DIY CNC mill from mainly salvaged and 3D printed parts

So the CNC is near ready for testing. I need to solder a connector on to the X axis stepper and I should be able to run some tests. I think the next step is going to be figuring out how to calibrate the GRBL controller.
Here are some pics of the build so far.

@dbemowsk A+ for sticking with it all the way to completion.
The main calibration number will probably be the revolutions per inch for each of the axises (axi?). From there you can start air carving.

@neverdie Thanks. I appreciate the tip and the compliment. Are you sure it is revolutions per inch and not steps per inch? The larger black motors I have for the X and Z axes are 400 steps per rev, but I think the Y axis motor is only 200 steps per rev. The Y axis is running on the large geared assembly though, so that should help more with both torque and revolution step count.
There is the talk about the rigidity of it. I am thinking if I run it a bit slower, the rigidity will matter a little bit less, but I'll see once I get it going. The MDF I used is 3/4", and it feels pretty rigid, but only tests will tell. I have my spindle chuck, a set of 7 coletts and some bits on order from amazon. Those should be here tomorrow I am thinking, since everything was prime.

@neverdie said in DIY CNC mill from mainly salvaged and 3D printed parts:
@dbemowsk A+ for sticking with it all the way to completion.
The main calibration number will probably be the revolutions per inch for each of the axises (axi?). From there you can start air carving.
I'm just going from memory. I think you're right, though: steps per inch. Or something like that.

So here is it's maiden voyage... It's first simultaneous run of all axes, AKA the initial X, Y and Z axis test.
Initial axis test – 00:23
— Dan Bemowski

I believe these are the settings that I need to change: https://github.com/grbl/grbl/wiki/ConfiguringGrblv0.9
I will be trying to configure things tonight. From the tracking information, I should have my chuck, coletts and the drills tonight, but the V bits won't be here til Monday. I am wondering if there are any test files that I can try to test my calibration? I will try to set up software on my WIndows laptop for now, but may migrate to a laptop running linux for the final setup.

I haven't had a chance to test the accuracy of the machine yet, but I did find a web page that has a VERY useful calculator for figuring out your steps per mm for a lead screw type system.
https://www.prusaprinters.org/calculator
Scroll down to the section labeled "Steps per millimeter  leadscrew driven systems". You just enter the parameters of your motor, microstepping, gear ratio (if any) and lead screw type/size. From that it calculates the steps per mm that is needed to configure your X, Y and Z axes for your GRBL controller.Figured this may be useful to others.

Or use a dial gauge and get an exact measurement.

@neverdie I'll check things with my micrometer once I get my bits and get a print on something.

That should work. Here's what I meant though:
CNC 6040 Router Accuracy vs Speed Testing – 08:08
— MBcreates

@neverdie Interesting video. It appears that I may have to get myself a dial indicator tool. Looks as if it will prove very useful. Using that calculator page that I found can at least get me to a starting point, and I can adjust from there.

So I am trying to get my spindle control set up and I am having an issue. I am checking with a volt meter between the spindle enable (SpnEn) and ground and I am reading 5v. No matter what spindle commands I am sending (M03, M04 or M05) I am always reading 5v. Is there a different command for spindle enable? If I check the spindle direction pin (SpnDir), I read 5v when I send M03, and 0v when I send M04. So that appears to be working.

@dbemowsk
On my board,
M3 SP1000
spins the spindle at maximum speed. Just M3 by itself doesn't.
It's not obvious from looking at your board where the spindle OUT voltage is. Maybe on the opposite side? I guess you'll have to probe around to find it.

@neverdie The SpnEn and SpnDir are control signals. For this board you need to have an external motor driver. After some looking, I may have found my answer. I am running GRBL 1.1. It appears that they swapped 2 of the pins. Pin 12 used to be the spindle enable pin in GRBL 0.9. In 1.1, they swapped 11 and 12 because pin 12 cannot be used for PWM which is how the controller limits the speed. I have not tried it yet, but I am going to try the Z+ pin which is pin 11. If that works, I may do a slight board mod.
Here is the post that explains it. https://github.com/grbl/grbl/issues/1187

BTW, I am using an external H Bridge to control the spindle.

Just tried that and it worked perfect. I don't use SP though, I just use S. So M3 S1000 is full speed, M3 S500 slows the motor, and M5 stops it.

Yes, my typo, just S, not SP.
I do wonder whether some of the more "advanced" boards, like the Duet WiFi, actually perform better, or whether the results are the same.
I think I may get a RAMPS board, if only because it supports Marlin, and that's what the MPCNC uses.
On the other hand, there is a smoothieboard clone on aliexpress for $40. . Hmm... It's tempting....
The jump from GRBL 0.9 to 1.1 convinced me that the firmware can make a difference, that it's not just all equivalent.

@neverdie I have always said, at least for 3D printers, that RAMPS was the way to go if you had to change your main board. Many of these 3D printer main boards have everything integrated into them. With RAMPS, it is all modular. If something dies, you are replacing 1 part rather than an entire board.

@dbemowsk I'll give it a shot. I ordered a mildly upgraded RAMPs board (so called "version 1.6"). It doesn't have the resettable fuses, which I guess have a dodgy reputation (or so Tom Sanlanderer seems to imply).
https://www.aliexpress.com/item/BigtreetechupgradeRamps15BaseonRamps143DcontrolpanelprinterControlReprap/32822038995.html?spm=a2g0s.9042311.0.0.9zbnJj
I'll be curious as to whether it can accept either the TMC2130 or the TMC2660 modules.

@neverdie I think most of those stepper driver modules run the same footprint. Check out this link. It is from Tom's 3D forum. People there are talking about those as replacements for the DRV88256's, which are the ones that I have. May be some useful info for you.
https://discuss.toms3d.org/hardwaref6/drv8825vstmc2100vstmc2130vstmc2208t250.html

@dbemowsk Short of making a very careful study of the datasheets, the other info that's available is awfully sketchy, so I ordered one of each module, and I'll see if I can get either one to work on the RAMPS board that I ordered. I'm not completely sure, but I get the impression that after they are properly configured, they can maybe just plug and play.

So, here is the latest update with pictures. I have the whole setup mounted on a leftover piece of MDF. I am using an ATX computer power supply to run everything. The fan pulls air from the back of the setup and blows it over the heatsinks for all of the modules.
For spindle control I have 3 different modules. The first is a buck converter to boost the 12 volts to 24 for running the spindle motor.
Next I have a dual HBridge that I had in my parts bin. I am only using one side of it. This handles the motor direction and speed. One problem with it that I had to overcome was that it had separate logic inputs for forward and reverse. The problem was that the CNC shield had a single output for spindle direction. To overcome this, I made a simple not gate circuit using an NPN switching transistor which sends a normal logic level to one input pin and an inverted signal to the other. I then use the enable line to start and stop the spindle. This setup works well.
This is the entire spindle drive circuity.
Here is an angled front view.

Don't forget to include a snub diode on the motor, if you haven't already.

@neverdie I thought that that was integrated on to the HBridge controller.

@dbemowsk If that's what it is, then I guess you're covered.

I like the idea of recycling an old PC power supply with a boost converter. For instance, a lot of the 48v power supplies don't come with regular 110VAC plugs, and you're even left with semiexposed 110VAC wiring, so this kinda works around that. It's a bit ungainly, but it works.
The only problem is you probably can't get to more than 240w, as that would be 20amps at 12v to the input of the boost converter. Actually less than 240w because of conversion inefficiency. At best probably just 0.85*240=204w. Maybe it would be good enough for milling PCBs though.

So I am trying to test the new machine and am having some trouble. I am running into an issue with some gcode I am testing. The gcode was generated from inkscape and I am including the gcode below. The way I am testing this is just using a terminal connection to the CNC and pasting the gcode into the terminal window. If there is a better way to test this let me know.
When I paste in the gcode below, the CNC runs through part of it and then stops. If I then hit enter in the terminal window I get this:
error: Invalid gcode ID:35
From my research on this error I found this:
A G2 or G3 arc, traced with the offset definition, is missing the IJK offset word in the selected plane to trace the arc.After testing in chunks, I have found the line that appears to be causing the error.
This will cause the error:G01 Z0.125000 F100.0 G03 X44.448347 Y19.159901 Z0.125000 I203.958107 J224.353401 F400.000000 G03 X45.751092 Y20.363421 Z0.125000 I235.328819 J256.037427 G03 X47.053649 Y21.586232 Z0.125000 I48.170466 J52.617095 G03 X47.737750 Y22.275812 Z0.125000 I14.623944 J15.191857 G03 X49.369789 Y24.042092 Z0.125000 I12.444180 J13.135542 G03 X50.077180 Y25.172247 Z0.125000 I4.326712 J3.494655 G03 X50.505064 Y26.430623 Z0.125000 I5.413285 J2.542606 G03 X50.652755 Y27.790183 Z0.125000 I6.183798 J1.359560 G03 X50.459010 Y29.287714 Z0.125000 I5.884361 J0.000000 G03 X50.002913 Y30.259582 Z0.125000 I2.876467 J0.756965
If I run it just to the line that ends in J0.000000, I don't get the error. From all the testing I am doing, it almost seems like a problem with the version og GRBL that I am running. If anyone can help, it would be greatly appreciated.
Here is the full gcode file I am trying to run.
% (Header) (Generated by gcodetools from Inkscape.) (Using default header. To add your own header create file "header" in the output dir.) M3 (Header end.) G21 G00 Z5.000000 G00 X43.225993 Y18.042555 G01 Z0.125000 F100.0 G03 X44.448347 Y19.159901 Z0.125000 I203.958107 J224.353401 F400.000000 G03 X45.751092 Y20.363421 Z0.125000 I235.328819 J256.037427 G03 X47.053649 Y21.586232 Z0.125000 I48.170466 J52.617095 G03 X47.737750 Y22.275812 Z0.125000 I14.623944 J15.191857 G03 X49.369789 Y24.042092 Z0.125000 I12.444180 J13.135542 G03 X50.077180 Y25.172247 Z0.125000 I4.326712 J3.494655 G03 X50.505064 Y26.430623 Z0.125000 I5.413285 J2.542606 G03 X50.652755 Y27.790183 Z0.125000 I6.183798 J1.359560 G03 X50.459010 Y29.287714 Z0.125000 I5.884361 J0.000000 G03 X50.002913 Y30.259582 Z0.125000 I2.876467 J0.756965 G03 X49.239064 Y30.916004 Z0.125000 I1.644692 J1.141216 G03 X48.146224 Y31.169360 Z0.125000 I1.092840 J2.230286 G03 X47.289509 Y31.048092 Z0.125000 I0.000000 J3.086831 G03 X46.475200 Y30.686621 Z0.125000 I0.908316 J3.144182 G03 X45.866393 Y30.136858 Z0.125000 I1.149043 J1.884428 G03 X45.713957 Y29.684007 Z0.125000 I0.596437 J0.452850 G03 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X35.980838 Y25.190815 Z0.125000 F400.000000 G01 X35.999408 Y27.233175 Z0.125000 G03 X35.574593 Y26.748497 Z0.125000 I52.703425 J46.622391 G03 X34.773990 Y25.822090 Z0.125000 I191.750900 J166.520630 G02 X33.983162 Y24.922179 Z0.125000 I36.848082 J31.584152 G02 X32.917298 Y23.761165 Z0.125000 I62.405165 J56.220956 G02 X31.819666 Y22.649912 Z0.125000 I29.726417 J28.264352 G02 X30.726405 Y21.625970 Z0.125000 I26.328768 J27.015589 G01 X33.028700 Y21.607400 Z0.125000 G01 X35.980838 Y21.607403 Z0.125000 G00 Z5.000000 (End cutting path id: path4516) (Start cutting path id: path4516) (Change tool to Default tool) G00 Z5.000000 G00 X40.399760 Y21.607403 G01 Z0.125000 F100.0(Penetrate) G01 X42.590657 Y21.607403 Z0.125000 F400.000000 G01 X42.590657 Y20.809024 Z0.125000 G01 X40.399760 Y20.809024 Z0.125000 G01 X40.399760 Y20.084915 Z0.125000 G03 X40.407178 Y19.750985 Z0.125000 I7.520648 J0.000000 G03 X40.436895 Y19.249405 Z0.125000 I17.002115 J0.755670 G03 X40.546108 Y18.791102 Z0.125000 I1.970229 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To add your own footer create file "footer" in the output dir.) (end) %

@dbemowsk said in DIY CNC mill from mainly salvaged and 3D printed parts:
The way I am testing this is just using a terminal connection to the CNC and pasting the gcode into the terminal window. If there is a better way to test this let me know.
This may be your problem, or at least a contributing factor. Try using a gcode sender, such as ChiliPeppr, instead.

@neverdie Thanks a million. I tried the online version of chilipeppr and it seem s to be working.

So I did a test run of an old style font carving my house number into a piece of wood. I created the gcode using Inkscape which is a popular vector graphics program. For a test run I think it went fairly well.
I did a video of it carving. The spindle is spinning much faster than it looks like in the video. It has to do with the recording frame rate on my phone.
Test run of my CNC – 12:00
— Dan Bemowski

Looks like your spindle may have really bad runout.

@neverdie I don't think it's runout. If you look, a lot of the video is shaky. I think it is vibration from the V bit cutting into the wood. The tip of that bit may be bent a little which would cause vibration like that. I guess I'l find out when I try cutting a PCB. When I do one, I'll change to a new bit. I ordered a pack of 10. I have to see if I have any copper clad laying around.

@dbemowsk As it turns out, I too will have to make something similar to:
in order to install my new brushless motor on the zaxis. What parts should I order to go inside the plastic? I mean, obviously two ball bearing something's and some kind of threaded nut or something. I'm just not sure exactly which something's I should get, if you know what I mean. Did you buy your something's, or were they junkdrawer parts that you had laying around?The zaxis that came with the 2418 is just a unit that came preassembled. I'm not even sure how I will take it apart. I suppose I could maybe extract the parts that are in it and reuse them, but they're melted into the plastic, so if I do that, I'm burning my bridges back to the system as it currently is. It does work, so I'm reluctant to wreck it.

@neverdie I wouldn't advise tearing apart your old one. As you mentioned, you could at least fall back to that if it came down to it. I am assuming that you are getting a different spindle motor?
To make that part I just used 3D printed linear bearings that the smooth rods slide into. For the threaded rod/lead screw, I used a threaded rod coupler nut like this one:
I just hollowed out the hex shape inside the plastic so that when it is tightened on it holds it snug. I designed the part in OpenSCAD. Because I was designing the part myself, I had free reign on the design.

Sorry, meant to include a pic of the bearings. These fit into the outer recessed areas in the frame. I did it this way so I could change them if I had to.

So, I was doing some reading on how to use autoleveling with GRBL and the CNC shield that I have. What I read was that for GRBL on an arduino, the probe needed to be connected to analog pin 5 and ground. For the shield that I have, this is the arduino pinout that I found on it:
Turns out that A5 is not connected on my shield and is labeled (not used/reserved). Luckily, in my parts bin I had a couple arduino uno prototyping boards. So I made a board that stacks in between the CNC shield and the uno. Here is the board with the probe attached:
The probe wires are made from an old dupont header cable that was salvaged out of an old PC. I figured that fit right in with the theme of the project.And here is the stack.
I did a test and the probe seems to work. Tomorrow I will probably do a test mill of a small pcb to see how that works out.For a junk parts build, I am pretty happy with the way it is turning out.

So, turns out the shaft couplers that I got are kind of crappy and seem to come loose every so often. These are the ones that I got which have their set screws on opposite sides from each other:
I am looking to get some replacements, but am wondering which style would be best to get. There is this style which has set screws at 90 degrees to each other:
There is this style which actually clamps around the shaft:
Then there is this style that also is a clamp style which says that it is somewhat flexible. The thing with this style is that I don't know if it separates at the red part:
The shaft on my stepper is a D shaft, so I am wondering how well the clamp style ones will work, at least on the motor side. The lead screw is round, so that should be fine for the one clamp.
Any thoughts?

@dbemowsk My kit came with the same blue couplers, and they came loose too. However, loctite fixed the problem.

@neverdie I'm assuming you used loctite blue?

@dbemowsk Yes.

I believe the flexible couplers are for when the stepper axis isn't colinear with the threaded rod.

@neverdie I still may buy another set. I think the clamping style would be the best, but as I said, not sure how that would be on the D shaft.

@dbemowsk Are these not something you can 3D print? Then you could customize to the D shaft if you like.

BTW, I suspect that using longer linear bearings will lead to less slop:
http://a.co/0yWkPgi

@neverdie said in DIY CNC mill from mainly salvaged and 3D printed parts:
@dbemowsk Are these not something you can 3D print? Then you could customize to the D shaft if you like.
I guess I hadn't thought about 3D printing them. I did order a pack of two though.
https://www.amazon.com/uxcellEncoderCouplerCoupling8mmx5mm/dp/B01E0CTI42/ref=sr_1_14?ie=UTF8&qid=1522050398&sr=814&keywords=5mm+8mm+coupler
@neverdie said in DIY CNC mill from mainly salvaged and 3D printed parts:
BTW, I suspect that using longer linear bearings will lead to less slop:
I would tend to agree. Does your CNC use linear bearings?

@dbemowsk said in DIY CNC mill from mainly salvaged and 3D printed parts:
Does your CNC use linear bearings?
Yes.

Just a note to everyone. These style couplers are NOT good for the X axis, or Z axis if the motor is vertical and facing down.
The problem is that the spiral part is actually quite springy. When say the X axis motor spins to pull the X axis to one side, the springy part seems to really stretch. Pushing the X axis works fine. Since my Z axis motor is mounted on top with the weight of the axis being downward, this will cause the coupler to stretch even more. My 3D printer uses these on it's Z axis which works fine because the motors face up with the pressure of the Z axis down on the couplers.The only thing about the ones that I got that I liked was the way that it clamps to the shaft. I think the clamping action is better because you get more surface area grabbing the shaft.
Something like this may be the best because it is solid and there is no stretching. It also has the clamping action.

@dbemowsk they should work if used as intended. These couplings are supposed to be stiff in only one direction of freedom: Rotation of the axis (=transfer the torque of the motor to the axis). The other 5 degrees of freedom should be of low stiffness to absorb misalignment between motor and axis. So the correct type of bearings should actually constrain the axis to only rotate in one DoF and not translate into the coupling.

@technovation DIDn't think about that when I bought them. I will save them for spares for my 3D printer.

I notice that the kit from CNCrouterParts does appear to use the springy couplers:
John Park's Workshop: CNC Machine Kit Build @adafruit @johnedgarpark #adafruit – 09:28
— Adafruit IndustriesSo, I guess it can't be bad, because they seem to make very nice kits.