3020T- DJ CNC Users thread

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Rochey said:
There's a GRBL shield available from amazon. that's where I got mine from.
https://www.amazon.co.uk/ARDUINO-SHIELD-A4988-POLOLU-DRIVERS/dp/B018SSLWV6/ref=sr_1_3?ie=UTF8&qid=1463775335&sr=8-3&keywords=grbl+shield

I just ordered this from amazon:

https://www.amazon.co.uk/gp/product/B019SXNJ0W/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

could not beliveve the price.

Cheers

Ian
 
not sure about this model, but some models are capable of marking powder paint coated surfaces!


 
I finally bit the bullet and ordered a 3020-T from eBay. I'll let you know how I get on with it. Thanks for all the useful input. I have  an Arduino with a GRBL shield and I already have Linux CNC installed as an alternative boot (which I should not really need with the Arduino doing all the hard work).

Cheers

Ian
 
audiomixer said:
Now we know were to place our faceplate orders, great! looking forward to see your first chips!

- Michael

As well as face plates I am looking forward to no longer having to hand file IEC socket holes or XLR ones. Some simple gcode should be all that is necessary for simple shapes like those.

Last night I got grbl loaded onto the Arduino and managed to send commands to it which is encouraging. One thing does puzzle me. I have seen several videos and Instructables for using the Arduino AND a CNC shield to completely replace the parallel driven stepper drivers of a CNC machine. I don't understand why you don't wire the Arduino outputs straight into the the printer  socket of the CNC thereby using the stepper drivers already in there and eliminating the shield. I did later find one video where a guy did something similar and it seemed to work well. Check this video at 6 minutes in.

https://www.youtube.com/watch?v=sGzLnUrcYYY

Cheers

Ian
 
Rochey said:
many CNC machines don't come with the drivers... in which case, a simple shield with stepper sticks are all that are needed.

That I can understand; it makes obvious sense but I have seen videos where people remove the existing driver card and replace it with Arduino + shield when the could have just fitted an Arduino. When mine arrives I think that is what I will try.

Cheers

Ian
 
You will always have a driver, whether it's on the arduino shield (with multiple A4988 Driver sub assemblies on the shield) or in a control box. in there you might have stronger drivers, like the gecko driver or the ubiquitous 3-Axix CNC board.... your example video does just that - connect the arduino to the drivers in his control box, no worries. you might have to mess around with signal polarity, as some drivers have optocouplers and some expect a commen +5V and a negative (- eg. ground ) signal. strange but I have seen that on several driver boards. usually nothing hinders you of changing that to common ground of course.

it is possible to let the arduino control a stepper directly of course,  using individual pins to run two H-Bridges, but that is a waste of pins and resources.  GRBL is set up to give step and direction commands per axis.

the drivers also provide over current protection, micro stepping and other motor control voodoo/goodies.

have fun,

Michael
 
I have ordered a db25 breakout board so I can wire the Arduino to it and then just pug it into the CNC.  That way I don't have to do anything irreversible to the CNC. I'll let you know how that goes.

Cheers

Ian
 
I tried the arduino way with no luck, but IIRCit was problem of my arduino board.

Anyway I think it's easy and cheap enough to get a old pentium4, install Mach3 and remote it via Ethernet cable and Remote Desktop.  Also Mach3 is supposed to be more powerful than GRBL, not sure why, but I remember to read about that.

There's also PidiCNC, a set of raspberry pi daughter boards to control steppers, servos and provide digital and analog I/O's for the machine, nice for limit switches or control pendants.

It works on LinuxCNC, but seems a bit slow in its development and commercializing. Anyway I think that's the best solution, a full PC is wasted power and space just to run three steppers and a on/off switch for the spindle...

EDIT: as I posted this I looked for PidiCNC web and it seems to be selling the board already, but every product shows 1,20€ and the texts are not in English so I guess they're struggling with the webshop
 
I struggled for a while to get the grbl code into the Arduino until I discovered my IDE was out of date despite using the latest Ubuntu. After that it was quite easy to burn the code into the Arduino.

Cheers

Ian
 
My 3020T arrived yesterday and last night I got it assembled and working using an Arduino loaded with grbl. I used the stepper drivers in the 3020T and wired the Arduino direct to the 25 way connector using a breakout board. I stumbled a couple of times en route. First, there is a lot of different information on the pin out of 25 way D connectors for CNC. In some, the order of the axes is X, Y, A, Z. Mine is wired X, Y, Z. Some docs say the axes wiring starts at pin 1 others at pin 2. Mine starts at pin 2 (at least that was included in the documentation that came with it). Only one mentioned that pin 14 is an enable pin. If you don't connect it low nothing happens. Lastly I had to tweak the settings of the grbl software in the Arduino. This is well documented and quite easy to do using the Arduino serial monitor. I set the maximum feed rates and acceleration rates for all three axes. The only other thing I had to adjust was the step mask which needs to be set for active low step pulses (again actually mentioned in the 3020T docs) which you do with the command $2=7. Once I had done all that I could move all three axes.

A few small niggles with the 3020T itself. First the three steppers come with different couplings. One seems to be a flexible one but there are no instructions about which axis to fit them to. I just guessed. The knurling on the spindle connector seems to be cross threaded and does not tighten up properly.  Before I fitted the stepper motors I tried turning the lead screws by hand. The Y axis one is quite smooth. The X axis one was smooth, then stiff then smooth again, as if the lead screw was warped or binding. The Z axis was similar. After I fitted the stepper motors I tested this again using the large knurled knobs on the steppers. It was much easier to turn the lead screws because of the larger diameter of the knobs but I could still feel some variation in stiffness. Lastly the supplied mains cable has an IEC connector at one end and a two pin  European connector without a fuse at the other end. They supply a European to UK adaptor. This means the mains safety earth would not be connected! Also, it is illegal to sell a new product in the UK without an properly fused UK mains plug. I have emailed the supplier and asked to be sent a proper UK IEC cable (fortunately I have one I can use for now).

Despite the minor niggles, it seems to be basically working.

Cheers

Ian
 
electroslut said:
I have a home brew machine that uses a $50 ebay stepper controller, I am running XP
with a true parallel port, using mach3. I use Vcarve to generate Gcode or Eagle.
I love it and built lots of cool stuff with it!

I am planning on using circle milling to make holes of various sizes without changing tools. With a 3.175 mm chuck it's the only way to make larger holes. For aluminium I am planning on using Z increment of 0.5mm so it will take 5 passes to make a hole in a 2.5mm panel. My smallest hole size if 2.5mm so I plan to use a 2.5mm end mill for all holes.

Does this sound reasonable. Is it close to waht you do?

Cheers

Ian
 
when doing holes and cut outs you might want to go 'almost to the line' in a first pass and do a finish pass with minimal cut. lets say you rough out your cut outs leaving  0.25mm per side and go around a last time with a finisch path taking 0.25mm over the full height.

you should also read up on conventional and climb milling. I haven't found a way to memorise which is which, but it makes a big difference on smaller mills, due to the limited stiffness.

- michael
 
audiomixer said:
you should also read up on conventional and climb milling. I haven't found a way to memorise which is which, but it makes a big difference on smaller mills, due to the limited stiffness.
With an experienced machinist, on a real rock-solid milling machine that weighs more than your car with the X-Y drags set right, climb-milling can achieve a somewhat better finish with a light final cut, as you suggest. Any flex or slop in the setup, do not climb mill.

Take a rotary wood saw, Skil-saw, whatever, squeeze the trigger, and the teeth sticking out the bottom move away from you. You cut a 2X4 by pushing the saw through it, as the blade rotation fights the direction of cut. Conventional milling

Now imagine lifting the safety guard, starting at the other side of the 2X4, and pulling it through, with disastrous and painful results, most likely requiring medical intervention involving people with latex gloves, trucks with sirens, and all that. The blade rotation would help pull the saw into the work, and you can't physically hold it back from climbing into the work too quickly, your arms have flex and are not rock-solid. Climb milling.

Gene
 
I find it hard to get my head around mechanical things but doesn't this mean that with the  mill cutter rotating clockwise you always get conventional milling and to get climb milling you need to rotate it anti-clockwise?

Cheers

Ian
 
as far as I get it you need two set of rules,  one for 'outside' work and one for a pocket.

in the end it's about where the chip is formed, bottom or top. the details - depending on your machine - whether you move the tool or the work moves makes makes my head dizzy, but in general I find this image helpful:

38772d1317680462-climb-milling-conventional-when-using-carbide-climb_conv1.jpg


you will have to sacrifice a frontplate anyway to see how far your CNC will go....

- Michael
 
audiomixer said:
you will have to sacrifice a frontplate anyway to see how far your CNC will go....

- Michael

Thanks for the picture. That makes it a lot easier to understand.

I have ordered some 2.5mm aluminium sheets for sacrifice test cutting.

Cheers

Ian
 
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