Linear Motion

[8wt Man]

I am new to CNC and I am looking to build a very precise with high resolution CNC. I want a cut area of 10"x10" with a Z clearance of 6" and Z travel of 8". I am looking to go SLOW not fast, I am not looking for speed. I will be doing some engraving, wood, and thin Aluminum 1/8" or less. I am looking to build the frame out of aluminum and 8020. I want to build a fixed gantry for rigidity and because the size allows it.

I have seen many different options for linear motion and I am trying to figure out the pros and cons of each. I am also trying to keep costs down as much as I can. I am currently looking at cncrouterparts linear carriage because of the cost and the fact that it is more rigid that the unsupported rails. What are some other options on a tight budget.

Another question is that I have AutoCAD already what other software pairs well with autocad to produce G-Code

What are my options for drivers, I have seen and heard about gecko. I know nothing about electronics but I am quickly learning. Any advice is welcome. I am sure I will have plenty of other questions as this takes place.

[Dan911]

Try This!

The CNC Woodworker

[louieatienza]

Originally Posted by 8wt Man I am new to CNC and I am looking to build a very precise with high resolution CNC. I want a cut area of 10"x10" with a Z clearance of 6" and Z travel of 8". I am looking to go SLOW not fast, I am not looking for speed. I will be doing some engraving, wood, and thin Aluminum 1/8" or less. I am looking to build the frame out of aluminum and 8020. I want to build a fixed gantry for rigidity and because the size allows it. I have seen many different options for linear motion and I am trying to figure out the pros and cons of each. I am also trying to keep costs down as much as I can. I am currently looking at cncrouterparts linear carriage because of the cost and the fact that it is more rigid that the unsupported rails. What are some other options on a tight budget. Another question is that I have AutoCAD already what other software pairs well with autocad to produce G-Code What are my options for drivers, I have seen and heard about gecko. I know nothing about electronics but I am quickly learning. Any advice is welcome. I am sure I will have plenty of other questions as this takes place.

DonFrambach and PEU both have machines with a similar work envelope to what you're looking for. I would check both their builds out (both fixed gantry and 8020/aluminum plate) for inspiration.

As for cutting slow, that depends. Wood doesn't necessarily like to be machined slow. Then again, neither does aluminum. I say you might want to consider what accuracy you would like to hold, and use that as a starting point for what screws/linear rails you need. Let's say you want positional accuracy of .001". You'd be lucky to have an ACME screw with a lead error of .004"-.009". The CNC Router Parts positional accuracy is somewhat dependant on the accuracy of your cold-rolled-steel rails. Bottom lime: be realistic what accuracy you need, and that will dictate your drive system.

For creating G-Code form AutoCAD, you will need CAM software. I think the CAM software you'll pick is related to the complexity and type of things you are making. For basic pocketing and profiling, Cut2D would be fine. If you were dealing with mostly .stl files, check out Cut3D or MeshCam. I think ArtCAM does .stl but not sure. A lot of folks use CamBam. If you were doing parts with 3D features and geometry you might have to step up as far as CAM software (BobCAD, VisualMILL, OneCNC, SprutCAM, etc). You will also need controller software, that will allow your computer to "talk" to your motor drivers. Mach3 is very popular, but a lot here use EMC, and it's free. I found Mach3 easier and worth the money.

The Gecko G540 is a very reliable performance driver. On a budget there are some really good kits from Xylotex, HobbyCNC, and Probotix. CNC Router Parts sells Gecko kits as well.

[8wt Man]

Thanks Dan911, I have downloaded and will keep but it will not always work for the stuff I intend to do.

Thanks louieatienza,
I have looked at those machines and they are similar to what I envision mine being. They are great builds.

As for accuracy I will be using it for intricate engraving and design mostly. So I am looking hoping for around 0.004~0.006" with the first build. Would it be possible to get this kind of accuracy from a acme screw and cncrouterparts carriage? I may be asking something unreasonably for a low budget, but that is why I am posting here. What can I expect if using Acme thread and the steel rails vs commercial linear slides of some type.

I think I am going to settle on a machine design before I go into the details of software and drivers, to much at first is overwhelming.

[louieatienza]

I think .004"-.006" is a reasonable and attainable goal. You should be able to adjust most if any screw error in your controller software, and with your small machine, you can get real accurate with the CNCRP stuff easily. Another idea, since you're making a small machine, might be to use ground tool steel instead of cold-rolled for more accuracy.

With the ACME screw I'd definitely use anti-backlash nuts...

[judleroy]

If your using autocad 2007 or later you can use bobcad v21 with good results. Output 3d files as .sat format. It will also directly import .dwg and .dxf for 2d but not good for 3d in those formats. Earlier autocad versions never worked well importing to bobcad for me. I always had to import to another software and change formats to .Iges or .step to get working 3d files. If you transfer 2d data to bobcad that's taken from a 3d file with the solids and surfaces deleted you will have problems also. You need to delete the 3d objects then copy all the entities you want to use as frame reference or hole reference then open a new autocad drawing and paste them into it. Save it under a different name then merge it with the .sat file in bobcad. Sat files are the only reliable way to get 3d to bobcad from autocad that I have found. Keep in mind that it took me years to find a reliable way to get good file transfer for 3d to bobcad without guessing what will work this time. Lol. That makes this info a valuable trade secret for me. Lol. Now bobcad and autocad are my mainstay where as before I had to play with many programs to get what I wanted. Just remember if you go with bobcad it must be autocad 2007 or later. I hope this helps to keep people from pulling there hair out for years like I did finding a solution. Once I figured all this out making 2 and 3d parts in bobcad has become a stress free breeze. Just to show how long I worked to make these programs compatible for me I'll say I started with autocad 2000 and bobcad v17. Good luck.
Judleroy

[RomanLini]

Hi 8wtMan, you might want to take a look at my machine build too;
http://www.cnczone.com/forums/cnc_wo...ll_router.html

It was fairly cheap and built with aluminium plate and some tube section, and designed for high precision. The plastic leadnuts are tight around the leadscrews so there is practically no backlash and the plastic Igus brand linear bearings are fairly cheap and also have no slop or backlash (much better than linear ball bearings especially Chinese ones).

One thing I would suggest is to reduce that Z of 6" travel right down, it will introduce a lot of leverage and slop. Especially if you will be cutting flat sheet.