So here is my CNC mill up to this point.... also note that this is my first build, I'm by no means any kind of expert in this field, but I'm a bit crafty and that helps a lot. I'm trying to put this post in some sort of order to tell the story of how I've gotten to where I am with this project, sorry if it seems to ramble on or jump around topic/subject matter. Just ask if you have questions, I'll do the best I can to clear up the confusion I've caused.
Most items have been purchased from the 80/20 Garage Sale on eBay or Home Depot. When you see part #[xxxxxx] then I'm referring to something I purchased from 80/20.
I'm using 1530 series T-Slot for framing here. The cutting area will be about 2" X 4", but this could be changed to whatever size you want, just use longer pieces.
I've cut the 1530 T slot with a Rigid brand compound miter saw using this blade:
That blade does a great job of making very clean cuts. I purchased it from Home Depot. The model number is D1084L.
The base is made from two 4 foot pieces of 1530 T slot, with 4 27" wide pieces. It is bolted together with part #4304 corner brackets, part #3279 economy T nuts, part #5/16-18 x .687 FBHSCS bolts on the inside corner holds and just plain old 5/16 X 3/4" bolts from Home Depot and 5/16 flat washers.
Luckly me, I have a pool table to work on. I slide some of the #4304 brackets into one of the 4ft long pieces of 1530 T slot.
I then fitted the 27" long pieces of T slot to the #4304 brackets and capped off the other ends with another 4 foot piece of 1530 T slot.
The pool table came in handy here because it is a large flat surface. I wanted the 1.5" sides of the T slot to all be on the same plane. I used several carpenter's squares to make sure everything was lined up correctly then tightened down there bolts and went back and double checked my work. Also, the reason for using the black #5/16-18 x .687 FBHSCS bolts on the inside of the holes of the #4304, the regular bolts from Home Depot don't fit with the holes that close to the inside corner. The #5/16-18 x .687 FBHSCS bolts cost a lot more than the plain bolts and washers from Home Depot, so the fewer I can use, the more I can spend elsewhere on this project.
Linear bearings... each to his own and it kind of shows with the number of different ways this problem been solved... or created.
The bearings I'm using are based on Geeksgonebad use of Butcher Boy bearings as detailed here.
So the backbone of my linear bearing starts off as part #4370 that is uncut. Normally part #4370 has the corners cut off, so the uncut version is key here.
Also note in that photo above is a small corner bracket, part #4303. It serves 2 purposes... it is of course a inside corner brace for the gantry and also used as a spacer of sorts, the part #4370 plates will be butted against the part #4303 brackets, thus be at the same height on the gantry.
The part #4370 plates do have to be cut down on a band saw, so I bolted 2 plates together to mark my lines where I want to cut:
Then off to the band saw:
I needed 1" square stock, not a size that I was able to source locally, so my friend milled some for me, super fly cut.
The 1" square stock was cut into 6" lengths. For an "off the shelf" version, McMaster-Carr does sell 1" square stock.
I scored a center line down the 1" square stock, and then about .75" I scored another line and with an optical center punch made my dot.
I center drilled the dot punches:
Followed up with a 3/8" drill since I'm using 3/8" bolts in the bearings.
In order to help figure out the distance between the upper and lower centers of the bearings, I fitted the bearings into the freshly drilled out 1" square stock blocks and clamped them to a piece of scrap T slot. For the rails, I'm using 3/8" round rod that, so I taped a couple of pieces to another piece of T slot. I got the bearings as snug against the rail as I could and then measured the distance between the bolts.
I transfered that info to the #4370 plates, used a alignment punch to mark my drilling points. Again, I then center drilled followed up with a 3/8" drill. I then bolted it all together for a test fit:
On my test fitting, I found I had the holes in the #4370 plate a little too far apart, too much free play in the bearing asm. In the photo below, I could move the bearing asm left and right, a gap between the V groove rollers and the track.
Took it back apart and with a rat tail file, I went to work:
I elongated all of the 3/8" holes that I had drilled just a little bit:
With that, I refitted the bearing asm back onto the rails, gave it a snug fit and tightened all the bearing bolts down. I made sure the 1" square stock squared off with the #4370 plate. I center punched the 1" square stock using the pre-drilled holes on the #4370 plate. You can see the dot marks in the middle two holes. Center drill then 3/8" drilled those spots.
With the 2 middle holes in the 1" square stock being 3/8" in size, there is some wiggle room for adjustment since the bolts going though those holes are 5/16" size. And with the 3/8" holes that were drilled into the #4370 plate elongated as well, the spacing between the upper and lower bearings can adjusted. This is in turn secured to the T slot with #3279 T nuts.
I was wanting a way to make it where I could fine tune the adjustment of the bearings so that the gantry to be leveled and squared off with the base. At first I would going to try the hard way, but other members here helped me out with something that should get the same result. 2 bolts that run between the 1" square stock blocks will allow me to fine tune adjustment and should also help make the bearing asm more solid. Getting 6.5" long 1/4" bolts locally wasn't happening, so I cut some 1/4" all thread into 6.5" pieces, and then used red thread lock to secure a nylon nut at one end. I drilled holes in the 1" square stock along a center line for the bolts:
Drilling the holes for the 6.5" x 1/4 bolts along the center line of the 1" square stock was a mistake, the bolts would just touch the T slot when I mounted the bearing asm. This issue was resolved by putting the bolts in a lathe and machining off some of the threads on the bolts.
When the 3/8" bolts for the bearings were tightened down, the outer race of the bearing would be pressed against the 1" square block, so the V groove roller didn't roll so good. This was resolved with a simple washer that only made contact with the inner race. This is a "AN washer" that just fits onto the 3/8th bolt.
The gantry is pretty simple, 3 pieces of T slot. For testing, I put the gantry together using just the small #4303 corner brackets, then dropped the bearing units on top of those, and fitted the gantry onto the base. I got to vertical arms parallel to each other and then scored the bottom piece of T slot for my cut.
I then tapped threads into the 2 holes at each end of the bottom piece of T slot for the gantry so that a #4366 joining can be used to help secure the bottom piece to the vertical arms.
The upper section of the gantry will have 2 cross bars as well, again using #4366 joining plates to help secure them.
I cut the upper 2 cross bars a few days after I had cut the bottom piece of the gantry. A concern I had was that if all 3 pieces were not same length, the vertical arms of the gantry would not be parallel to each other. And since I have to put everything away when I'm not working on this project, thus loose any setting I had with the compound miter saw, I decided to cut the bottom piece a hair shorter than what I though it should be and then shim it out later. So with the upper cross pieces bolted in and one side with the #4303 corner bracket loose and the bottom 2 bolts though the #4366 loose as well, I got the vertical arms parallel and sized up my gap:
Using automotive alignment shims I found that in my case, a 1/32" shim was a snug fit.
Another view of the shim in place. 2 shims were used, one behind each fo the bolts that are threaded directly into the T slot. The fingers of the shims point towards each other.
I tightened down all the hardware for the #4303 corner brackets and #4366 joining plates at the bottom of the gantry, removed the upper 2 cross pieces and secured some #4366 joining plates at the top of each gantry arm, as shown below, then measured the distance between the upper set of #4366 joining plates and compared them to the measurements I got from the ones at the bottom to make sure the measurements were the same.
The upper cross members of the gantry, pretty simple, cut to length T slot, tap threads into the holes at the ends, mount #4366 joining plates at the ends, and also set up the #3279 T nuts on them. The bolts that are being threaded directly into any tapped T slot, I'm using 1" bolts there, a little more thread bite can only be a good thing. The cross braces just drop right in, I got them cut 100% perfect length. If they were too long, I would of cut them back and shimmed if needed.
The going plan for now is to have just one of the upper cross members on the gantry to be a rail and carry the Z axis. I want a clamping force on the face of this cross member to press it against the front of the gantry as shown in the mock up photo below. The 2 hole plate is actually from the #4370 plate.
Gotta have legs. Cut some pieces of T slot to length, then secured a #4366 plate onto it, squaring it up nicely and using it as a guide for drilling. Center drilled first, but I don't remember what drill bit I used.... same size as whatever the holes are in the #4366.
With the base, the ends of the 4ft long pieces, I threaded the holes at the ends. I also have some #3320 T nuts in the cross members of the base. The legs will bolt in so that the 4 foot pieces and cross members at the ends are supported.
Of course off the shelf bolts are not a direct fit in a project like this, so a little cuttting here and there has been required. The cut bolts will go into the #3320 T nuts of the base cross members. The longer uncut bolts bolt into the threads that were cut into the end holes of the T slot.
Using more of the pieces that were cut from the #4370 plate, nothing goes to waste.... except the fact that the photo above showing me drilling the holes in the T slot for base legs.... I screwed up pretty bad and cut the legs too short, the gantry ended up being lower than the legs were as long. So 4 pieces wasted. While I plan on adding adjustable feet, for now I need to be able to set this thing on the ground. 10" legs cut, drilled and now bolted onto the base. Sad cat with extra toes inspects the new legs.
So here is what I've got up to this point:
I do have a racking problem, already purchased some cable, turn buckles and pulleys. I can sit on the gantry and it become the worlds shortest amusement park ride (and I've got more teeth than a whole crew of carnies that put the tilt-O-whirl together).
One thing I think I'm going to change are the #4366 plates on the y axis cross member. The plan in my head is to make something like the #4366, but that extends beyond both edges of the gantry. One side to the cross member like it already does, and the other end for a mounting point for the stepper motor and lead screw support bearing.
Speaking of stepper motors, I purchased my stepper motors, power supply and Gecko G540 from CNC Router Parts. There was a issue with one of the items when it arrived, I posted a video up on Youtube for them to see the failed part and a replacement was shipped out, no hassles. Thumbs up to them for good customer service.
pencilneck, you have a very unique guide rail for your bearings and I have to say I like it a lot. are you using drill rod, or cold roll stock? also how did you attach the guide rail to the alum frame.
i had considered using angle for my guides, but your round bar does save some height and of course weight.
Very nice, similar to what I did. My bottom length is cut a hair shorter as well, I use brass sheet stock you can by at the hobby store for my shims. How are you securing the rods to the 8020? I used 1" cold rolled stock and skate bearings for my XY axis, it was pretty easy to drill into the 1" stuff but that small diameter stuff might have been harder to drill.
Our builds are very similar with yours being about a 25% larger. I'm sure you will have great results. I'm very happy with mine.
When I first got the wild hair to make a CNC mill, I was looking at MDF... cheap stuff. But after reading several comments along the lines of "making 2nd CNC mill out of T slot to resolve issues of MFD mill", figured I'd skip the MDF go with the more stable/solid material.
Cost so far is about $1000 give or take a little.... that includes the stuff I purchased from CNC Router Parts. They sell 380oz-in Nema 23 motors. I haven't purchased a router or tools/bits yet. And I'm sure there will be some other items. I think when it is all said and done I will of spent about $1300-ish.
Plain round rod used. Drill rod would be better, but very costly. The linear bearing units hold the round round in place for now, but will somehow secure it better. Not sure how just yet.
The cat doesn't have any issues with it's extra claw per paw. It, and a black tailless cat are often inspecting the workmanship of my mill as seen in this load test:
If I had access to a tool shop and the skills to drill those holes accurately, I'd prefer that approach, but with the V block, wouldnt you need to unclamp and reclamp as you worked along the rod? How would you get each set of drilled holes perpendicular? Forgive me if I'm missing something.
but I wonder if this epoxy type of stuff might be an alternative approach - I'd imagine that if the 8020 was straight, then a decent clamping force would be enough to glue the steel rod into the gap nice and tight, and straight, too.
I have no experience with this type of adhesive either, so if anyone else has, please chip in.
Pencilneck, with the mill shown in your pics you should not have any problems drilling and c'boring holes into the round rod
#1--drill and ream a hole somewhere on the length of the bar, of course you will tram the bar to guarantee that you are in the center. keep in mind that this first hole is used for alignment only.
#2--once your alignment hole is reamed, insert the appropriate dowel pin into the hole and this will serve as a line-up pin to keep all of the following holes parallel.
#3--using a v-block or vice that you have centered on your table you can now place the round bar into your holding device and begin drilling and c'boring your mounting holes. Note; use a dial indicator to level the dowel (horizontal position)
#4--drill and c-bore holes per your design, using the indicator to level the dowel for each hole.
it sounds more complicated that it really is, and it does go pretty fast
OBTW--I only refined the round bar scheme and everyone should share the accolades for a group effort.