machine
Oh No! Again
Broke a coupling again, one of the new ones. So the new coupling isn’t any stronger than my original design. This time it was in the X axis where there has never been a problem. I replaced a perfectly good original style coupling with the new one and the trouble began.
This kind of “random error” coupling failure has been driving me crazy, especially now in a place where it has never been an issue. It is a good example of how powerful the stepper motors are at low speeds. They can break things well above their holding torque ratings.
What I think happened this time is I may have changed the preload on the X drive screw end bearings when I replaced the coupling. Those bearings are straight radial bearings not designed to take end thrust loads. After I replaced the new failed coupling, I could hear a slight binding (groaning noise) near the middle of the axis nut travel. I spent hours fine tuning the X axis and double checking every alignment. The problem was I could not tell what component was generating the sound. The steppers themselves make a buzz type noise when rotated, even when not powered.
Finally I backed off on the axis bearing cap to as loose as I could make it without end play. I would say as near zero end load as can be set. The groan went away and the X axis started running extremely smooth with no complaints of a binding noise.
Now I am thinking my oversize screws may drag on the case or outside rim of the bearings when under any type of end loading. The original design was to use 1/2 inch screws. I am using 5/8 inch on X and Y. There could be some… Continue reading
What will it cost to make this for me?
I receive requests from designers and people with ideas asking if I can make something for them. Most of the time I say no, because I have enough projects of my own on which I would like to be working. There are also some designs that are beyond my means, usually because it is too large or requires special tooling and materials. (I wish I could charge the designer for the new tools!!) Some if not most of the designs also suffer from knowledge of how things are made on machine tools. The sketches and drawings show holes where they can’t be drilled or unnecessary and difficult areas requiring multiple setups.
These requests show that there is a need for prototyping services and these inventors and idea people have problems turning their ideas into products.
But prototyping is not as simple as sending out an unproven design for bids. (Yes, I know it is done.) But I am talking about solicitations from hobbyist and small time inventors who have never worked with a prototype or even in a machine shop. A good design is one that can also be made as inexpensively as possible on standard machines and tooling. That seldom happens on the version #1.
What I am saying is the folks who approach me don’t realize their design may need a lot of cooperation (face time) between the designer and the maker. Of course I am not talking about a bar of aluminum with two holes drilled into it. The designer can do that himself. I see the hard stuff, like machining threads on a very thin tube and the tube is thinner than the thread depth. (Yes, I have seen this.)
Outsourcing prototyping is not inexpensive. Building a prototype may cost 100 to 1000 times what… Continue reading
PD400 in Action
I know some readers just like to look at action shots. So I have thrown a few pictures in here for your enjoyment. This is the Proxxon PD400 lathe and I am making the standoffs shorter that I use on the HB2 router. I installed the new couplers on the HB2 this weekend and I discovered I can bring the screw shaft and the motor shaft closer together using the new couplings.
I needed to remove 3.18mm from each end of the standoffs then extend the threads a bit deeper into the aluminum standoff. That was about 1/4″ overall for you non metric holdouts. 🙂
It was short work and the HB2 is purring along just nicely. So you see the PD400 does get a little workout from time to time. Oh, and it didn’t hurt that the lathe was about 2 feet away from the HB2…
Fixing the Broken Axe
I received the new couplings today for the HB2 from PDJ, Inc.. The new one is the bright and shiny one in the picture. The black one is the original style that has been giving me problems with breakage. (6208K6 @ McMaster-Carr)
The new one is rated for 495.6 oz-in. The old one is rated for 42 in-pounds (peak). That is 672 oz-in! So the old one should be the strongest, right? The new one LOOKS stronger and is a different style. They are both considered Helical Beam Couplings. If you want to see what a broken one looks like check HERE.
So what gives? Well, the old couplings certainly do. Maybe the key word is the “peak” rating rather than a continuous rating. I can’t tell. The Mark One eyeball says the new one is stronger. That’s old Navy jargon for eyeball engineering.
I think I will soften the acceleration on the steppers a bit more to lessen the start stop shock loads.PDJ has been using these shiny couplings without failure so I hope my problems are over, at least with the couplings.
Weekend Puttering
While waiting for the new stepper couplings for the HB2 to arrive, I decided to do a little house cleaning around the shop. After pushing things around for a few hours, and sucking up what debris I could with the shopvac, I figured I should lube the ways on my machine tools. I can appreciate a one shot lube system as I have to do mine the long slow way. I finished and every machine is operating pretty slick now…
I spent a lot of time detailing out the Taig CNC mill. It is still in wonderful shape after all the machining it has done. That is really a great little milling machine in its size and class. I had to fire it up with the MACH3 in control and it wasn’t long before I was dreaming about the next project I should be running in CNC on that machine. In fact I “air cut” a couple of projects just to give the parts (mechanical and electronic) a little work out. It runs so sweet!
I have added a new Proxxon rotary hand tool to my workbench. I have more than I can handle (literally) but there is always room for just one more. This new tool is the Proxxon Micromot 50/E low voltage rotary hand tool. This is the first one of the 12-18 volt tools I have tried and I am amazed!
I already have and operate the Proxxon IB/E professional 120 Volt rotary tool. It is wonderful and definitely exceeds my two Dremel rotary tools in quality.
The 50/E is about ½ the size and power of the IB/E but is every bit as good. It is lighter, smaller and easier to hold for long periods of detail rotary work. I think I will prefer using… Continue reading