Beginners CNC Kit

[gfc62]

Originally Posted by hexdump The lumenlab micRo you link to looks good but I'm not sure that it looks any better than the ZenBot. It's hard to say though since I can't really find any pictures of the machine as a whole. I guess I'm asking: is there any advantage over the Zenbot that I should wait a few weeks for? Precision is somewhat important. Like I said, I'm going to be doing double sided circuit boards. They're not going to have tiny traces or anything like that, I just don't want to purchase a machine designed for machining huge parts when I just need mostly small circuit boards. It should be able to comfortably do circuits like this: http://youtube.com/watch?v=SlGcgQJRncc (look at the last few seconds of the video).

I don't know anything about the Zenbot machine other than what's in the eBay listing, a very little IRC chat, and one or two web pages apparently created by a Zenbot customer using the previous design of their machine.

I don't think it's fair for me to say which machines are better or worse than others. All I can give is my opinion about what's important and suggest some options you haven't looked at. Since I don't do PCB work, my opinions probably aren't all that helpful to you. It sounds like you're pretty close to deciding on the Zenbot machine. If you're looking for someone to talk you out of that or affirm your decision I'm the wrong person. In the end, buy what you feel comfortable with just make sure the vendor can support their products.


Hopefully someone else will jump in with other opinions. (Any one else out there tempted to jump in and criticize my oversimplified explanations please apply your energy more directly to help hexdump rather than being an '41 73 73 68 6f 6c 65')

If I were buying a pre-built machine I'd want to know more about the linear bearings and drive system.

It's unusual to use a belt drive on such a small machine; be sure you're satisfied that the minimum addressability is adequate for your application.

Stepper motors typically have 200 steps per revolution, meaning they can be positioned every 1.8 degrees of rotation. This positioning can be interpolated or smoothed using a micro stepping driver board, again with trade offs. The drive system the motors connect to use those steps to move the cutting tool (and/or the table) There are many different designs for drives. None are absolutely 'good' or 'bad', they each have benefits and limitations.

Machines this small more commonly use drive screws which provide a built-in gear reduction. A 10 thread-per-inch drive screw will move the tool an inch when the motor turns 10 times. Even using full steps, this gives 2000 steps per inch, resulting in a high degree of addressability (and additional torque) by trading off fast movement. A belt drive works differently, trading off some addressability for fast movements. Depending on the belt drive design you may end up with fewer than 200 steps per inch reducing the theoretical ability to position the tool at an exact location. Then again, for some applications this could be adequate. If your application doesn't require high addressability then a belt drive may be a good solution, particularly if it's well designed.

Note that addressability isn't the same as accuracy, the two are complementary properties. Accuracy is the result of the design, materials used, manufacturing processes, and many other factors.

Speaking of design, the X&Y bearing design isn't discussed in any detail on the web site. From the little I've read (this, this and this ) the previous design used hardened ways and nylon or HDPE bearings on X&Y. The new design apparently uses ball bearings on square steel tubing. Does this new design have any provision for adjusting the bearings?

I suggested the Lumenlab micRo after reading your comments about price and concern about buying from a person rather than a company. It's not shipping and I have no experience with it but it will likely be a bit cheaper than the Zenbot. Lumenlab is new to CNC but has been around for a while supporting hobbyists building DIY video projectors. They have an active support forum.

[Crevice Reamer]

Maybe THIS is what you need:

http://www.kdntool.com/_sgt/m2m3_1.htm

CR.

[analogman]

Take a look at the fireball. Sounds like it will suit your need perfectly. Around $1k for a turn key setup wo software. Here are some sites:

The fireball site:
http://www.fireballcnc.com/machines-...terceptor.html

Retailer that sells turn-key kits:
http://www.probotix.com/

A user that mills very fine double sided boards:
http://millpcbs.com/

[hexdump]

Originally Posted by gfc62 I don't know anything about the Zenbot machine other than what's in the eBay listing, a very little IRC chat, and one or two web pages apparently created by a Zenbot customer using the previous design of their machine.

True, the information about it is very scattered at best. A good support community to turn to is important for a beginner like myself. The ebay feedback is good but that's not really saying much these days.

Originally Posted by gfc62 I don't think it's fair for me to say which machines are better or worse than others. All I can give is my opinion about what's important and suggest some options you haven't looked at. Since I don't do PCB work, my opinions probably aren't all that helpful to you. It sounds like you're pretty close to deciding on the Zenbot machine. If you're looking for someone to talk you out of that or affirm your decision I'm the wrong person. In the end, buy what you feel comfortable with just make sure the vendor can support their products. Hopefully someone else will jump in with other opinions. (Any one else out there tempted to jump in and criticize my oversimplified explanations please apply your energy more directly to help hexdump rather than being an '41 73 73 68 6f 6c 65') If I were buying a pre-built machine I'd want to know more about the linear bearings and drive system. It's unusual to use a belt drive on such a small machine; be sure you're satisfied that the minimum addressability is adequate for your application. Stepper motors typically have 200 steps per revolution, meaning they can be positioned every 1.8 degrees of rotation. This positioning can be interpolated or smoothed using a micro stepping driver board, again with trade offs. The drive system the motors connect to use those steps to move the cutting tool (and/or the table) There are many different designs for drives. None are absolutely 'good' or 'bad', they each have benefits and limitations. Machines this small more commonly use drive screws which provide a built-in gear reduction. A 10 thread-per-inch drive screw will move the tool an inch when the motor turns 10 times. Even using full steps, this gives 2000 steps per inch, resulting in a high degree of addressability (and additional torque) by trading off fast movement. A belt drive works differently, trading off some addressability for fast movements. Depending on the belt drive design you may end up with fewer than 200 steps per inch reducing the theoretical ability to position the tool at an exact location. Then again, for some applications this could be adequate. If your application doesn't require high addressability then a belt drive may be a good solution, particularly if it's well designed. Note that addressability isn't the same as accuracy, the two are complementary properties. Accuracy is the result of the design, materials used, manufacturing processes, and many other factors. Speaking of design, the X&Y bearing design isn't discussed in any detail on the web site. From the little I've read (this, this and this ) the previous design used hardened ways and nylon or HDPE bearings on X&Y. The new design apparently uses ball bearings on square steel tubing. Does this new design have any provision for adjusting the bearings?

All good information here. I greatly appreciate it.

Originally Posted by gfc62 I suggested the Lumenlab micRo after reading your comments about price and concern about buying from a person rather than a company. It's not shipping and I have no experience with it but it will likely be a bit cheaper than the Zenbot. Lumenlab is new to CNC but has been around for a while supporting hobbyists building DIY video projectors. They have an active support forum.

The LumenLab does have an advantage in that it seems like a community-supported project. I certainly have no problem trusting them, it's just a matter of the machine not existing yet...perhaps it would be worthwhile to wait...

Originally Posted by Crevice Reamer Maybe THIS is what you need: http://www.kdntool.com/_sgt/m2m3_1.htm CR.

I've looked into that. It certainly seems very professional and nice but $1k is a bit much for me at this point.

Originally Posted by analogman Take a look at the fireball. Sounds like it will suit your need perfectly. Around $1k for a turn key setup wo software. Here are some sites: The fireball site: http://www.fireballcnc.com/machines-...terceptor.html Retailer that sells turn-key kits: http://www.probotix.com/ A user that mills very fine double sided boards: http://millpcbs.com/

I've looked at that one and contacted the seller as well. He says that the V90 probably isn't that great for PCB milling. The site you link to (http://millpcbs.com/) is by a user of the F90, which is no longer sold by Fireball but was better for PCB work (according to the guy I contacted at Fireball CNC).

So, at this point it's a matter of waiting for the ZenBot (sold out) or micRo (not yet available) or saving up some money until I can get that converted Proxxon. Suggestions?

[bitbanger]

If you are comparing the V90 to the ZenBot, then you will have similar results with milling PCBs because they are both flying gantry machines. True, that the F90 may have been more suitable for PCB milling with it's moving table design, but that is apples and oranges.

You can get good results with the V90. It's a matter of how much time you are willing to take to dial in the table. The F90 also requires a lot of patience. Having the right engraving bit, finding the perfect feed rate, and figuring out how to level the PCB substrate to the cutting path is the key to good PCB milling.

>Len

[Kelinginc]

check this package
http://www.kelinginc.net/CNCNEMA23Package.html
Ready and plug controller
http://www.kelinginc.net/ControlSystem.html

[samco]

One of the emc2 developers purchaced a zenbot..

http://axis.unpythonic.net/01188338604
http://axis.unpythonic.net/01188441458
http://axis.unpythonic.net/01215190154

sam

[bitbanger]

Keling,

This thread is about hardware, not electronics and motors. Perhaps you linked to the wrong page. All I saw there were motor/driver kits.

>Len