A different kind of build.

[Max Z]

FF, I have been following your report with interest. I already have access to cnc capacity, so I do not intent to build one for myself, but I like to follow others with an original design, like yours.

I was wondering, with a cantilever type like you have designed, does it not suffer from inaccuracies due to the deflection of the Y-axis beam varying with the travel of the laser head? I don't suppose the beam itself is bending, but more like some flexibility in the X-axis guide system.

[Erfolg]

Max

Let us assume there is deflection. Which is will also be true of systems built on Portal frames. As Beams bend.

I assume there will be twisting also due to torque effects.

In my brief time in the Machine Tool Industry and additionally in classification of installed machine tools for class of production accuracies, does it matter? What accuracy is required for model parts?

Having been out of manufacturing industry for now 40-50 years, I can remember that some horizontal boring machines had a cantilevered boring head. Radial arm drills obviously were the same. In those cases I guess the manufacturers ensured that the sections and mechanisms were sufficiently rigid under loads.

In my case I just need sufficient performance to match my needs, rather than the accuracy that some applications may demand.

[Max Z]

Not so much the accuracy of the cut, but the effect on the focus of the laser and on the efficiency of the burn, and hence the number of passes and the width of burn zone. I have no idea how critical this is, that's why I am asking

[FlyinFlynn]

I really cannot see the gantry bending..providing it is not 10 meters long . There is very little extra load on the gantry when the laser moves to its outermost end - and there are no 'loading' loads that you would get with a router that is pushing down on the work piece so.... no..I don't see any degradation of the cut.. Both axes have fine adjustments to get the carriages slop free but 'fluid'. Also, we are in modelling territory here, not precision pcb etching territory. As you go longer in either axis you could start to run into issues with the belts stretching and vibrations caused by lack of sufficient supports, although so far my 1020mm cutter seems ok, and no one would want anything longer surely

The laser focus is also a bit hit and miss.. it is not that critical, if it was you would have to lower the laser head for every pass as it cuts about half a mm per pass. I find cutting 6mm balsa without adjusting the focus is no problem, of far more use is blowing away the smoke and debris from the cut. TBH if the laser has to do 20 passes instead of 18 on 6mm balsa so what? 6MM ply might be more problematic I suppose, but I think I would use the 2.5Watt laser to mark the piece out and then cut it on my bandsaw

[Erfolg]

Flyin, your comments on belt stretch, rekindled memories of the difficulties that the then a local machine tool manufacture encountered. There had been a step change in speeds and feeds, again, if my memory serves me well, due to the introduction of "Coated Carbide" cutting tools.

In conjunction with the digital controls, the much higher traverse and feed rates, stretched the lead screws, causing overshoot, in conjunction with a poor damping characteristic of the negative feed back control system, lead to a lot of hunting. The solution was obvious, but a chancellor who was going to squeeze the rich until the pips squeaked, the company threw in the towel, if the government was going to take the profit, without the risk, with hind sight, I cannot blame them.

All I look for is something that works for me as a modeler, that I can afford and provides a useful tool. Yes there will be limitations and tweaks required.

So keep it up

[Bob Smitham]

Great simple design Flynn the the 3D parts are rolling off the Ender3.

The feet cups will need opening a little maybe 2mm for the feet to fit.I also can't see the X tensioner on the cloud ?

My shopping basket at the moment totals £56 for extrusions pullys, belt,motors.I will be going for a 1000mm x 400 for a shed work bench fit .For the controller board It's looking like the UNO CNC expansion.Bangood currently have them for £10 with stepper drivers and a UNOrev3( I do have an UNO but the expansion card doesn't appear to be sold separately) Not sure I could source the individual components for much less.

So that would bring me up to the £66 mark leaving me enough wallet wriggle room for a decent laser unit and still come in cheaper than the budget one third of the working area ready made items.Thank again for posting this.If you don,t have the X tension files I am sure I can manage something in fusion.Regards Bob

Edited By Bob Smitham on 26/12/2020 11:06:01

[FlyinFlynn]

The adjusters are in part 3...I have incorrectly called them Y frame assembly adjusters..... Doh!...I've renamed them now

I always find I have to fettle parts others have designed..it's down to flow rates and nozzle sizes I'm sure.

All looks good. The cncshield is sold separately but the package is usually more cost effective. You'll only need 2 of those drivers

I reckon I could get close to £10 for the electronics using stuff I designed myself, but for all the trouble unless you specifically need a particular sized controller board then the uno/cncshield is very hard to beat.

Happy building!

Edited By FlyinFlynn on 26/12/2020 19:08:16

[Bob Smitham]

A big thank you for sharing this FlyinFlynn.The CAD files made changes to the head carriage to accommodate my unit easy.All tested and firing.

Now the hard bit for me plouging through config.h files and GRBL settings for the end stop set up .Then the dialing in of settings which I imagine will be trickier than the build.

[FlyinFlynn]

Great!!....glad it was of some use. you really don't need the endstops. you can just move the laser head to a convenient place, fire up the laser at 2% and place your workpiece beneath the laser spot. If you want you can then 'frame' your image with this macro -

G90G0X[left]Y[bottom]F6000
M3 S5
$J=G91Z0.0001F2000
G90G1X[left]Y[top]F6000
G90G1X[right]Y[top]F6000
G90G1X[right]Y[bottom]F6000
G90G1X[left]Y[bottom]F6000
M5

It will trace the boundry box.

If you really do want the homing then you just need to turn homing on with $22 = 1

Set the homing direction with $23 = (0 to test if both x and y are going the right way, then if x is wrong the value needs to be 1, if y is wrong the value needs to be 2 and if both are wrong then the value needs to be 3....mine is 3)

set $24 = 500 and $25 =5000 as a start point, these are seek and locate speeds

$26 = 250 (debounce delay)

$27 = 7.0 (pull off distance after the initial seek home - this may need to be adjusted )

[FlyinFlynn]

Here is my GRBL config if it helps 

$0	Step pulse time	10	microseconds	Sets time length per step. Minimum 3usec.
$1	Step idle delay	25	milliseconds	Sets a short hold delay when stopping to let dynamics settle before disabling steppers. Value 255 keeps motors enabled with no delay.
$2	Step pulse invert	0	mask	Inverts the step signal. Set axis bit to invert (00000ZYX).
$3	Step direction invert	0	mask	Inverts the direction signal. Set axis bit to invert (00000ZYX).
$4	Invert step enable pin	0	boolean	Inverts the stepper driver enable pin signal.
$5	Invert limit pins	0	boolean	Inverts the all of the limit input pins.
$6	Invert probe pin	0	boolean	Inverts the probe input pin signal.
$10	Status report options	1	mask	Alters data included in status reports.
$11	Junction deviation	0.010	millimeters	Sets how fast Grbl travels through consecutive motions. Lower value slows it down.
$12	Arc tolerance	0.002	millimeters	Sets the G2 and G3 arc tracing accuracy based on radial error. Beware: A very small value may effect performance.
$13	Report in inches	0	boolean	Enables inch units when returning any position and rate value that is not a settings value.
$20	Soft limits enable	0	boolean	Enables soft limits checks within machine travel and sets alarm when exceeded. Requires homing.
$21	Hard limits enable	0	boolean	Enables hard limits. Immediately halts motion and throws an alarm when switch is triggered.
$22	Homing cycle enable	1	boolean	Enables homing cycle. Requires limit switches on all axes.
$23	Homing direction invert	3	mask	Homing searches for a switch in the positive direction. Set axis bit (00000ZYX) to search in negative direction.
$24	Homing locate feed rate	500.000	mm/min	Feed rate to slowly engage limit switch to determine its location accurately.
$25	Homing search seek rate	5000.000	mm/min	Seek rate to quickly find the limit switch before the slower locating phase.
$26	Homing switch debounce delay	250	milliseconds	Sets a short delay between phases of homing cycle to let a switch debounce.
$27	Homing switch pull-off distance	7.000	millimeters	Retract distance after triggering switch to disengage it. Homing will fail if switch isn't cleared.
$30	Maximum spindle speed	1000	RPM	Maximum spindle speed. Sets PWM to 100% duty cycle.
$31	Minimum spindle speed	0	RPM	Minimum spindle speed. Sets PWM to 0.4% or lowest duty cycle.
$32	Laser-mode enable	1	boolean	Enables laser mode. Consecutive G1/2/3 commands will not halt when spindle speed is changed.

Edited By FlyinFlynn on 10/01/2021 11:20:16

[FlyinFlynn]

$100	X-axis travel resolution	160.000	step/mm	X-axis travel resolution in steps per millimeter.
$101	Y-axis travel resolution	160.000	step/mm	Y-axis travel resolution in steps per millimeter.
$102	Z-axis travel resolution	425.000	step/mm	Z-axis travel resolution in steps per millimeter.
$110	X-axis maximum rate	5000.000	mm/min	X-axis maximum rate. Used as G0 rapid rate.
$111	Y-axis maximum rate	5000.000	mm/min	Y-axis maximum rate. Used as G0 rapid rate.
$112	Z-axis maximum rate	500.000	mm/min	Z-axis maximum rate. Used as G0 rapid rate.
$120	X-axis acceleration	200.000	mm/sec^2	X-axis acceleration. Used for motion planning to not exceed motor torque and lose steps.
$121	Y-axis acceleration	200.000	mm/sec^2	Y-axis acceleration. Used for motion planning to not exceed motor torque and lose steps.
$122	Z-axis acceleration	10.000	mm/sec^2	Z-axis acceleration. Used for motion planning to not exceed motor torque and lose steps.
$130	X-axis maximum travel	1100.000	millimeters	Maximum X-axis travel distance from homing switch. Determines valid machine space for soft-limits and homing search distances.
$131	Y-axis maximum travel	250.000	millimeters	Maximum Y-axis travel distance from homing switch. Determines valid machine space for soft-limits and homing search distances.
$132	Z-axis maximum travel	35.000	millimeters	Maximum Z-axis travel distance from homing switch. Determines valid machine space for soft-limits and homing search distances.

[Bob Smitham]

Thanks for the settings.Been going through the Github wiki.(link for anyone going down the CNC shield with UNO route)

GRBL wiki

Not used Arduino since I installed a BLtouch on my printer.It doesn't take long for me to forget anything I don't do daily.

A big help in setting up that avoids swapping between apps and editing config.h has been the open source LaserGRBL s/w. Can't see it being much use for cutting plans. But it does have a built in config editor allowing you to make changes and test without swapping apps and compiling .A bonus for the technically challenged and easily confused such as myself.

If any one is building using UNO CNC shield This is a nice case found on thingyverse.Chosen because I had a 40mm 12v fan in my box of scrap PCBs.

But there are dozens of other designs that will suit what you have lying around.

Once again thanks for this.Most satisfying project Iv'e done in a while.

[Flying Squirrel]

Brilliant. Any reports after 'long' term use before I embark on this? Any products around now that you wish were around before? The actual laser in particular.

 

I don't really need it but will be a good project to do with my son.

 

Thanks FF for putting the thread together and supplying the files.

[FlyinFlynn]

I've not had any long term use problems although I haven't done loads with it, an occasional tweak to take out any slop in the carriage wheels and very minor belt stretch. I would suggest you consider adding some form of air assist to blow the debris away and keep the smoke out of the lens, it would be simple to edit the stl's to incorporate an airline.  I used a NEJE laser but things have moved on a bit now with 20Watt output power lasers now being available, albeit at a price. Others have taken this design and modified it to their tastes....that is what makes it all the more interesting!

[Flying Squirrel]

I've been looking at the laser tree heads, specifically the LT-40-AA which looks like it ticks a lot of boxes, lots to try and digest though, like fixed vs variable focus etc. 

 

Any suggestions for a laser under say £100 for general modelling use?

[Flying Squirrel]

Hi, thanks @FlyinFlynn for putting the files and parts list up, much appreciated.

 

I'm looking for some helpcalibrating this thing now it's built. I've set Vref as per various instructions but movement is waaaay off.

 

To get x and Y movement close to being as instructed I've had to set $100 and $102 to 5, of course this is new to me but compared to all other sources it doesn't appear to be right, movement is also very slow.

 

The setup is a Arduino Nano

CNC sheild V4

Nema 17

GRBL loaded

using both laser GRBL and USG for basic control

 

I'm kind of grasping in the dark here!

[FlyinFlynn]

14 hours ago, Flying Squirrel said:

Hi, thanks @FlyinFlynn for putting the files and parts list up, much appreciated.

 

I'm looking for some helpcalibrating this thing now it's built. I've set Vref as per various instructions but movement is waaaay off.

 

To get x and Y movement close to being as instructed I've had to set $100 and $102 to 5, of course this is new to me but compared to all other sources it doesn't appear to be right, movement is also very slow.

 

The setup is a Arduino Nano

CNC sheild V4

Nema 17

GRBL loaded

using both laser GRBL and USG for basic control

 

I'm kind of grasping in the dark here!

Have you fitted the jumpers under the stepper drivers? Without then, and dependent upon the actual model of stepper drivers you are using you might be employing full step mode. If you fit the jumpers you will need to multiply your 5 value by 8 or 16 (A4988 and DRV8825 respectively)

 

 

 

[Flying Squirrel]

Thanks FF, yes these are fitted, they are 4988 drivers. I did actually remove them as I suspected they could be involved but it didn't appear to make any difference to either travel distance or speed?

[FlyinFlynn]

On 30/03/2023 at 11:19, Flying Squirrel said:

Thanks FF, yes these are fitted, they are 4988 drivers. I did actually remove them as I suspected they could be involved but it didn't appear to make any difference to either travel distance or speed?

...well they should make a difference! The 3 microstepping pins should be tied to +5V in order to utilise 1/16th microstepping. Perhaps check with a multimeter?

 

Post your GRBL config.

[Flying Squirrel]

5 minutes ago, FlyinFlynn said:

...well they should make a difference! The 3 microstepping pins should be tied to +5V in order to utilise 1/16th microstepping. Perhaps check with a multimeter?

 

Post your GRBL config.

I did some more testing and they make zip all difference, looking in to it it appears to be an error in the design of the V4 Board, those pins all go to GND so no way to apply the 5v without serious modification (for a novice at least) there are also some other pi out errors. I've bailed out and ordered a v3 board and associated UNO

 

[FlyinFlynn]

Ah yes... indeed....someone dropped the ball!

 

https://www.instructables.com/How-to-Use-the-CNC-V4-Board-despite-Its-quirks/

 

Sounds like a lot of work to me, easier to buy the older board as you say! The older boards mate with an uno though, so you will need one of those too.

Edited April 1, 2023 by FlyinFlynn
adding uno

[Flying Squirrel]

2 hours ago, FlyinFlynn said:

Ah yes... indeed....someone dropped the ball!

 

https://www.instructables.com/How-to-Use-the-CNC-V4-Board-despite-Its-quirks/

 

Sounds like a lot of work to me, easier to buy the older board as you say! The older boards mate with an uno though, so you will need one of those too.

It's not going well!!

 

New shield and cloned uno - won't upload anything...arrrrghhh

[FlyinFlynn]

22 hours ago, Flying Squirrel said:

It's not going well!!

 

New shield and cloned uno - won't upload anything...arrrrghhh

Oh dear!  Does it show up in device manager ports?  It may require CH340 drivers installing. 

[Flying Squirrel]

6 hours ago, FlyinFlynn said:

Oh dear!  Does it show up in device manager ports?  It may require CH340 drivers installing. 

Yup, showing up as com 5, and tried reinstalling CH340 drivers....nothing, appears to connect but won't upload.  Bit the bullet and bought a 'genuine' Uno and we're rocking and rolling!!  

 

Now I need to fugure out why circles aren't round, calibrated both axis and no slop anywere that I can find but at least I'v emade progress!

 

I'm sure I've said it earlier but thanks again for putting the files and parts list up, not a small amount of work I'm sure.

[FlyinFlynn]

On 02/04/2023 at 17:46, Flying Squirrel said:

Yup, showing up as com 5, and tried reinstalling CH340 drivers....nothing, appears to connect but won't upload.  Bit the bullet and bought a 'genuine' Uno and we're rocking and rolling!!  

 

Now I need to fugure out why circles aren't round, calibrated both axis and no slop anywere that I can find but at least I'v emade progress!

 

I'm sure I've said it earlier but thanks again for putting the files and parts list up, not a small amount of work I'm sure.

Circles not round, after checking for the right steps per mm can be down to the dreaded loose grub screw! Is it a regular eclipse or does it vary with each print?