Second build, slow progess but better result then the Alpha...

[Witsenburg]

Hi,

my first successful build was this machine (Click), which worked, but is had some flaws. First and foremost, it was glued together, and it could pass though the garage door in our old house, but it couldn't fit through the door of the workshop in our new house. Hence, it is now in many pieces. Hmm...
Secondly, the machine is slow. The machine moves (x and y) 4mm for every motor turn, so machining at 1500 mm/min is 375 rpm. It does that, but not happely.
Thirdly, the gantry is way too heavy. Accellerating it often causes the x drive motor to stall. I've interchanged motors and drives between x and y axle, but the problem persists. BTW, it's all solid MDF with think walled SS tube, so it does weigh a ton.
Fourthly, there is no way to adjust the perpendicularity between the axles.

So, for the next build, here are some of my ideas.
1) It will bolt together, hence it can be unbolted.
2) I would like the thing to become belt-drive, with the belt-wheel directly on the motor axle. Hence, not 4mm/turn but 75mm/turn (20RPM for machining speed of 1500mm/min). If I'm not mistaken, the bipolar motors are strongest at low RPM, so this should be an improvement. Microstepping 1200 steps/turn would still be 0.0625 mm/step.
3) The table will move on the x axis. Hence, the gantry is stationary and there is a lot less weight on the move. And the moving Y cart and Z axis will be made of birch ply, lighter then MDF. Downside to moving the table is that the machine will become larger.
4) It will get space to adjust the axis relative to each other, using slotted holes where the parts are bolted together.
5) All electronics and motors will be taken from the previous project.

OK, that's my idea. Please comment if you have a better idea or suggestion. I like building the machine, but it is not my goal. Building guitars is, this beta build should be a machine useable for a longer time than model alpha.

Cheers,

Hugo

[jckstrthmghty]

I don't want to stiffle your creativity but any reason why you wouldn't go with a proven build like joes 2006? Would be fairly easy to cut the pieces with your current cnc and there is ample online support.

[Witsenburg]

True, but there are a few hick-ups: for one, the old machine is en 43516.413221436174.65416841.681. pieces (+/- a few). So I cannot use that. Secondly Joe's, although a very well designed machine, has no means of aligning the axles. For instance, if your X and Y axis are not perfectly perpendicular (and since I build by hand, there is a risk of that happening), there is no way to adjust it. Or did I miss something in the e-drawing?

Cheers,

Hugo

[jckstrthmghty]

I believe just how joes 2006 is engineered promotes good alignment. Adjustments are done on the skatebearing rather than the rails themselves. Overall cutting area is optimized as well. Can't go wrong. I do see a deliema with cutting pieces without access to a cnc router. This issue is what stopped me from making joes as my first machine. However there is an excellent thread on how someone did it with hand tools.

Take a look here.

Handcut Joes in Sydney, Australia

I know there is another link with a modified plan for the support rails do you don't have to cut the rail supports in half circle, just a groved channel, but I can't seem to locate that lhread.

I have no idea what your budget is but buying a kit might be the way to go since you already have all the electronics and such.

[BobF]

Here it is.
http://mikehiggins.home.mchsi.com/cnc.html

[Witsenburg]

Ah, nice build. BTW, I did the routed channel for the tube on my first build, too. Only I'm not too pleased with MDF, because of the weight and it's habbit to warp and expand due to humidity.

Anyhow, not meaning to be rude, but I will make my own design for this new machine, of course nicking good ideas from others.

Cheers,

Hugo