All posts by Zac

My low cost three axis CNC controller

 

three axis CNC controller build - insides

I recently decided that it was high time to upgrade the original electronics I built for my CNC milling machine conversion on a RF7045 style milling machine.  The original electronics, shown below in the mess of wires and full size metal enclosure,  used a unipolar 4 axis control board and huge banks of power resistors to limit current.  It was poorly thought out and an ugly mess, but fully functional  The drawbacks to the original set up were primarily excessive heat generation (overheating in the summer) and an inefficient design.  Unipolar driven stepper motors produce considerably less torque then the same motor driven by a bipolar controller.   It was also a huge ugly mess with wires everywhere and heat sink banks outside the box.  The upgrade to the new CNC control unit was all spawned by Pololu’s black friday super sale on all of their great robotics and motor drivers.  If you haven’t been to Pololu’s website, definitely check out their products. Very good stuff at a good price, and on Black Friday 2011 a very very good price.

 

original unipolar four axis cnc controller hooked up to the RF 7045

The new low cost three axis CNC controller uses three Pololu A4988 stepper drivers in what I call the “Tie Fighter Configuration”.   I’ve  sandwiched them perpendicular to two larger circuit boards creating a channel for air flow.  With a   high velocity cooling fan and a custom heat sink mounted to Allegro’s A4988 microstepping bipolar stepper motor driver chip I hope to use these at or close to their 2.0 Amp max rating.  Eventually, when my reprap 3D printer is completed, I’ll print out a fan shroud to further increase airflow over the chips.  The data sheet for the A4988 is here,   pdf of the website for the pololu board is here,  current pinouts for board are here.  (data for me in the future)  As I continue to add or improve the CNC controller I will update this post.

million out the control panel for the ver 2.0 cnc controller  I/O board for the low Cost CNC controller

 The first version of my cnc controller had wires coming out of it connecting to the steppers.  This turned out to be terrible in use and was very unclean.   Version 2.0 had to have external mounted plugs for all of the external connections to the stepper motors, limit switches, power supply, and computer.  A bit of research on connector dimensions, a bit of CAD design, converting CAD to g-code (cnc machine program language) and the cnc machine running on the v1.0 cnc controller machined the next generation I/O board you see in the sequence of images above on the left.   In essence my CNC machine built parts to upgrade itself.  I think this is the coolest thing ever!  Having a machine that can make upgrades for itself.  Not quite self replicating like the Reprap 3D printer project but still pretty exciting stuff. As a kid this was the thing of Science fiction and not reality.

Connections to the milling machine and power supply labeled

The connections are labeled in the above photo showing the pre-testing assembled unit.  Post testing I realized I should add an on LED to the top as a main power indicator,  along with an LED indicator for the cooling fan power.  I ended up not being able to scrounge a usable DC/DC power supply chip.  I wanted to use a DC/Dc converter to  internally converting the 33V from the power supply into 12V for the cooling fan.  Instead I ended up using  a wall wort (aka plug in dc transformer) to supply power to the cooling fan and added an external plug jack to the case.   The bad part about this set up is there is no interlock.  In theory,  I could run the controller and not have the cooling fan powered up resulting in some sort of thermal meltdown.  The Ver 1.0 CNC controller had dozens of similar issues.  I had hoped to avoid this situation in this unit.   I plan to order a dc/dc converter  from Digikey in the near future and add the power for the cooling fan internally to prevent the possibility of thermal meltdown.

The above picture is of the “Tie Fighter Configuration” I’ve created.  The three little Pololu A4988’s are stacked in between the top and bottom boards.  This should create a nice cooling duct for the air supplied by the cooling fan to run over them to remove excess heat.  I will also make some copper u style heat sinks and mount them with Akasa double sided heat sink tape.  I’m hopeful that with this set up I can drive these little boards at close to their 2 amp max rating.  The CNC machine also made the aluminum bracket that mounts the boards to the right side of the case. More self upgrading on the machines part.  The Pololu’s are being run in their most basic configuration, ie. full step, with only step and direction imput from the computer to each board.   The three axis CNC controller also has a built in NC (normally closed) chain of limit switches and an E stop.  This set up uses a pull up resistor on the computer side.  When any one of the grounded NC switches is hit the output goes high and the computer instantly shuts off power to the motors sensing a mechanical limit or emergency.   Limit switches and an Emergency stop switch are necessities on any CNC controlled machine.  They keep  those G code programming errors from breaking something.  I’m using pc side controls, rather then the on board enable/disable built into the Pololu A4988 boards.

New three axis CNC controller in place and connected

 

Here she is, all hooked up and running the machine.  The Akasa heat sink tape has not arrived in the mail yet.  The CNC controller was run at only 0.7 amps for “testing” purposes.  Everything hooked up and worked well.  I was half expecting something to go up in smoke.   I am very pleased with the considerably smaller and less complicated version 2.0 CNC controller.  This new unit will drive the motors with about 40% more oomph which means faster machining time for me.    This is an ongoing project and I’m sure  I will continue to add and evolve in the coming months.  I’ll post more as I make changes.

 

Installing a Gentran 3028 transfer switch

I lose power here, on average 2.7 times per month.  I’ve been keeping a log of all the power outages for the last year.  I was not sure if we were losing it all the time or it just seemed that way due to unhappiness over losing power.  I did some homework, talked with folks who have transfer switches, and those that install them regularly to make a decision on what transfer switch to put in.  I settled on the Gentran 3028, a PREWIRED 8-Circuit Transfer Switch, for up to 7500 watts.  This is larger then my current generator, but I plan to upgrade that to match the Transfer switch in the future.  I bought my gentran 3028 from Amazon and it arrived in 3 days with super saver shipping.

My reasons for selecting the Gentran 3028 versus other prewired models, or wiring my own subpanel as a transfer switch are as follows:  First, it’s pre-wired with nicely labeled wires going into the box.  This covers the inconvenience factor, which made the installation a lot smoother and easier.  Additionally I didn’t need to buy a bunch of  various wire in different sizes and colors to wire my own.  Second was the load meters in line on the Gentran 3028 transfer switch. This allows me to balance the loads on the generator.  Third, I didn’t want to spend a week of evenings wiring up my own subpanel.  There is a lot to be said for a prewired unit you just connect in place.

 

This is not a project for the unskilled homeowner.  If you do not know exactly what you are doing when it comes to electrical wiring, then you need to hire a professional electrician to have him install a transfer switch.

First up is turning off the main breaker, aka service disconnect.  I always  make sure to shut down and unplug all of the sensitive electronics in the house prior to powering down a main panel. I like to take each breaker down one by one before switching the main. That way when you turn it on, there’s not a massive surge to everything that’s plugged in.   The main panel was recently replaced by an electrician due to corrosion damage to the original.  This was my first time in there since then and I was not impressed with some of what he did.   I had to move the outlet you see in the right photo.  I put it back after mounting the transfer switch in place.

The prewired Gentran 3028 transfer switch is just wonderful.  The labeled wires make installation very easy.  You simply wire in the transfer switch main feeds to a 60 Amp breaker you install in your existing main panel.  Then just disconnect the hot wire from the breaker for each circuit you are moving in your box, twist and wire nut them to the clearly labeled wires from the Gentran transfer switch.  I was impressed with how well everything went, and the clearly labeled wires made the installation go much faster then I anticipated.  I definitely recommend this transfer switch in a big way.

The only other piece of the puzzle is the plug in the garage.  I didn’t want to spend another 50 bucks on the fancy outlets they sell premounted. The transfer switch came with the NEMA L14-30 male wall recepticle, so I used an octagonal boxe, and had my cnc machine make me a nice mounting plate from some 1/4″ aluminum stock.

I’m now ready for the power to go out.  Instead of a 2 hr hook up time running 5 large extension cords everywhere, I’ll now be able to simply wheel out the generator, plug it in and flip the switch.  I’m absolutely certain now that I spend all of this money and time installing the transfer switch in place I’m not going to lose power for a long long time… *sigh*

CX 500 Cafe Racer progress report

CX500C tank fit on the CX500 Cafe Racer

Time for a progress report on the Cafe Racer build.   I rebuilt the carbs completely stripping them and put them back on the bike.  She ran well for about 15-20 minutes in the garage. I then took her out for 15 minutes of riding up and down the driveway.  It was fun to ride, even if it was a short trip.  Since she was warm I changed the oil and filter afterward.

Everything mechanical seems to work great.   The CX500C fuel tank came in and I’ve test fit her in place.  I think it looks awesome and I’m starting to see the total bike “vision” come together.  I’ve picked out my headlight, but have yet to find a tail light set up that makes me happy.  I am considering making my own using  Luxeon Superflux LEDs at this point as none of the tail lights out there really fit with what I want for this bike.

CX500C tank fit on the CX500 Cafe Racer  Honda CX500 Upper tri hole moount  Honda CX500 with front suspension removed

   Based on a couple friends suggestions, I plan to do a few how to posts in the near future.  I don’t think I want to turn projects by zac into a how to/tutorial site, but I understand people want more informative and less documentary type posts.   I’ll be starting with a post on how to change and clean out the front forks on the CX500.  I’ve pulled them off the bike along with the rest of the front end to start cleaning, refurbishing and painting the various parts.  I’m leaning towards clip on handlebars at this point.  That way I can machine smooth the upper triple clamp.  I really want to remove the key/ignition switch, but I’ve learned with my 67 Vespa VLB Sprint how critical it is to have a bike that has at least the appearance of being secure.

Building an English Wheel Part 1

Many years ago I ordered hardened wheels so I could build myself a bench top English Wheel.  Since that time they’ve sat on the shelf in the garage waiting for motivation and need. For those of you that don’t know an English Wheel is a metal forming tool that allows you to gently stretch and form curves in sheet metal.  I’ve found ways around using one many times in the past.   The CX-500 Cafe Racer build is the straw that broke the camels back and has motivated me to finally build one for myself.  I often use a pneumatic plannishing hammer up until now to form compound curves into sheet metal.  However to make the fenders fit tightly to the wheels for the Cafe Racer I need an english wheel. With no way around it, I got to building.

I used whatever I had on hand for the C frame.  In this case, 2×4 and 2×3 tubing.  I’ll reinforce the structure beyond this quite a bit with 45 degree corner gussets and possibly full lengths of 2″ x 1/4″ angle iron.  At this point the frame is just tacked together to make sure that it all fits and works.  The bracing and reinforcing will be done after I’ve finished with the mechanisms.  It is important to make sure everything fits and is aligned correctly before you weld up all the joints.   It is a lot easier to cut a few solid spot welds then to cut fully welded seams when you realize something’s off a bit in the end.

 

   

The upper wheel is very heavy. Not a surprise at 6″ in diameter, 3″ wide and solid alloy steel.  The upper mount is fabricated from some 2″ x 1/4″ angle iron.  The pin I turned from some 1″ rod I found in the stock rack.  It’s been there for ages from the amount of dust on it.  I”m not sure what it is, but I needed Carbide tooling to turn it and bi-metal hack saw blades weren’t hard enough to cut it.  Whatever alloy it is certainly something hard and strong.  Hopefully suitable for the 3/4″ pin that the wheels will rotate on.  If it bends I’ll just make another set of pins from something stronger like 4140.

More on this project soon as I hope to finish it in the coming week