Replies to This Discussion

DistributorPermalink Reply by Dany Thivierge on May 27, 2012 at 12:11pm

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 http://www.liming.org/cnc/page5.html

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! 

Permalink Reply by Ellison Chan on May 27, 2012 at 11:56am

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.

Permalink Reply by j.baum53 on May 27, 2012 at 1:48pm

for this, what microcontroller are we using? arduino? or is there something better control-wise for A CNC?

Permalink Reply by Ellison Chan on May 27, 2012 at 2:40pm

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.

DistributorPermalink Reply by Dany Thivierge on May 27, 2012 at 3:00pm

Steppers for me! :) 

hehe 

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! 

Permalink Reply by Ellison Chan on May 27, 2012 at 3:04pm

Also, after reading this discussion on stepper vs servos, one of the Moderators there answered like this:

Mach doesn't know or care whether you have a servo or a stepper system. It just sends out step and dir signals and trusts that whatever's attached does what it's meant to. The only difference is that with a servo drive you can connect the servo drive's fault output to Mach so that Mach get's to know about it. What does Mach do? It stops sending signals. Of course you can put encoders or whatever you like on a stepper. But you would have to get that "whatever" to detect a missing step and let mach know and Mach would do exactly the same thing - just stop sending signals. AFAIK there are no systems for steppers that will "re-position" after a lost step and to be honest if there was IMHO it would be pointless. In fact it would be as pointless as a servo system that tried to re-position after it had exceeded it's allowable following error. If you REALLY want the warm feeling of knowing that your system has lost position and that Mach will stop, then personally I'd go servos. Each motor brings there own advantages to the party but If it looks like a duck and quacks like a duck then it probably is a duck - no point in trying to pretend it's anything else. 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.

Permalink Reply by Ellison Chan on May 27, 2012 at 3:16pm

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.

DistributorPermalink Reply by Dany Thivierge on May 27, 2012 at 3:21pm

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? 

Permalink Reply by Ellison Chan on May 27, 2012 at 3:25pm

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.

Permalink Reply by Eoin on May 27, 2012 at 3:11pm

Hi Guys,
I'd like to help in this if I can but I'm a bit out of my depth.
What thoughts should go into the design if one wanted to make PCB's ?
After getting stung in the Lumenlab Micro debacle last year for a grand, I have almost given up on having a capable CNC. If I had a dollar for every time I've thought 'if I only received that machine I could do x' I'd be able to buy two of these :)
I'm very happy to see this group !

Permalink Reply by Ellison Chan on May 27, 2012 at 3:20pm

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.

Permalink Reply by Ellison Chan on May 27, 2012 at 3:45pm

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.

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