Setting this discussion up to gather up and brainstorm ideas.
LIST OF EQUIPMENT AND MATERIALS UNDER CONSIDERATION:
Materials to be Used:
Some design considerations:
Everyone feel free to inject any comments. This is your chance to provide input on what features go into the DIYDrones CNC Machine!
Current Bed Size:
Currently we're thinking the bed size will be 18x24 inches.
Insights from bGatti:
Some observations I can offer from experience:
1. Inexpensive skate bearing are not well sealed, and will likely stick if exposed to wood dust.
2. The most vibration on my machine is twist across the gantry - so make the gantry height ~twice the height of the lower extremity (from the table).
3. Parallel ports are increasingly harder to find - especially on laptops.
4. It doesn't take a lot of power to move a cnc machine - you will probably want to turn down the power to avoid breaking bits / bending the spindle shaft anyway - so don't specify a motor system which is stronger than your specified spindle. Anything which can be cut quickly on a strong machine, can be cut slowly on a lesser machine. $1000 is a lesser machine.
5. I have a wooden bed; I'd love an aluminum bed, but with $1000 to spend, the wooden bed isn't my biggest challenge. (It's gantry twist and probably runout for PCB Boards).
6. 3D printers want speed more than brute rigidity - most blogs on the subject of hybrids concede this point - which said - there are many parts which can be made slowly - but some parts call for a flying buttress - which does depend on a certain rate of speed.
well main attractive feature for me was that it reduce the speed so the noise is more manageable. Most of us (if not all) will have it in the basement or garage so noise level should also be part of the design.
A router at full speed makes a lot of noise, even when not cutting, just the fan inside to cool it is crazy.
From day one, the biggest single problem I had using my table was the noise it generates. Most of the noise from a router is the noise generated by the fan inside it, not from cutting anything - the difference in sound level from cutting to not cutting material is hardly noticeable. I measured a whopping 105 dB from my table with the 33,000 RPM router and my shop vac running. Couple that with a one to two hour carving and the fact I have a basement workshop means that I usually have to wait until others in the house leave before I can do much work while wearing shooter's hearing protectors.
one more variable to make it a winner CNC for DIY guys!
Interesting. I'll add that to the list. As Monroe says, we could probably build a router with a servo motor, but we still need a controller, and this could be a candidate.
for this, what microcontroller are we using? arduino? or is there something better control-wise for A CNC?
I put a list of servo controller's that we are considering on the top of the discussion. Personally I prefer that we don't have to come up with new driver software. DQ5420MA stepper controller above already has an associated controller, which works with EMC2 and other popular software and can handle motors up to 50V. The DC1 from Makerbot is a servo controller, which I think we can use for the spindle. Personally, I ok with using the steppers for the axis drives, and doing a servo controller for the spindle. I think that's a good compromise in terms of cost, and performance.
Steppers for me! :)
thanks for making this as modular and as open to customization as possible without derailing the "project"... I work in IT so scope creeps are dangerous!
Also, after reading this discussion on stepper vs servos, one of the Moderators there answered like this:
So from this I would say that only advantage we will get out of servos or encoded steppers, is to be able to stop the cut, if a slip occurs, if using software like Mach.
Sorry Monroe, don't mean to be stubborn. Just making a point. If we can go with servos, I also have no problem. Just want to make sure we are going to come up with the right design at the right cost and feasibility. We are not at the point of ruling out anything yet.
well maybe we can decide that later... when you present us "real" price difference... I am with you on better things but this might be a thing we upgrade later... not sure...
what are we looking at in terms on cost difference?
Just from my browsing around, looks like about $200+ per axis with a servo system, and ~$100 per axis with steppers. For instance that 6-axis stepper system I have listed above is $132 per axis.
Eoin, if all your going to do is just PCB, the 3020, I mentioned my blog is more than sufficient, I think. However, we would like to do this much more capable CNC machine for $1200 range.
Of, course you don't have to convince me that servos are more accurate. I don't doubt what you are saying, at all. But, as you say, we should design it with the ability to use either servos or steppers. From the software point of view, lime in the case of Mach, there is very little difference.