The Frog: CNC Router

Inspired by the OX (really cool!) the "Frog" is a CNC Router, using many parts from OpenBuilds.

2/13/2015 update -- Done for now. Someday if I feel inspired I'll make a beefier machine, taking into account all I've learned (which is a bunch!). In the photo here and in the discussion, I've added dust shields for the X-axis screws, installed a new independently adjusted transparent dust boot, and re-installed the LED laser crosshair. Sorry, the Altoids tin had to go. Time to make parts...

1/31/2015 Update -- Now installing a DeWalt 611 spindle motor, a newly designed dust shoe system and dust/chip covers for the x-axis rollers and leadscrew. I'll publish photos as it goes.

1/1/2015 update: Z axis now operational with new leadscrew. This, in combination with a carriage stiffening bracket has made the entire system much more rigid, finally cutting as I hoped it would.

Please see YouTube video at:


12/28/2014 update: I'm about to add leadscrew drive to the Z axis (finally), that should complete this phase of the upgrade. BTW, with the many small (and some not-so-small) changes, the cutting is going much better -- better accuracy with more aggressive cuts. Truthfully, the process has been like painting a house -- you paint one room, and all you see is the rooms not yet done!

I'm adding photos of this Z-Axis update over in the discussion area; I hope to have it functioning this coming week.

12/14/2014 update: The X and Y axes are now both acme leadscrews rather than belt. The system rigidity is much better, but I still have this yearning to build a REALLY stiff cnc router (project to come...). In the meanwhile, I'm enjoying the improved performance. New photos posted over in the discussions area. This latest invocation has 5-start acme leadscrews from McMaster, anti-backlash nuts and adapters from DumpsterCNC (Nice!), and various custom sheet metal parts courtesy my plasma cnc table. Also BTW I'm getting better with Artcam Express, a really great value in 3d design CAD/CAM software.

11/14/2014 update! After months of frustration with poor system rigidity, I have determined the biggest contributor -- belt stretch! I've had to keep my cuts very shallow, otherwise deflection at the router tip is huge. Experimentally, with the motors fully energized but not moving I can force the carriage in both X and Y directions (and stretch the respective belts) 1/4 inch or more with fairly little force, and without the motor shaft(s) turning at all. Yes, I installed the bigger belts and gave it plenty of tension -- still not good enough.

I then considered installing racks and spur gears (like my plasma CNC has), but there's really no good place for them in the current design. Finally I decided to bite the bullet and rework the X and Y drive systems to use precision Acme rods and nuts. Preliminary design trials indicate they should fit without major rework of the current bearings and other frame members, and with the added benefit of moving the Y-Axis motor off the carriage, and the two X-axis motors off the gantry.

I will post photos and info as they become available.


2/14/2014 Update: After a couple weeks of usage, here's my take on how the Frog is performing:

1. The reliability has been excellent, particularly the (admittedly cheap) electronics, in conjunction with Mach3. I made the right choice for this one.
2. The rigidity of the overall system is OK but not super. I have noticed a small bit of chatter on some cuts, mostly due to slight flexing of the various frame components (actually it's the belts, see above). Depending on the speed and depth of cut, sharpness of the bit, hardness of the material, climb-milling or not, I can occasionally get slight "corduroying" of the cut surface. Only happens on rough cuts.
3. I've had to tighten the long x-axis belts due to a bit of detectable backlash in the pulleys. I am getting ready to change to 3mm GT2 parts, interested to see if this helps.
4. I built a vacuum motor box with speed control for the vacuum table, see photo. Much more reliable than using a shop-vac. Notice the muffler, home brew and quite effective. The vacuum table itself has worked very well, particularly with the new vacuum motor.
5. I made my first 3-d shaping cuts, a sample from ArtCam Express (which I have ordered). 1/4" roughing, then 1/8" ball nosed bit for detail. See photo, took almost 2hrs to make, but the result is good.

1/27/2014 Update: The Frog LIVES! Today I made the (obligatory) name plate for the Mrs. The machine worked without a hiccup, definitely need to install some kind of chip vacuum system. My next endeavor is checking out software that can do contouring -- ArtCAM Express looks like a good deal.

1/25/2014 Update: The build is going well, have created a few helper features, such as belt tensioners for x-drives, a z-axis limiter (it falls when the power is off), and hose-clamp mounts for the router motor.

1/4/2014 Update: I have modified the rail mount a bit to allow for a simple vacuum box. Not fully detailed yet, but here's the concept (SolidWorks models have been updated in the Files area). I have added a third 2x3 wood strut in the middle.