Hi all, long time lurker, first time poster and absolute newbie, please be kind! I have searched extensively but need to ask a few questions. I am planning and designing a new workbench for my very small shop that combines a number of functions. I've been collecting parts for a while and I am working on getting kit to make a gantry mounted to the workbench. This will be for milling timber primarily. Stage 1 will be manual movement, stage two in the future will be motorisation. Anything I build now needs to support motorisation and automation down the track. Question is, will my design work? I have 2 variants. The difference is the Y axis. I have copied the Openbuilds 1515 gantry but modified the Y axis to mount into my workbench. The first, I (perhaps supidly purchased already) the linear guide rail from Igus https://www.igus.com/product/723?artNr=NS-01-27S along with 2 carriages per side https://www.igus.com/product/1156?artNr=NW-11-27-80. -If anyone has experience with these, do you think they will be rugged enough? -Will the whole X axis rack from side to side and bind? -The negatives: -Automation will be difficult compared to Openbuilds -If I get the OB gantry compatibility with motors etc. may be difficult? -The C-Beam in design #2 would ensure a flat work bench plus support a myriad of other attachments The second variant uses C-beam for the Y axis. You cant see them but there are 2 gantry carts mounted 400mm apart inside the C-beam channel. Things I dont know and need help with are: -I want the 500mm Z axis, too high and unstable? -Would the Y axis rack from side to side and bind? I need to able to push it along from one side of the bench. -Is C-beam available longer than 2000mm? I need around 2900mm. -Can anyone suggest a more powerful spindle that will fit? I reckon I need over 3hp for the hardwood I mill here in Australia. I have so many questions but I think thats a good starting point. TIA. GH
Overall, I think you are setting yourself up for disappointment. Aluminum extrusions are nowhere near stiff enough to accommodate what you're trying to accomplish here. A 3hp spindle dangling down from a high gantry will follow the path of least resistance and in hardwood that is rarely a straight line. The other issue noted here is the wings supporting the gantry. These will lack the stiffness to keep the gantry from riding up and over tough spots in the wood. They will also tend to want to pry the Y-axis rail off the face of the bench. The key to proper CNC design is to keep it as low and tight as possible. This provides the best possible stiffness in the system such that the bit stays engaged properly with the material and follows a straight line. Design for exactly what you intend to cut now not the 'someday I mights' as every little bit of overage weakens the system and strength is key to a proper cut. Keep us informed. We are happy to help no matter what path you choose.
Thanks Rick, if I lowered the height and reduced the spindle size do you think I could get decent results?
You'll also need to bring the sides in. But let's start with the basic question, what sizes and thicknesses do you intend to cut?
Rick I would like to do 1000mm wide table tops or slabs. The bench is around 750mm wide hence the 'wings'. If having a system that worked well then I would prefer that to be able to joint boards and flatten prior to thicknessing of around 2-300mm wide.
More like this? 250mm actuator and about 750 wide? If you think this is workable can you assist with a parts list? Im totally new and so far away I want to try and get it right the first time. GH
Much better but you're still reaching down too much. I suggest taking a look at how the gantry on the OpenBuilds LEAD CNC Machine 1515 (60" x 60") | OpenBuilds is framed. The single rail on the LEAD CNC 1010 (40" x 40") | OpenBuilds would probably also be viable due to the short distance you're spanning. Only difference from those examples I would suggest would be leaving the 20x80 side verticals extra long, extending down past your attachment points. That way you can keep it low for normal use and then should you ever need a bit of extra thickness you have the capacity to raise it up. Other build concepts from the past that you may be able to draw some inspiration from include Slab Flattening Table, Need help with x large build for slab flattening, and surfboard machine. These are all stand alone systems but could easily be morphed into tabletop overlays.
Thanks for the input Rick. I just have a couple of last questions if you would be so kind? -For future automation so I get the Y C-beams the right length, can a belt drive run on the inside of the C channel as pictured? The NEMA 23 motor mount doesnt look like it will fit inside, is there another option? -Is C-Beam available up to 2900mm? -Can the stepper motors be reversed so I can mount them on the same end as pictured? -While its non-automated in the short term, is there a way to lock the axis'? Thanks, GH
You can run as shown but it's not ideal. The full loop system you have shown will have significantly more stretch than a single run belt which means increased backlash. For this application I would probably use a single run 15mm belt. Threaded Rod Plate - NEMA 23 Stepper Motor (openbuildspartstore.com) will mount on the face of the C-beam to hold a NEMA 23. No but it's available in 1500mm lengths and then you use Quad Tee Nut - MAKERLINK (10 Pack) - OpenBuilds Part Store to splice the lengths. With careful alignment you won't know the splice is there. Yes, but it's easier to mount them as noted above. The simplest brake mechanism is a threaded knob run through a hole in a plate on the moving part engaging a t-nut in the fixed rail. Some basic thoughts on what you have shown: Turn the Z-axis around, fixing the Z-axis beam to the X-gantry plate and having only the Z-axis gantry and router move. This allows you to reduce the height of the overall system which in turn makes it stiffer. Set the bottom plate of the Z-axis beam just above the typical material thickness with the X-axis down as tight as possible to that. The timing belt you have as shown may be useful in the period up until you do automate the system. You are going to have an issue keeping the Y-axis gantries moving at the same rate, keeping the system square. I would suggest putting in a connecting rod across the end with fixed pulleys at each end causing both belts to move in unison.
Not sure what constitutes a belt and pinion. Belt starts at one end, crosses over and around the motor pulley, then goes backward a few inches over/around an idler pulley, and then off again forward to the far end. Think in terms of a horizontally stretched, vertically flattened 'S' with pulleys forming the curves.
Hey Rick, are these images like what you were suggesting? Motorised version first then manual version. For manual version I can add some kind of crank wheel to move the gantry on the Y axis. Lastly, I;m sorry I dont follow the single S shaped belt. Do you have an example?
Motorized version needs to be attached to the gantry plates with a single run belt going end to end. As for the S style belts, this is what I was referring to: This style allows for greater contact between the belt and the timing pulley. The upper concept will be easier to integrate into your system though. I've attached a very rough Sketchup model. I didn't have time to track down the proper pulleys so the belt is not shown 15mm width and the idlers are not shown as smooth face roller bearing idlers. Plate attachment screws are not shown. You'll notice that the placement of the motor interferes with your gantry risers but the gantry risers shouldn't be centered anyway. The center of mass of the whole gantry assembly including the spindle should align with the center of the Y-gantry plates.
