So here is the layout as of now (still very much in flux) A couple things were on my mind when I started this venture. The C-Beam design allows for a few of these. I need to be able to cut a 36" x 24" sheet. Want plenty of fixture room, for other projects. After the router is working properly I will add a second gantry that will have a laser. X axis rollers can be moved away from the chips and dust. (C-Beam lets that happen easily) In order to span greater lengths the Y axis needs stiffened. (Overhung loads need minimized) The X axis rollers not be under the extrusion (thanks to C-Beam). (Allows full length support) Design around Open Builds parts Keep plate costs down (waterjet patterns with secondary ops) Be rigid enough to support higher cutting speeds than the cheapo china routers I've had.
Here is the X axis slider. Earlier designs had the motors attaching directly to the vertical plates. The Y beams would then require a pair of perpendicular plates. That revision did not allow for the strength I wanted without adding more plates elsewhere. The result would not allow removal of the Y-Z carriage without removing too may parts. This revision of the X slide does several things I am happy with. It allows for imprecise Y-Beam lengths. By pointing the X motors up the added length of stronger motors is not a space penalty. The extra rollers required for the belt will be able to aid in keeping twisting forces at bay and reduce side loading forces on the main roller bearings. The bottom 20mm of the C-Beam is left open for securing to table or adding height. And, at least right now, without a cutter, the carriage can pass through without disturbing the alignment of the machine. Some things that concern me.. It uses 60mm more space than other designs. (can be reduced, current plan is to try multiple plates) I do think the gussets will need an alignment sleeve in the Z direction (on the vertical plates) to make setup reasonable. The builder will have to use a quality square to align the Y beams. (My thought is to add press in dowels to aid in alignment and assembly) The motors pointing up use at least 2 rollers, 3 in the current revision. (I think the gained control of side loads will be worth it to me. )
As is, the Y-Z carriage is not satisfactory to me. I chose to use the C-Beam screw drive early on. Once it arrived I was excited to get it together and see how it felt. Assembly was straight forward, the resulting feel is smooth and slop free. While I would like to keep this in the design I'm wanting to use some of the space it occupies. However, if I'm to keep the cost viable for others to recreate many other choices are eliminated. In the future I hope to see Open Builds offer a version with a ballscrew and thrust bearings, for now the C-Beam stays. The current carriage used the same notched in perpendicular plates as the previous X slides. This assures a square build, and more precise machining of the plates. I initially designed around the motor being inside the the rails. This results in some loss of Y axis travel, but as it can pass over the X slides, not much is lost. The cage surrounding the spindle greatly reduces the cutters moment over the rollers. Not intentional, but the design supports multiple Y axis motors. Also not planned is not needing the secondary extrusion for wire routing. As shown in the pics, I'm kicking around ideas for moving the motor to the outside of the carriage. I really like the idea of controlling side load forces, and reclaiming the lost travel. Hoping to stumble into a decent path forward. Things that concern. It will be difficult to package a dust collector. Tool changes will be more difficult. Gantry weight is higher, as is cost. Difficult to keep debris out of roller path, difficult to see and clean the path. Limited support for spindle sizes. (design is for 65mm)
A quick search returned footwear.. Uhh, Thanks.?. So anyway, this is what I've been working on. Looking forward to any help you guys care to offer. Happy New Year! Sam
Hi your z looks good, I would not keep the 2 motors for x outside of your (already considerably grown) construction). Turn them 180 deg horizontally so they facing inside out and rotate them another 90 deg so the belts run horizontally on top of your extrusions. this even helps if you are going to convert to belt-on-belt drive. get the wheels on top and underneath the extrusions to give better leverage and these wheels could than even double serve on your belt-hold down (lesser part count) Why a two motor setup anyway? you realise that you are running a 5motor cnc only serving 3 axis? One shoud do easylie. I would even skip that stage and run a trapeziodal or even ball-screw on one motor - like the c-beam is designed to -not going to be far more expensive than one aditionall motor, power supply for this ,belt, wheels, pinion, ballraces... (all adds up) The x- extrusions themself only sit on the y-carriage? what keeps them from Collapsing once the spindle has moved away a little direction center? (card-house) brace them against each other and attach more securely to the y-carriage. just my opinion greets flo
Been trying to catch up on things.. Got a wild hair last night and decided to let SW update to 2016. Not a bad thing, just forgot how slow my internet is. Wanted to get the solid parts into a google drive folder(for easy sharing), but the suck internet has me waiting until the next bed time. I've been reading through Flo's post several times now. Really only makes sense if we are calling the axis out differently. Made a pic to show what I'm calling them, let me know if I'm rotated wrong. Also, I had two motors floating in the model for brainstorming. These should have been at least hidden so as not to confuse. The below pics has the junk removed. Flo, The plan is to have two motors on the lowest (X?) axis, one for the gantry, one for the Z (four motors total). I think that the added weight and span of the gantry as well as the desired speeds I'd like to get as a laser warrant two motors. As for lead screws, I've had bad times with screws. This has been over distances, and at higher speeds. Found they would start whipping, would suffer harmonics, and then stretch badly. A plastic (vs brass) nut would have helped greatly with the harmonics and the destruction incurred. Not sure I follow about the rotate 180 and then 90 with what I think I call the Y axis motor. I was brainstorming having the motors outboard, it wouldn't impact travels, would make the belt more accessible, and could create more side loading control. Rollers outboard of both beams would prevent the beams from spreading apart. One of those arrangements may allow a little more travel too. If I was to move to the outsides of the beams for rollers and belts like an ox, but with a beam on each side... The carriage could not be slid out the side. C-Beams are not needed, something like a 20-80mm extrusions would be great. This would bring the total width, lost travel, down to 200mm or 20mm lost compared to an OX. Bottom rollers are more exposed to debris. If I kept C-Beam but move to the top for top roller but inside for lower rollers I can slide out the sides still. Not sure how beneficial that scenario would be. Unsure if I follow the comment about leverage gains. Rather than the wheels being high and low I've gotten the distance by surrounding the spindle. however, neither approach addresses side loading. This is apparently less of a problem than I would expect as I've not noticed anyone complaining of hurt bearings. I do plan on belt on belt. I don't have any GT3 in house yet(on the way), but hope it works with the current design methods. Ahh, packages just got here, maybe I do have GT3 belt in house. If indeed the Y axis you refer to is what I think of as X then the gantry extrusions attach with 8 bolts per C-Beam. It would be easy to add a plate to the top side of the extrusions, but I do not see a need. Putting a strap across is a super easy thing though, might as well. As for the considerably grown.. I'll attach a pic. This is using the assembly I found in an "Aluminum OX" build I downloaded JustinTime, Forgot to mirror the parts over. Both lower sides will be driven. Thank you both very much for helping me with this endeavor! Looks like I've got lots more to consider. Things I'm hot on now are to look into moving rollers out of the C on the gantry, maybe reclaim some of the travel. Try to understand the 180 and 90 rotate suggested. Look at every part and see if impacts performance when removed (great way to say this Flo)
It has been argued a number of times here on the forum and the greatest consensus generally comes back to the side rails being the Y-axis and the cross rails of the gantry being the X-axis.
No problem, all the industrial machines I've had are setup as X being the longer, didn't know the hobby crowd was a different standard. I'll just rotate the brain 90 and keep moving on. Thanks Rick
It has nothing to do with "the hobby crowd" or the length of the rails. When standing at the front of the machine, X increases left to right, Y increases front to back and Z increases upward. (Hint: If you are standing looking broadside at the side rails, you are not at the front of the machine.) CNC routers can also be built in 2x4 or 4x2 configurations or even 3x3 configurations. This is why using length is a problem as length varies with configuration. Its far easier to go with the front location method as the parts will always have the same label.
The reason industrial standards are different is because nobody would stand front or aft of the machine. That is where the heavy/big parts are slide in or "fall out" (aft) (often automatic by robots) - so restrictet for access. You are only alowed to look at it from the side for beeing save. All cnc i have ever seen have their controll board on the side - parallel to the gantry. Ok, in the first set of pics your motors is shown front and aft of your c-bams, now they are between. That was what i was on about. If one Motor should apear not strong enough get a stronger one, two of them have to be running perfectly matched and it is additional cost and effort for hardly a noticable effect (my opinion). Have a look at "momos cnc" on youtube to get an opinion about a single (simple) belt setup. It is not even belt-on-belt. If your setup can slide "out" of the extrusions sidewards than there is nothing to prevent the two extrusions to bend/twist like this // So it needs a plate or whatever to brace them against each other. Otherwise you will have a machine that might end up considerable less "strong"than a standard ox -even if your intention was opposite. It is not about how much material is wasted - it is how to use it the most clever way. That i already mentioned in the other thread and above in my comment about the card-house. Building Machines is always about levers, momentum and (clever) bracing.. Flo
Flo, Sorry for that first pic, it had 3 motors on the X. Not with the intention of using that many, just in the model for brainstorming. I liked how the inside motor would package, but it would also be very tricky to route a belt and maintain. I've started reworking the carriage, and like the direction it's headed. The side plates need some rework to match up again. It looks like an 8 degree pivot of the X motor would allow a couple mm of tension in this layout. Ohh, and with this layout the C-Beam becomes the travel restriction. The X travel is is now 841mm with 60mm being bolted to the Y slides on each side. I'll add a brace across the top of the gantry beam, just have not take the time. Seems like it will be a low risk design item and can be left for last. Now I'm off to youtube to check out that momo machine. Thanks again!
