MadModder

This evening, I did an experiment with the CNC router. I have no more single flute bits, so I tried a cheap (5 for $20) double flute 1/8 carbide bit that I had on hand. It's a SpeTool M03008. I set the router at its slowest speed (8000 rpm) and ran it at 8 IPM and a shallow 0.020" DOC. I was cutting .250" scrap aluminum -- probably 6061-t6.

I periodically sprayed WD-40 from the can on the cut. The router cut the piece out quite cleanly, but naturally took a long time, since it was 13 passes at only 8 inches per minute. Swarf built up all over, while cutting. I need something to remove it. (Suggestions?)

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I'm surprised the cheap two flute cutter did better than the specialty Amana single flute designed for aluminum. I'm going to work on increasing DOC -- this first trial was just an experiment to see if it would cut at all.

I have a CNC router, which I have used very infrequently over the last ten years or so. Like ten times. It's basically a bare bones 22" x 11" usable table machine with a Bosch Colt router for a spindle. It has microswitches for stops. It is controlled by a parallel port type controller with opto-isolated I/O and three drivers. It has the usual range of available ports. It runs on LinuxCNC.

I've mentioned the stepper driver elsewhere on the forum, when I thought I was going to have to replace it because my dedicated parallel port laptop computer had died. That was solved when I found I could use another old laptop I had. So I'm back with the original setup.

Anyway, I'd like to get more use out of it now that I'm doing hot air engine experiments. My latest use for it is for cutting out small parts for a Scotch yoke drive in aluminum .084" thick to .25" thick. Simple cutouts, not profiling. 

So far I've only done simple cutouts, nothing profiled or pocketed, and that probably will be my lot for the near future, at least with the Colt as a spindle. Minimum speed for the Colt is 8000 rpm, and max is 35000. I just use the onboard switch for speeds, and on/off. I don't have spindle control.

I have used only one type of bit, an Amana # 51471 Solid Carbide CNC Spiral 'O' Single Flute, Aluminum Cutting 1/8" Dia Up-Cut Router Bit.

I had two of those, and just broke my last one. They aren't cheap. I'm thinking about alternatives, and would appreciate suggestions.

To cut a piece of aluminum, I have been either drilling holes in an oversized blank, and screwing it down onto the sacrificial MDF router table surface, or holding it down with small square tabs of thin plywood, screwed down with wood screws as toe clamps. I have sometimes had problems with the toe clamps not holding, so prefer the direct method of holes in the blank with screws -- but it's wasteful. I'd appreciate any suggestions of a better way to go. (However, not at great expense, or complexity. DIY best)

I generate G-code with Sketch-UP and the Sketch-U-Cam add-on. I run it in LinuxCNC (V 2.5.4).

I have no homing setup presently. I do it manually, which is very time consuming, and also not very accurate. I jog the tool to about where I think it should be on the blank. I have a small X and Y allowance before the bottom left corner of the part will start cutting and then zero X and Y. I jog over to a clear area of the MDF tabletop and jog Z down to a slip of paper on the table. When it is a little hard to pull out from under the bit I zero Z.

When writing the G-code I allow a slightly thicker material thickness to allow for (I hope) complete penetration into the table top a little. This doesn't always work out because of the approximate nature of my setting up above. Sometimes the metal is pressed down into the mdf. Sometimes I'm too far through, and I cut though my tabs that are supposed to keep a completed part from coming loose and breaking the router bit.

I'd like to do better than what I have been. I know it's far from ideal. I'm open to suggestions from everyone here about basic improvements I can make that are reasonably simple and I hope inexpensive, ideally DIY, or in methodology, etc. Not things like "buy a water cooled spindle, glass scales, there's a better machine for sale on ebay, etc." -- does that make sense? What can I do that's simple to make things better.... and ideally be specific if you have a construction suggestion -- link to how to, video, or a parts recommendation.

Thanks!

I haven't tried mine yet.

Do you have specifics for what kind of spot welder it was and what the SSR's and the MOVs ratings were?

That was excellent, Joules. 

I'm not casting steel, of course, just iron (lower temp, higher carbon) but it was very interesting anyway. More information than I have found on my own.

My guess is that pure silicon is pretty ephemeral in a melt, and more so than ferro-silicon. Generally in home foundry work, the effect of ferro-silicon addition is said to last no more than 5 minutes after addition, so you don't add it until the very end, before pouring the mold.

I do use ferro-silicon to prevent chill (hardening -- carbide formation) in melts for thinner castings. Or if a scrap type seems to chill easily, by experience.

I originally bought the pure silicon in hopes of adding it to aluminum to try to make aluminum extrusion scrap a better sand-casting material. But shortly after receiving it (EBay purchase) I read that others had tried to add it to an aluminum melt, and hadn't succeeded because of its high melting temperature (1414C). So then I thought about using it for iron, and wondered why ferro-silicon was normally used, and I'd seen no mention of pure silicon.

I've since heard of one person who said they were successful in adding pure silicon to aluminum, but no explanation (so far) of how that was achieved.

I have personally dissolved copper in aluminum at much lower than copper's melting temperature, so I don't discount that it may be possible with silicon. That's dissolution, not melting. I would like to know about that if it's been done.

I've also seen one video on YouTube where a very amateur melter, with poor stock (beverage cans?) did seem to combine silicon and aluminum in a covered electrical muffle furnace at very high (for aluminum) melt temperature. Maybe he got it to silicon melt temp? If so, and somehow he kept oxygen out, I guess it's possible. But in a normal aluminum melt, gross overheating is asking for a big loss in quality, and wholesale production of dross. Considering what he started with the metal quality of the final castings looked poor, with the Si/Al example slightly better than without, to my eye.

Anyway, thanks Joules, and nope not a fab lab, just EBay, and at a price for a small quantity not much different that the ferro-silicon I purchased in the past.

Tried that, Tom, but no reply -- at least through the forum.