Building my first CNC router.
A few weeks ago I resolved I had already mulled enough over the idea of making a CNC router so I began it, more or less ad lib it using some aluminium I had bought for that purpose some time ago.
So far I've finished the X axis rails and rollers. For this I used ball bearings, six each side.
The vertical bearings are mounted by pairs on an aluminium, the bearing screw fits on a threaded hole while the holes for the two screws that secure the bar are over sized, therefore this allows me to adjust the alignment of the assembly.
Two of the bearings, the horizontal bearings are mounted on L shaped flanges, for those the bearing screw fits on an over sized hole so again they can be adjusted for a good fit and alignment of the assembly.
The thing rotated 90 degrees CW to show the vertical and horizontal bearings. I chose this arrangements instead of the 45 degree ball bearing assembly because I though it easier make and align this setup.
One of the carriages (that's not the right words, is it? :p ), all screws are M6 except the two holding the L flange which are M3.
So far this things work great, I'll have to see how they handle wear. I bought a stainless steel tube (same dimensions) to use as railings but it turned out that the profile wasn't constant, it was actually quite distorted so it was useless.
A couple hours ago I ordered a ER11 chuck (plus three collets) with the idea of making a spindle using a brushless motor, instead of using my Proxxon minitool as a router.
Here I'd appreciate some advice on the motor choice and how to best couple it to the chuck shaft. I'm thinking of using a belt and pulley assembly, or directly use the chuck shaft as the motor shaft. I don't know what motor I could find with an 8mm shaft, that is, that wouldn't be excessively large for this router.
So suggestions sought and appreciated... :D
By the way, I forgot to mention that the router will have a table size of 60x40 centimeters and a Z travel of at least 10 centimeters.
Oh goodie! today I received the ballscrews for the machine. In the end they cost a lot less than I first thought, I got the three for 133 USD including shipping, which took 4 or 5 days.
The ballscrews are 60, 40 and 25 centimeters in length, diameter of the screw is 16mm which I think it's overkill for a machine of this size, right? But better too strong than too weak I guess.
This are the three stepper motors I bought some time ago (second hand motors but they look OK to me). However I'm very fuzzy on how to drive them and what voltage and amperage to use for the power source, if anyone can give some ideas I'd be very happy to hear!
By the way, for the controller I'm planing to use the USB controller from Planet-CNC.com
Does this motor look familiar to anyone?
Putting the pieces made so far together, to give an idea of the size and shape of the router. I'm still quite undecided on how to make the gantry, the Y and Z axis. I have linear bearings for them, I'm just pondering on the best arrangement of elements.
The voltage for the power supply can be tricky, when you don't have the spec's on the stepper. Normally the maximum voltage is based on the wire insulation, that is the do not ever go past voltage. Then there is the lower operating voltage. If you had the inductance rating, a formula could be used to calculate the voltage for the power supply. Without that number, a general figure could be used. I go with10 to 20 times the operating voltage. The higher voltage equals more speed, but also more heat. So if its getting to hot, you'll need to lower the voltage. The only info I could find was 3.6 volts. This was from a stores web page, so not known if reliable. So now you would look at what power supply voltages are practical. The voltage has to be within the rating of the motor driver circuit for the stepper. And a readily available voltage. Looks like a 48 volt power supply might work ,if you get a motor driver rated that high. I wouldn't go higher, and might go lower since the steppers data is not well known. The current rating of the power supply needed is about 2/3 the rated current of the stepper, times the number of steppers, plus what ever else its going to power, plus a safety margin.
Thank you Rob, the power source is one of the blank areas in the design. From what you said I guess a 36V source would be a good starting point, just to make sure. Better a slow motor than a smoking motor... :D
Now I have to look for the current figures, or an approximation, for this motors. I'd like to add a fourth motor running an A axis some time later so I'll have to keep that in mind too.
The current is on the label is 1.8 amps. Or, would be half that, depending on how you wire it. I would select the power supply for slightly larger motors (2.5 amps each), incase you want to use it in something else.
Sense I was going over budget anyway, i decided to spend a few more $ and go with the MakerSlide rail system and save myself a boatload of fabrication hassle. Anyway, I'll be watching and if you decide to go with a brushless setup, I'll be very interested to see what you come up with.
Your machine is looking good and I'm sure it will bring you a lot of good service, After all, just get a load of those ball screws!;) Things have come a long way sense I built my first machine some years back. Big heavy steel thing being driven with an amped up HP plotter driver taking signals from an old i386 running DOS and an early version of DanCAD / DanCAM back around '87. Ah, those were the days. now I'm looking forward to getting back in it.
Nice work. Where did you order the ball screw assemblies?
I'm almost finished with the Z axis assembly, I got some dimensions wrong so I'll have to redrill some holes but overall it came out OK.
Here's a view of the assembly with only one of the linear bearings installed.
The timing belt pulley on the ballscrew gave me a bit of grief because I had to (well I didn't had to ;) ) enlarge half of the hole from 10mm to 12mm so it would fit over the threaded part of the ballscrew. If not I would had to mount it upside down and that would add 3 or 4 cm to the height of the assembly, also complicating the motor installation.
The Y axis rails and ballscrew will pass in between the linear bearings and the right angle rear supports, it's going to be a tight fit but I want this to be a compact design.
I made a mistake with the motor mounting plate and it ended up being about 3mm too short to stretch the timing belt properly. The thing is I decided to go from a 30 tooth pinion to a 20 tooth pinion (the large one on the screw is 40t) so the difference in diameter messed up the dimensions. I already fixed the problem by drilling and tapping two more holes for the screws holding the plate and enlarging the screw slots so that now it's two continuous slots instead of two pairs.
I want to add a rubber gasket in between the motor mounting plate and the rest of the assembly to reduce the noise from the motor, I'd like the machine to be as quiet as possible.
A view from the front, you can see the two bearing blocks supporting the ballscrew, I had to file the large, top one so it would fit inside the aluminium tube.
The bottom bearing block, showing the four mounting bolts and the holes through which they are inserted and tightened.
The top bearing is fixed, but the bottom one can be adjusted a little in it's oversized mounting holes so I can align it perfectly to the linear bearings on the sides.
I made some changes to the design for the base of the machine, so it would be less complex, smaller and somewhat easier to build. I'll see if I post some drawings later.
Now back to the work table. :D
The neighbours complain about the noise, the girlfriend about the mess and my hand about so much sawing and filing, but I keep at it. :p
I nearly finished the Z-Axis assembly, the only thing left to do is to add the top limit switch and making the spindle/grinder attachment.
Here's a view of the assembly with the ballscrew in place but without the linear slide bearings.
The left side is the part that goes up and down with the spindle...
Another view but this time on the other side and with the ballscrew removed and the linear slide rails and carriages in place.
I couldn't get two identical rails so the top and bottom are different. The top one has three carriages but only one on the bottom. Seems sturdy and rigid enough for my purposes.
The top carriages are mounted one in the center and two in "wings" bolted to the sides.
A detail of the Z axis bottom, notice the linear slide carriage on the left and the limit switch next to the vertical rails. The Z axis ballscrew is barely visible behind one of the vertical rail carriages, just right of the dome nut in the center of the image. I think it's a rather compact mechanism.
Here's the three stepper motor drivers and USB controller from Planet-CNC. They look well made but I haven't tested them yet, I want to focus on the hardware at the moment.
I redesigned the router base, if you compare with some of the earlier photos you'll see how different it looks now.
At the front and rear there are two 1x2" aluminium tubes (1/8th wall thickness) supporting the 600mm X axis rails made of the same material.
The Z-axis is just placed on top of the gantry posts to get an overall idea of the size and layout of the machine, I have yet to make the horizontal beam of the gantry.
A closer look at the front of the base. The transverse support can be seen showing how the belt and pulleys are mounted, although the ballscrew bearing block is not mounted yet.
I think it took me 3 or 4 days to make this particular part, with nothing else than a small drill, a hacksaw and files. I was very happy when everything fit together!
The stepper motor is mounted on the back with four long screws that fit in slots on the support, so that the belt tension can be adjusted.
As you may notice the longitudinal rails protrude a 1 or 2mm over the front piece, I'll have fix this so that they fit flush.
I was thinking of housing the electronics and power supply in a separate box but I changed plans and added four legs on the sides so I can mount everything within the machine itself. The sides are going to be close and at the front I will make a panel with the switches, connectors and status lights.
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