A couple months ago, a co-worker told me about his CNC machine he built at home. He answered A LOT of my questions on the general building process and I then began searching online for more designs, tips and tricks.

I finally embarked on my very first router. If anything seems wrong, please let me know, I won't get offended, I'm here to get things right and learn.

Here's a list of specs:

-Material used is 3/4" MDF
-I'm using a HobbyCNC controller with 305 oz-in steppers
-I'm hoping to cut mainly wood and plastic, and maybe try aluminum.
-The guide shafts are 5/8" diameter.
-I'm using PTFE linear bearings, since they are cheap, I figured I could just upgrade if they didn't perform well. (so far they seem okay)
-I bought a porter cable router, but I think it will be too heavy for the machine, so I'm probably going to using a dremel instead
-The Z-axis has not been designed yet.
-The platform (for the workpiece) has not been assembled yet.
-I'm using 1/2 - 10 precision acme rod
-I don't have exact numbers for travel, but its roughly 36" x 36" x 4". The overall dimension of the machine is 41.5" x 41.5"

What do you guys think? Overall it seems pretty sturdy. I'm using wood glue and nails to secure the thing together. The thing is so big I had to build its own table. The table is 4' x 8', I tried to make it big enough to also support a desktop computer.

http://img.photobucket.com/albums/v717/eguy208/CNC_build001.jpg
http://img.photobucket.com/albums/v717/eguy208/CNC_build002.jpg
http://img.photobucket.com/albums/v717/eguy208/CNC_build005.jpg
http://img.photobucket.com/albums/v717/eguy208/CNC_build008.jpg
http://img.photobucket.com/albums/v717/eguy208/CNC_build009.jpg
http://img.photobucket.com/albums/v717/eguy208/CNC_build012.jpg
http://img.photobucket.com/albums/v717/eguy208/CNC_build013.jpg
http://img.photobucket.com/albums/v717/eguy208/CNC_build014.jpg

-Levino

eguy208,

Your machine is looking good. No problems that I can see so far.

I think that you will find that a Dremel tool shaft bearing flexes the plastic housing too much under heavy side loads and will cause chatter. Mine does when just using their router base attachments. Lots of people use the Dremels though. For fine detail work where small cutter bits are needed and speed isn't a factor the Dremel will work fine.

You can swap out the plastic bushings for bronze bushings, or you can modify the z axis assembly to install linear bearing blocks on the shafts. If the Porter Cable router is heavy enough to cause flexing in the y axis shafts near mid span, then something lighter like a trim router can be used.

CarveOne

Hi Eguy,

There may be a couple of potential problems with this design. I made the same mistake when I made the first version of my CNC.
The guide rods are not supported, you will be surprised how little weight it takes to deflect this metal, and the defelection will change from the center to the ends.
I notice your guide rails do not have a means of adjustment on the ends, no matter how hard you try and bore the guide rod mounting holes perfectly it is almost impossible to get them perfect, this will cause excess drag if they are out of alignment in any direction with these type bearings.

Don't give up, it is a fun project but there are certain rules that are hard to bend.

Hager

Hi Eguy,

There may be a couple of potential problems with this design. I made the same mistake when I made the first version of my CNC.
The guide rods are not supported, you will be surprised how little weight it takes to deflect this metal, and the deflection will change from the center to the ends.
I notice your guide rails do not have a means of adjustment on the ends, no matter how hard you try and bore the guide rod mounting holes perfectly it is almost impossible to get them perfect, this will cause excess drag if they are out of alignment in any direction with these type bearings.

Don't give up, it is a fun project but there are certain rules that are hard to bend.

Hager

Yeah, I can tell the shafts are deflecting when I push on them. I was hoping it wouldn't cause too much trouble for me. When I get to the point were I'm needing fine detail, I think I'll be able to swap the lower guides out for supported shaft, that way I don't have to build a new machine. The deflection is also in the Y-axis, is it okay to use the supported shaft there as well? Or will the bearing not like being mounted sideways?

As far as shaft alignment, I haven't made those alignment blocks yet. I drilled the holes just big enough to slide the rods in and mount things up. I can tell there is a slight misalignment. My fix for now was to bore the holes bigger until the shafts weren't binding, and then add the alignment blocks.

Thanks for the comments, this is definitely a fun project that look forward to advancing.

-Levino

Nice start on a project - already further along than I am.

I am not sure about nails and MDF and vibration. Maybe screws would be more resistant to pulling out ? I assume the nails are there to hold it while the glue dries, which might be ok as well.

Nice start on a project - already further along than I am.

I am not sure about nails and MDF and vibration. Maybe screws would be more resistant to pulling out ? I assume the nails are there to hold it while the glue dries, which might be ok as well.

Yes, all pieces are held together with carpenter's glue. The nails may provide extra strength, but mainly it allows me to keep working on the machine without having to wait for it to dry.

I'll probably add some screws later on just to be sure.

-Levino

on useing a dremel..i was wanting to use a drimmel also..but was thinking of making a mount to remove the internals "the motor" taking all the plastic off the drimmel and replacing it with an aluminum "case"sort of mount them in a solid aluminum block this would make it super ridged i think....still just a thought nice looking build so far ,any reason you want a moving table vs. a moving gantry? (im still in the designing stage)

any reason you want a moving table vs. a moving gantry? (im still in the designing stage)

I figured the less mass the steppers have to move, the easier it will be it making a sturdy structure. I'm sure you can see, moving the gantry would have been more mass then moving the workpiece.

A downside that I knew of, is the machine will need room to move it's X-axis. My next machine will mostly likely have a moving gantry.

-Levino

It is much easier to make a non moving gantry much more solid than a moving gantry. That is for the typical hobbist that doesn't have access to a machine shop full of equipment.
It is I guess cheaper also to build.

My 2 cents worth.

Yeah, I can tell the shafts are deflecting when I push on them. I was hoping it wouldn't cause too much trouble for me.

-Levino

i tryed the same thing on my first setup but the weight of the gantry was too much for the rail so i cut some mdf and slid it under the rails on the x axis for support and used the skate bearing design , it made all the difference in the world , it would be a simple and effective mod for you at this point of the game

you can see what i mean in the pics
http://www.cnczone.com/forums/showthread.php?t=20494

Some have substituted a Proxon for the Dremel. I have no experience, but have not seen negative comments on this subistute.

Made a little progress. I've got the acme rods installed (not the nuts though). I'm using shaft couplers to mount them to the motors. The workpiece platform is just laid in the machine and not mounted yet....it will be removable.

http://img.photobucket.com/albums/v717/eguy208/CNCPart2004.jpg
http://img.photobucket.com/albums/v717/eguy208/CNCPart2005.jpg

The MDF got chewed-up when making the motor mount hole. I didn't use clamps and the wood began vibrating and chewed up the hole. It still works, just looks like crap.

http://img.photobucket.com/albums/v717/eguy208/Coupler002.jpg
http://img.photobucket.com/albums/v717/eguy208/Coupler001.jpg

-Levino

i tryed the same thing on my first setup but the weight of the gantry was too much for the rail so i cut some mdf and slid it under the rails on the x axis for support and used the skate bearing design , it made all the difference in the world , it would be a simple and effective mod for you at this point of the game

you can see what i mean in the pics
http://www.cnczone.com/forums/showthread.php?t=20494

Cool, thanks for the tip!

-Levino

Can I find off the shelf adjustable guide rail mounts. Something like what this guy is using (the metal block with 4 bolts that allow the guide rails to be adjusted)

http://cnczone.com/forums/attachment.php?attachmentid=21508&d=1156234731

I could probably make them, but I'd rather put my time into other parts.

-Levino

The acme hardware is finally installed. I used "Precision Acme Rods" instead of "Precision Modified Acme Rod". Precision Modified Rod is a lot more expensive. Because of this I had a crappy selection of Acme nuts, none of them had flanges, so I had to make a clamping flange from a washer.....turned out pretty good.

Here's the acme nut (black), hole and washer:
http://img.photobucket.com/albums/v717/eguy208/Acme_installed003.jpg

Installed nut using 4 screws and washer:
http://img.photobucket.com/albums/v717/eguy208/Acme_installed004.jpg
http://img.photobucket.com/albums/v717/eguy208/Acme_installed005.jpg

Installed on machine, X and Y axis:
http://img.photobucket.com/albums/v717/eguy208/Acme_installed006.jpg
http://img.photobucket.com/albums/v717/eguy208/Acme_installed007.jpg

For a controller, I'm using the 3-axis kit from www.hobbycnc.com.

Here's the motors wired up, I don't have the Z-axis wired up yet:
http://img.photobucket.com/albums/v717/eguy208/Acme_installed008.jpg

http://img.photobucket.com/albums/v717/eguy208/Acme_installed010.jpg

I might need to purchase a desktop computer. I don't have a 25 pin plug on my laptop, so I'm reduced to using a usb => 25 pin adapter. I'm guessing if there's too much lag in the adapter, the machine won't work properly.

Here's the front of the unit:
http://img.photobucket.com/albums/v717/eguy208/Acme_installed012.jpg

-Levino

you will propably need to buy a desktop computer, CNC does not work through the USB->Paralell adapters, but there is a quite expensive PCMCIA card that have a paralell port that CNC control works with...

Okay, here's a little progress. I finally worked on the Z-axis. Here is the finished Z-axis (one bearing isn't installed). I should have ~3.5" of travel. I need to move those shaft collars to the outside of the wood to get the full 3.5":
http://img.photobucket.com/albums/v717/eguy208/Z_installed003.jpg
http://img.photobucket.com/albums/v717/eguy208/Z_installed004.jpg

I bought a porter cable router off ebay a while back:
http://img.photobucket.com/albums/v717/eguy208/Z_installed005.jpg

I'm waiting for the mount in the mail, should arrive by the end of the week. I got the K2 mount:
http://www.k2cnc.com/ebay/Mounts/PC_690_Regular/PC_690_Iso_640.jpg
http://www.k2cnc.com/ebay/Mounts/PorterCable/Mount-And-Router-side.jpg

Here's the Z-axis on the gantry:
http://img.photobucket.com/albums/v717/eguy208/Z_installed006.jpg

And the motor for size comparison:
http://img.photobucket.com/albums/v717/eguy208/Z_installed007.jpg

Also me holding the motor:
http://img.photobucket.com/albums/v717/eguy208/Z_installed010.jpg

The motor weighs 8-10 pounds, so it causes the Y-axis guides to deflect a little too much. To discourage this, I want to incorporate a L-bracket that hooks to the back of the Y-axis, and use bearings to decrease friction:
http://img.photobucket.com/albums/v717/eguy208/Z_installed008.jpg
http://img.photobucket.com/albums/v717/eguy208/Z_installed009.jpg

I don't know exactly how I'm going to go about it, but if I can't mount the big motor, I'm going to have to use a dremel instead.....which would suck.

As soon as I get the motor mounted, I'll only need to get the computer stuff figured out and I can then begin cutting stuff :biggrin:

-Levino

The real deflection problem will be in the other direction. When you start plunging the Z will tilt back a lot more than just the weight of the router tilting it forward.

The real deflection problem will be in the other direction. When you start plunging the Z will tilt back a lot more than just the weight of the router tilting it forward.

Ha, didn't even think about that. Cool thanks! I'll see if I can come up with a solution that makes it rigid in both directions

-Levino

Have you thought of putting the bearings into the back of your Y carriage? This just popped into my head - might be totally useless but its a thought.

Have you thought of putting the bearings into the back of your Y carriage? This just popped into my head - might be totally useless but its a thought.

Yeah, I need to do something like that, Thanks.

UPDATE:

I got the motor mount installed tonight: (sorry for the blurry pictures)
http://img.photobucket.com/albums/v717/eguy208/Mount002.jpg
http://img.photobucket.com/albums/v717/eguy208/Mount001.jpg
http://img.photobucket.com/albums/v717/eguy208/Mount003.jpg
http://img.photobucket.com/albums/v717/eguy208/Mount004.jpg

And I'm currently set with computers!! I've got 2 setup, one for part design and another for working the machine. I got one for free and another for $60.....such a sweet deal!! They are networked together so I can drag and drop files across them. I've got a couple programs I can start trying out.

I'm still having motor problems The Y and Z axis are quitting on me mid operation. The only way to recover them is to cycle the power on the controller. I haven't a clue on the reason, so I'm trying to figure it out. I'm running Mach3 and the HobbyCNC chopper board. I'm currently seeking answers from the online yahoo groups forum.

I'm so close to cutting my first part it's driving me crazy, lol.

-Levino

Well it won't be long now, said Mrs. Bobbit.

Levino

To the point, who is the manufacture of the shaft connectors, they look really sturdy?

Thanks
Hager

Well it won't be long now, said Mrs. Bobbit.

Levino

To the point, who is the manufacture of the shaft connectors, they look really sturdy?

Thanks
Hager

I got them from mcmaster.com. They are a vendor of lots of things. Go to mcmaster.com and search for part number 3084K31. They sell different bores.

-Levino

The thing is so big I had to build its own table. The table is 4' x 8', I tried to make it big enough to also support a desktop computer.

http://img.photobucket.com/albums/v717/eguy208/CNC_build014.jpg

-Levino

I put my CNC on a table and was so suprised at the amount of sway of the table there is a lot of momentum built up and what with stopping and starting, changing directions you might find that diagional braces are necessary. Mine is a fixed gantry also. So a movable gantry would be even more tendacy to sway.
Any way just a thought.
Hager

Yeah, I probably should add some bracing. I never thought the project would get this big and heavy, lol.

UPDATE:

I got my motors running. I set my Vref voltages wrong on the hobbycnc board, so they were cutting out after a few seconds of use. I reset them and now the motors work much smoother and quieter.

I've decided to swap out the PTFE bearings for self-aligning linear ball bearings. I have too much friction in the axis right now. I'm going to use the new bearings and also make some alignment blocks for the guide rails.

As far as I know, I'm set with the programming part :-). Now I just need to button up the mechanical details with the machine.

My goal is to create a carving from an image by Thanksgiving day (November 22nd).

-Levino

Hi Levino,

Yep thoes are pains and hassels we all go through, but sounds like you are in the home stretch and a easy finish by Turkey day. Good luck and keep the pictures coming.

Hager

If you continue having Z axis motion challenges, it is possible to sort of neutrailize out the weight with constant force springs ( mcmastercarr.com )

I will be needing them in my build.

Holy Crap!! I got the linear ball bearings in and WOW. The axis are sooooo much smoother. Also the linear ball bearings are able to self-align up to 1/2 degree, which is helping alot.

Here's the diffference:
http://img.photobucket.com/albums/v717/eguy208/Ball002.jpg

The linear ball bearing has a plastic tube inside it's inner bore. This is so the balls don't fall out. You push the guide rail in and let the rail push the tube out.

Here are the new bearings mounted:
http://img.photobucket.com/albums/v717/eguy208/Ball003.jpg

I can't believe how smooth the travels are now. I won't need to worry about making alignment blocks anymore :-)

I'm making an arm that will help support the router motor. I want to make sure it's fully cured before applying stress, so it will be mounted tomorrow night.

Here's the arm drying:
http://img.photobucket.com/albums/v717/eguy208/Ball005.jpg
http://img.photobucket.com/albums/v717/eguy208/Ball004.jpg

I'm using some old bearings I had laying around from an old Battlebot (http://www.geocities.com/eguy208/Tetanus.html). I'll have pictures later of the mounted arm.

I'm starting to figure out how to hold the bits in the router. The collet that came with the router was crap (and broke). And all the collets I have from my manual mill are too big. So I need to find another collet that fits this motor and can use my bits.

Here's the motor, my bits and my collets:
http://img.photobucket.com/albums/v717/eguy208/Ball007.jpg
http://img.photobucket.com/albums/v717/eguy208/Ball008.jpg
http://img.photobucket.com/albums/v717/eguy208/Ball009.jpg

It's getting there :-)

-Levino

No ball nose tool????

No ball nose tool????

Nope, never needed one. What you're seeing is from what I've needed in the past.

-Levino

I'm in the home stretch. I installed the support arm for the Y-axis:
http://img.photobucket.com/albums/v717/eguy208/Support001.jpg
http://img.photobucket.com/albums/v717/eguy208/Support002.jpg
http://img.photobucket.com/albums/v717/eguy208/Support003.jpg

Those are actually little pullies. I had them laying around. With the arm, it can support the big motor just fine. I'm thinking the force of cutting into material won't be big enough to deflect the axis upwards with soft materials like wood. If it does deflect I'll address it later.

I also now have a video on youtube showing the axis moving. The clicking is from the Z-axis stepper motor, it's resonating through the MDF:

http://www.youtube.com/watch?v=ZyT0-UOT19E

Last thing I need are some bits to begin cutting stuff. The cutting bits and collets have been ordered.....I have no idea when I'll get them :-(

I'm really interested in seeing what kind of resolution I can get from this thing!

-Levino

Finally made a couple carvings. I need to work on the resolution:

http://img.photobucket.com/albums/v717/eguy208/Carvings002.jpg
http://img.photobucket.com/albums/v717/eguy208/Carvings001.jpg

-Levino

good job done:)

you will propably need to buy a desktop computer, CNC does not work through the USB->Paralell adapters, but there is a quite expensive PCMCIA card that have a paralell port that CNC control works with...

Hi Meduza - do you happen to have a source for that card or brand ?

Thanks