Desktop size DIY build

[gasmasher]

After getting a ton of help from other members and reading through threads I am ready to start my build. I have a lot of parts on order so in the meantime here is a sketchup of my plan. I appreciate any criticism. I've included the sketchup file in case anyone wants to borrow from it.

My original plan was to have a cutting area of 12" x 12". After browsing for parts and drawing the design I should have a cutting area of 18" x 17" x 3", which is fantastic. Linear speed is going to be fairly slow but my goal was resolution over speed. I'm fine with it taking an hour for a single cut since it is just a hobby machine until I build something new and better.

[jalessi]

Gasmasher,

You may have a problem with unsupported round rail 22" long.

Jeff...

[gasmasher]

I'll keep an eye on the deflection. My intention is only to cut 2D items so a 16-32th of movement won't be a problem. At the very least I can move my X axis blocks closer to my 12" goal and nothing in my crude sketch has to change. The screw and shaft will just stick out the back of the rear block.

Thanks for the warning. I've probably exacerbated the problem with the tiny diameter 1/4" shafts on which I settled. I can always upgrade to 1" shafts when I get tired of a 5" X axis

[bkboggy]

Very interesting looking design. Makes me think of this: http://www.8linx.com/cnc/cnc.htm when I look at it. I like simple designs like that. Definitely interested in how this will turn out.

Probably a stupid idea, but: I would some kind of plate or something along the 22 inch axes under those rods. I would extend the blocks on both sides down. I would put some kind of bearing system on the bottom to slide against the plates. That way the weight does not rest on the rods. I too, think the weight will be an issue since you will have the whole y axis, z axis, y and z motors and the router/spindle/whatever-it-is-that-you-use rest on those 22 inch rods.

[TOTALLYRC]

I'll keep an eye on the deflection. My intention is only to cut 2D items so a 16-32th of movement won't be a problem. At the very least I can move my X axis blocks closer to my 12" goal and nothing in my crude sketch has to change. The screw and shaft will just stick out the back of the rear block.

Thanks for the warning. I've probably exacerbated the problem with the tiny diameter 1/4" shafts on which I settled. I can always upgrade to 1" shafts when I get tired of a 5" X axis

Thos 1/4" shafts may well flex more than that under cutting forces. Unsupported rods for the x and y are a bad idea. If you have not already ordered them, I would seriously reconsider.

Resolution over speed sounds great but you need some speed to cut properly or you are just grinding you way thru and not cutting. Not to mention having to listen to it for an hour to make a single small cut.
Of course it all depends on what you are going to cut.

Mike.

[ger21]

I've seen 1/2" shafts across a gantry flex over 1/4" with light finger pressure on the Z axis.

[gasmasher]

OK, on your guys advice I am at least upgrading the X axis, for now. I already ordered the 1/4" shafts and bearings, but I'm sure I can put them to use in something else. Instead of a single 1/4" shaft on each leg it will be a 1/2" shaft with a rail support. I also got a pair of open bearings to ride the new shafts.

I think I am going to take my chances on the twisting of the gantry until I have it up and running just to see how bad it is. At the worst case there is plenty of room in the blocks carrying the Y axis to upgrade all the way to 1" shafts. With the X axis supported on rails the additional weight shouldn't be a problem.

[gasmasher]

I have a few pictures after a few hours of work today. The X rails are built and I should have the Y axis drilled tomorrow and the beginning of the Z.

[Hirudin]

It looks like you're making some very good progress! I thought real hard about building a machine like this and using it to make a new one... looking at your pictures makes me think it would have been a good way to go.

This looks a lot like the Lumenlab "micRo" desktop CNC machine...


Check out the forum thread (it's like the ultimate "build log"), you'll probably find some good ideas.

[gasmasher]

A lot of my plan did come from the pictures on the lumenlab site but I didn't realize they had a forum thread for it, thanks for the link. Once I have this running I plan to cut new blocks out of plastic. It has been a real pain drilling all the holes without a drill press but it seems to be coming out okay.

The Hobby CNC 4 axis kit came in yesterday and I put the driver board together last night. I still have to build a case for it and the power supply sometime this week. Here are some pics of the driver.



I also took a little time today to drill the uprights for the Y axis. All I have left is to build the Z and mount the motors. Then comes the tedious task of double checking everything before I take it out for a test drive.

[gasmasher]

My transformer arrived on Monday and I put the power supply together. I am building a plexi case for the driver and power supply instead of the one hobbycnc recommends. No smoke came out when I powered it up tonight and I bench tested the board with a meter but I can't spin the motors until I pickup a parallel breakout bracket for my controlling PC. Hopefully tomorrow I can see if this board works.

[gasmasher]

Yesterday I installed EMC2 on my controller PC (running Slackware). I am slaving the two X motors in software and it appears to be working fine. I have seen the problem that others have had with the hobbycnc board missing steps after going into low power mode. I have disabled it for now by installing jumper 4.

Right now the machine doesn't look all that great but all the axis are moving good enough for now. I really screwed up on the Z and cut it 1.5" inches too short and didn't realize it until I installed the screw. Here is a picture of littleugly with the messed up Z.