One thing to avoid is fitting a drill when a mill was called - bad things happen. Don't ask me how I know!

Hi,

Oh funny you should mention that, I was thinking of trying a carbide drill bit to etch at one point too, ha ha. I guess that doesn't work. Too bad, I have multiple sizes down to #75 which has a tiny diameter.

What about if you grind a different cutter tip to a regular drill bit?
I am guessing that we do not want any upward lift force while etching, which a drill bit could cause.

 

I must have missed this somewhere. Did you acquire a CNC machine? Which one did you get?
I think they are called T-nuts. There are tricks you can do to install them.

Hi,

Oh sorry I guess I forgot to mention that.
Yes I just got one yesterday. I've been putting it off so long so I figured it was time to move on this.
The one I got is a 3018 made by L-Star. It's a sort of cheap one under $200 but I got it with an offline controller too.
The motor is only 100 watts, but it looks pretty beefy. I think it will go 10000rpm max. It's not very loud either I was surprised.
It's all metal except for the linear bearings that are what look like ABS plastic, but the plastic is thick, and they do have pressed in real linear bearings.
Oh the head is plastic too, but very thick.
The controller is what I guess is a standard now based on a low-end Arduino like the Uno or Nano, although the controller does not contain either, it probably just has the chip (I did not check that yet).
It seems to have all the right inputs and outputs like the limit switch inputs, but unfortunately they did not include the limit switches nor any sensor. I found out after reading your post that the sensor is probably only needed for nonmetallic work pieces like wood, where you want to sense the top surface (I am still guessing here though).

What is the trick you know for working with those T nuts? Some of them gave me a real pain and I'm still not done with the assembly.

 

Hi,

Oh sorry I guess I forgot to mention that.
Yes I just got one yesterday. I've been putting it off so long so I figured it was time to move on this.
The one I got is a 3018 made by L-Star. It's a sort of cheap one under $200 but I got it with an offline controller too.

Post a picture or a link to where you got it so that we know for sure which one it is.

 

Post a picture or a link to where you got it so that we know for sure which one it is.

Ok here it is:
Amazon.com: CNCTOPBAOS 3 Axis 3018 CNC Router with GRBL Offline Controller,DIY Mini Desktop Engraver Machine,Carving Aluminum Acrylic PCB PVC Milling Cutting Wood Engraving Machine : Arts, Crafts & Sewing

 

I wonder if there is a maximum diameter you can use for the cutter because I have some as large as 3/8 inch diameter with an 1/8 inch shaft

For my 3018 machine, I purchased a set of collets similar to these from Ebay.

Then, after screwing a bit of pine board onto the platform, a large diamater bit from my hand router was used with the suitable collet to make a flat surface. I ran the cutting speed very slowly and it worked well. So you can use larger bits, just be careful of the speed.

 

Ok, thanks. The spindle motor bracket is made from plastic. Hence the motor housing is insulated from the rest of the machine. I would slip a piece of stranded hook-up wire in between the motor and the plastic and connect the wire to the controller COMMON. This is the return connection for your probe switch.

As for stopping T-nuts from sliding away from you, stick a tiny piece of masking tape on to the nut so that the nut just slightly jams in the rail. Slide the nut into position with an L-shaped Allen key (hex wrench).

 

Any CNC machine should have an earth grounded spindle body, in fact all metallic parts of the machine should be at earth potential ending up at a star point GND.
It is called equi-potential bonding and ensures that no random tripping such as E-stop etc. occurs.

 

For my 3018 machine, I purchased a set of collets similar to these from Ebay.
View attachment 305729
Then, after screwing a bit of pine board onto the platform, a large diamater bit from my hand router was used with the suitable collet to make a flat surface. I ran the cutting speed very slowly and it worked well. So you can use larger bits, just be careful of the speed.

Hello there and thanks for joining the discussion.

That's an amazing idea, with the wood, which must create a surface plane perfectly parallel to the plane of movement of the cutter. As long as the circuit board is perfectly flat, I would expect that to work well. I guess that means you don't have to make a surface plane map?
Thanks a bunch for that, I am going to try that soon.
I guess you just go all the way across, then down one bit diameter, then across the there way, then down another bit diameter, etc., etc.

Yes I see those collets on Amazon also, another good idea.

 

Ok, thanks. The spindle motor bracket is made from plastic. Hence the motor housing is insulated from the rest of the machine. I would slip a piece of stranded hook-up wire in between the motor and the plastic and connect the wire to the controller COMMON. This is the return connection for your probe switch.

As for stopping T-nuts from sliding away from you, stick a tiny piece of masking tape on to the nut so that the nut just slightly jams in the rail. Slide the nut into position with an L-shaped Allen key (hex wrench).

Hello again,

Oh ok thanks. I'll try that. Almost done now.
I am inquiring about the limit switches at the moment.

BTW, this controller has a "sensor" input connector. I am guessing that has a ground pin but I'll double check that.

 

Any CNC machine should have an earth grounded spindle body, in fact all metallic parts of the machine should be at earth potential ending up at a star point GND.
It is called equi-potential bonding and ensures that no random tripping such as E-stop etc. occurs.

Hello there,

I am not sure what you mean here. Do you mean there could be some sort of noise that interferes with the control board signals?
I do not know what an "E-stop" is ... yet.

 

E-Stop stands for Emergency Stop, "The hardest button to find in an emergency"
Your machine should have a GND conductor that bonds all metallic, moving/stationary parts to earth GND at a central Star point in the control enclosure, this should include the earth conductor.
This is to avoid spurious electrical noise issues causing problems.

 

E-Stop stands for Emergency Stop, "The hardest button to find in an emergency"
Your machine should have a GND conductor that bonds all metallic, moving/stationary parts to earth GND at a central Star point in the control enclosure, this should include the earth conductor.
This is to avoid spurious electrical noise issues causing problems.

View attachment 305785

Hi,

Oh ok thanks for the info.
I'll check on this soon.

 

Hello again,

Another little question.

Since the work piece is clamped down and the control board always sees the x axis as the x axis and y axis as the y axis, etc., is there any reason why we cannot run this thing while it is sitting on its side?
That would make the x axis go up and down, but the control would not care. The y axis would go in and out as usual, and the z axis would go left and right.
The work piece would look like it is sitting on its side, but really it is just clamped to the slide table.

Sounds funny but I think it might work. What do you guys think?

 

Hello again,

Another little question.

Since the work piece is clamped down and the control board always sees the x axis as the x axis and y axis as the y axis, etc., is there any reason why we cannot run this thing while it is sitting on its side?
That would make the x axis go up and down, but the control would not care. The y axis would go in and out as usual, and the z axis would go left and right.
The work piece would look like it is sitting on its side, but really it is just clamped to the slide table.

Sounds funny but I think it might work. What do you guys think?

You can even run the machine upside down for all it cares.
But why would you want to alter its sitting position?

 

Incidentally you can you use it for things other than PCBs. Today I made the parts for a coil former. Eagle thought it was making a PCB with no tracks!

 

Oh ok thanks for the info.
I'll check on this soon.

All here.
Check equi-potential bonding CH-4

 

You can even run the machine upside down for all it cares.
But why would you want to alter its sitting position?

Hi,

Just for a possible better sitting position to fit in a special place. The total height is 11 inches, the width is 17 inches, the 'depth' is 12 inches. If standing on one side, the height is 17 inches, width 11 inches, depth still 12 inches. 11x12 stands in a floor space smaller than 11x17. That's really all, except maybe the dust and debris will fall to one side now which means it may not get into the lead screws. One side has no mechanics at all, so standing on that side it would just create a small pile of debris, and I would think less could get on the lead screws. I'm not really sure how much of a difference it would make though as I have not tried that yet. Maybe once I get up and running and familiar with everything.

 

All here.
Check equi-potential bonding CH-4

Ok thanks I will take a look.

 

Hello again,

Ok on first try I learned a few things after trying a simple etch in small piece of pine wood, making straight cuts forward, backwards, and left and right.

First, all the bolts have to be very tight. Some of the bolts where slightly less tight and it was causing the bit to follow the grain of the wood in places where the density of the wood changed from less dense to more dense. More dense would be for say a knot in the wood, but the density variation was not that extreme.
What happens is the bit goes straight until it hits the more dense wood, then it may curve slightly off the straight path, but it's only a little so it is hard to notice until I go back over it from the other direction. Going back (-x) the bit actually takes a different path which may be straighter. This is probably caused by the way the bit bites into the wood and tends to grab the wood less in one direction than the other because of the multi-directional change in density, and the direction of rotation of the bit (like a hard ball thrown in such a way that it has a spin that reacts with the air friction so it causes it to curve like in professional baseball).
Anyway, tightening the bolts again seemed to help a lot.
Another key point is probably that I did not have the spindle speed set high enough because I forgot how to do that with the manual control I was using for basic alignment testing. It's a combination of button presses I had to look up again in the manual.
I am glad this happened though because it allowed me to see what happens and be aware of it in the future.
Another issue that came up was one of the T nuts was not positioned right so one of the pillar blocks was not flush up against one of the frame rails.

Second, the engraving bits are not very good for making holes in the wood, maybe only 1/16 inch deep but that's about it. I did not expect too much out of this though as they have a 30 degree angle on the tip.

I was surprised though I did not break any bits. I had to be very careful with the Z axis though as it comes down to meet the wood surface.

I did install a temporary STOP button as suggested. I could not find a real and regular stop button that seemed ok for this so I ended up using a limit switch from the set I bought. I bought the set getting ready to install the limit switches (6 of them in total) but the mounting needs to be customized for this particular CNC machine.

In regards to the limit switch for the Z axis though, it seems that it would be hard to get it set just right so when the spindle comes down it shuts off if here is a problem. It seems like this will be far too variable to be able to set a limit on the travel. For example, with this wood test the wood is 3/4 inch thick so the limit would be 3/4 inch or just slightly below that. If I changed the wood to 1/2 inch, I would have to have a way to set the limit to around 1/2 inch. I don't see an easy way to do that without some sort of lever on the switch, but then i would be setting the switch as well as the Z axis lower limit itself, so i don't see how that would prevent any problems. This is because it seems to get the right height you have to have the work piece already under the bit tip so when it comes down you can see when it touches.

I have to wonder what happens if the limit switch does not detect a fault, and the mechanical stop prevents the travel from going farther while the controller thinks it can still travel a bit more. Does the stepper motor burn out, or does one of the driver transistors on the control board blow out, or it bends the frame, etc. I can see bits breaking, but does anything bad happen that is so bad it severely damages the machine?

Thanks.

 

In regards to the limit switch for the Z axis though, it seems that it would be hard to get it set just right so when the spindle comes down it shuts off if here is a problem. It seems like this will be far too variable to be able to set a limit on the travel. For example, with this wood test the wood is 3/4 inch thick so the limit would be 3/4 inch or just slightly below that. If I changed the wood to 1/2 inch, I would have to have a way to set the limit to around 1/2 inch. I don't see an easy way to do that without some sort of lever on the switch, but then i would be setting the switch as well as the Z axis lower limit itself, so i don't see how that would prevent any problems. This is because it seems to get the right height you have to have the work piece already under the bit tip so when it comes down you can see when it touches.

I have to wonder what happens if the limit switch does not detect a fault, and the mechanical stop prevents the travel from going farther while the controller thinks it can still travel a bit more. Does the stepper motor burn out, or does one of the driver transistors on the control board blow out, or it bends the frame, etc. I can see bits breaking, but does anything bad happen that is so bad it severely damages the machine?

Thanks.

Are you using work offsets for the program or from machine zero reference?
https://www.cnccookbook.com/g54-g92-g52-work-offsets-cnc-g-code/
Your drives should be set to the motor current limits, so no overcurrent should normally exist.
Steppers motors should be operated at their rated current from zero RPM to Maximum.
Normally LS are set up in the Normally closed condition, so any open circuit in E-stop line should stop the M/C.