First MDF CNC 3 Axis or how not to build a CNC

10 Dec 2014

This machine was more of a learning bug finding machine and here is a little about what i plan to accomplish with this machine. I am hoping to end up with a 5 Axis CNC machine that will have a cutting area of about 1300mm x 1000mm x 240mm. I will first build a 3 Axis Gantry CNC with hand cut 18mm MDF and then use that machine to cut better quality parts in the hope that a can start to machine aluminium. Then if all goes to plan start making aluminium frame work and build it up to a 5 Axis CNC. Once that phase is complete i will move onto building the stand alone control panel and motion controller using a combo of AVR, Ardunio and TI Stellaris Arm Micro controllers which i hope to use to make a closed loop system using some AS5048A magnetic rotary encoders on each stepper motor shaft. From there i will start work on accessories like auto tool changers, 3D digitizers and all the other fun stuff. i am still looking for any other parts people could donate like sheets of Plastics ie delrin, hdpe or aluminium that would be great even old machines that i can salvage buttons, electrical and mechanical parts from would be great.

More Updates To Come Soon
The geek will inherit the earth. :-)


i`m using an old AMD sempron 2800+ board with 1GB ram and 2nd PCI Parallel port for extra I/O`s	4 heavy duty limit switches for the X Y axis i will need some more for the Z but i might use some micro switches, hall sensors or IR interrupters because i will need things to be compact to make it easier to up grade to 5 Axis
Top of heatsinks	i`m going to remove the trim potentiometer use for controling the current limiter and the dip switches used for setting the micro stepping and replace them with a AD5206 digital Potentiometer and digital switches controlled by an arduino so that later on i can if needed via the motion controller i am building using a Stellaris LMF4 120XL ARM controller
I got this vicor 3x 24v 8.3A 200w PSU for a steal on ebay it sells new for £300 i got it for £30 delivered. Because it has load sense on each output i am going to parallel the outputs to give me 1 24v 24.9A 600w rail which should power all four 4A stepper motors and maybe the 2 smaller motors i will use for the 4th and 5th axis i plan to add later.	These dual shaft stepper motors are 200 step beasts with holding torque of 4NM / 566 ozin i will be using 2 for the gantry X axis to make sure there is plenty of power for cutting the big jobs.
i got 2 different break out boards just to see which is better and i found a problem with the one on the left for some reason the opto isolators dropped the voltage to low for the driver board to see a logic high it could be possible that this happens because the drivers also have isolators on but i will look into that later.	The 400w ATX PSU will supply the mainboard, all the 3.3v, 5v logic power and also the 12v fans. the 160GB harddisk is a bit over kill for linux cnc but its all i had spare.
it was going to cost £9 for each lead screw nut and i was going to need at least 4 but i really wanted to use 6 so i bought a length of Delrin and a 16×4 Tap to make my own for £45 which was a bargin.	The smaller Hiwin rails are perfect for the z axis
Tap and matching leadscrew 16×4	cant wait to get these installed
maybe i will get 2 extra blocks for the x axis when i can afford them	PC PSU and shaft couplers
Motherboard and vicor PSU	Motor Drivers and Fans
Breakout Boards	Stepper Motors
A new TB6600 Stepper Motor Driver	All 4 drivers mounted on the heat sink with some nice new Arctic Ceramique 2 thermal compound in stead of the nasty cheap silicon paste that is used by the manufacturer.
All 4 drivers mounted on the heat sink with some nice new Arctic Ceramique 2 thermal compound in stead of the nasty cheap silicon paste that is used by the manufacturer.	i will be adding 2 or 3 LM35 sensors to the heat sinks and using the built in tachometers i should be able to use PID to keep things cool but for now i will just run them at 75% power to keep everything nice and cool
Side view of motor drivers	all 4 heat sinks joined using aluminium tape which is surprisingly strong. i might at some point try some epoxy to join them or if the heat transfer of the epoxy is low maybe try brazing them together.
i`ve add mounts for the motors, 2 clamps for the spindle motor and a matrix of boxes on the cutting bed to add strength and for mounting a sacrificial MDF sheet. also i have managed to get the shaft supports and other things to show in the rendering with a nice science lab background to give some idea of scale	Front of machine
Side of machine	Rear of machine
i`ve lengthened the cutting bed so it over hangs to compensate for the distance the spindle is from the center of the gantry.
My new Bosch POF 500 A Router that i picked up second hand for a tenner and its had very little use. It will be a great starting milling head for the machine. All i need to build for it is a PID Pulse Width Modulation speed controller because the 27,000RPM it runs at is far to fast for most materials other than wood.	Getting ready to glue the printouts of Z Axis parts to the MDF

	First ruff cuts
	end of a bloody hot day but one step closer to my machine coming to life.
Almost finished the Z-Axis it still need a bit of sanding to make sure every thing fits flush but it only needs to good enough so that the machine will be able to cut more accurate parts for the final build.	The sides slot into the back plate and hold together even without glue or screws. I plan on making all parts slot together for the final build to help add to the overall machine rigidity.
Pillar drills are an essential tool for any workshop, with out mine all these holes would have been a total nightmare to get straight.

	i`m starting to get an idea of the overall size of the machine and i got the Z-Axis attached to the Y-Axis today once i fit the Z bearings the rest of the machine will be plain sailing until i have to add all the electrics.
I`m thinking of adding some plastic sheathing to the rails to protect them from sawdust getting into the bearings or bicycle inner tube.
Nice and close	Finally all the wooden parts have been cut and well ahead of schedule the only problem is it has turned out a little bigger than i pictured in my head.
Y Axis Gantry	Still need to cut holes

The Z Axis is the most complex part of the machine.	The 25mm Hiwin bearings work a treat they are only preloaded to Z0 but you can so no movement.

A quick test of the 20mm steel shafts and kinear bearings, they are slightly misaligined but stil work well.	Lots of hot glue to hold the delrin nut in place
	i had fun grinding the screw down so it would fit in the coupling.
	the screws with hot glue on will be use for the limit switches
	1 complete Z Axis it is strong enough for my daughter to stand on while it moves.
Because it is much bigger than a normal case i can install all the electronics in the one case	This is an old PC case i found in a skip about 6 years ago i knew i would find a use for it
its hard to see from this pic but the vicor power supply for the motors is install on the side of the drive bay.
i have managed to tuck the Hard drive out the way in the back of the case	Many lesser women would murder their husband if their front room looked like this. Love you my beautiful lady.
This all happened due to the fact that the first motherboard i was using thought it would funny to crap out once i fitted most of the electronics in the case. Fault finding is so much fun, it also turned out that one	4 Ammeters 1 for each of the motors so i can keep track of each axis power usage with out having to break out the multi meter.
	4 screw in 8 pin sockets for the motor cables

	Every thing back in the case i still need to play about with wire routing so data and power cable do not cross but everything seams to be working ok for now.
Ammeters all powered up and testing 1 axis at half power. i still need to add a power switch for the vicor power supply and the motor drivers fans plus lots of indication leds.	Quick and dirty router clamps
Gantry added	Finally got the Z-Axis Mounted and the Y-Axis leadscrews fitted
Quick picture with my 13 year old son next to the machine to give some sense of scale.	All of the motors are now fitted
Just need to fit the limit and home switches, then route the cables to prevent strain on them when the machine is moving.	Watch this space more pics and videos to come and then i will show the Aluminium Build i am doing currently

DAB over 10 years ago

Looks like you have a good build.

I will be watching to see how you bring the hardware up to make things.

DAB
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