Doing some upgrades to my CNC router (thread here) CNC Upgrades | The Home Foundry …..and it needs some castings. This is the traveling portion of the Z-axis that mounts the router and linear rails. So the old CNC makes the new CNC parts. After some run time the foam pattern was born. …..add feed system …..Dip coat ……..it’s a nice casting. In the heat treat oven until late tonight. -More to come. Best, Kelly
Kelly: When I first looked at the pattern I saw the tunnel where the lead screw will live and I was wondering "How the hell did he cut that undercut with his router?" Eventually I saw the joint line between the upper and lower parts of the tunnel. Nice pattern, and even nicer casting. Even your feed system is a work of art. Don
Kelly, Casting looks almost as pretty as that foam pattern! Thing of beauty! Version 2 needs to be in Cast Iron .
Thanks Don. It is one of the beauties of LF casting......stick ons. After the pictures, I actaully made a few pattern mods before I dipped it. I cut a small window midway in that section you commented on for extra mold support. I added this because it really stiffened up the pattern and the casting. All of the boss work at the top of the casting was also added after the CNC work because the additional set ups just were not worth it. This was much faster. Same with the boss work on the end where the ball nut mounts. Somewhere along the line I knocked off one of the 8 drying legs attached to the runner. I didnt notice it until I was just about to dip it so I stuck another one on with hot melt. After the coating dried, I cut those feet off with a blade before casting. I've been working with what I call high contact area feed systems. You can't see it, but there is a cove cut on the runner/gate that skinnies down the width of that runner from 1/2" to a little under 3/16" the length of the part. It makes it very easy to degate by just setting the fence and ripping on the table saw. You can see what I'm talking about on the underside of the the casting photo. The four little wings on each side are just for added support rather than feeding. With this type of feed system I'm pouring much cooler....1350F now, but you really have to be on the ball because once it starts taking metal from the cup, it really takes it quickly. I let it dry in this position. Keeps the pattern nice and flat/straight while the refractory dries, after which it is much stiffer. The resulting casting was also very flat. There was slight twist, with one of the four corners about .060 higher than the other three. I clamped 3/4 corners to my milling table and pulled the offending corner into position while the casting was still soft before heat treat. Though I strive to be careful to keep the patterns and castings flat, I've learned not to fret too much because they are easy to straighten. Only took about 15 minutes. It has a lot of features, but it was just a lot of feature copy and pasting in CAD. I'd sure like the mechanical properties of iron, but cant stand the weight for this piece. Other than drilling/tapping a bunch of holes, it gets very minimal machining and stock removal, but they are critical features to function. Best, Kelly
Kelly: I was wondering what those pegs on the feed system would be used for. NOW they make sense. I agree, iron would be nice for the vibration dampening, but without some really beefy steppers or servos the weight would have killed your acceleration/deceleration during direction changes. If you haven't already seen it, you might want to check out Terry Mayhugh's build of his scale Merlin engine on HMEM. https://www.homemodelenginemachinist.com/threads/quarter-scale-merlin-v-12.24153/ He really had to jump through some hoops to straighten some of the warped castings that he had for that engine. As new castings are unobtainium, he had to use the ones he had. Don
I got the Z axis casting machined. Have some more castings on the way.....router mounting clamp and dust shoe. The router mount is pretty straight forward. Since the vast majority of my machining is from sheet/board/plate, I made the dust shoe adjustable over 10 inches in height but fixed with respect to the Z axis travel. The duct exits at rear so I can retract the router and have open access for tool changes. There will be a vented insert with open center that magnetically installs in the upper dust shoe opening. I may make another dust shoe that travels with the Z axis for larger envelop 3D machining. I could have cast the shoe and elbow in one piece but figured I may want to change that at some point in the future so did it in seperate pieces. They're dipped and when dry, will be ready for molten metal. Hopefully tomorrow. Will post up the machined castings in the near future. Best, Kelly
This version of the dust shoe will be at a fixed Z height? What will you be using to ensure that the chips thrown off the bit will be sucked up and not just go flying off in all directions, some type of brush? If so, which one and how do you plan to attach it to the shoe? Don
Yes fixed (but adjustable) in relationship to the Z axis but moving in X&Y of course. Though it could use a brush, since I can set the shoe fairly close to the stock so I dont think I need the felixibility of a brush and think a short rubber skirt with vertical slits cut into it will be fine. If you look at the the dust shoe casting below, there is a 1/2" projection on the bottom side to attach that skirt. I was planning to use a vented lid on the top opening of the shoe to supply the majority of the make up air for the vacuum. As far as attaching that skirt......zip tie, thin hose clamp, two-sided tape...... Best, Kelly
Those really turned out! That ribbed section on the Z axis looks so cool. Will you be making more pieces like it for the X and Y gantry bits??
It was brought on by the desire to achieve maximum stiffness/lb of moving Z mass along with the product of an overactive imagination with judicious use of the copy and past function in my CAD program. Wait until to see the brace that bolts onto the the top side of those bosses on that casting. They'll be more pedestrian by comparison. The plates on the end of the traveling X gantry beam that mount the steppers and linear bearings will be 7000 series aluminum plate. There will be new risers needed on all four corners to raise the entire gantry assembly (need/want about 10-12" under spindle). Haven't decided if those will be castings or fabbed steel. Will probably fab up a 2 x 2" square tubular frame weldement for the base. The plasma table that it's bolted to aint cuttin' it (sorry, couldn't resist). I'll post up over in my other thread in CNC section. Still a bit more work to do on the Z, but basically a stationary plate from the same 1/2" 7000 series tooling plate to mount the linear bearings, thrust bearing block, and Z stepper. That should getter done. I'm liking how it's coming together. Best, Kelly
For CNC we need stiffness and lightness. In round numbers steel is 3 times as stiff as aluminum and also a little less than 3 times the density. So pretty much pick one. But: Cold rolled is also about twice the strength of cast 356. So for equal strength steel looks to be the better option for CNC structure that needs to move. The nice thing about y0ur kind of casting is that it is easier to optimize the structure for strength vs using standard sized metal stock.
The corner posts and Y beams are stationary, so there is no weight penalty for those. Stiffness (and maybe vibration dampning) is the only thing that matters for them. The traveling X axis part of the gantry and Z axis.....different story. Best, Kelly
Kelly, that is looking great. I look forward to the displays on the table saw/ surface plate. Uncluttered horizontal surfaces are an endangered species around me. I was going to ask about the router with regards to vibration, but you answered that. I used a Black and Decker for my cam grinder because it was what I had and I fought chatter while grinding lobes. Even some of the die grinders are unacceptable although they have a smaller armatures. The best balanced motors I have found have been on vintage tool post grinders.
Thanks ESC. Similarly afflicted. I turn 180 degrees and take one step from my bench to the saw......the bench is always busy. Well it certainly isn't a spindle, but it's really not bad. I'll take the additional power but will be really happy to have a 1/2" collet. I bought a speed control called Super PiD. www.SuperPID.com - Super-PID Closed-loop Router Speed Controller Besides closed loop control from 5k-245krpm and CAM interface/control, it claims noise and vibration reduction. Haven't run it yet. We shall see.....I'll take what I can get. Best, Kelly
Kelly, I spend hours learning fom your posts. Literally hours. I'm getting ready to build a small table to route (mill) pink foam. I am thinking I need two diffferent shapes - one is bullnose bit to take out the majority of the meat, and the other is a straight shank bit or end mill ( shank same diamtere as the cut) to define the final corners. Is there a difference between a router bit and an end mill in the quality of cut? And for the straight square bit, do I want an upcut or a down cut?
Either will cut foam but router bits usuaully cut foam better than metal cutting end mills because the have more suitable cutting edge geometry and they clear chips better. I use upcut because it lifts and clears the chips from the cut kerf. A flat bottom bit can be used for roughing and heavy stock removal too. Best, Kelly
