[mduckett]

When the motors came in, the X,Y axes motor mount brackets could be made and fitted to their respective bearing blocks and motors. Alignment of the motor shaft with the ball screw shaft is critical, and I wanted the couplings (Oldhams) with as little misalignment as possible. To align the motor shaft with bearing center when marking the holes for the motor mount brackets, I made a coupling shaft from 1/2" CRS, with a 10mm OD section and a sectoin supporting a ¼” hole in the opposite end to allow engaging the motor shaft and the bearing block together.
Then, to get the proper length for the motor brackets, the bearing block was assembled onto the ball screw and the coupler installed. The other half of the coupler was installed on the motor shaft and the two were mated together. Careful measurements of the spacing were then taken and the bracket pieces cut to length (errors here should be on making the bracket too long; too short and there is no way to correct it). The motor holes were then transferred to the brackets and the clearance holes drilled through. Unfortunately my design resulted in some clearance issues between the motor mount bottom and some of the bearing cover bolts in some places so relief was milled into the ends of the brackets to clear some of the bearing lid bolt heads, but eventually everything fit. Then, the ball screw was removed from the bearing, and the alignment coupling shaft put int the bearing and slid onto the motor shaft. The drilled motor brackets were put into position and the motor pulled tight and a transfer punch inserted through the mount bracket to mark the bearing block. I did one side at a time, drilling and tapping the 10-24 holes into the bearing block. With one side in place, the other side went quickly. The final thing to do was to bolt everything together and identify any areas that needed to be corrected (remember the .050 oversize to allow for some final machining to make things look nice).
The first two pictures show the coupling shaft fitted on the X-axis bearing and motor brackets, the last two pictures are the completed motor/bearing assemblies.

[luv2ride]

Nice write up and great looking parts. Keep up the quality of work and documentation.

[mduckett]

Nice write up and great looking parts. Keep up the quality of work and documentation.

Thanks!

[mduckett]

The Z axis bearing block evolved into a combined bearing block and motor mount as a result of playing with the 3D CAD models. I wanted to stay consistent with the X, Y bearings and use the 30mm OD dual row angular contact bearings for the Z axis also, so that helped define the size of the front portion. I also wanted a clean look, which meant that the block would need to match the column width and extend at least to cover the column stiffener. Once extended, it was easy to see the natural place for the Z stepper motor was to fit down inside the C-channel. With a little more modeling the distances between the motor shaft and the ball screw were known, so timing belt pulley and belts could be figured out. The first place to look at was Econobelt, but they don’t carry the GT-series profiles that are specifically designed to reduce backlash, so the pulleys and belts were purchased from B&B Manufacturing (bbman.com). Their online selection tool allowed specifying the pulleys and shaft center distances, and the tool gives the correct belt length, which was later verified perfectly. They also had 3D models for the pulleys, so that helped to improve the model. I also found a model for the bearing, so more fidelity was added. The final design is probably overkill, but I wanted to have two bearings to ensure stiffness in the belt drive, especially with the relatively small 10mm journal size. A modular approach was also desired to eliminate the need to machine a large blind pocket for the bearings. Therefore, the final design consists of a top, middle, and bottom layer. The middle is the bearing holder and basically holds everything together, and is two bearings widths thick. The bearing holder is a through-hole, so at least it is straightforward to make. The top piece retains the bearing outer race and at the back has the bolt pattern slots and motor shaft cutout for the Z axis stepper motor. The motor is mounted to the underside of the top layer and hangs down through a cut-out made in the middle and bottom layers. The bottom layer also retains the bearing outer race and forms the base that interfaces with the column top insert. Three @ 3/8” bolts are used to secure the assembly to the column top insert.

[mduckett]

The construction of this part is unremarkable except that it consists of large hunks of 4” wide aluminum that needed to be faced. I ended up buying a 4” vise, which looks ridiculous on a mini-mill and requires a mounting plate to lift it up to clear the rear column bracket, but it works great. I used 1 ¼” 6061 aluminum for the middle, ½” for the top, and 5/8” for the bottom. All were faced with a 1 ½” R8 carbide insert end mill, which passes for a face mill on this machine . The 30mm OD hole was plunged in the middle layer piece with end mills to 1”, and then I got my first experience with the boring bar. Except for needing to sharpen the boring bar, this went well by taking light cuts and checking often. I got really lucky though, as my cheap boring head has a lot of slop in the adjusting screw and near the end instead of taking off .002” as intended I got about .008” and somehow the hole ended up about .0015 oversize—perfect fit! Pure luck but I’ll take it. The rest of the parts had their features milled and the unit was assembled. A .020" shim was placed between the two bearings to relieve inner races, and another .002” shim was needed to make the bearings tight against the top/bottom pieces. The shims were bought from McMaster Carr. With the top layer removed and the middle/bottom firmly bolted together, the motor cutout was made. The sides of the cutout were band sawed and the end was then cut free using a ½” end mill. It took a while to get through almost 2” thick. Once separated, then the band sawed edges were cleaned up. With the functional machining complete, the front corners were band sawed with a radius and then smoothed on the belt sander.

Edit: I try not to revise history, and that means recording the screw ups that happen no matter how dumb. On the top side of the block (fourth picture) that recessed cutout is not supposed to be there--I got carried away and marked it out on the top side and then machined it out. It adds a little clearance for the pulley, but it's not supposed to be there--easy mistake to be on guard for--practice for the bottom side .

[BAMCNC.COM]

Great documentation of this!

[mduckett]

Great documentation of this!

Thanks for reading. I know some of the posts are painfully long, but hopefully they are useful at some level. Thanks again!

[mduckett]

After completing the Z bearing block and the column insert and stiffener work, the next thing to do was to drill and tap the three 3/8”-16 holes into the column insert to hold the Z bearing block in position. I had the locations of the holes from the CAD models, but I wasn’t comfortable just making the holes without doing a fit check, so the carriage assembly including ball nut and ball screw were slid on to the column and the gib adjusted. The ball screw was inserted into the Z bearing block and the 10mm jam nuts tightened against the bearing. The Z bearing block was then pushed down against the column top and clamped snugly with a long pipe clamp that reached to the bottom of the column. (The column was resting on it's back with the bearing block hanging off the edge of the table). The bearing block was snug but still able to be moved with some effort. With the right side of the bearing block aligned with the side of the column, the ball screw was dead straight down the channel in the column (this verified the CAD model and the location of the bearing center w.r.t. the ball nut center and axis for the side-to-side location). Next the bearing was moved up and down to adjust the ball screw parallel to the front of the column. With the carriage at the top of the travel I put a 1-2-3 block next to the ball screw and made a reference mark at the contact point, then checked the screw at the bottom end and adjusted the bearing position until it was the same in both places. The clamp was snugged and the ball screw could be turned by hand to move the carriage. It seemed to move smoothly, but it was taking too long so I chucked the end into my cordless drill and slowly ran the carriage to the bottom and then back to the top. The drill torque seemed pretty consistent so I called it good and used a transfer punch to mark the hole locations in the column insert, which was then removed, drilled and tapped for the three 3/8”-16 holes. With the insert re-installed in the column, the Z bearing block was then bolted on, but this is where I found that the bolts were too long by about 3/8”. I had tapped the holes to the limit of the tap, but they weren’t deep enough. So order new bolts, or cut these down? It took five minutes to cut the bolts down and then the Z bearing block was firmly attached to the column. One tip here—I used the minimum tap drill size because I wanted these to be very tight threads, and they are, but with aluminum there is the possibility of galling or seizing, so I used a little anti-size grease on these bolts. It’s nasty stuff, so use a small amount, but at least the bolts won’t get stuck. The attached show the Z bearing block and column with the belt drive and motor attached also for a fit check. Later, I had the left side of the bearing block machined to the exact width of the column as it was about .060" over size.
Edit: When I finally got around to trying the spindle with the motor attached on the column, there was interference between the Z bearing block and the motor. This wasn't a problem to correct as there was plenty of margin at the front of the bearing block. The CAD showed only about 1/8", but I made it about 5/16", no need to make it too close. That's why the front profile of the block is flatter than shown in the CAD drawings.

[mduckett]

With the work major work completed on the painted parts of the mill, I had to work in some time to re-paint the parts. The replacement spindle carriage was in that wonderful HF red and the new base came in with the cream color instead of the LMS blue. I liked the light/dark theme that LMS puts on their machines so I went to look for some similar colors at Lowes. They really didn’t have anything that close, so it was either mix and spray, or just buy spray off the shelf. I didn’t feel like a painting adventure so I picked out a cream color and a metal flake blue in Rustoleum. I have no idea if this paint will stay on over time, but it can’t be that inferior to the stock paint. The parts that needed paint were the spindle carriage and spindle box, base, round column support, non-crank table end, and the spindle belt/pulley cover.
All painted areas got lightly sanded, then everything got cleaned with Simple Green and rinsed well, and dried with paper towels. When dry the machined surfaces and any place that paint didn’t belong were masked off with blue painter’s tape. The tapped holes got rolled paper towel screwed in and sliced off flush with a razor blade. Some 2” wide blue tape really helped out with the larger areas on the base, and the rest used ¾” tape and some masking paper. I didn’t paint the top of the spindle box because it was very rough and really need some major work. It’s hidden anyway…. I used gray primer on the carriage because I was painting cream over the HF red, but elsewhere I just painted over the existing paint. Everything got two coats, and I let it cure for several days as it was pretty cold and my garage is only warm when I’m heating and I wanted it to be hard before touching it.
The new steel motor plate also needed some treatment but I didn’t want to paint it. The original came with what looks like black oxide coating. I remembered that I had bought some gun blue for a project so I tried it. I didn’t get anything that looks blue, but the resulting grayish tone actually looks ok and you only see the edges anyway. The attached are the results. I already scuffed the spindle front a little but oh well, it looks a lot better than before, especially getting rid of that HF red. At some point I might need to paint the electronics box, we’ll see how bad the mismatch is. May need to do something with the column stiffener too, but I’m done painting for now.

[mduckett]

I didn’t want to spend much on an enclosure to house the power supply, breakout board, and stepper drivers. That’s pretty hard to do, but I found a barebones PC case at geeks.com for $13 with $12 shipping—sold! In hindsight, I should have just gone to the local landfill where they have a dropoff for electronics, and there are always tons of junk computers in there (I’ve put two in there over the years) and it would have been better than what I bought and free. The case arrived and I think the cardboard box was stronger than the case. It is really flimsy, but I had to add some structure for mounting the various hardware anyway so it worked out ok, and at least it looks good. I saw a guy on YouTube (CNC G0704 Part 2 - Assembling the Control Box - YouTube) doing almost the exact same thing I was planning so I copied his idea of attaching Plexiglas to the case bottom as a mounting surface, and I also installed an inside layer for the whole back panel. I had also purchased the same 4-pin XLR connectors shown in the video for the x,y,z drive and limit switch connections. The connectors came from UGRA CNC, but later found they can be had for about $1.50 each or less on ebay straight from China with free shipping (search for "aviation connector" on ebay). For wiring, I had access to a lot of scrap CAT5 bury-ready cable and it looked good, with black, tough cover, but alas it turned out to have solid wires. I made up some cables with it before that fact sunk in, but after reading some other posts on cabling I finally realized that with flexing/vibration solid wire is very prone to breaking over time. Also, the ampacity of the 24 AWG wires, even paired up as I was planning, is very nominal at the upper end of my setup (3 Amps/phase). So after a lot of searching I found some 4 conductor 18 AWG stranded wire with a tough black EPDM sheath for $0.43/ft at wesbell.com and I ordered 40 feet. The jacket is called SJOOW, which means oil, solvent and water resistant, and its extra flexible—seems perfect for the CNC environment. This is not shielded cable, so we’ll see if that becomes a problem. The connectors strain relief clamp will be tight, but should be ok. If too tight I will cut it back, heat shrink the clamp area, and then heat shrink the cable and back part of the connector with large tube to seal and stiffen it up.
The build up in the box is pretty straight forward, just install the Plexiglas bottom and back pieces, then layout the locations for the components. I drilled most holes in place, marking with a Sharpie. While the Plexiglas is convenient, it can be trouble to drill, especially larger holes. I used a 5/8” Forstner bit to drill the connector holes. Use some oil and compressed air to cool it (or just blow on it like I did) and clean the bit between cuts as the plastic will melt onto it. I used a hole saw for the large hole for the power strip, make sure to drill half way from both sides for a clean cut. The breakout board slot through the Plexiglas in the back was a real pain—I drilled holes in the ends and used a coping saw. If you have a scroll saw this would be a simple cut. I also had a large round hole too big for a hole saw to cut out for the fan, also done with the coping saw. Making straight cuts for length in Plexiglas is easy, just score and support along a sharp table edge with a piece of wood or a straight edge and snap off smartly. You can also cut it with a saw. The pictures are the box with the CAT5 wiring, soon to be changed out as I got the new cable a few days ago. The power supply is mounted on two painted wood rails in the bottom using some aluminum angle and the wood is screwed down from outside into the bottom with black 1” drywall screws. Went to Best Buy and there was an open box LED case fan for $3, so why not?, it fit perfectly and jazzes it up a little. To accommodate the the various items that need AC power, I decided to install a power strip onto the top-side panel and place it so it can be operated by reaching a finger in through the same hole that its cord comes out. This way I only need one AC hookup to the outside. I built a small 5 Volt regulator to supply isolated 5V power to the CNC breakout and drivers and plan to have it share power with the fan's 12 volt wall wart, which is also plugged into the power strip.

[TroyO]

I like the way you explain not just what you did, but in many cases *why* you did it that particular way.

I'm going to be starting a SX2-ish cnc thingamabob (LOL... I have some SX2 and some X2 parts) here soon and I fully intend to steal a lot of your ideas. ;-)

[mduckett]

I like the way you explain not just what you did, but in many cases *why* you did it that particular way.

I'm going to be starting a SX2-ish cnc thingamabob (LOL... I have some SX2 and some X2 parts) here soon and I fully intend to steal a lot of your ideas. ;-)

Thanks for the comments, and glad if the thread can be of use. I've committed more than my share of "theft" from these forums , so I'm happy to pay back something. Good luck with your build, hope you plan to post your progress.

[mduckett]

After convincing myself that I need to have limit switches, I searched around for some ideas on how to mount them. I saw an installation I think on Bob Warfield’s CNC CookBook website where the X-axis limit switches were mounted to the front of the table where the table power feed switches are normally mounted. I like the simplicity of the cabling and also that one housing/mount handles both switches, so I used this design concept for the X-axis. For the Y-axis I just made some half size, single switch versions of the X-axis switch housing. The switches are standard snap action micro-switches, and the CAD models for them are available at McMaster-Carr, making it simple to model the housings. Each switch/housing has 4 basic parts: housing, plunger retainers (cylinders), plungers, and lid. The drawings show how it is assembled and how the potato masher shape of the plungers works to push on the switch lever, and the retaining cylinder acts as a bushing/guide for the small shaft of the plunger, and the wide end of the plunger keeps the plunger from falling out. The design intent is to have a plunger that can't over-travel and break the switch, and also can't pull out, and use the spring action of the switch lever to return the plunger to the un-actuated position. The plunger shafts will be cut to length so that at full travel they are flush with the outside face of the retainer. Housing and retainers are aluminum, the plungers are brass, and the lid is Plexiglas. While functional, these didn't turn out as compact as I had hoped, and they are kind of odd looking, but I figure I can design and make something better with the CNC later.
As you can see my milling skills are a little inconsistent but the parts are functional. The retaining cylinders were turned and die-threaded 1/4"-20, and the housing drilled and tapped to accept them. Since the thread area is so short on the retaining cylinders, my friend RT had a tip; use the die in the normal position as far as it would go, then turn it around and it will get cut a little more thread as the back side of a die doesn’t have the tapered entry shape and will cut a little more thread. Still need to make the actuator stops to install in the front slot of the table for the X-axis, and drill the holes in the housings to pass in the cable. I’m waiting a bit to see if a side or bottom hole is better depending upon the cable routing.
I ordered six switches from Mcmaster-Carr along with some #2-56 x 3/8” screws to install the switches and also to fasten the lid, and some 4mm x .7mm bolts to mount the X-axis switch box to the front of the table. Also bought some #4-40 x ¾” to mount the Y-axis boxes (bought #4-40 nuts and washers also and used some of these for mounting the CNC electronics too). Bought a couple #2-56 taps on ebay as my set only had down to #4-40 size. The lids will be sealed with silicon. Switches for each axis will be wired in serial using the normally closed (NC) position of the switches. The Y-axis switches will be mounted apart, with one attached in the back to a rib on the round column support bracket (under the way cover), and one to the side of the Y-axis bearing block in the front (also under a way cover).
I haven’t figured out the Z-axis switches yet, so I think I’ll wait and design/make those housings using CNC when the mill is up and running, and just temporarily mount the switches initially.

[mduckett]

I have looked around a lot for low cost way cover solutions and it seems that the simple solutions such as rubber sheeting, rubber bellows, and home-made metal arrangements are the most often used. I believe that the existing rubber bellows on the Y-axis are sufficient for this mill, possibly with some additional side shielding. I am strongly leaning towards replacing the front rubber bellows with a rigid plastic or metal solution that can extend back over the motor also. For the X axis, I’m not sure if anything is required. Maybe a flare “skirt” around the table could help divert coolant/debris away but I think the screw and ball nut are pretty well protected underneath.
The Z-Axis is probably the most challenging. I already bought an extra piece of the rubber bellows from LMS. It can be installed as a vertical shield in front of the ball screw but it may need to have some guide rods punched through on each side to keep it from folding forward into the work area or backward into the screw. Also thought about using the Z-bellows part from a G0704 but I’m not sure of its width and length—maybe one of the G0704 guys can help out with dimensions and comment on whether it would work on an X2 column? The front edge of the ballscrew is about 1.4" in front of the column.
For stepper motor covers I’m thinking about either a Hoss type of bent thermoplastic cover, or maybe a cover made from that clear vinyl material used in some packaging. For example, I saved a clear square tube from some blinds packaging that is about the right size. If that will shrink/form with heat, it will be interesting to see if that kind of tubing can be made into a lightweight cover.

[mduckett]

So this thread has finally caught up to the realtime status of this conversion, which means I can start getting some sleep again. It’s been well over a year since this project started, and about 3 months since the mill cut its last chip . I’ve been trying to finish up all of the odds and ends (I could get a lot more done if I didn’t have to work). So this is the final stretch, ready to get the mill put back together with the CNC elements installed. The laptop has Mach3 installed and I did a single axis motor test a while ago and that went well, so it's pretty much a matter of keeping the energy going to the finish line. To get organized I made a checklist to list out the remaining tasks in detail. The following is a more general plan forward listing the things left to do to get this little beast up and running. I'll issue posts to track the progress on these areas:
1) Finish up re-packing the ball nuts with oversize balls. To date I’ve been experimenting with re-packing the ball nuts with .1256 balls for the Z axis (the one that had stock .1250 balls to begin with). I tried some .1257 and they were ok but had a couple repeatable spots where I could detect some binding. Repacked with .1256 and this feels smooth throughout. Bought two packs of the .1256 and one of the .1255 size to allow fine tuning the x,y ball nuts also. These came with .1254 balls from RBS and I measured the backlash on these to be about .002”, not bad but probably can be improved. My initial method for measuring was not the best either so that will be improved. Need to finish up the X and Y-axis ball nut repacking.
2) Finish up the column-related items including making the triangular column braces that sit on the two flat areas on either side of the column. These areas were milled flat so I can bolt down a gusset plate to stiffen the column. The plan is to make the L-shaped braces by splitting a piece of 2” x 6” steel tube diagonally to make a pair of brackets. This tube has ¼” walls, so plenty of thickness to allow milling the outsides flat (and shiny) and to sharpen up the corners, which are radiused. Plan for 2 tapped holes into the base and two in the column on each side. Another column item is a mount for the spindle “backpack” electronics box. The channel stiffener and the z stepper motor are now in the old mounting location so need to fab some brackets for that.
3) Finalize plans for way covers and stepper motor covers make/modify the parts as required.
4) Figure placement of the CNC electronics box and the wire routing for axis cabling and limit switches and EStop. Also figure out the mounting scheme for the laptop computer and location.
5) Assemble the mill—all aspects mechanical and electrical, when complete the mill should be ready to do some work under computer control.
6) Finish the mill enclosure using already purchased aluminum channel and install Plexiglas panels. Also finish up the flood system.
7) Begin test trials and post lots of videos.:cheers:
8) Start planning follow-ons, including power draw bar, ATC, and 4th axis.

[109jb]

The G0704 Z-axis bellows is about 4.7" wide and 1.4 " high. The back side of the bellows cover has some plastic tabs that ride in the dovetail and keep the bellows tight against the column. The dovetail is about 3.1" wide and 0.6" high. Hope this helps.

[mduckett]

The G0704 Z-axis bellows is about 4.7" wide and 1.4 " high. The back side of the bellows cover has some plastic tabs that ride in the dovetail and keep the bellows tight against the column. The dovetail is about 3.1" wide and 0.6" high. Hope this helps.

Thanks for the info. Sounds like it could work with mabe a spacer behind it, cost from Grizzly spare parts is ~ $30 delivered, so not too bad.

[hoss2006]

Excellent work so far, Kudos!:cheers:
Hoss

[TroyO]

I ordered some of this bellows material from McMaster and was pleased with it....

McMaster-Carr

Item #
1320K34

It's a woven nylon material that's slightly stiff. If collapses well (better than the stock rubber) and is a decent replacement. You can cut it with scissors but it's held up fine on my X2.

That being said... I'd want a better sealed environment on a CNC machine if possible.

I'll be interested in what you come up with.

Have you given much thought to the coolant systems? Mist, flood etc? (Edit: LOL, never mind... went back to page 1 of the thread and said 'Doh! Flood it is... )

[mduckett]

Excellent work so far, Kudos!:cheers:
Hoss

Thanks Hoss!