I should mentioned that I am totally newbie to arduino ...
First of all , I would like to verify if the following components list is good starting point or not :
( the list was suggested by some guy from a local shop in my town ; but he mentioned that they use these components mainly for 3d printers, so I am not sure if it's good also for my project )
is the Arduino Mega 2560 working well with the Grbl software ? What I understand so far is that Grbl is not compatible, but it's possible to modify/hack it to make it work.
do the motors seem powerful enough for moving the Dremel router ?
( it would be nice to have the possibility in future to upgrade to a standard router instead of the Dremel , but only if the extra costs with components are small ).
what do you think about a different approach : instead of arduino , try to use some motor driver control board connected to pc on parallel port , using the software like mach3 or linuxCnc .
What would be the advantages and disadvantages of arduino compared to such a board ?
The A4988s will be struggling with 1.7amp motors. The Pololu DRV8825 can manage a bit more current.
I have not used it (I wrote my own code) but I believe GRBL works well.
If your mechanical system has low friction the motors will have no trouble moving the Dremel. The more important question is how much torque is needed to move the Dremel against the cutting load.
The choice between an Arduino and a PC with an old-fashioned parallel port (a USB-parallel will not be suitable) depends on your own level of knowledge. Personally I would choose the Arduino - but its a long time since I had a PC with a parallel port.
I've been there done that and wasted loads of money but not with arduino. Looking at the build quality of that link you posted in my opinion you would be waisting your time and money
The amount of play you would have in the table only held in place with stand off bolts one can only imagine the amount of play you would have in that system plus I tried a dermel and found it was useless. But this all depends on what you want to do with. I wanted mine for milling PCB'S my wooden one was know where near good enough in the end I went and brought a 6040 CNC machine, carried out some improvemeants and now produce some excellent PCB'S. I have and am considering the tinyg CNC controller but don't think it's got enough current capability.
Robin2:
The A4988s will be struggling with 1.7amp motors. The Pololu DRV8825 can manage a bit more current.
I have not used it (I wrote my own code) but I believe GRBL works well.
If your mechanical system has low friction the motors will have no trouble moving the Dremel. The more important question is how much torque is needed to move the Dremel against the cutting load.
When I mentioned moving the dremel , I also had in mind that the main difficulty is when the motors have to move the dremel against the material .
Perhaps I should begin by experimenting with the mechanical part before purchasing any electronics or motors.
The choice between an Arduino and a PC with an old-fashioned parallel port (a USB-parallel will not be suitable) depends on your own level of knowledge. Personally I would choose the Arduino - but its a long time since I had a PC with a parallel port.
I don't have experience with either. My feeling is that it would be easier to use a parallel port controller board , but there is some risk for incompatibility .
With Arduino i'd have to study more for understanding the needed components and putting them together - but on the other hand I see the advantage that I could later reuse the components for other projects.
Thanks for the answer and for the link about motors.
Steveiboy:
I've been there done that and wasted loads of money but not with arduino. Looking at the build quality of that link you posted in my opinion you would be waisting your time and money
The amount of play you would have in the table only held in place with stand off bolts one can only imagine the amount of play you would have in that system plus I tried a dermel and found it was useless. But this all depends on what you want to do with. I wanted mine for milling PCB'S my wooden one was know where near good enough in the end I went and brought a 6040 CNC machine, carried out some improvemeants and now produce some excellent PCB'S. I have and am considering the tinyg CNC controller but don't think it's got enough current capability.
Thanks for the warning about wasting time and money : I'll think well before starting the project.
I'm not worried about spending too much ( it is not a fortune to buy an Arduino, three motors and a few more components) , but wasting too much time for a bad result would not be nice.
Regarding the use : I'd use it for wood - for example cut gears out of thin plywood, or carve letters on wood surface .
Steveiboy:
The amount of play you would have in the table only held in place with stand off bolts one can only imagine the amount of play you would have in that system plus I tried a dermel and found it was useless.
Do you mean sideways play in the table due to flexing of the stand-off bolts?
Thicker bolts? More bolts?
You don't say why the Dremel was useless?
I have recently replaced my Dremel with a Proxxon mini-drill primarily because it has a much simpler and more accurate steel locating collar so it fits quickly and accurately into the Proxxon drill stand. The Proxxon also has the on-off switch separate from the speed control. When I first switched the Proxxon on I thought it was broken because I could not see the chuck rotating - it was running so smoothly.
problems :
beam flex. unless you are using something along the lines of 1 inch steel rails, the flex of the beams will be noticeable.
if you want to do anything with metal, then you need even thicker beams.
you you take two 1 inch steel beams and use a small screw in the middle, you will see them flex a couple mm before you start to feel pressure on the wingnut as you tighten.
wood uprights.
there is no cross support, they will sway with moderate load when you are cutting sideways.
generally speaking the machine is a toy. it might do some wood carving with light finish passes and a very tiny cutter tip
Dremel:
dremel is plastic and is no designed for side forces on the housing or bearings.
bearings are not designed to carry away heat and are not designed to support side loads
failure is based on continuous run time. if you put an hour meter on the dremel, you should get 500 hours out of it.
does not sound horrible, but since your machine can only take light cuts, you will need to run it for hours at a time.
figure 100-300 pieces per dremel.
buy stock in the company. when you buy a new one every couple months, it will feel like you are investing in your future.
what you do not see is the table . supported on the ends. it too will flex.worse than the rails.
spend some time in the CNC forums, you will understand how much engineering is needed to make a USEABLE machine, and how easy it is if you use some simple machine assembly practices.
when you do the math on screws and stepers, you will find that 300 pounds of force is not that hard to get with your steppers on a lead screw. and the fact you can bend the bars with hand forces, well, the result will be obvious.
what makes matters worse is that on flex, the shaft will vibrate and bounce. maybe only a few thousandths of an inch, or 0.2mm, but once it starts vibrating, you have to reduce the depth of cut and slow the feed rate.
dave-in-nj:
problems :
beam flex. unless you are using something along the lines of 1 inch steel rails, the flex of the beams will be noticeable.
if you want to do anything with metal, then you need even thicker beams.
you you take two 1 inch steel beams and use a small screw in the middle, you will see them flex a couple mm before you start to feel pressure on the wingnut as you tighten.
wood uprights.
there is no cross support, they will sway with moderate load when you are cutting sideways.
generally speaking the machine is a toy. it might do some wood carving with light finish passes and a very tiny cutter tip
Dremel:
dremel is plastic and is no designed for side forces on the housing or bearings.
bearings are not designed to carry away heat and are not designed to support side loads
failure is based on continuous run time. if you put an hour meter on the dremel, you should get 500 hours out of it.
does not sound horrible, but since your machine can only take light cuts, you will need to run it for hours at a time.
figure 100-300 pieces per dremel.
buy stock in the company. when you buy a new one every couple months, it will feel like you are investing in your future.
what you do not see is the table . supported on the ends. it too will flex.worse than the rails.
spend some time in the CNC forums, you will understand how much engineering is needed to make a USEABLE machine, and how easy it is if you use some simple machine assembly practices.
when you do the math on screws and stepers, you will find that 300 pounds of force is not that hard to get with your steppers on a lead screw. and the fact you can bend the bars with hand forces, well, the result will be obvious.
what makes matters worse is that on flex, the shaft will vibrate and bounce. maybe only a few thousandths of an inch, or 0.2mm, but once it starts vibrating, you have to reduce the depth of cut and slow the feed rate.
This about sum's up in what I was going to reply, I spent about £500 on all the bearings, precision rod and lead screw's and steppers motors and wood. I spent in total about 60-70 man hours in building it I added extra support and doubled the sides up, but still had slop in it, don't get me wrong I had fun along the way and enjoyed building it, but if I knew then what I know now I would have just brought one. The Arduino and driver board would not cost much it's just the rest it all mounts up.
I still have all the stuff not sure what to do with them yet
