CNC BEGINNER GUIDE MUST READ.

[clockmaker]

This is good start, but after six months of frustration I have decided that the Mega V with Fusion 360 and UGS is a complete waste of time and money. Should have bought just about any other system. All I want is a simple list of instructions for positioning the bit on the corner of the stock and running a job without the system going off in who knows what direction and alarming. If it would just do the same wrong thing twice in row, I might be able to figure it out. The system will home with no problem, the XYZ Probe works just fine, but there is no way to get it process a job without crashing. I know my test job works because it actually worked a few times (it is a ridiculously simple facing operation).

[Bruce]

Fusion 360 can be frustrating to learn. Usually G28 in the post processor can cause issues you describe. Do you see G28 in your G-code?

[JoeE]

Hi clockmaker

I literally just went thru the same issues. For me 6 full days and then I got it. On the resource page, there is some videos by (Clark?) FatMan Black Tshirt building his M3. If you follow that path to YouTube, he has a video (2 parts) on a simple project start to finish. It filled in all the gaps I was missing. He shows how to disable G28 in the post processor tool before you save the file which was one of my problems. This stopped the erratic behavior.

Good luck

[Bruce]

It might also help if you go to YouTube and do a search on "fusion 360 tutorial beginner" and pick a series to go through.

[clockmaker]

I think I have what might be useful for setting up a job in UGS after posting from CAM software

I think what I need to figure out is the following set up.

I used this site as a reference for G Code: linuxcnc.org/docs/html/gcode/g-code.html#cha:g-codes
I also found this G Code Translator to be really helpful: www.warrensbrain.com/gcode-to-english-translator.html - Thank you Warren

I am using Fusion 360, but the following should work with other CAM software.

First, open the .NC file (G Code) in a text editor and clean up the G Code by removing everything except the G20/G21 command prior to the first milling operation (it is easy to find if you have named the milling operations in CAM). Then go to the end of the file and remove everything after the last G0 (Rapid positioning command). There are probably some commands that can be entered here that will safely move the router back to either the start position or home, i.e., G90 G0 Z0 or $H

If you have figured out how to not include all these commands from within your CAM software even better but I am always going to check just to be sure.

Second, run a setup and clean up routine (some steps below can saved as a Macro in UGS. Hoping to figure that out after confirming that it is correct)
1. G21 //Programming in millimeters (if the G Code from Fusion was done in inches, then G20)
2. G43.1 Z0 //Tool height offset compensation negative
3. G49 //Tool length offset compensation cancel
4. G92.1 //Position register (programming of vector from part zero to tool tip)
5. G90 //Absolute programming - Using just G90 should clear the settings because no values are provided
6. G94 //Feed rate per minute - Using just G94 should clear the settings because no values are provided
7. G17 //XY plane selection (make sure this matches your Fusion 360 settings)
8. Home the machine ($H) - Home on my system is the back, left corner with Z at the top.
~ If you have homing switches, then $H, otherwise jog the machine into position.
9. Set the home position using G92 X0 Y0 Z0 so that Soft Limits will work (Maybe this command G10 P0 L20 X0 Y0 Z0)
~ The UGS Soft Limits are available via Machine >> Firmware Setting >> $130, $131, & $132 -- set these up to avoid crashing and system damage
10. If you have an XYZ touch plate
~ Place the XYZ touch plate on the stock
~ Jog to the corner of the XYZ touch plate
~ Run the UGS XYZ Probe macro (there does not seem to be any documentation on how to configure the Macro. There are some old YouTube Videos. With UGS, you do get what you pay for.
~ Remove the touch plate
~ Click Return to Zero
11. If not, locate the starting corner by jogging in small increments and using the paper method
12. Set the G54 origin using G10 L2 P1 X0 Y0 Z0 (G10 tells the system to input data, L2 tells the system which register G10 will edit, P1 in this case is G54, X0Y0Z0 says this is the location
13. Instantiate P1 using G54
14. Load the job file
~ If this is the first attempt, consider removing the stock, fixtures and the bit so you can cut air and not risk a broken bit, crashing, damaged stock etc.
15. Send the job file

I would really like a recipe for bit changes. I assume it would include the use of G28 and G28.1 to set a location for the flipped over XYZ touch plate, setting compensation values to accommodate the bit length difference using G43 G49 or some combination with reference to the G54 Z position, etc. Then retuning to G54 position with the adjusted Z height. This may be a waste of time since G Code does not seem to have commands to pause a job for manual bit changes. But even if I have to create multiple NC files to accommodate bit changes, I still need to be able to get back to the original G54 location with the Z adjusted for the bit length.

If anyone has suggestions or comments, please share. Sorry, I probably cannot answer any questions as I really don't know what I am doing.

[Bruce]

To change the endmill all you need to do is reset the Z axis workpiece zero to top of the material. X and Y will stay the same.
Typically I split my g-code up into separate files for each endmill type and toolpath. There is a option selection in the post processor to split the files.

[btreichel]

Sept 27, 2020 2:52:15 GMT Bruce said:

To change the endmill all you need to do is reset the Z axis workpiece zero to top of the material. X and Y will stay the same.
Typically I split my g-code up into separate files for each endmill type and toolpath. There is a option selection in the post processor to split the files.

Same here, but vectric tries to do that automatically.

[clockmaker]

It makes sense to split the job and run one job per bit, but the code below might work using a single G Code post. Resetting the Z axis is easy provided the corner or some other original surface is still available, but if a facing operation or any other milling occurs such that the original surface in no longer available, then either installation of the replacement bit has to have exactly the same stick out (not likely) or the Z axis has to recalculated based on the original height. I found this forum.v1engineering.com/t/tool-change-g-code-and-z-touch-plate/6456, but I think it requires watching the job for the 10 second pause signal. I would for sure miss it and destroy something.

Below is an edited copy of the code used. I have no idea what LCD refers to, guessing connecting a PC with a screen, The recipe seems to still require a reference to the top of the original work piece, which in some cases would no longer be available.

M0 Change bit to _____ \\ Pause code: The text after the M0 should be displayed. Fill in the blank with the bit type.
G0 X0.0000 Y0.0000 F2100 \\ Move to zero on X and Y at feedrate 2100. Might be able to click Return to Zero instead.
M18 Z \\ Disable Z Stepper Motor to allow for manually moving the Z axis up to get the new bit in. Could probably just jog the system instead.
M0 \\ Pause the code again until resume is clicked to set up the touch plate.
G28 Z \\ Home Z axis to touch plate. No sure about this command choice.
G1 Z2 F150 \\ Raise Z axis 2mm at a feedrate of 150 in order to remove the touch plate. Could just jog.
M0 \\Pause code until resume is clicked. This is to unhook the touch plate and turn the spindle on.
G1 Z-0.4 F150 \\ This sets the negative offset to the thickness of your touch plate. In this case, a .4mm feeler gauge. Make sure it is negative.
G92 Z0 \\ Sets the Z axis to zero at the offset above at the top of the workpiece.
Click resume

[hans]

On a job I repeat from time to time, changing bits is needed but the original surface is gone. My approach has been to use a separate block of wood of known height (and higher than the thickness of the workpiece) to set (and reset) the Z=0 for all bits. Using VCarve Desktop, I tell the program that my workpiece is the thickness of the separate block, but to start cutting at the height appropriate to the real workpiece. Easy, fast, and hard to mess up (I would know about that).

[clockmaker]

So I can deal with various thickness projects, I could have a stack of spacer blocks so I can use predetermined Stock Heights in my tool path setup which are always just a bit thicker when stacked to be thicker than the actual stock. Still hoping someone knows how to accomplish the same using offset commands.

[Bruce]

Theoretically you can set your zero anywhere on the work area of the CNC as long as you know the thickness (or height) of the work material in relation to that zero point. So you could set the zero probe anywhere on the waste board base and then just enter the differnce of the height of the material to the probe height (a positive number if higher and a negative number if lower) in the Z axis work zero.
(A trammed router and waste board surfaced flat would be required)
Similar to what Hans does, I'll stick a piece of aluminum tape next to the workpiece and use it as the probe surface to change tools. Entering the original material thickness minus the tape thickness (0.15mm) as the zero.

[clockmaker]

That should work. That is pretty much what I am going to do, but create a macro to do it. Since I want to be able to use both the XYZ touch plate and a fixed z-plate, I am going to install a three position switch so I can choose which one is connected to the control box. Because the Z-plate will be fixed, I am also going to mount a piece of light weight spring steel so that when the router is over the z-plate, the spring steel will make contact with the router collet. The spring steel will be wired so the connection will be automatic. Another option is to run a wire through the drag chains to the router. I need to see how that might work.

There's about 6" of wasted space at the back of the machine, so plenty of room to mount it along with a bit and tool box.

I have had lots of time to calibrate my Mega-V. I replaced the two piece MDF base with single piece made from two 1/2" thick MDF boards glued together and sealed. Should be quite stable. The table it is sitting on is also flat and stable. So that the extra thickness does not impact my Z range, I mounted the base under the side rails instead of top. That resulted in an extra 3/4" range, which I consumed with alternating t-track and MDF strips for holding stock. I also added additional bracing, and much longer screws to hold the side rail mounts to the bottom side rails. The result is a much stiffer and more stable assembly. Since there are no adjustments built into the Mega-V, calibrating is a matter of loosening and tightening fasteners. Not ideal, but with patience it is possible to get the router to move up and down vertically. Part of the problem was that the steel plates are not flat so the rails have to be shimmed. Using the existing mount to get the router itself vertical is was a real pain until I figured out that thin lead or aluminum tape glued to the inside of the mount provided just the right combination of give and strength to get it to stay where I tightened it. Also helped to replace the screw head bolt with a hex head bolt so it can be properly tightened. There was no way to get the gantry rail perfectly vertical. Played with the wheel adjustments for hours. I was only able to get the gantry rail face perfectly perpendicular with some of the wheels not even engaging the track. I ended up using shims on the lower z-axis wheels. Using the 3-4-5 triangle method I was able to square everything up. Before that I made sure the travel distance was exactly as entered. It was off a bit from the factory, so adjusted the firmware setting in UGS. For tramming, I used a dial gauge on a 12" boom. A bent coat hanger works just as well.

I actually brought the system into the house so I could play with G-Code in comfort. After I move it back to the shop I will have to go through the calibration routine again and then run a facing routine on the T-Track spoil strips. The overall dimensions of the spoil strips are just inside the max travel distance of the router, so no high edges when done.

[canadiannewbie]

WOW this is all good info for a beginner. thanks for putting this up for us. Not sure I understood all of that but I will come back to this thread for help as I start.

[smytty]

I hope someone can help with this problem, it started when I would zero out X,Y,Z to the bottom left corner of my material, start cut and the machine started to cut to the right and up by roughly .5". When preveiwing the project on the visulizer you can see that the project is shifted over, but on the preview in vcarve desktop everything looks good. So I decided to do a fine tune as shown on the millright site, did the calculations, entered $100=0.000 and $101=0.0000 for X & Y, now machine will not respond to commands at all and will not move. No alarms come up. I am running a carveking. Any help woulb be appreciated.

[johnm]

Hi Bruce. All my problems have been resolved now. I acquired ne boards from Milright and installed them. Everything is great accept that my limit switches aren't working that I know of. Occasionally I make the error of setting the distance too far on the Y gantry and the machine tries to power through it. This messes up my Home position.