Hi, Are there any designs that move the bed up and down, instead of the router head ? Maybe with four lab-jacks or similar ? It would make the z-axis a lot simpler I think,... Thank you,
Here's one I suggested a while back. It offers depth without the loss of rigidity from dangling down a long z-axis. The basic concept uses 4 C-beam actuators connected by a single belt to a stepper mounted at the base. Plywood sides attached to the vertical C-beams give the system its rigidity. It could also double as the world's most robust 3D printer although it probably wouldn't be very zippy.
Hi, thanks for the reply, I like the idea, although c-beams seem to be quite expensive. How about mounting four non-captive Nema's on the base plate ? Nema 11 Non-captive Linear Stepper Motor 34mm Body 100mm Lead Screw T5 x 2|11LS13-0754N-100B|Linear Stepper Motors (I only need about 5cm of depth) Thanks, Btw, what software are you using for your technical designs ?
The problem with using 4 separate motors is connecting them to a controller. Most controllers only have connections points for 3 to 5 steppers and such a design would require 7. While you could double tap a couple of the connections it can be a risky proposition should one of the steppers get out of sync. Using a single stepper and a connecting belt is also a far more cost effective method, a method which several of the larger printers over in the 3D Printer section use. Sketchup
Those are very good points My 3D printer almost tore itself apart when two steppers got out of sync ! What is the longest you can have a drive belt, do you know ? And could four lead screw carry the weight of the base plus material, or had you planned on some weights/springs ? Thanks,
You can get gt2 belts up to 2.2 meters from SDP/SI and 1.5 meters from Robotdigg. Other sizes have different max lengths. Just choose a screw appropriate to the load. I'm not a big fan of the TR8x8 screws for the Z-axis as they seem a bit too aggressive for an axis that doesn't go very far or need to get there very fast. I'd be more inclined to go with something along the lines of a TR10x2 which should carry just about anything and you don't have to worry about the screw turning the motor when the motor powers down.
I think I might go for something like this: A wooden frame, with v-slot linear rails, and one NEMA with one or two belts driving the four z-axiz lead screws. I am a bit unsure if simple bearings can carry the axial load of the lead screws ? (I apologize for the rendering, I only know OpenScad (guitar for scale))
I don't know how something like this would actually work because you are going to be limited by the height of the gantry. Yes you can have a long bit but you still have clearance issues. for a printer there wouldn't be an issue because you are doing an additive process then
You will only be milling the top surface of whatever you put in there. If you've got a 2" bit you will only be milling the top 2" of the object no matter how thick it is. The best example would be engraving the top of a fairly substantial (already assembled) jewelry box.
If you use separate stepper driver modules you can easily drive 4 modules/motors from a single set of Arduino outputs. Having said that, you may run into a bit of an issue with the maximum current sink capability of the Arduino outputs, but a simple transistor driver like a ULN2008 or even just discrete Mosfets would easily be able to do the job. Leveling the bed would be a challenge, however, since you could not independently control the motors. Leveling would be a manual process of turning the motors by hand. MG
