New Machine Build- First CNC - MDF Build

[ttjarrett]

Hi All

At the start of 2008 I decided to build myself an electric guitar. As I am interested in manufacturing processes, I decided it would be interesting to design my guitar in a CAD program and get it machined by someone rather than just make it by hand. "How hard could it be to find someone in Australia willing to machine something for you?" I pondered...

As it turns out, it's bloody hard! After a long and arduous search to find someone who would machine my guitar for me, here I am 12 months later with a worn out Yellow Pages and a design for my own CNC machine. Necessity truly is the mother of invention!

I have decided to build the whole thing out of 16mm MDF that I will need to have laser cut. My original design philosophy was simplicity, but that went out the window before I'd even sat down at the computer.

I am using the skate bearing/aluminum angle idea, but I have designed all axes with a group of bearings that slide onto their opposing aluminum angle rails to ensure a tight fit and hopefully no play.

The machining area will be:

Y Axis 700mm (27.5")

X Axis 1000mm (39.5")

Z Axis 150mm (6")

Please have a look at my pictures and tell me what you think. I have started purchasing parts, and will be starting the build soon. I will have some photos soon and will try to update this thread regularly.

Sorry about the crummy picture quality. Solidworks owns so hard in everything but for some reason can't seem to spit out good quality JPEGs.

[budP]

Hi:
This is a great design, some of the things that I really like are the adjustments for the x axis rail, a really good idea.

I also like the interconnection of the parts, good for stability and really strong.

budP

[ttjarrett]

Originally Posted by budP This is a great design, some of the things that I really like are the adjustments for the x axis rail, a really good idea. I also like the interconnection of the parts, good for stability and really strong.

Thanks budP!

I didn't show it very well in the pictures, but the bearing adjustments are on all axes so fingers crossed the machine has no play.

Yes, hopefully the interconnection of the parts increases the machines strength. I am also hoping that the interconnection of the parts coupled with the 'cross dowels' I am using to join the MDF will lead to a square machine.

[19roomer68]

Hi,

a good design.

How do you fix the rails or the bearings at the rail ?

How do you minimize the space between the bearings and the rail ?

Bye
Chris

[ttjarrett]

Originally Posted by 19roomer68 How do you fix the rails or the bearings at the rail ? How do you minimize the space between the bearings and the rail ?

Hi Chris

Thanks for the questions, I hadn't shown either of those things in my initial pictures.

The aluminum angle that holds the bearings will be fixed to their 'holders' with bolts and cross dowels. In order to do this, I will have to flatten small areas of the aluminum to allow room for the bolt head. Have a look at the Bearing Rail Fixture picture to see what I mean.

The aluminum angle that will serve as rails will be fixed by countersunk screws (X Rail Fixture picture).

Both methods will be used on all axes of the machine, but will have to be modified a little for each.

I minimize the space between the bearings and the rail by sliding the bearing 'holders' towards the rail and then locking them in place when they are snug against the rail. The X Axis Linear Assembly Arrows picture explains what I mean a bit better. On all axes, one group of bearings is immovable, while the opposing group of bearings can be slid towards the rail. It's hard to explain, but hopefully the picture helps.

Thanks

Toby

[19roomer68]

Hi,

thx for the answers.

Bye

[ttjarrett]

Hi All.

After an excited wait, some of my parts have started arriving!

So far I have purchased:

Bearings from VXB Bearings;

"Hi-Lead" Acme Screw and anti-backlash nuts from Roton;

a HobbyCNC PRO Chopper Driver Board kit with 205oz/in steppers and 3 1/4in to 1/4in shaft couplers from HobbyCNC;

a 240vac 24V 12A transformer from RS Components Online;

a heap of nuts, 305 bolts of varying lengths and cross dowels from a local hardware supplier "Fyshwick Specialty Fasteners";

all of the laser cut 16mm MDF from LaserCut Plastics in Melbourne, Australia (www.lasercutplastics.com.au);

a computer from a guy at work; and

a Ryobi TR50A router from the local hardware shop for the spindle.

All in all, I couldn't be happier with all of the people I have dealt with so far. For any Aussies reading, if you need anything laser cut, go straight to Graeme at LaserCut Plastics. The man is a dead set legend!

The only thing I am a bit concerned about from all my purchases is the Roton anti-backlash nuts. After fitting them to the screw for a test "screwing" I feel that they are too tight on the screw. Has anyone experienced this problem in the past? The nuts have a spring loaded mechanism that eliminates the backlash, but it seems too strong for the nuts. I may have to replace the springs to reduce friction on the screw (which may also increase backlash), but I'll see how I go!

I have started assembling the MDF and now that it's all coming together, I couldn't be more pumped!!

I have attached some pictures of some of the parts, check 'em out.

[ttjarrett]

Hi All.

After continuing to assemble the MDF parts of my machine this evening, I decided that I need to build a "table" to house my machine and all of it's electronics. This way everything is contained in one area and it gives the whole machine a nice "machining center" feel.

I have done a quick design of what I am thinking of doing. Simplicity is most definitely the name of the game!

See attached picture.

[koopman]

Hi,

Maybe you should consider to use 4 ball bearings (2 on each side) in stead of three in the z-axis linear assembly as shown in your design pictures.

I once used 3 on each side myself, but the z-carriage was able to move in the 45 degrees direction without much force. Since then I changed to the normal 4 and everything is just fine now.

Other than that: great design!

Cheers,
Richard

[ttjarrett]

Originally Posted by koopman Maybe you should consider to use 4 ball bearings (2 on each side) in stead of three in the z-axis linear assembly as shown in your design pictures. I once used 3 on each side myself, but the z-carriage was able to move in the 45 degrees direction without much force. Since then I changed to the normal 4 and everything is just fine now.

Hi Richard. Thanks for giving me a real life example of this, I spent a lot of time wondering if three were enough! If you had problems with three, that's good enough for me to go to four. It's hard to determine the amount of force exerted on the Z-Axis, but I imagine it would be quite a lot.

Thanks

Toby

[stevednz]

ttjarrett,

Would you be willing to share your CAD/G-Code files so I could look at getting this laser-cut in New Zealand ?

Steve

[ttjarrett]

Originally Posted by stevednz Would you be willing to share your CAD/G-Code files so I could look at getting this laser-cut in New Zealand ?

Hi Steve,

I don't mind sharing my design with you, but I think I should finish my build first to confirm that it all actually works!

I spent a lot of time designing the machine in Solidworks, which allowed me to make sure everything was good to go, but the design won't really be confirmed as 'fully functional' until I have seen it cut something.

Would you be happy to wait for a month or two until I finish my build and test the machine? Then I can iron out any bugs and make available a set of files that will actually deliver a working CNC.

Thanks,

Toby