Even worth fixing?

[obfuscode]

Hey guys, long time reader, first time poster.

So... being the obstinate SOB that I am, I decided to do things completely backwards. I got all my electronics and started building my gantry without following a plan or cad drawing.

I have neither the proper tools or space to build anything decent so I was hoping to kind of fudge it enough to use the first machine to build a better second machine but I'm having major issues.. the whip on my 3/8 all-thread is so bad that when the gantry gets even half way down, the motor (270oz NEMA 23) starts grinding and either turns super slow or not at all. I don't currently have ABEC bearings with a large enough bore to fit over the lead screw so the only connection points are at the motor (lovejoy 3/8 -> 1/4) and the nut under the gantry.

Do I just need to get larger bore bearings and put them into a wood block with two 3/8 nuts on each side?

So regardless of fixing the whip, does this design even look feasible? When the gantry does move, it's very jumpy.

[LeeWay]

Not really.
The way you have it, you have nowhere to place the cutting table. If you just reverse the gantry sides and rails, then you could attach table braces to the rails.
As for the growling the stepper is doing, you really can't test it until you have a complete axis. Otherwise you are just playing. Nothng wrong with that though. It can point to where you need upgrading or some better alignment.
That little rod will surely whip anyway with any kind of speed. You will likely need to make this one a slow mover.

[obfuscode]

Hey Lee, I was planning on building the cutting table on legs that went over the stepper motor (to which the motor would be attached) and over the top of the lower gantry piece - like a tray table. The stepper motor position is temporary and only held in place by a few screws. I like the idea of reversing the legs although I didn't know how I would connect the cross brace without it being above the rails - currently there are only two supports for each rail but I was planning for more. The rails roll very coarsely as opposed to a linear slide bearing or ABEC bearings but I wanted to try it out. You still think I should start over with higher quality components? My goal was to build a sub-$1k machine including electronics... so far I'm under that but I won't be if I get an acme screw and roller ball bearings. I got the v-groove bearings for a steal on eBay.

[Guldberg]

I have never seen anybody using only the stepper and nut as support for the leadscrew. The bearings in the stepper are by no means designed for axial loads. It will probably work, but im sure you will kill your motor over time.

Your own suggestion with the bearings would probably work. Either that or you should turn down the leadscrew to fit some smaller bearings. This way you can avoid the nuts

[obfuscode]

Yeah the nut/motor only points are only proof of concept - this is not even close to being done. Just never built one before so I'm second guessing every step.

If I encased the nut under the gantry in such a way to prevent y-axis movement but allowed it to move x and z, would that ease the torque it's putting on the motor? Theoretically that would accomodate slight whip without affecting y-axis movement no? Or am I completely off my rocker?

[FandZ]

I would chalk this one up to a lesson learned. You have the electronics and that can be one of the biggest hurdles. It was for me.

Tool wise, when you really boil it all down, all you need is a drill press, a hack saw, drill bits, a ruler, a digital caliper, a ratchet set, and a few other odds and ends.

Here is my elcheapo one that I built.

YouTube - cnctestrun

YouTube - cnctestrun

I think all the hardware came out to under 200. I learned a lot on it. It's only downfall is the Z axis. And really I just threw the Z axis together with a lot of oh that'll work ideas. It will do wood fine but the way it is now if the operation is too long or too aggressive the router will shift a degree here and there due to some slack in the z axis mounting.

I really do enjoy designing these machines though. If you need someone to draw up some ideas or give you some desighn suggestions let me know. I'm a cnc addict.

Chris

[obfuscode]

Chris, very cool. I don't have a drill press or a digital caliper or a ratchet set :P. I think I am going to scrap my current design and go with a bolt-together solution like a lot of the MDF machines; although I think I'll stick with making it out of pine. Any suggestion one way or the other?

I'm also going to take LeeWay's suggestion and reverse the rails and mount them on one large piece of MDF/Pine for the table portion, put 2x4s under it so it's off the table and the gantry will clear and mount the stepper motor on the side.

You think a router without guides is sufficient to make all the holes, slots and shapes that I need to get it together enough to make better parts for itself or should I get a jigsaw? I live in an apartment so I'm literally doing everything in my carpeted spare bedroom and can't spring for a decent workshop setup.

I'm considering getting rid of the all-thread and going with some cheap ACME rails from roton.com

As for the electronics, I went back and forth between a number of solutions and ended up buying a pre-made 4-axis board from Rockcliffmachine.com ( http://www.rockcliffmachine.com/electronics.htm ) and it was pretty inexpensive ($330) compared to some of the individual axis controller packages and it's a nice neat kit that contains everything you need (except wires from the power supply to the board). It even has an XML config for Mach3.

I'll post more pics as I start re-building it - but with my work schedule it'll probably be a few weeks. Thanks for all the comments - it's good to finally be part of the community.

- Jace

[Dman65]

Chris,

Would it be possible to get the Google Sketchup model of your machine?

Thanks,
Darrell

[FandZ]

Originally Posted by obfuscode Chris, very cool. I don't have a drill press or a digital caliper or a ratchet set :P. I think I am going to scrap my current design and go with a bolt-together solution like a lot of the MDF machines; although I think I'll stick with making it out of pine. Any suggestion one way or the other? I'm also going to take LeeWay's suggestion and reverse the rails and mount them on one large piece of MDF/Pine for the table portion, put 2x4s under it so it's off the table and the gantry will clear and mount the stepper motor on the side. You think a router without guides is sufficient to make all the holes, slots and shapes that I need to get it together enough to make better parts for itself or should I get a jigsaw? I live in an apartment so I'm literally doing everything in my carpeted spare bedroom and can't spring for a decent workshop setup. I'm considering getting rid of the all-thread and going with some cheap ACME rails from roton.com As for the electronics, I went back and forth between a number of solutions and ended up buying a pre-made 4-axis board from Rockcliffmachine.com ( http://www.rockcliffmachine.com/electronics.htm ) and it was pretty inexpensive ($330) compared to some of the individual axis controller packages and it's a nice neat kit that contains everything you need (except wires from the power supply to the board). It even has an XML config for Mach3. I'll post more pics as I start re-building it - but with my work schedule it'll probably be a few weeks. Thanks for all the comments - it's good to finally be part of the community. - Jace

Hey Jace, I've been thinking about it for a while. I wouldn't know where to begin without a drill press. I think in metal though, I'm at a loss when it comes to wood. I'm in the same possession you are in. I live in an apartment type situation. Actually it's a town house but it might as well be an apartment with how close my neighbors are. (I'm moveing to a cnc friendly house a next month Yipeeee!)

One think you could do is buy a complete machine. I think this one is under 300 shipped. It's plastic but I would think you could use it to build a bigger machine. http://cgi.ebay.com/CNC-Carving-Mach...d=p3286.c0.m14

THen you have the likes of K2 cnc's. http://cgi.ebay.com/2009-K2-CNC-Rout...d=p3286.c0.m14

Anyways I'm going to think about it some more and post back.

[FandZ]

Originally Posted by Dman65 Chris, Would it be possible to get the Google Sketchup model of your machine? Thanks, Darrell

Here's my build thread. There is a rough sketch up of my machine there. I'm currently redoing the z xis and changing a few things on it. If you want to do something similar let me know and I'll send you some other files too.

[obfuscode]

Wow, that little machine isn't bad for under $300 but a bit too small for my purposes. I like the K2 one but it's a bit over my price range.

Ideally I'd like to make a complete CNC incl. electronics for under $1k and I have a few friends that would want one as well. I just have to re-buy all my parts. The v-groove bearings I bought are too loose and have some linear play in them. I guess I'll have to spend the money on proper v-groove bearings. I also need to buy proper screws, anti-backlash bearings and bushings.

I /really/ like the buildyourcnc.com Blacktoe 2 drive chain setup but I don't really know the first thing about that (not that I know much about anything else apparently) and a few people talked about wear issues with it pressing up on the motor all the time.

I think I'm going to get a trim router. That is what I was planning on putting on the machine anyway and should be sufficient enough to slowly cut the general shapes and slots that I need.

[FandZ]

OK, I thought about it some more and did up a rough sketchup. I kinda tried to stick to the materials you were useing and walla. With this one you would need a hand drill, a tape measure, a yard stick, a hand saw, hack saw, drill bits, and some spade drill bits. Also some good V bearings like you mentioned. The roller assembles are all metal slotted metal. Just didn't get that far into the details.

Doesn't look too bad if I say so myself. I need to add in corner brackets and the likes, but the thing I like about it is nothing has to be cut to an exact length. Gives you a little wiggle room.

It is fun to draw these things up.


Chris