DIY CNC mill from mainly salvaged and 3D printed parts

[dbemowsk]

As some of you may have noticed, based on the earlier cad drawing, I had to make some adjustments to the large white bracket. The adjustments were there to let the spindle motor pass by the bracket. On the first attempt, the back of the spindle motor was hitting the bracket restricting travel. Also, the lower lip of the spindle motor assembly was hitting the lower part of the bracket. A few tweaks later and this was born.

[dbemowsk]

So, the project is nearing completion. I have an amalgam of colors used in the setup as I was trying to use up some rolls of plastic that I had on hand. I now have a gantry assembly that is held together at the top with some 3D printed T-Slot channel that was part of a failed print. There are 3 pieces strung together with some 10-24 threaded rods run through the center holes.

The bottom is strung together with a custom 3D printed I support that also has a piece of 10-24 threaded rod through it. That too was done in two pieces because I could not fit the whole thing on my print bed.

I am in the process of printing the drill guides to drill the holes in the MDF sides that will hold the smooth rods and the X axis stepper.

Here are the latest pics of the assembly so far.

Once I have the gantry X axis rods in place with the Z axis carriage, I will then be able to do a full test of the electronics. I opted for now to keep the salvaged Y axis motor assembly since I had that working. Once I have everything working, I will post a video.

[zboblamont]

@dbemowsk MDF? That is chipboard or particle board, no?
I very much doubt you will get sufficient rigidity even were you to glue/screw ribs on those side plates, and as a material it behaves badly with vibrating bolts etc...

[NeverDie]

If it doesn't work out, maybe you will want to build an MPCNC instead?

[dbemowsk]

@zboblamont I'll see how it goes. It is a big experiment at this point. If it doesn't work out I may be able to have a frame milled pretty cheap. I work for our local school district and I know the shop teachers at our high school that run the large CNC mill that they have. I may be able to have them mill me some parts. I do have all the needed steppers and things, I may just need a frame, worst case.

[dbemowsk]

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.

[NeverDie]

@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.

[dbemowsk]

@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]

@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. ;)

[dbemowsk]

So here is it's maiden voyage... It's first simultaneous run of all axes, AKA the initial X, Y and Z axis test.
https://www.youtube.com/watch?v=8diihXJwMj0

[dbemowsk]

I believe these are the settings that I need to change: https://github.com/grbl/grbl/wiki/Configuring-Grbl-v0.9
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.

[dbemowsk]

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.

[NeverDie]

Or use a dial gauge and get an exact measurement.

[dbemowsk]

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

[NeverDie]

That should work. Here's what I meant though:

https://youtu.be/rr42kPzL7js

[dbemowsk]

@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.

[dbemowsk]

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.

[NeverDie]

@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.

[dbemowsk]

@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

[dbemowsk]

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