Ideas always start somewhere. For me they often start first in my head (duh...) where they turn around and around and around. Go away, come back etc... Not something I can really show. In this case ever since getting my printrbot a couple of years ago I have wondered about strapping other equipment to it than a hot end. But I don't want to ruin my first printer... so the notion of building my own creeps in. You see a lot of designs going across Kickstarter with the same idea but none seem to stick. How hard would it be to take inspiration from my printer designs with cheap parts, put a Dremel on there and mess around.... Spinning around and around in my head. Sooner or later I get some paper and a pencil and start trying to visualize.
Nothing special... often I don't get a lot of real usable info on paper. In some ways it is just a way of helping focus what is going on in my head. The rough notion I had here was to double most of the rep rap design parts from two shafts and 1 lead screw to 4 shafts and 2 lead screws (maintaining cheap easy to power NEMA 17 motors). If looking to do a router... why not go the traditional router design route? Well... wasn't my intention to follow the known path. I am fairly certain the cantilevered arm approach to cutting something is iffy at best. Have a notion that vibration in the arm and a laser engraver may not go so well either. But it offers a surprisingly compact set of parts which gives me a bit more freedom in what I can design myself with printing bits. I also have a nice example sitting there in my old printer to draw inspiration from on how to solve all sorts of problems I am not considering yet (sensor locations, wire routing etc...). Also, the long rails and sturdy gantry solution of typical CNC routers requires some large precisions parts I can't hope to replicate, and even extrusion solutions are relatively expensive compared to what I am attempting. So I settle on my already compromised design choices and head off looking for parts. Some noodling around on amazon and later bang good and some trips to the grabcad portal to find some bits and bobs and off to CAD I go.
First notion is to use some block bearings on aluminum plate. Maybe get a drill press to pilot the holes before tapping...
At some point my head keeps turning the design around and starts wondering about the forces through the central blocks if they are not joined... so instead of a larger block of aluminum I think about connecting the plates with a large central 3d printed block of plastic.
Well.... costing of the block bearings vs the cost of ubiquitous LM8UU cylindrical bearing in rep rap and other 3d printing systems and the fun of connecting the aluminum plate makes me shift to a more printed design. Central XY block with 16 bearings (45mm long ones at this point). Looking at my printrbot and its sheet metal single arm in addition to the shafts has me wondering again about loads so I add a printed shell concept on the outside of the Y axis.
First take on the base and top plate for the z axis. Earlier version of this had a separate rear section into the X axis bed and I realize the pushing force of a cutting tool when pressing down would lever the whole assembly back. decide I need a full metal plate.... Still not sure about this. Have another idea on this... but not sure about it yet. This bit is kind of on hold for now... Not like this is going to work for metal cutting....
Some fun learning how to do assembly of parts in Fusion 360. Still a hot mess organization/component wise but the parts slide and move and have limits and hey... it almost looks like something at this point. Probably would work but if nothing else it has been fun to get a relatively whole set of major parts of a design together on the screen.
Small parts printed out... this was from before I figured out the leveraged plate problem. The ribbed side panels turn out a lot better than I expected. The reason for the ribs was inspired by the Hovalin build using a carbon fiber tube as the backbone. The 3 ridges are tubes for carbon rods which are cheap up to a certain size for quad copter/RC plane designs. Don't know how much strength they will add or even if the panels will provide much relevant strength.
First full size y panel printed.... getting more than width of X or Y axis by printing on the diagonal at 280mm length. With a 60mm central block that means a possible 220mm stroke on the y. However.... warping is a real problem. I had been planning to do this in ABS... but my ABS Benchy adventure put paid to that until I can get an enclosure sorted out. The tubes I want to try to use are out of stock on banggood so I alter from 6mm tubes to 5mm rods and instead of the exposed rib I double the width to enclose it and make it shorter. I also have decided to drop the doubled up shafting and probably any real chance to handle a Dremel for more than foam, maybe soft wood in order to keep costs way down while I am learning. Also lets me reduce the central block from ~100mm to 60mm giving me a much better stroke size on the y and z axis vs having such a large block... also cuts down on filament mass needed. 4-600 grams down to 180ish... This is also the point I finally pull the trigger on about 60$ of parts from banggood and around 20 from amazon. Selection of M3 nuts and bolts, 5mm carbon rods, a printer motion kit (12 bearings, couplings, belt gears etc...) 300mm hardened chrome linear shafts, 2 lead screws etc... I already have plenty of electronics to play with though I may still need to get some limit switches and z probe at some point.
New two shaft, single lead screw 60mm central block.
New shorter, wider panel. Also now on a single arm panel instead of dual. Still thinking dual on the Z axis but not there yet on the designs. You can see the insert rectangles for the M3 nuts. I settled on this design vs a long threaded rod with nuts on either end compressing everything together in the middle tube. Not certain about it... but the one I got put together you can see below is feeling very stout even without the carbon fiber rods in place. What you can't see here is some of that "impossible" internal geometry (for standard fabrication techniques) in that I have internal hollows to reduce how much plastic is needed along with fileted internal rounds to allow successful printing. There is about 20mm of solid block at each end for the inserted nuts and to support the rods. The rod tubes all run the entire length. Print is ~130g. You can also see the mouse ears I added... these are 10mm and ultimately were not enough (at least with PLA). I think I may be able to go as far as 20mm before running out of space in the corners. This is damn near a worst case part for warpage... really need a heated enclosure setup to do this right I think.
First render of the new design on the y axis with the Z central block. Components in Fusion starting to make sense but still have a habit of executing design changes with the wrong component selected... seems odd that would count as work under a different component. Anyway... back to the task at hand.
New y panel prints. Still warping but the one in the middle I did actually use to build a first semi assembled version. But I was using shafts from my old printrbot X axis which were not 300mm. But my banggood order hasn't shown up. So I printed a shorter version (230mm for 250mm shaft... ~170mm stroke possible... but it also goofs the lead screw I got... so probably will print out a longer one once all that stuff arises. Was just really wanting to see how strong this was going to be just using the M3 square nuts imbedded as the attachment.
And yes.... I also just wanted to see it almost all put together. Surprised by how rigid this feels. Also... as you can see I was out of the orange PLA. This is actually a PET-G print with almost no Warpage. Was on the bed flat, showed a slight warp after I released it.
Designs are never done. This is where I am on this one now. The end plates are to wide... need to tighten them up. Have not designed any mounting solution to the implement end such as an extruder, engraving laser, pen, Dremel or small spindle. I have some long m3 bolts for the lead screw nut... but they are the same width as the central block so I am going to recess the nut and the nuts the bolts will screw into. If you are sharp eyed you may notice the Z Y block is missing some bearings. Something happened in that print that impacted the diameter of the holes. 6 of the bearing went in with a good friction fit. Went to far attempting to get the others in and ruined at least one bearing and had to cut the block up to get it extracted. Going to have to reprint it anyway due to the recessed lead screw nuts so it will be in PET G as well at this point. I am pleased with how the recessed M3 cap head bolts worked out. May need to make the y end plate thicker to allow for more clearance of the 300mm lead screw as I didn't account for the flexible coupler. or I can add some to the motor plate. Thinking the added material will make more sense on the implement end to give me more meat to design a robust attachment point solution around.
Needless to say I have enjoyed having a more dimensionally accurate producing system in the Prusa I3 MK2s. Also liking PET-G a lot. Its habit of bonding to PEI and having to use glue to keep it releasable had me hesitant but so far it has worked rather well. Not happy about the glue... but getting something that long and skinny to not warp off the bed was damned impressive. Bit more flexible overall than the PLA though. Still thinking ABS, or maybe a carbon infused nylon would be the best ultimate option. Very curious how much stiffness the carbon rods will add. They are 300mm so 10mm embedded in the end plates and its all held together my 8 m3 20mm bolts going to inserted m3 square nuts about 5mm into the panel.
Now to get the Z axis, base and X axis sorted out....
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