WoodWorkerB CNC Router Project

Cable Tray Details

2011-05-11T19:08:00.000-07:00

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Here are the details for building the cable tray. You can 'futz' with these dimensions. Make the angle sharper for a tighter turn, make it wider, narrower, whatever suits your design. I started by ripping two lengths if 1/2" plywood to a width of 1 1/2 inches. I ripped two equal length strips of 3/16" hardboard to a width of 1 1/4 inches. I glued-and-clamped the hardboard strips onto the 1/2" plywood, forming a U-shaped 'trough'. In the drawing you can already see how the tray will fold. However, just adding the "duck cloth" at this point will allow the tray to curve neatly as desired, however it will 'collapse' when it is upside down. To avoid this, cut the other 1 1/2 inch strip onto segments exactly as long as each of the tray segments (2 5/8" in my case).
These small segments are screwed to the "bottom" of the tray - this will prevent unwanted bending in the "wrong" direction when the tray is suspended upside down.

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Once the glue dried, I set the blade on my table saw to 20 degrees and cut the assembly into the smaller segments.

Cut a long strip of duck cloth 1 1/2" wide. I lined-up all the cable tray segments and secured them between two boards so the wouldn't move during the gluing step. I coated the underside of the tray and one side of the duck cloth with contact cement. Once dry per the instructions, gently stretch the duck cloth and glue it to the tray. Two people works best here.

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In this photo I put together one segment to demonstrate the "sandwich" of materials. The duck cloth is bright orange. The bottom piece is carefully lined up and held in place with a #6 x 3/4" wood screw (no contact cement).

A small bit of bent coat-hanger completes the assembly.

Check this post to see the completed tray.

Configuring EMC2 for Limit and Home switches

2011-05-08T21:01:00.000-07:00

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Responding to a question, here is how I configured the EMC2 software for "All Limits" and "Z Home". The configuration for the inputs is in the Stepconf utility. In the upper image is how my system is wired. The pin numbers I selected follow the wiring recommendation from the HobbyCNC site.

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Select the desired input pin(s) and choose from the pull-down the feature(s) you want enabled (lower image).

For my setup, I currently only home the Z axis to pin 12 and I have all 6 limit switches wired in series to pin 10. Soon I hope to have homing set up for all 3 axis.

Y-Axis cable management

2011-05-08T18:06:00.000-07:00

I didn't have the room for a nice cable-tray like I made for the X-axis. A simpler approach was to use a scissors-type of assembly that just kept the cables neat, yet out-of-the-way. I ran both the stepper cables and the router power through this arrangement.

At each joint of the scissor is a 3/8" OD nylon bushing, cut just slightly longer than the material thickness to avoid binding the joint when the nut is tightened on the screw. Click on the image to see a larger version. All 3 joints are made in a similar fashion, with the length of the nylon bushing and the 8-32 machine screw adjusted to fit the materials and washer thicknesses.

After the first test, I realized there was no good way to support the cables, so I made the 8-32 machine screws a bit longer and added a wire loom clamp between the nut and the last washer. I sized the clamp large enough to allow the cable to move freely.

It seems to work great.

Opto isolation board

2011-04-30T10:45:00.000-07:00

Keeping the nasty outside world away from the HobbyCNC driver board is important. I made a simple 5 channel isolation board - to match the 5 inputs on the HobbyCNC board. At the right is the wiring diagram from the Hobby CNC website showing the 5 inputs and limit/home switch wiring.

Here's the schematic. 12 volts in is fused. Opto outs go straight to the HobbyCNC board. The Zener diode sets a 4.7 volt reference which each of the PN2222 transistors uses to create a basic constant-current source of approx 20ma. This allows me to add up to 3 extra LEDs in the circuit without having to worry about changing any resistor values.

Board design is very simple, single sided - which is why the SMT opto isolators mount under the board. I used isolation routing on my mill to make the PCB. I never got around to puttng the actual resistor values in the schematic. If you are interested, drop me a note and I'll go write 'em down for you.

Z-axis homing & opto-isolation board

2011-04-28T21:18:00.000-07:00

It is always uncomfortable bringing logic-level signals outside of the "box" and into the real world. Any excess voltage can wipe-out your stepper controller board - and since the inputs are fairly high impedance, these lines are very susceptible to induced noise - especially from the nasty spikes caused during the driving of the stepper motors.
I designed a 5-channel opto-isolator board to keep the ugly outside world away from my HobbyCNC controller board. I designed the board to run from around 12 volts, but I added a constant-current source to each input line. This ensures 20ma flowing through the opto isolator LED. The added benefit is I can add extra LED's to the 'chain' without affecting the signal and I can safely run the limit switch wiring through the same wiring harness as the stepper motor cables with no fear of interference.
I added a yellow LED on the board for each of the 5 inputs - this allows me to verify an input is working without needing to grab a voltmeter. The constant current source also allows me to put another LED out where the work is done.
To complete the board is a green power LED and a fuse. In the images, the opto chips are actually surface-mounted on the underside of the board - the one lit yellow LED is for the limit switches - this tells me all 6 limit switches are closed (good).

I created a special rig to set the z-axis home. It uses an alligator clip and a precision brass 1/2" square bar. I added an LED in the bar so I can confirm all is good before I press "home". Any problem with this setup and the system will drive the tool into the workpiece - a real big issue if using small drills for PCBs. The short video shows the Z axis home setup being tested to confirm continuity, then the video shows the opto board during the same test.

The new build - the base

2011-04-21T22:46:00.000-07:00

I kept the base design similar to the original - using a torsion box design. This provides a considerable amount of strength and rigidity with minimum mass. It is important to have a very flat surface to assemble and glue-up the frame. Even with all the care, I ended up in excess of 30 thousandths out of square. This is excellent accuracy for a woodworking project, but it is not all that great for a milling machine.

Taking care at every step means less fine-tuning later. Cut the components carefully, make sure to get the angles as square as possible. Ensure the top (facing downward in these images) is flat-and-true against your flat surface.

Here is the finished torsion box. I changed the design of the x-axis rails - both to provide extra strength and rigidity, and to get the x-axis rails inset just enough to keep them out of the way of most of the dust and debris created during milling.

Cutting Guide

2011-02-17T19:35:00.000-08:00

I slept on the design - no changes. Here is the cutting guide. The whole router will fit neatly on a single 4x8 foot sheet of Baltic Birch 3/4" plywood ($64 USD). I chose this plywood for a couple of reasons. First it is a good looking wood. It has a furniture-grade finish on both sides, no knots, no blemishes. Second, it is made up of many more, thinner veneers. On this website: www.leebarry.com is an excellent photo of "regular" 3/4 inch plywood next to the nice stuff. More layers, better strength. Also no ugly 'voids' in the inner veneers when you cut it. Sand the edges, some polyurethane, and it's damn good looking. 3rd, I just like the idea of the CNC machine being made of wood.

Preparing for complete redesign

2011-02-15T18:29:00.000-08:00

One learns so much from the "first time around". I plan to take what I've learned, go a bit slower, use better materials (like 3/4 inch Baltic Birch plywood) and add the things I was missing - like limit switches and some better resistance to torque. Here's the new design. It's all on Google Sketchup in the event anyone wants a copy. Just add a comment or send me an e-mail WoodWorkerB (at) gmail (dot) com. Here's how the new design will look.

The new design provides additional strength (due to material selection), higher quality assembly practices, recessed lower bearing races (to hopefully minimize the amount of crap that gets on the bearings).

I am considering incorporating small brushes on the bearings to keep them somewhat clean.

I will "tear apart" the drawing and create my cutting guide. I plan to start cutting and assembly this weekend.

Recent addition - a UPS

2011-02-09T21:14:00.000-08:00

Simply plugging in my welder caused a power glitch in the middle of routing a PC Board - the glitch caused the computer to re-boot. I was not happy. I decided to purchase a Uninterpretable Power Supply from APC. It only provides 10 minutes of backup - but that's plenty to make it through the occasional power glitch and even the careless tripping over the power cord. I have both my CPU and monitor powered via the UPS. The mongo power supply for the Steppers can ride through powerline glitches with ease.

I also isolation-routed another PCB, this one a simple linear-regulated 12VDC power supply to drive the case fans. I was much more comfortable with Eagle CAD this time around. I set up the raw PCB, hit "GO" and came back 45 minutes later to have it all perfectly done. Sweet!

Upgrading Ubuntu & EMC2

2011-01-17T21:25:00.000-08:00

This weekend I upgraded from Ubuntu 8.0.4 to Ubuntu 10.04 & EMC2_2.4.4 Release. The install went without a problem. However, I couldn't get the steppers to move. I recall having parallel port configuration issues the first time. I wasted 4 good hours of shop-time with no success. Then the proper information turned-on the light for me, and all is working well. This page on HAL drivers did it for me. I mistakenly thought the "in" and "out" parallel port settings meant the parallel port was installed (in) or not (out). Since I was using an add-in parallel port, I was attempting to set parallel port 2 as the port to drive the steppers. Wrong.

The "in" and "out" refer to the signal directions of the parallel port (I wanted "out"). Here's a hint how to find the address for your parallel port setting (the 'stuff' after the "0x").

The cable track

2011-01-15T08:26:00.000-08:00

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It is frustrating having to keep your wires out of the way of the moving parts, especially if you are in a hurry and just leave your wiring laying about. I experimented making a cable tray. The results are pretty good. The tray is made from a 'sandwich' of three parts, the tray itself, a layer of canvas-like "hinge" material and a plain flat bottom piece. The flat bottom piece prevents the cable tray from collapsing downward when it is up-in-the-air.

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The cable tray is in use, and is working as intended. Let's see how it holds up to the environment.

Update: Check this posting on Cable Track Design for drawings and details on assembly.

New Router Table as-is

2011-01-14T21:37:00.000-08:00

Here's how the stand looks so far. Only two drawers, but it covers the basics. I've got the keyboard/mouse tray and computer/control electronics. I left room around the router table for an eventual plastic cover to control dust and noise.

A large challenge was mounting the monitor - I wanted it convenient, but not in the way of the plastic dust cover. I decided to mount the monitor on top of an extra length of steel pole I had around. Consider using a heavy-duty closet pole from Home Depot. You need to make sure that the power and video cables will fit through the tube first!

Monitor Mount: I made the monitor mount from a couple of scraps of plywood. The bottom and middle parts are bored-through with a 1.5 inch hole (the same diameter as the support tube). The top hole is a 1/4 inch smaller. This design allows the cables to be fed through the center of the tube and for the monitor to spin 90 degrees so it's out of the way during storage. There is a similar block under the surface of the table to support the tube.

Electronics Drawer: The drawer is roomy enough to hold the computer, power supply for the steppers and the stepper electronics. I added a master "mains" switch and a switch to control the router to the front panel. Also a big "stop" switch (Rockler) at knee height - for those times when things don't go as planned.
Hitting "stop" kills power to the router and to the stepper motors. A pair of filtered, computer case fans provide positive pressure to (hopefully) keep dust out of the drawer. An aluminum cover sits over the drawer.

New CNC Router table

2011-01-12T11:50:00.001-08:00

I need to re-build my CNC router from scratch - taking into account all I learned during the first build. I decided to start with a stable, portable stand that would house the computer and electronics in a clean, safe space. I went with a simple MDF carcass with drawers. The computer drawer would contain all the electronics and would be positive-pressurized via two filtered case fans.

I can provide the sketchup drawings for the stand and the cutting guide if you're interested. Just drop me an email at woodworkerb [at] gmail [dot] com. The core case is built and the electronics installed. Not all the drawers are made yet, but that's coming - I am tired of leaving tools & such laying on the router table - just begging for trouble.

2010-12-17T22:57:00.000-08:00

I noticed a problem when I tried to machine two "mirror image" parts, and when I tried to match-up the parts, they would not align. It seems my router was built out-of-square. I have decided to completely re-build the router, taking my time, and making sure all the parts are square. Before I make the new router, I needed a solid, mobile table on which to hold the router, PC, power supply keyboard and some extra storage. I will provide the plans and images of the table.

Fifth time is the charm!

2010-07-05T15:08:00.000-07:00

My 5th attempt at isolation milling the PCB was finally a success. After experiencing just about every failure mode, here's what I learned.

First, be sure you've calibrated your milling tool. See "Calibrating PCB isolation routing with Eagle/pcb-gcode" by Poul-Henning Kam. He created a simple PCB design that mills traces of a particular width across from isolation paths of the same width. Compare the two - if they are the same width, you are good to go. If they are differing widths, then your bit is either too deep or too shallow.

Second, is your table surface 'flat' in comparison to your milling tool? Mine was out by just under 2 mils, which is a lot, considering 1 oz copper is only 1.4 mils thick. To test, I took one of my mill bits and inserted it upside-down in the Dremel. I moved the tool to each of the four corners and found the highest corner. I use an axillary 9 x 12 inch "sacrificial" board to which I attach my PCB stock to - with double-sided tape - so that any drill-through would not damage my router table. To the underside of each corner of the sacrificial board I added 10-32 tee nuts, countersunk slightly. Into each I used 10-32 x 1/2" set screws with a hex-head. Update - a machinist friend of mine advised me to have have two set screws on one side and only one setscrew in the center of the other side - forming a tripod. This makes adjustment super-easy and much faster than one adjustment screw in each corner.

I repeated the leveling exercise, again starting at the highest corner, and using a feeler gauge - update: I have since converted to a dial indicator - about 10x faster - I lowered the set-screws until each corner was lifted to the proper height. I kept gentle clamping pressure on the board so it wouldn't move during the leveling process. The thickness of the feeler gauge is not important, just use the same thickness gauge everywhere.

Finally, align the PCB square on the routing table and test by moving the X or Y axis along one edge of the board - I use the point of the router bit as my reference. Adjust the PCB (carefully) into square. Update - it is important to adjust the PCB to be 'square' against the path of the router, not square to the table as shown here.

Now we're ready to route.

Next post I'll cover what I learned on the Eagle CADsoft PCB design software.

PCB isolation routing - attempt 2

2010-06-26T18:12:00.000-07:00

Much better results this time. Milled-and-drilled with excellent results. I decided to switch from my 1/4" router to a Dremel tool - this required a new mounting bracket. Naturally, I used the router table to make the new parts. The process is starting to get easier. I routed two brackets from 3/4" MDF and glued together.

I carefully added the mounting holes so I can easily switch from the router mount to the Dremel mount with only 4 bolts. Works great. Another benefit is the Dremel is considerably less noisy than the router, and the Dremel runs cool the whole time. Running a homeowner-quality router for an hour gets scary - you can smell the varnish on the motor windings getting hot.

Added a saw kerf and a bolt to "pinch" the Dremel into place. Like a rock.

Here's the Dremel mounted.

I secured special 1/8" milling bits from DrewTronics. It was the 1/8" shaft that made the Dremel the easy choice. I ordered 30, 45 and 60 degree bits with the idea to play with them all over time. I had to throw 'em under the microscope - here is a 45 degree bit at 20x magnification.

Routing went perfectly. Tooling still a bit to deep. Milling time was shortened considerably by using the gcode optimizer.

After routing, I decided to try drilling too. Snapped the first bit after drilling the 4th hole. Checking the setting of the gcode converter - I found one setting at zero inches - this caused the tool to move to the "home" position for a tool change, but didn't lift the drill out of the PCB first! Changed the number to one inch, and it worked fine, returned the router to the 0,0 position, raised an inch for easy drill changes.

Drill bits are from Jameco and seemed to do an excellent job.

Here's some of the traces at 20x magnification. I did nothing but scrub the board a little with a Scotch scrubbing sponge - no abrasives, no sanding. Was able to get a trace between two 0.100 inch IC pads.

Next I'll ring it with a volt meter, and if all is good, actually build the circuit.

Gcode optimization

2010-06-23T20:46:00.000-07:00

I tried the Opti - PCB-Gcode Optimizer from JayC. Tried it on Ubuntu under Wine (Windows emulation), it opened, but wouldn't do the optimization. Had to resort to MS-Windows to run the optimizer. Seemed a bit finicky, but once it ran - WOW what a difference. To the right is how the gcode looks coming straight off the Eagle CADsoft program. Click the image to zoom. All those grey-green lines are where the router is moving in between milling actions. The damn thing spends 60% or more of it's time just moving the router from point A to point B.

Enter the optimizer. DAMN! I'd say 95% of the wasted movement is just GONE! This should have an amazing impact on the overall time to mill.

Now if I only knew enough about C++, I could probably re-compile onto Ubuntu!

I ordered some PC milling bits (30, 45 and 60 degree) from Drewtronics. I should have them in a few days. My router is a 1/4" shank, and these itty-bitty PCB router bits are 1/8" shank. I'll need to track down a reducer.

PCB isolation routing with a real PC board

2010-06-21T21:50:00.001-07:00

I did not have the proper milling tool. I had a pointy router bit (60 degree) that is supposed to be used for engraving wood. Fiberglass and copper was too much. Nevertheless, the results were very promising. The router bit was more like a snow blower, just heaping the copper up on each side of the trench it dug.

Here is a close-up of the IC pads. It's tough to see, but it is pretty much a mess. I went at it with some 220 grit sandpaper to get rid of the bulk of the nasty high spots so I can get a peek at what was underneath.

To the right is a 20x image of some of the pads for a .100" header - after sanding. I pulled the board off the router before the pads on the right were finished. I also think I had the bit digging-in a bit too deep.

At the left is a 40x image of one of the IC Pads. In both images, even after sanding, the "piling up" of the copper around the edges of the trench is clear.

Couple of early learnings: The cool dust brushes I made obscure the PCB. This isn't a problem for routing, but it makes setting up the tooling a real nightmare. I've got to re-design the brushes such that they are either fully or partially removable.

Second, the CADsoft to gcode converter does an excellent job, technically, but the resulting gcode is very far from being optimized. I'd estimate 40 - 60% of the time to route the board is the router moving from one end of the board to the other. More than half the milling time is just plain wasted.

Next Steps: Order some real router bits. Consider using a dremel tool rather than a wood router. Try to make a gcode optimizer that I found work.

PCB isolation routing - first attempt

2010-06-19T12:48:00.001-07:00

Last night I downloaded CADsoft Eagle schematic drawing and PCB design software. Learned just enough to make a basic board. Used an Eagle to Gcode converter and created the gcode.

Tie-wrapped a rollerball pen in place of my router, added a flat (MDF) auxiliary table on the Router base, got the paper flat.

Started the EMC software, opened the gcode file. It looked perfect with a "rats nest" of jogs. I set X and Y to home, set the touchoff, and hit 'go'. Board is about 2.5 by 2.0 inches.

Son-uv-a-gun. It did pretty damn good. I am pretty sure I had some of the feed rates too high, and I think I skipped a step or two. Nevertheless, I was blown away. It takes a L O N G time to route. One key learning: keep as much copper on the PCB as you can!

Here is a close-of the bottom left of the PCB. The holes are marked quite well in the pad centers. This was not the case everywhere, though. Next time, I will slow down the steppers.

This will make prototyping PCBs fun, clean and fast (faster than the chemical options!).

I will document my complete setup and experience.

Here is a 73 second video of the CNC machine drawing with the roller-ball pen. You can see the pen flex and the paper move - these are, no doubt, large contributors to the inaccuracy.

Software - Introduction

2010-06-16T21:06:00.000-07:00

The Software. Now this is where things get confusing for me. CAD this and CAM that. I have successfully milled some parts, but I've not yet figured out all the bits.

For the CAD software, I stick with Google Sketchup. Sketchup is a really amazing product. First, it's free. It is 'easy' to learn (for a 2D CAD package, anyway). There are a lot of great tutorials available. I used Sketchup to create all the CAD drawings for building the router, and all the drawings I posted to this blog. Since it's free, you can get your feet wet while preserving some cash.

For the CAM software, I am playing with the demo (40 uses) version of CamBam. The CamBam website says it best: "CamBam is an application to create CAM files (gcode) from CAD source files or its own internal geometry editor".

There is also a free add-in for Google Sketchup that will cleanly export a Sketchup drawing into a format ready for CamBam.

Take some time to read the three-part software tutorial by Patrick Hood-Daniel on his buildyourcnc.com website.

There is a lot to learn about the CAM software, and I'm only just starting. I've found the CamBam documentation to be very weak, almost useless. I did most of my learning by trial-and-error.

For the machining software, I am using EMC (Enhanced Machine Controller). From the EMC site: "EMC2 is software that runs on Linux, on most standard PCs, that can interpret G-code and run a CNC machine." In my case, I use Ubuntu. I had an extra PC, the EMC software installed and ran first time, no problems. EMC plays perfectly with the HobbyCNC stepper driver board.

On a side note: If you have not considered a Linux system, Ubuntu 10.0.4 is amazing. It is quite Mac-looking, fast-as-hell, robust and stable (my server ran for well over a year with zero issues). And with a product called Wine, you can run most windows applications. It's pretty sweet.

I do suggest you use a separate computer to drive your router. It will suck in dust and crap like you won't believe, and you'd hate to trash your home PC. I open my PC regularly and blow out the collected dust and debris. One challenge, is finding a PC with a parallel port, which is required for the HobbyCNC stepper controller. Most new laptops don't have a parallel port. My Ubuntu system had no issue accepting a parallel port card, tho I do remember having a challenge finding some I/O port address or other. But once I figured that out, all was well.

I hope to give some tutorials or other helpful guidance on getting these three products playing together nicely, but time is a rare commodity at the moment.

Dust Control - making the brush

2010-06-16T20:29:00.000-07:00

I settled on the idea of a 'brush' or at least 'bristles' for my dust curtain. I couldn't find anything ready made, so I made my own. Works pretty good, and I'm confident when I upgrade to dual 2" vacuum lines, it'll be smokin'. I started by taking pliers and tearing out the tufts from a Harbor Freight workbench brush.

Try to carefully yet securely grab the entire 'tuft' of bristles with the pliers and rock the pliers to pull out the 'tuft'. Some will get messed-up. Keep going. It takes a hell-uv-a-lotta bristle tufts.

The Harbor Freight brush had a neat little staple like gizmo around the 'tuft' of bristles. This came in very handy when inserting the tufts into my motor mount.

I tried drill bits in the holes left in the brush to determine the proper hole size.

I flipped the motor mount upside down and put holes around the perimeter of the router in a highly un-precise fashion - just guesstimating the spacing.

Then I took a small nail set, and with a file, put a very slight "V" in the end. I would open the bristle bunch a bit, line the "V" of the nail punch over the small metal staple, align it with one of the holes I just drilled and smacked it with a hammer. Repeat until you start talking to yourself.

To the left is a close-up of the bristles in the motor mount. It actually worked quite well, and the bristles are held in quite firmly.

I didn't count 'em, but it took a lot of the little buggers to circle the router and dust port.

Dust control - the background

2010-04-06T22:00:00.000-07:00

If you haven't used one of these devices, there are two issues you will need to deal with - noise and sawdust. And these routers produce both in ample amounts. The noise can be dealt with using hearing protectors. IMPORTANT SAFETY NOTE: eye, ear and dust protection is mandatory. You may feel like a goober wearing all this protective gear, but at least you will still be able to see and hear and you are less likely to cough up bits of your lungs years from now.

Regarding the dust, goodness only knows what carcinogenic crap is in that stuff, and these machines produce a lot of very fine particles - I'd bet these are the most dangerous.

I needed something that would include a vacuum system, and there had something that would enclose the router bit, extending all the way to the surface of the workpiece. Upcut spiral router bits really sling the sawdust - somewhere between a speeding bullet and the speed of light.

I am a firm believer in intercepting the dust as close to the source as possible - especially considering my garage is attached to my house - and all that fine dust will work it's way inside - and my wife will find it - and I will be in deep, deep sh_t.

Whatever I used needed to be flexible - it has to bend against the work surface when the router cuts deeper. It had to be firm enough to not get sucked into the router bit or the vacuum system.

I've seen some builders used a 'skirt' around the router mount, others suggested brushes (called 'door sweeps'). Yet others just put the whole-damn-thing into an enclosure (thereby addressing both dust and noise). I will eventually do the enclosure route and a dust-pickup at the source. Sort of like wearing a belt and suspenders.

This looks like an industrial router, but I really like the dust control.

Router Mount

2010-04-04T20:36:00.000-07:00

Since I had to take the whole thing apart to replace the drive screw for the x-axis, I decided to replace the left-and-right side of the z-axis assembly with two parts I made on the CNC router.

The photo (above, left) shows the router mounted in the original mount. I had to raise the router in the mount so that the router bit did not extend past the dust brush (details on that later). That moved the router too far away from the table, so I had to jury-rig it to lower the whole router/mount assembly lower toward the table. The new sides to the Z-axis assembly (above, right) includes a "jog" to hold the router mount lower.

Here is the router mount. I designed it in cardboard, transferred the design to 1/4" hardboard. I verified the fit of all the components. I used a pattern bit on my router to duplicate the shape on two 3/4" pieces of plywood. I stacked and glued the plywood together.

The small hole to the upper right is for the vacuum attachment. It works fairly well, but I will re-make this with a 2 1/2" vacuum attachment. The more air you can move, the better.

Mounting the Steppers

2010-03-31T22:32:00.000-07:00

For mounting the steppers, I cut a stack of 1/2" and 3/4" plywood squares 2 1/2" square. By testing various combinations of different thickness, I determined the right size for each stepper.

I marked the center of the square and drilled a 1.5" hole with a Forstner bit and drilled the four stepper mounting holes in each square. Glue, stack and press them together. When dry, cut a notch to allow the block to be slipped under the stepper. This is necessary because of that three-part coupling spider - you really need to get that assembled first, then slide the spacer under the stepper. The notch must be wide enough to allow the coupling to pass through.

To the left is my Z-axis stepper where you can see the stack of plywood for mounting.

To mount the motor, I used 10-32 x 3" machine screws. All I could find were round-head slotted screws, and the head diameter was a bit to big. A few seconds on the grinder and they fit fine. The screws to through the axis assembly - I pressed in four T-nuts. (for the Z-axis, the T-nuts were pressed into shallow holes bored into the plywood.

Connecting the drive screw part II

2010-03-31T19:45:00.000-07:00

Sometimes I get an idea in my head and I can't seem to see other alternatives. As I mentioned yesterday, the quick-and-dirty X-axis coupling nut broke off the X-axis assembly. So I pulled out my wire-feed welder and welded a mending brace across the coupling nut. This should last longer then the rest of the assembly!
My welding skills are pretty much non-existent, but it should hold.

Had to take the whole damn thing apart to get to the broken epoxy joint. Here's the half-assed epoxy job with the fixed drive screw shown in the inset image.

Connecting the drive screw to the axis assembly

2010-03-30T23:02:00.000-07:00

I have seen many clever ways to attach the drive screw to the axis'. The more durable the connection, the better. I took a 'cheap-and-dirty' approach that I will no doubt pay for later.

I used a coupling nut and attached this to each of the three axis assemblies.

I cut matching dados into one part of the axis assembly and a smaller "cover", shown at the left. I sized everything for a very snug fit. Using a chisel or sharp knife, I notched the bottom of the dado (image on the right) to accept the point of the coupling nut. I added liberal epoxy around the coupling nut and glued and pressed the two parts together.
I selected a dado over drilling through the piece because, as I was using plywood and not MDF, I couldn't get the drill bit to track perfectly straight through the center of the plywood.

Note: for the X-Axis, I just did the dado and epoxy with no 'cover' glued and pressed over the coupling nut. the epoxy just broke loose two nights ago. I will design a much more robust attachment.

To the right is a photo of my Y-axis drive screw. You can see the dado in both pieces.

Backlash: Yes, I am aware that this type of nut is not ideal and that it can fall prey to excessive backlash. As the first version of my router is my "proof of concept", and I'm not machining to the micron, I don't currently care about the tiny bit of backlash present. I must say, however, that it's not too bad. We'll see after 10,000 cycles how it looks and feels!

Drive Screws

2010-03-27T23:01:00.000-07:00

There are three drive screws needed (one for X, one for Y and one for Z-axis). I used 1/4-20 threaded rod from Home Depot. Make sure to get them long enough - and keep them a bit long until you are 110% sure your design is set. Threaded rod is easier to make shorter than it is to make longer.

I finished the ends of all the drive screws the same way - with two nuts turned into each other. The second nut is referred to as a " jam-nut". This locks the two nuts in place very effectively. Notice the bearing is always towards the "inside" of the two nuts.

The bearing is a R4ZZ (1/4"x5/8"x0.196" Shielded) from VXB Bearings. 10 bearings for about $15.

Where I mounted the bearings, I used a 5/8" Forstner bit to bore a hole just deep enough to hold most of the bearing. Then I finished by drilling a 1/4" hole for the drive screw. It's a little difficult to see in the drawing, but the photo shows the double-nut arrangement and the bearing is counter-bored almost completely into the plywood. (this is the end of my Y-Axis drive screw). Sometimes I used a washer between the nut and the bearing, but It didn't seem to make any difference so I ended-up going without a washer.

A trick to remember when cutting the all-thread: Put a nut onto the bar before you cut the threaded rod. Cut the rod and file the end to clean off the burs & junk. Then, by taking off the nut, you will clean-up the threads (somewhat) where you cut them. Not perfect, but better than nothing!

Wiring the steppers

2010-03-27T18:09:00.001-07:00

Here is the wiring diagram. Depending on your definition of "forward" and "backward" or "up" and "down" - your steppers may end up going the "wrong way". The best choice is to see if you CAM software can invert the outputs. Or you can swap the stepper windings. It's not obvious what to do, if you need to know, drop me a line and I'll draw the "swapped" version.

The nature of this type of project is that it goes together - and it comes apart. Often. So I used connectors (from Jameco) that had enough pins (9) and sufficient current carrying capacity. Get at least one M and one F for each motor, you need to order the individual pins and sockets a-la-carte. Get an extraction tool also. If you have the extra $, the proper crimping tool would be nice too.

Here's the Y-Axis motor showing the 9-pin Molex connector. I opted for the 9-pin connector vs. a 6-pin as I am planning to run my limit and/or home switches through the same connector.

Stepper motors

2010-03-27T11:58:00.000-07:00

I purchased the steppers from Keling. I got three KL23H276-30-8A steppers - 8 wire, 1/4" Single Shaft with flattened area on shaft.
Steppers were delivered quickly, although their packaging for shipment was not ideal and the steppers were pretty much "flopping around" inside the package. All seemed OK, and the steppers are working perfectly.

You can also secure steppers from HobbyCNC - if you think you will be needing support from Dave at HobbyCNC, then it might make excellent sense to secure as much as possible from him.

To connect the steppers to the drive screws, I used a device called a "shaft coupler with rubber spider" - it's a three-piece arrangement that provides a rubber 'spider' that isolates the motor from the drive screw - allowing for some minor mis-alignment between the drive screw and the motor shaft as well as some forgiveness in distance between the motor shaft and the drive screw. These are available from Jameco. Just search for "spider". For each stepper, I used two PN 162270 (.250" ID hub) - labeled in the image below as "couplers" and one rubber spider.

Here's the spider assembly in use. The set-screws (visible in the photo above) in the coupler were pretty small, and there is only one, so I drilled-out the existing hole an re-tapped at 6-32, and added a second set-screw at 90 degrees, just to be safe. This device is going to take a beating.

The electronics

2010-03-27T10:41:00.000-07:00

I purchased the HobbyCNC PRO Chopper Driver Board Kit from HobbyCNC. The price was good and delivery was quick. Kit went together with clear assembly instructions.

HobbyCNC has a new board, with fewer features that would most likely work just as well: HobbyCNC EZ Driver Board Kit. $64 vs $79.

I managed to blow one of the driver chips, though I tried to be ultra-careful. I replaced the chip, added a big heatsink, and all is now good.

Here's the bare board. The quality is first-rate, as are the assembly instructions. Take your time, double-check everything.

I checked every solder joint under an inspection microscope - my soldering skills are excellent, however my eyesight is not.

Pay attention for any solder bridges or cold-solder joints.

The completed board "in action". For the heatsink, I used the same material that was used for the linear bearings and the rails. I put some heatsink paste between the driver IC's and the heatsink. I'm sure all the sawdust isn't ideal, but I'm not done yet!

Progress so far

2010-03-27T09:55:00.000-07:00

All the major axis' have been cut and assembled, and the entire project is now beginning to look like a real 3-axis router. Still no motors, drive screws or electronics, but it is fun to slide all the parts around. The real challenge is trying to explain to your friends and family what this gizmo does and what it's for. The most common question: "What'er you gonna make with it?". Love 'em, but they just don't get it. It's the building that's the fun.

The Base

2010-03-26T16:59:00.000-07:00

The base of the entire system must be rigid (no bending or flexing), but I didn't want it to weigh a ton, nor did I wish to use steel. So I went with an old furniture makers trick - a torsion box. If you are interested in the details, check out this really great and quite entertaining site: thewoodwhisperer.com. Mark shows the construction and benefits of a torsion box.

First, let's look at a drawing of the complete base. Here is a front, side and bottom view. This will be helpful in explaining the construction of the torsion box. I did mine differently than Mark did on thewoodwisperer, but the idea and results are the same.

Cutting diagram. I went with cutting notches in all the cross braces so the framework slipped together snugly - I added glue to all the joints and used wood screws around the perimeter.

It is as solid as a rock. There will be some trimming necessary for the base to make sure of a solid fit against the bearings on the X-Axis assembly, so you might make it a bit bigger than the 22 21/64" that I had so you can trim off bits until the fit inside the X-Axis assembly is perfect.

Since the assembly of the torsion box may not be too clear, here is an exploded assembly drawing.

Here's an underside-shot of the base. I am sorry to say I don't have any 'under construction' images.

X-Axis rail

2010-03-26T16:41:00.000-07:00

This is the final assembly that hold both the Y and Z-Axis assemblies. By now, the concept is pretty familiar.

The positioning of the Y-Axis rail is 1.5" in from the back and the height depends on the type of router you are using. For a little router, like a Dremel or a laminate trimmer, the Y-Axis rail will move closer to the table top, for a larger router (I used an old Craftsman router I inherited from my dad), the rail will move farther away.

Here's all three axis' together for a test fit (again, still with wood screws). This is where you begin to see the project really start to come together. Still no motors or electronics, but pretty cool nonetheless.

Y-Axis Rail

2010-03-26T13:11:00.000-07:00

The Y-Axis rail is the track upon which the Y-Axis assembly will slide. Cut two aluminum angles the length of the Y-Axis rail.

As with the front of the Y-Axis assembly, there is the same "flat spot" on the 45 degree beveled top-and-bottom of the rail.

The aluminum angles just sit on the rail. They will get firmly captured in place and will not move around once it's all put together.

Here's the Y-Axis assembly and the Y-Axis rail together, from two different views.

Here's my initial test-fit of the Y and Z-Axis components. In this early version, I had used wood screws instead of the cross-dowels. After lots of screwing and un-screwing, I converted to the cross dowels. So much nicer.

You may be wondering why I used plywood instead of MDF (Medium Density Fiberboard) like everyone else. Being basically cheap, my next-door neighbor had just finished a kitchen remodel and he gave me loads of left-over plywood. Pretty easy decision.

Y-Axis Assembly

2010-03-26T10:39:00.000-07:00

The Y-axis cutting guide, including the aluminum angle brackets. The angle brackets are the same throughout this project, both for the linear bearings and for the mating surface. With the 'front' and 'back' parts, you may need to 'futz' with their length in order to secure a good, solid fit against the Y-axis frame. At this point, I have not included instructions for where/how to mount the nut that accepts the drive screw. I'll get to that later.

Notice the detail when cutting the front. I set my table saw for 45 degrees (you can also use a router with a 45 degree bit and a guide bearing). I left small flat ends on each side (detail inside circle), not a sharp point. This is to allow a good, straight surface to rest against the fence of the table saw (or the bearing of the router bit).

Here is the entire assembly. Again, you may need to 'play' with the length of the front and back to secure a good, solid fit of the bearings against the Y-axis rail.

Now you can trial fit the Z-Axis assembly onto the "front" of the Y-axis. Again, some experimentation with the width of the Z-Axis to fit snug.

The Z axis assembly

2010-03-25T17:11:00.000-07:00

Here is the cutting guide for the first part of the Z-axis. The second part, the router mounting bracket comes later in the process, depending on the type/size of the router and how far your Z-axis assembly ends up from the table. You will want to make all 4 of the pieces that hold the linear bearings at the same time as they are almost identical for both the Y and Z-axis assemblies (Z-axis is 1/2" longer than the Y-axis part).

I have the luxury of a table saw, which I used to make the grooves to hold the linear bearings. To make my life easier, I made a small shim, 0.90" wide that I used to get perfect spacing between the grooves. One pass with the shim, second pass without and we're all good.

I set the blade to 45 degrees, and set it to just make nice 90 degree notches. The linear slides can be left loose, but it makes assembly of the pieces a 3 or 4 handed job - a touch of epoxy held them nicely in place.

Here is how it all goes together, using the cross dowels. The open end will be "filled" later with the router mounting bracket.

Holding it all together

2010-03-25T16:02:00.000-07:00

I opted to use a "cross dowel" to allow for a strong connection that can be easily and quickly assembled and dis-assembled. A cross dowel is a small metal rod, with a 1/4-20 threaded hole through it and a slot cut across the top to aid in alignment. I got mine on sale at Rockler woodworking (www.rockler.com).

Since many of the assemblies were too large to fit in my small benchtop drill press, I made a quick-and-dirty drilling jig that worked perfectly. I used brass inserts (1/4" and 3/8") to protect the wooden jig from repeated drilling. I clamped the pieces together, with the drilling jig and - perfectly aligned holes, every time.

Here's how the finished product came out. They are nice and flush with the wood surface, hold the thing together beautifully and are easy to un-do and re-do quickly and neatly.

Y and Z axis linear slide bearings

2010-03-24T14:59:00.000-07:00

I used 3/4″ aluminum angle stock from Home Depot. It is important to drill holes off-center, closer to the corner of the L.

Click the image for a larger view. (Note: You may want to stagger the holes so the bolts do not bump into each other when assembled. I was lucky and my bolts just missed each other)

I got clever and did my first set of brackets with the holes centered on the side of the bracket – and it didn’t work. You can see from the photo that the two angle brackets hit each other. Too bad I made all 4 brackets before I tried them out.

The holes are drilled and tapped. I used bearings from VXB Bearings.com (www.vxb.com/). The price was great, less than $4.00 for 8 bearings. Delivery was very quick. Article number sk8zz – 8 Skateboard Bearings 608Z Shielded.

Be sure to either use a template or a drill press to get the holes placed as accurately as possible. This way the bearings will ride evenly on the track. You’ll need to make 4 of these.

Drill the holes at 17/64" and tap 5/16-18. A 5/16" bolt has a diameter of .3125" and the inside diameter of the sk8zz bearings is .3150" (8mm) - a very nice fit. Attach the bearings with a 5/16-18 x 3/4" bolt, capturing the bearing between a nut and the bolt head. No washer is used.

The 8 inch X axis linear slide bearings are identical in design except they are, you guessed it, 8 inches long.

Here's how the finished bracket rides on the opposing rail.

All bearings contact nicely and the two angle brackets are now nicely separated.

Build your own CNC machine

2010-03-24T14:57:00.000-07:00

I was looking for an interesting project that would combine several of my hobbies. I found a “build your own CNC machine” posting at buildyourcnc.com. It seemed straight forward enough and worth a try. First was to build the “Linear Bearings". Pretty basic affair. It is really helpful if you have a drill press.