bind), quality of materials etc. bronze bushed bearings and the acme screw and nut are basic, but again might work for you. the main thing i'd be worried about is you will get fair bit of flex with 7/8 shafting over 48". This starts you down the path of figuring loads, beams and deflections - not impossible for us amateur engineers, google beamboy, its a free calculator.

Good point. That was my concern too (load, vibrations can be an issue for sure). This is why I would like to know if somebody built one using them.

to your last question re frame, that would depend on your design. my preferance would be metal but there are many machines here built in wood. There is good thread in here somewhere on torsion box design - you can search for it.

I'm sure metal would be better but unfortunately I have extremely limited capabilities + skills to do it from metal.

In a general sense, I encourage you do spend a lot of time reading and designing before buying. That link you presented may be a quality effort, but its no fleabay pennies on the dollar deal - it;s fully priced so don't spend $600 until you know your design.

I work wood as a hobby. I do a lot of things using the router and the designs usually involve a very elaborate process.

1. Create the design on the computer
2. Print it on paper
3. Cut the template from paper
4. Copy it on thin plywood
5. Cut the plywood to get the final template
6. Copy the template on wood or plywood
7. Rough cut using jigsaw
8. Clamp template + wood and route the final form
9. Do this for all pieces + other fabrication and the product is done :-)

So, I'm willing to spend some money to simplify the process. A CNC router was in my mind for a long time but I never considered one for two reasons. Buying a commercial one would be expensive and to create one totally from scratch I'm sure at this point either would take me forever or simply would be beyond my skills.

This is why I'm looking to a road in the middle. I would rather buy the precision part that has to be metal and assemble it in a wood frame using the tools+skills I have. The electric part is piece of cake (again I have the tools+skills).

So any suggestion is welcomed (even a good source to buy a commercial one).

[dertsap]

not bad bit of hardware for 95 bucks , depending on the material the ground shaft is , i wouldn t think it would sag much if it was drill rod type of material 7/8 is thicker than a lot of machines i ve seen over the web

[dertsap]

holy crap 95 was the shipping to canada , go with something else thats a rip off

[Switcher]

.

By the time you build up your "Y & Z-axis", and add a router, I'm thinking the "X-axis" will flex big time on the 48" span.







.