CNC Router v1.0, The Work table

For the work table, I got some 80/20 extrusions off eBay. I used the metric, 40-8020 extrusion, which provides a ready-made t-slot for workholding. Once cut to size, I used a simple angle stock to hold it in place.

 

 

Spindle Mount (65mm)

Time has been short these past weekends. Progress is a bit slow, specially when the build process approaches the detailing part.

There isn’t much originality in this spindle mount. In fact, it’s a variation of another one I had build for a small Zen Toolworks CNC router. The difference is that this one uses a thicker 6061 aluminum plate (0.5″) and an M5 socket screw to hold it in place. The four holes on the x,y plane are for future accessories such as vacuum attachment and whatnot. The holes are fitted with an M4 set screw for holding things in place.

NEMA 23 Motor Mount

In the search for NEMA 23 mounts, I came up with a really simple design for the stepper motor mounts. I had two problems: The mount had to have wider than usual footprint as a regular one would bump right into the mounting bolts for the BK12 bearing block, and my milling/machining limitations prevented a more complex mount. I was a bit concerned about having it built into two separate parts. I wondered how it would handle axial forces. Once (my rather limited) mathematical models suggested plenty of rigidity, I built one to test. Indeed, these mounts don’t even notice the 400oz/in motors.

CNC Router v1.0, The Gantry

I did a big, 2-day push this weekend and got the gantry done. At least all the mechanical parts. I made several pieces on the little Sherline, which chug along all weekend long. Not too much to talk about but a whole bunch of self explanatory pictures.

 

 

 

CNC Router v1.0, The X Ball Screw Nut

Today I spent some time working with the ball screw nut support for the X axis. Like the Y axis, I used the stock 2″ square tube. The machine is beginning to take shape and I can tell this will be heavy. I had computed the final mass at 65kg (143lb) before I even started but it’s a different story to go from just a number to actually trying to lift it.

 

 

 

CNC Router v1.0, The Gantry Support

This has been quite a project. Not only the actual project these postings are all about but also the picture taking, downloading to the computer, preparing the post, it seems to be just as much work as the metal cutting. It’s all fun though, I just wish we had 48-hour days…

CAD visualization of the CNC machine base and gantry support. The rightmost slanted support is missing to allow seeing the inside.

Today I completed the gantry support. This required quite a bit of CNC machined parts for the compound slanted support. As I had mentioned earlier, I could not build it from one single piece as nothing I have would handle something that large. So instead, I designed a compound system using pieces no wider than my 140mm limit. With a bit of creativity, I was able to come up with a slanted support that gives me a proper center of gravity for the cutting tool.

All important CNC machined pieces are designed slightly larger in the needed dimensions as I do not trust the precision of the little Sherline mill. These pieces are way beyond the specs of this little machine and the stresses cause all kinds of rattle. To be on the safe side, I cut it larger (or smaller in the case of holes) and machine to size manually. Basically, the reason I am building this machine in the first place. A very rigid, large area machine.

600mm Digital Caliper

Tired of trying to measure long pieces accurately I ended up getting a long (600mm) caliper. What a difference it made. As most everything else in this project, I found it on eBay. I got it from someone in California but it obviously came from China. Given that it is a copy of a $860 Mitutoyo for about 1/5 of the price, it’s a great bargain. It performs well and I am surprised by its accuracy and repeatability.

The eBay seller goes by “ISoldIt”. If they are around or not by the time you try the link I can’t tell. These eBay sellers all seem to be quite sporadic. If you can’t find them, just look for “600mm digital caliper”.

CNC Router v1.0, The Base

I had already quite a bit of stock aluminium but ended up having to order a few odd sizes I didn’t have. I’ve been ordering everything from onlinemetals.com, which so far I am very happy with. The UPS guy seriously hates me by now but the stuff gets here quickly.

I rough cut the pieces and machine them to size. Getting something 831.00mm to size was a bit of a chalenge. My caliper ends at 150mm and errors accumulate quickly if you are not careful. Once cut to size, I mark the holes and drill them (and tap when that’s the case). I started tapping with the SX3 but in the end, it’s a lot simpler to use my hand drill to tap. Just make sure you have plenty cutting oil and I can tap and remove the tap at full speed. All 400 or so holes…

The entire base was cut and machined manually. The larger holes were started with a 0.5″ drill and bored to size using the boring tool. Speaking of inches, my head works in metric while I live in an Imperial world (no pun intended). In the end, I use whatever is in front of me. The entire project was done in metric while the stock aluminium is all in inches. It makes for some complicated numbers but that’s what computers are for. Most my drill bits and end mill cutters are Imperial though I ended up buying a set of M4, M5 and M6 drills, couterbore and taps for this project. The advent of eBay  and the ubiquitous Chinese vendors are making life easier for metric tools.

CNC Router v1.0, The Project

CAD output for the CNC router project.

For a while I’ve been thinking about building a CNC machine from scratch. Not that I could not find one that I wanted, I just wanted to build one. It was just an idea. Until I bumped into Graham Ham’s web site and his CNC router. His postings of the entire process were so well detailed that it inspired me to get started (not to mention to clean up my workshop as it usually looks like a cyclone went through it when compared to his). And started I did. My design is loosely based on his design, taking in consideration my abilities and work limitations and the sizes of the main components I had and/or could find.

The main limitation, aside from the fact 2 years ago I thought milling machines were used to turn wheat into flour, is the size of stock material I can machine. My current CNC mill is a miniature Sherline mill (where it all started) and even with some modifications, which allowed for extended X and Y travel, it cannot handle widths larger than 140mm. I have a larger manual mill but some of the parts will have to be done through numeric control. Not to mention that even the larger mill, a Sieg SX3 (labeled Grizzly G0619) is also limited at 150mm of Y travel. This is all after all, just a hobby setup in my basement. This machining limitation is obvious when you see the compound side posts that hold the gantry. I just could not machine one single 250mm x 390mm piece of aluminium plate. I had to make it using pieces no wider than 140mm.

Stone age meets high-tech. Ball screws and linear rails wrapped on newspaper and hand-woven sisal rope.

Following Graham’s ideas, I found and ordered a set of Chinese ball screws and linear rails off eBay. I bought it from an eBay seller called “Solar Jean”, who sells an interesting combination of nail art stickers and CNC machine parts. I fail to find the relationship but I assume there is one in there somewhere. The items arrived in less than a week and it all were in fine shape. One thing to keep in mind, and a lesson I learned, don’t trust engineering drawings from these Chinese components. I had started my project based on these “documented” dimensions just to find they were all quite off once the parts arrived. The parts are OK and overall well done. Just not to spec. I had to measure everything and adjust all the plans accordingly. The fact that the parts arrived wrapped with hand-woven sisal rope should tell you something.

If the link above no longer finds Solar Jean, you can always look for “ballscrew set” directly on eBay and see what comes up. These are pre-machined sets of ball screws and matching linear rails. Makes life quite easier than trying to source these things individually. But that also means your machine’s size will depend on the combination of sizes you find. If you want something specific, you can always email the vendor and they will cut and machine the parts to your specification.

Speaking of plans, I designed the entire machine using a solid modeling tool before cutting the first piece of metal. Software, not hardware, is my background. This allowed for a very accurate design with very tight tolerances. It also allowed to experiment. Using the solid modeling program’s constraints and analysis tools, I was able to see what would or would not work before any real machining started.

This is the beginning. In the following weeks I will try to describe the process through which I will go to get this project going. I chose this “blog” format because it was really simple to install and maintain. Let’s see where this will go. And to Graham, thank you!

The Grizzly Arrives

Grizzly g0619

I was looking for a better drill press. The one I had was over 20 years old and there was no way to drill precisely with it. It was also too short so by the time I added a vise that afforded some control, I could not fit a drill bit. Brilliant… So I went looking for something to replace it. While looking for it, I bumped into these American branded Sieg milling machines. Grizzly, Shopfox, etc. The price was right, it would do exactly what I needed plus a whole lot more. I was just worried about its immense mass. And heavy it is. I knew the main issue would be to get it into the house and up on top of my workbench. Slowly but surely I got it disassembled and moved it bit-by-bit. All the while cleaning the nasty protective grease it comes all smeared with.

There were only two days between ordering it from Grizzly.com and its arrival. UPS (Freight) will bring to your door, provided a massive tractor trailer can come to your door. That was not my case. I live on a dead-end street with no way for a large truck to turn around. That meant I had to rent a pickup truck from Uhaul and go pick it up directly from the UPS dock. Hassle aside, it’s actually cheaper that way, even considering the pickup rental. It also allowed me to take my time with the machine as I brought it down from the bed of the pickup using an engine hoist.

In summary? I love this thing. Eventually I will find a way to motorize the movements, specially the Z axis but for now I’m really happy with it. I have no plans to convert it to a CNC. Primarily because it would be a pain the neck to disassemble it all over again. I just want to get the head up and down without breaking a sweat every time.