CNC router build


difalkner

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While I didn't really do anything on the CNC today I did do something needed for the CNC; I built a mobile cart for the computer.  I don't have room to have a dedicated spot for a computer and related peripherals so a mobile cart was my only real option.  This is narrow enough to fit between the table saw and CNC and also narrow enough to go against the wall at the front end of the CNC but it is wide enough to be stable.  I can't mount anything to the wall at the front of the CNC even though that spot appears to be available because the attic stairway folds down right there so it's really not usable space, at least not for anything mounted permanently. 

I made this with some of the boards from the CNC shipping pallet and some MDF I had sitting around.  The only thing I bought for this project are the HF casters and outlet strip.  Both the Ethernet and Modbus cables are 15' long so I have a fair amount of travel available.

So here's my afternoon project (for me to start and finish a project in one day is close to miraculous!!) -

137 - Mobile computer stand.jpg

138 - Mobile computer stand.jpg

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When the machine came in it was missing a few links in the cable chain and those arrived today so I was able to complete the cable run on the gantry.  I need to get the correct bolt and then decide how I'll secure the cables and water lines but at least now the cable chain is in place.

140 - Cable chain added.JPG

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I set up the homing based on what I've read and seen online but I'm not certain I have this correct. Many machines I've seen move very quickly toward home and when they approach the sensors they slow down. The way I have it set it's just slow across the board. It's ok if I jog it to a couple of inches away from home but if it has a long way to travel I might as well pack a lunch. So... I wonder what I have not yet set or if I'm just mistaken on how it is suppose to act.

Here's a short video of the homing -

 

Homing Speed is set to 20% but it was 5% so it is much faster now but not sure it's correct.

141 - Homing screen.jpg

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Doesn't look slow to me at all. Much faster than the Techno machine I've been working on recently. One thing I've gotten in the habit of doing is parking the gantry and spindle near home before powering down the machine. Otherwise it's lunch time when you home the machine.

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10 minutes ago, micks said:

Doesn't look slow to me at all. Much faster than the Techno machine I've been working on recently. One thing I've gotten in the habit of doing is parking the gantry and spindle near home before powering down the machine. Otherwise it's lunch time when you home the machine.

Cool, Micks!  Maybe I'm just thinking of another set of circumstances and expecting something that isn't going to happen.  I can speed it up but don't want to crush (another) sensor. 

Yesterday I jogged it about 30" on the Y axis at 100% and it's almost scary how fast it moves.  And I don't have it set anywhere near as fast as Nate at Fine Line Automation said I could set it; X and Y motors are at 750 with acceleration at 75.  Nate said I could take it up to as high as 1800 but he recommended not going over 1200.  That would have to be some serious rapids!!

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11 hours ago, difalkner said:

Cool, Micks!  Maybe I'm just thinking of another set of circumstances and expecting something that isn't going to happen.  I can speed it up but don't want to crush (another) sensor. 

Yesterday I jogged it about 30" on the Y axis at 100% and it's almost scary how fast it moves.  And I don't have it set anywhere near as fast as Nate at Fine Line Automation said I could set it; X and Y motors are at 750 with acceleration at 75.  Nate said I could take it up to as high as 1800 but he recommended not going over 1200.  That would have to be some serious rapids!!

For your purposes and especially for a machine in the price range of yours, that's plenty quick. I don't know of a competitive router that comes close to that.

For other purposes, higher accelerations and speeds can be important. Here's a combination router and knife cutting machine I used to sell. I don't know what the accelerations were set to, but it's tuned to 7000 ipm - at 30% of the capacity of the motors and drives!

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The rack and pinion can definitely handle 1200 just fine. I recommend starting lower just to get a feel for it. We have had the higher rapids walk machines across the floor with the momentum switches. You want to be sure the machine is secured well before attempting the higher speeds. If you have it just on locked casters you might need to switch them out or bolt into a floor bracket. Most leveling feet should be good enough to keep the router in place.

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27 minutes ago, micks said:

For your purposes and especially for a machine in the price range of yours, that's plenty quick. I don't know of a competitive router that comes close to that.

For other purposes, higher accelerations and speeds can be important. Here's a combination router and knife cutting machine I used to sell. I don't know what the accelerations were set to, but it's tuned to 7000 ipm - at 30% of the capacity of the motors and drives!

I watched the video - that's moving pretty fast!

21 minutes ago, FineLineAutomation said:

 

The rack and pinion can definitely handle 1200 just fine. I recommend starting lower just to get a feel for it. We have had the higher rapids walk machines across the floor with the momentum switches. You want to be sure the machine is secured well before attempting the higher speeds. If you have it just on locked casters you might need to switch them out or bolt into a floor bracket. Most leveling feet should be good enough to keep the router in place.

Nate, do the settings on my Homing/Soft Limits screen look about right?

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Nate is right, you should keep the speed down until it's all assembled and ready. I can neither confirm nor deny that I ran my gantry off the table by being a little over zealous with a partially assembled machine.

What are your settings in the motor tuning window? There is an acceleration setting there that I think comes into play here.

Also, homing speed will vary based on the distance it needs to travel (and your Z axis will always be slow). If it needs to travel a short distance, it will jog slower than if it has to cross the entire table. But your XY speeds look way too slow, even for a short jog.

-E

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3 hours ago, Elroy Skimms said:

Nate is right, you should keep the speed down until it's all assembled and ready. I can neither confirm nor deny that I ran my gantry off the table by being a little over zealous with a partially assembled machine.

What are your settings in the motor tuning window? There is an acceleration setting there that I think comes into play here.

Also, homing speed will vary based on the distance it needs to travel (and your Z axis will always be slow). If it needs to travel a short distance, it will jog slower than if it has to cross the entire table. But your XY speeds look way too slow, even for a short jog.

-E

I'm not seeing a speed change in homing regardless of starting position.  I can go to one inch off the sensors or anywhere on the table and the homing speed is the same, so I'm not seeing the speed vary based on distance to travel.  The acceleration on the motor configuration page has to do with the acceleration rate as a percentage of the full motor speed.  If you lower the feed rate, jogged or programmed, the acceleration rate is suitably lowered.

I can changed the speed on the homing page from 20% to anything I want but whatever I choose it's the same across the board.

This is the X and Y motor configuration prior to tweaking it for accuracy this afternoon but it's close enough to show you -

142 - Motor configuration - X, Y.jpg

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I set up to do a little calibrating and found the machine was out more than I thought it would be.  The first test on the Y axis was 0.014" out in one inch.  In the full travel of the Y axis, 50", that is almost 3/4" off (0.700")!  So I used a dial indicator and did a little tweaking to the motor configuration and the Counts per Unit in Mach4.  Now when I tell it to move an inch it moves an inch - poifect!!  The only drawback is that the DRO on the screen in Mach4 is off by 0.0002" which isn't very much at all but I just don't see why it isn't 0.0000".

Here's a video to better show what I'm seeing -

 

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If you watched the previous video you probably noticed that I wasn't satisfied with the slight error in accuracy.  So, I changed my methodology and process and now it is dead on and I'm good with dead on.  I wrote a spreadsheet to use the current motor settings, take the error in accuracy, and then calculate new motor settings.  Each time I ran it the errors became smaller and the accuracy got better so after running it about 5 times it is now dead on.

 Here's the new process and video -

 

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After all the calibrations for accuracy I put the machine to a field test for about 10 minutes.  I used simple G-code to feed at 300 ipm and then to various positions all over the machine.  About 90% of the time it was spot on the number I put in the parameters and the other 10% it ended up on xx.9999" and I don't think I'll get it any better than that.  I also picked up some reusable tie straps from HF so I could clean up the cabling yet still have the ability to redo something if necessary.

Machine calibration testing -

143 - Machine test for accuracy.jpg

144 - Cabling cleaned up.jpg

145 - Cabling cleaned up.jpg

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After calibrating I thought it would be good to run some very simple patterns in the X and Y directions, no cutting so Z isn't involved.  There's not much to this but it does show me that the machine is smooth and does what I asked it to do, at least cutting air anyway.  This is a short video, about 42 seconds, so you won't be bored very long.

 

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9 hours ago, difalkner said:

After calibrating I thought it would be good to run some very simple patterns in the X and Y directions, no cutting so Z isn't involved.  There's not much to this but it does show me that the machine is smooth and does what I asked it to do, at least cutting air anyway.  This is a short video, about 42 seconds, so you won't be bored very long.

 

Awe you got me all excited i thought you were going to cut something. I look forward to seeing the first video of you cutting something.

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On ‎10‎/‎21‎/‎2016 at 7:31 PM, difalkner said:

I'm not seeing a speed change in homing regardless of starting position.  I can go to one inch off the sensors or anywhere on the table and the homing speed is the same, so I'm not seeing the speed vary based on distance to travel.  The acceleration on the motor configuration page has to do with the acceleration rate as a percentage of the full motor speed.  If you lower the feed rate, jogged or programmed, the acceleration rate is suitably lowered.

I can changed the speed on the homing page from 20% to anything I want but whatever I choose it's the same across the board.

This is the X and Y motor configuration prior to tweaking it for accuracy this afternoon but it's close enough to show you -

142 - Motor configuration - X, Y.jpg

I can try and poke around Mach4 later this week and see what I can find.

My X & Y config screen is below. Obviously the values are going to be different based on our motors, steppers, and motion hardware, but looking at the motion curve, your acceleration is almost non-existent. It looks like your machine is going from 0 to 100% in 0.2 seconds, while mine is setup to go from 0 to 100% in 1.6 seconds. Also, your G Force values are 10x what mine are, which I believe is a function of your acceleration. Maybe decrease your acceleration and then you might be able to increase the jog speed on the main screen. Give your machine some time to ramp up to full speed and time to decelerate to a complete stop. IIRC, I usually have mine set to jog at 100-150% on the main Mach 4 screen.

Config_Tuning_0.jpg

-E

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36 minutes ago, Elroy Skimms said:

I can try and poke around Mach4 later this week and see what I can find.

My X & Y config screen is below. Obviously the values are going to be different based on our motors, steppers, and motion hardware, but looking at the motion curve, your acceleration is almost non-existent. It looks like your machine is going from 0 to 100% in 0.2 seconds, while mine is setup to go from 0 to 100% in 1.6 seconds. Also, your G Force values are 10x what mine are, which I believe is a function of your acceleration. Maybe decrease your acceleration and then you might be able to increase the jog speed on the main screen. Give your machine some time to ramp up to full speed and time to decelerate to a complete stop. IIRC, I usually have mine set to jog at 100-150% on the main Mach 4 screen.

Config_Tuning_0.jpg

-E

While I truly hate to admit this I owe it to you guys to let you know what I found out; the guy who built this machine and did all the programming thus far, doesn't know the difference between X and Y... ugh! 

I had been working with the Y axis for calibration and switched to X because it was easier to set the scale on the table and view it as you can see in the video. Turns out, though, that I only switched where the scale was set but didn't change what I had been doing in Mach4.  I continued to modify the Y values when I was really working with the X axis.  So while I would love to tell y'all I found a glitch in Mach4 and fixed it the true glitch was between my ears... :o

But I can say that X, Y, and Z are now all calibrated and do exactly as they're suppose to do and I'm learning to operate a CNC machine while looking through all the egg on my face. :D

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While I truly hate to admit this I owe it to you guys to let you know what I found out; the guy who built this machine and did all the programming thus far, doesn't know the difference between X and Y... ugh! 

I had been working with the Y axis for calibration and switched to X because it was easier to set the scale on the table and view it as you can see in the video. Turns out, though, that I only switched where the scale was set but didn't change what I had been doing in Mach4.  I continued to modify the Y values when I was really working with the X axis.  So while I would love to tell y'all I found a glitch in Mach4 and fixed it the true glitch was between my ears...

But I can say that X, Y, and Z are now all calibrated and do exactly as they're suppose to do and I'm learning to operate a CNC machine while looking through all the egg on my face.

We have all had those moments. The important thing is everything is calibrated and that's one more thing off the list!

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Nice! Fun to see the machine cutting something! There's definitely a learning curve to using a CNC router. Probably the single biggest obstacle for the new users I trained (and quite a few that have been doing it for a while) is determining the proper feeds & speeds for the tooling and material. You will break several more bits, but you'll learn something each and every time.

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