Hello, I made some progress today and cut the backing plate for the 5th axis assembly. I will have to form the squared end to 90º as I used .125" aluminum instead of .25" thick material and there is not much room to drill and tap threads into a .125" thickness unless you go with a very small screw. The formed end will be better and stronger than a bolted assembly anyway, but it does involve forming the flange. Not sure if my homemade Gignery metal brake will handle .125 alum. very well, but if it does not work well I will just do it with my 12 ton press and some makeshift brake punches. I will see if I can do a mock-up of the parts tomorrow for fit etc. Take a look at the pictures.
Hello guys, I guess I should have posted the redrawn sketch of the formed back-plate prior to posting the cut part so here is a shot of the back-plate drawing and the back-plate with the sprocket, pinion and motor shown in position. I hope to get the back-plate formed today in my 12 ton hydraulic press and a makeshift forming set-up. This should be fun in itself as I don't have an easy way to set up to bend it like one would in a brake press with the proper tooling. I have done much heavier material(.25" HRS channel and flat bar) before and there is plenty of tonnage to form the aluminum part, it is just a matter of finding the needed scarp metal etc. to use for tooling and then positioning on the part in the frame of the press so as to get the bend along the correct location. All this becomes fairly easy with the appropriate machine and tooling, but my homemade Gingery metal brake is designed for only thin gauge steel(about .030" crs up to 30" long) and even this short 5" length of .125" thick will probably cause the bending leafs to flex. It is not worth damaging the light gauge brake, so it will get done in the 12 ton press. I will try and get some pictures of the set up and the bending along with the finished part for your reference. Just keep in mind when bending something like this you must be very careful that it is done safely and there is no chance of a part coming lose and flying at you! The rectangular area near the squared end of the formed drawing represents the 'K factor' for this material and is how much the material will stretch for a designated bend radius. If you have a K factor chart you simply add the sides(flanges) of the part and then subtract a K factor for each bend. In this case my K factor is .215", but I am not using exact forming punch and die so there may be some differences in my calculations and the final part. I can simply mill the flange to size if it is too long.
Hi Nick, I originally thought of making the 5th to go on the machine I built last year, but it has now moved to my sons place and I don't want to interrupt his use of it by adding the 5th axis to it right now. I am beginning a new build for a 48" x 48" CNC router/mill and I figured I would just try and implement the 5th axis on this build for the proto-type. There are not a lot of reasonable software alternatives that support 5th axis so I know this is a big concern for anyone that would like to have and use a 5th to their advantage. I do want to make this in such a way that it will be like an accessory that can be added to most machines, but first of all I have to come up with something that actually works and performs decently. My version of the pinwheel/sprocket drive mechanism still has to be built and tested before I do much more planning. My trial assembly with the parts somewhat in location looks to function correctly but I need to get it all together before I will really know. There is also the mentioned inadequate torque due to the 3:1 reduction so I will most likely have to add a second stage to the design to get a good torque reduction for it. Right now I just want to get what I have together and see if the mechanism will work to some degree and I will workout any improvements that are needed into a second proto if needed. Today I followed through with my makeshift idea for forming the .125" aluminum with my 12 ton hydraulic press and some scrap metal - tools I found in my roll-away and shop. The finished results are not as good as I would normally expect, but I think for the most part it is due to using a very sharp angled punch that I had. In retrospect I think I would have been better off to take a piece of say .25" thick flat bar and ground a V on the edge with say a .062" radius at the tip. The bend line did crack a little bit which does not usually happen with 5052 alum. if the correct radius punch and die is used, but both the punch and what is being used for the die have sharp edges and I think this contributed to the stress of the metal and the crack. It is not cracked all the way through and I don't feel it is structurally weak, but it does not leave a good cosmetic appearance...for the prototype this should function but I will do better the next time around. I tried to get enough pictures to document the process in case someone else ever needs to bend something perhaps this may work for them. You can bring the ram down slowly until it just about touches the material and then line the punch up on the bend line. Bring the ram down slowly to remove any slack, recheck the alignment and if all looks good proceed to bring the ram down slowly until the angle of the flange comes to 90º or whatever angle you need. It worked very well with my setup and it did not seem unstable at any point of the forming process. By being able to inch through the bending process it is easy to abort the process at any point if it becomes unstable. Take a look at the pictures.
Hello, I put some more time towards the B/C head assembly work today. I needed to get the bearing for the back-plate secured and decided to use a flat plate on the outside surface and dimple a thinner plate to use for the inside surface to trap the bearing in its place. I did the dimple operation in the 12 ton press using an set screw collar of the same diameter as the bearing(I had it in my misc. lathe accessories) and an old flanged retainer of an appropriate diameter to create a dimple tool(probably 1/2" larger in diameter than the bearing). With the bearing resting in the back-plate I could see that I needed to draw the dimple to a depth of about .175", so I shimmed up the bottom of the ring I used for the die so that I could get the needed depth and then the tool would bottom out(coin) on the shims. This helps make the tool similar to a regular dimple tool that has a solid bottom, and without this one could possible press the collar too deep and actually end up punching the bottom out of the dimple. I hope my going into detail is not dragging these posts out too much, because I like to make these operations clear as possible being as I am using substitute tooling especially. Let me know if I need to reduce the text. The dimple worked out exactly as I had planned and the bearing is very securely trapped in location while the center race spins freely. I would like to have a bored bearing boss plate but it is a lot more work than fabricating the alternative from sheetmetal. This is just a small step in the build but each step puts me closer to the next and soon I will be able to test the assembly.(if I keep at it!) I have a picture of the inside with the bearing in place, and retainer attached.
Hello, I did some more work with the 5th axis build today. I got the set screw boss for the sprocket cut from 6061 aluminum and mounted to the sprocket. I also got the .25" ID x .375" OD adapter sleeve made for the pinion wheel and pressed into place so now the pinion can be mounted to a .25" dia motor shaft. It took considerable time to do but you wouldn't know it when just looking at what was accomplished. It is sometimes depressing to spend a lot of time working and seem like you accomplish so little, but each step moves me closer to the finish so I accept the progress as it comes. Here's a couple of pictures. Oh, I also got the cover side for the drive drawn and ready to cut so here is a shot of the drawing
Hello, I couldn't give all the information at the time I posted the backplate for this 5th axis project(beta testing), but this is another example of using the tiled toolpaths and cutting this part on my small SX3 CNC mill. Here is a snip of the tiled toolpaths as I applied them to this part and I must say although I repositioned this part 4 times to get it cut, the finished result was very good. I believe I had a minor mismatch on the large bearing cutout but is was not substantial and the part was good the first time. The biggest concern for all of the repositioning work I have done is the indexing of the material, and if you plan the work well in advance you can avoid any shortcomings from mis-aligned toolpaths and I have an idea for a repositioning jig/fixture that it seems I can never get started on that would greatly improve my work with doing large parts on a small machine.
Hello, It's been a while since I worked with this project and what I have done today is more along the line of designing the next parts I will need to make than any actual work on the 5th axis assembly. I am posting a snip of the current parts as I have drawn them today. I plan to make the cover plate for the assembly from .125 5052 aluminum and the perpendicular pivot plate will be made from .375" thick 6061 aluminum. I still have a lot of parts to design to finish the build and I will post them as they are drawn. Take a look at the current plan and if you have some input please do post your remarks to the thread. I am hopeful that someone will see the things I overlook or offer additional ideas that could be implemented to achieve a better finished item.
Hello Bill, Thanks for posting the link to the Calvino 5th axis page. I am aware of his work with the 5th axis machines and I had also seen some of his other information I had obtained from a Yahoo group we are(were) both members of(if I remember correctly) I was not aware of the open source plans he has posted and there really is a lot of good information there for anyone interested as well. Thanks again.
Hello, It's been a while since the last post for this thread and I have not had much time to apply towards the build of the 5th axis. I am always thinking about these builds and contemplating the needed changes even when I am not putting any time into the actual cutting or assembly of the parts, and I have decided to modify some of the parts of the B/C head assembly again. I reduced the length of the spindle motor mounting plate to accommodate the use of some .375" thick plate remnants I have n the shop and also the bearing plate that will rotate the head is going to be made from the same .375" thick aluminum plate. I am planning on cutting the parts from this blank today and I am not sure if I will get it done, but I will post more information and pictures if I do actually get some of them cut. I'm posting a couple of pictures to show the changes to the assembly and to show the layout of the parts on my small blank as I am planning to cut them.
Hello, I didn't get as much done as I thought I would today, but I got the rotation plate cut for the B/C head. I managed to break (2ea.) .125" diameter end mills in the process of cutting the profile and dig a minor gouge in the material along the long radius where the first end mill broke, but it will not affect the fit and function of the part. The end mills that broke were 4 flute .125" dia. and I switched to a .187" dia. EM to finish the profile cut which finished without incident. This rotation plate will mount perpendicular to the back-plate of the head and it will have a boss attached to it for the shaft to be locked onto it from the drive above it. It will also get the front cover of the drive mounted to it and that is what the notches are intended to be used for along the flat side. Take a look and I really would appreciate any suggestions, comments or questions that someone may have.
Hello, I have made some more changes to the parts of the 5th axis assembly as I am trying to get the spindle rotation head parts completed for a trial assembly. I have reduced the rotation plate size and feel it is still large enough to support the head and provide a good fit and function without extending too far. The spindle-side cover plate has also been changed to remove the flange and a tab & key is being used for a positive registered fit with the other cover and rotation plate. I am planning on cutting the spindle-side cover later today if time permits and then I will use it to finish the assembly of the rotation plate and both covers. The rotating axis will have a bearing in each cover and the pin roller sprocket and drive wheel will be located between each cover. I still need to make the arbor that will rotate the spindle/router, but it should not take long to make once I have the assembly assembled to this point for sizing. I am attaching an updated snip of the current parts.
Hello again, I didn't get to cutting the back cover until today, but I finally got it done. I used tiled toolpaths to cut the profile of the cover and the bearing hole and counterbore were done with a single toolpath. Prior to cutting the part I added a dimple to the material at the center location of the arbor to create a partial clearance for the thickness of the bearing(dimple is about .125" deep). I set the material up on top of some .75" scrap redwood(sacrificial plate) that had a hole to clear the dimple so I could mount it with the dimple facing down. Proceeded to cut the .485" dia. hole and then cut the counterbore at close to 1.124" dia. by .085" deep for the bearing OD. The first tile for the profile did not require me to move the material, and when it was done I loosened the clamps and slid the material through the Y 3.6" to locate it for the second tile toolpath and re-clamped it. I posted some pictures of cutting it and a trial assembly with the parts to see if it is all going to fit correctly.
Hello, I have finished assembling the backside cover and the front cover assembly to the rotation plate since the last post and I did a mock-up for the vertical rotation drive and the 5th axis head today. I did not do any physical assembly work with it but merely was testing for fit and function and location for the center line of the vertical rotating axis and possible gantry clearance issues. I know the drive set-up on the motor in the pictures will probably not be a low enough ratio but I wanted to see if this might be a possible drive set-up for this axis. Here are just a couple pictures of the parts as they were positioned. Not much real work involved today but the trial assembly helps me visualize how things will fit for the next steps.
Hello, Today I put some time into cutting the thin gauge aluminum cover strip that wraps around the perimeter of the head assembly. I had drawn it yesterday, so finally getting it done today was one more step down. It is made from some thin aluminum flashing material and is basically just the width of the head with tabs attached and mounting holes in the tabs. I just lay out the part on the metal with a scribe or marker and then proceed to cut with snips. The notches are probably the hardest part but using left and right hand snips and starting from the center of the notch and working both ways to the tabs it is not too bad. I added a small miter on the exterior corners of the tabs to remove that sharp edge and I think it leaves the tabs with a more finished look than square corners. A lot of work with small brackets and other metal parts can be done much more quickly with a punch and some special tooling, and I have a small CNC punch press in the planning stages already that I wish was to a workable state. I mounted one end of the strip to the rotation plate and then proceeded to drill holes for a roll tap(6-32 UNF) for each tab into the side walls of the head. I worked my way around holding the strip flat and tried to hold all slack out of the assembly as I line drilled each hole and then tapped them. I used the rounded end of my anvil to slide the middle section of the strip over to from it to a radius close to the same as the head so as to keep the strip closer to the same shape. It is not a perfect fit and you can probably see some small gaps in the fit, but I plan on using some silicone or other sealer when I get to the final assembly and do not need to remove the cover strip anymore. All of the holes line up great but it is a matter of holding the thin material down tight and without an adhesive between the screw mounts there is too much flex.