Clueless Newbie Design?

[bigz1]

I hope to build a first CNC Router to fit 1400 x 600mm using mostly 18mm MDF. I intend to cut mainly balsa and plywood with the occassional bit of lithoplate for RC planes. Attached is a rough design. I am limited on time and finances so I have tried to make the design as simple as possible. I have also enclosed a few features to try and overcome the budget/time problem. The 2 main ones are twin bar design either side of the gantry plus a groove on base and top/bottom of gantry to support rails using open bearings to guide. Any suggestions would be most welcome.

I would also appreciate advice/links on drivers and software. As a cabinet maker I can handle a panel saw/CAD package but when it comes to electrionics all I know is one end of the soldering iron gets hot.

Liam

[ViperTX]

Okay....using supported open bearings is a good start, I would look at using ACME screws for each axis, go with steppers (see some of the vendors on this site for an inexpensive stepper and driver package).

The rest of the frame and gantry can be made of MDF to keep costs low.

This will give you a good machine.....a better and slightly more expensive then the JRGO that alot of the users on this site have or are building.

[bigz1]

Thanks for the posistive feeback ViperTX. I have revised the design slightly. I will also be using open bearing for the upper rail(something similar to Joe's design). The blue rod represents the ACME screw. What would you use to build the frame and gantry? I was thinking conformate screws and PU glue.

[joecnc2006]

With the lead screw on top you would be limiting the z axis travel and have a hard time fitting in the z axis motor. for learance under the leadscrew.

[bigz1]

Hi Joe. Yep I think your right. I want to still keep the lead screw on the top as I am limited on height in my workshop where this is going and was trying to save space by discarding the torsion box for the base(Its going on an accurate flat & level workbench that I cant rip out). Could you give me a rough height for a stepper and mount? I will see how much more space I can gain by lowering the y axis torsion box. I am only looking for approximately 80-100mm z travel anyway. An alternate idea might be to put the leadscrew offset to one side but I think this might would be a bad idea?

Joe when I get time to convert the attic I will be making your 2006 model or by then you might have an even more incrediable design.

[joecnc2006]

If i understand you, you will have 4 rails one in each corner as shown in picture with red circles, the I would install two leadscrews on the sides as shown in blue and remove the one ontop "X'ed" out. Use two small motors slaved for the X Axis. which can be installed on the outside overall frame.

Joe

[bigz1]

Got it in one Joe. I will follow your advice but couldn't I put the leadscrews inside by placing them slightly lower down(again lack of space!).

[joecnc2006]

The lead screws are ment to be interior, but anything is possible you just need to design for it.

[bigz1]

Put a proposal to the the boss today. Basically he has agreed to pay me £350 to build my machine and if its successfull build him something larger!!! Just to pick your brains again. What do you think of using square(25mm x25mm) bright steel bar instead of round bar to run bearings on similar to Joes design for the X and Y axis. Still using a routed groove to support the rail. This maybe a dumb question but how do I slave the 2 small motors?

[bigz1]

Just bought this on e-bay($212 plus P&P). Steppers are Nema 23's. Seemed like a good price as the first lot I bidded on went up to $310. So I guess this is for real now.

[joecnc2006]

Originally Posted by bigz1 Just bought this on e-bay($212 plus P&P). Steppers are Nema 23's. Seemed like a good price as the first lot I bidded on went up to $310. So I guess this is for real now.

What are the specs of the motors?

[bigz1]

3 ASTROSYN STEPPER MOTOR NEMA 23

1.8 DEGREE STEP (200 STEP PER REVOLUTION) FULL MODE

0.9 DEGREE STEP (400 STEPS PER REVOLUTION) HALF MODE

6 VOLTS

1.2 AMP PER PHASE

5.4 OHMS PER PHASE

116onz/INCH TORQUE

6 LEADS CONFIGURABLE AS UNIPOLAR OR BIPOLAR

6mm SHAFT 1/4 INCH PER 3/4 INCH LARGE

I was thinking maybe buying a larger 200onz/ inch torque for the z axis?