MDF CNC Machine Progress

[victorbl]

I've been trolling the forums for the past few weeks an have been really inspired by some of the machines that I have seen posted. I decided it was time to take the plunge and build one for myself as I can think of quite a few woodworking and electronics projects where the precision would come in handy. So, I spend about two weeks collecting/ordering parts, as well as drafting up a plan for the machine itself.

The hardest part for me was making design decisions for the machine based on the different feedback it has recieved in the forums. Things like fixed versus moving bridge, skate bearings versus bushings, etc. So, with this being my first machine, I decided to take a conservative approach, and borrow alot of the decisions from machines posted to the forum that were iterated on. Most of my design was inspired by jgro's second machine.

The specs 'thus far'
* Approximatly 17 x 16 x 5 cutting area
* Fixed bridge, moving X axis table design
* The Y and Z axis are supported with 3/4" drill rod riding on oilite bushings
* The X axis will be supported on 1" drill rod riding on oilite bushings
* All three motors are 116oz/in Pac Sci
* Driven by a Xylotex board with a 24v 6amp power supply
* Using 1/2-10 Precision ACME lead screws and home made Delrin nuts

I began construction three days ago, and have mostly completed the Z and Y axis. I still need to get the motors and screws mounted, then move to the X axis and table. Finally, wrap it up with some paint.

I wired up the motors/powersupply/driver board last night and had the motors turning with Mach2 (I know the superstition, but I'm too invested now to quit). I'm really looking forward to getting them mounted on the Y and Z to see it come to life. My first designated project for the machine (once I get the hang of it) will be to create a nice 1/2" baltic birch case for the electronics.

So enough talk and on to some pictures. I'll try and stay active on posting my progress...and plenty of pictures. I can appreciate how much the pictures helped me when I was designing.

(if your curious why the MDF looks two different colors, I shellac'ed some of the pieces to prevent any premature moisture damage before I got around to painting it)

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[BobLWeiss]

Looks good so far..nice job.

Can't wait to see more pictures! What software are you going to use with it? Are you using a dremel for the spindle?

Bob

[jgro]

Looking good Are your bushings glued in? Mine weren't, so I filed a notch into the flange with a round file and drilled a hole through the mdf so that I could put a bolt through to hold the bushing from pulling out.

jgro

[victorbl]

BobLWeiss: My 'real job' is in software development and graphics, so I have access to some modeling packages that we no longer use at the office. I'll probably use 3D Studio MAX or CorelDraw for my modeling, and I will most likely pay to register Mach2 as my driver. Any recommendations on a DXF->GCode converter?

For the cutter, I already have a dewalt heavy duty cut out tool, and a dewalt 2.25 HP router...as well as a dremel. I would prefer an off the shelf solution versus building a spindle if possible. I think my main goals will be some basic pen plotting, creating some 3D shapes in MDF, and hopefully a few circuit boards.

jgro: Thanks for the feedback, I should really be thanking you . I saw your use of the bolts to hold the bushings in and I actually predrilled most of the MDF around the bushings to accept a bolt to hold the bushing in place. I did drill the holes for the bushings just one size too small, and after shellacing the holes, the bushings are a tight friction fit. I think my plan in the end is to pull them all out before I paint the whole thing, then go ahead and secure them with bolts as you did as an extra precaution.

I did have a question...why did you choose to go with 'skate bearings' on your X axis? Was it so you could support the 1" drill rod from the bottom? I'm currently planning on using the 1" oilite bushings on my X just because they don't seem like they will carry much weight, but I could be wrong.

[jgro]

I spent about a month trying to get bushings to work on the x axis. I just couldn't get it to work without binding. I finally gave up and went the skate bearing route. Maybe you will have better success than I did.

jgro

[MrBean]

Any recommendations on a DXF->GCode converter?

If you're planning on using Mach2, it has a built in DXF->GCode convertor.

Regards Terry.....

[victorbl]

I'll have to try an import a simple DXF into Mach2 to see if I can understand how to specify things like cut depth, etc.

I'm curious if anyone has any recommendations of a good set of basic cutters that I should order/buy so I will have them when I wrap up the machine. I've heard words like 'end mills' and 'ball mills' thrown around. Can someone provide maybe a starter list of some good bits to get, and where to order/buy them from?

Projects I have in mind:
* Shaping 3D pieces with plastic or MDF - like clock gears
* Cutting 1/2" and 3/4" plywood - such as for a case for my electronics
* Circuit boards

Thanks!

[asher]

JGRO Could you please tell me where you got your wire track and how much?? Thanks in advance Jason

[jgro]

We got it at work from Igus. They sent us a sample pack when we were working on a project and the chain guides were a part of it.

jgro

[victorbl]

Things seem to be progressing well. I spent some time this weekend building the X axis table and a frame to hold it all. I also started to mount the motors/acme screws/drill rod.

I'm noticing that even though I spend a considerable amount of time setting up all of the drills for the bushings and support blocks, it is going to take a considerable amount of tweaking to get everything to slide around without binding.

I ordered three Flange Bearings last week to use at the opposite side of the motor for each axis.

jgro: I'm noticing when the bushings and drill rod line up perfectly after a ton of tweaking, they slide great. But, one degree off, and your fighting it. Do you lubricate your drill rod with anything to further assist the bushings?

[ger21]

Read post #5. He got rid of them.

[jgro]

I got rid of them on my long axis. My two short axis still have bushings. I put some silicone based lubricant on the shafts after every couple of uses. It keeps them slippery

jgro

[victorbl]

Well, after thinking it over, and some great advice from jgro, I think I've corrected my drillrod/bushing binding problems. Reguardless of the fact that I had spent time squaring my drill press, building a jig to align the bushing holes, and assembling the axis's with the drill rod in place, there was still some light binding of the oilite bushings with the drill rod. I had drilled my bushing holes such that they were a snug fit, but as I see now, that was a mistake.

Basically, no matter how square and lined up I had my bushing holes, it's still MDF, so there is always going to be just enough play (even if it's a fraction of a millimeter) to cause some unneeded binding. Granted, it wasn't locked, but it did require a little pressure to slide some of the axis's. So, to fix this, I took jgro's advice and bored out each of the bushing holes just enough such that bushing just slid into the MDF versus needing pressure to get them into the MDF (think exact fit, no longer a friction fit). This freed them up just enough to make the drill rod slide smooth as silk. Even adjusting the blocks wouldn't clear all the binding if your bind is just between two bushings.

If I were to do it all over again, I might have considered using UHMW flanged bushings from mcmaster. They are about $6 a piece versus $2 for the oilite bushings....but I think they might have been a little more forgiving. And my sanity is worth the extra $4 per bushing

[victorbl]

It's finally starting to resemble a real machine. Still alot left to do, but I'm starting to believe that this thing might actually work when I'm done with it!

[jgro]

Looking good!

[BobLWeiss]

Where did you get your threaded rods from? I love the design and it looks like it gonna work out nice for you.

[victorbl]

I purchased the Precision ACME threaded rod from MSC Industrial Supply

link to Precision ACME lead screw

Overall, I have been really satisfied with the design, though, if I were to do it again, or give advice to those building a similar machine to this one, go with 1" UHMW flange bushings on the X axis instead of the cheaper bronze bushings. My X axis is now setup so that there is no detectable binding between the bushings and the drill rod, however, the force required to overcome friction and start the X axis in motion is just high enough to make me a bit concerned. I think this is contributed to the fact that the X axis tends to be a bit heavy, and i'm dealing with a metal bushing on metal drill rod.

I'm going to try and use my existing setup this weekend to make some sample plots/cuts to see if everything is acceptable, I'll keep you posted.

[BobLWeiss]

These flanges you are talking about using instead, did you get them at the same place as the rod?

I am thinking of making another machine using JGRO's plans...nice design.

[victorbl]

For reference, here are the oilite flanged bushings that I purchased

From www.mcmaster.com
* SAE 841 Bronze Flanged Bearing for 1" Shaft - 6338K437
* SAE 841 Bronze Flanged Bearing for 3/4" Shaft - 6338K433

However, later, I may "upgrade" my current bushings to UHMW which can be found here:

From www.mcmaster.com
* UHMW Flanged Bearing for 1" Shaft - 57785K28
* UHMW Flanged Bearing for 3/4" Shaft - 57785K27

[BobLWeiss]

Thanks for the links!! One last question, how did you make the nuts for the threaded rods? I have been looking on McMasters for nuts and they are expensive and come in 2 peices each. THey are not antibacklash type either, just plain nuts with mounting flanges...like $50 each. I would love to make my own since you need 3 of them.

Thanks again!