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Actually on cast iron you will get practically no distortion around the chisel cut. Some cast iron, after appropriate heat treatment, may be described as malleable or ductile iron but it is nothing like steel, very little deformation plastic occurs during cutting.Originally Posted by BobWarfield
An open mind is a virtue...so long as all the common sense has not leaked out.
Wow, that casting (saddle?) is massive!
It must be handy to have a spare mill around.
[While I was thinking about Dremel's awful speed control, a thought occurred to me: Dremel makes some pretty small ball mills, although a 1/8 channel seems to get lost on the bottom of that that dovetail"]
BrendaEM, the casting seems small compared to most of the other parts. The IH is a big mill, as benchtops go.
Got the X-axis grooved finally (some interruptions):
Be sure to avoid the access hole for the Y-nut bolt on that one!
Now that the grooving is done, I need to drill some intersecting holes and tap for fittings, figure out how to mount various brackets, engineer oil to the ballnuts, and probably a lot else!
Meanwhile, I'm getting ready to pour epoxy granite in the base. I may do the column too, but haven't decided. I've started a page on the 'cookbook for the Epoxy Granite too:
http://www.cnccookbook.com/CCMillEpoxyFill.htm
My inspiration is our very own Davo727 for this work. Epoxy Granite is cool stuff. It has 8x the vibration dampening of cast iron, so with the iron for strength and the E/G for dampening, I'm hoping surface finish and ability to take deeper cuts without chatter will be greatly improved. When you consider how much more than the IH even small VMC's weigh, I feel better adding a little mass. Besides, playing with sand and gravel is good for the inner child!
First step is a containment system for the epoxy:
I need to seal those up so no epoxy can escape. Still consideration how best to do that. My inclination is a bead of 5-minute epoxy on the tubing, and RTV fillets on the plates. Not sure how RTV will play with the Epoxy Granite though, so I'm going to check in over on the E/G thread and see if anyone knows.
Cheers!
BW
Looking good and nice website
A one shot oil system is on my to do list along with Turcite http://www.midlands-slideway-grinding.com/products.html on the saddles and gibs eventually.
John
Being lazy, I might just gluegun the dams in, depending how much you are going to tamp the EG in.
If you do use epoxy, perhaps you could add some filler (thixotropic stuff) in the epoxy to make it hang better. Body filler would be thicker, and so would Rot-Out which is basically bondo (microspheres) with fine fiberglass (rods) in it. The bodo (polyester) and the EG (epoxy) may react, but by then it will hardening. Bondo would be nice and thick.
I see a little oil film in the upper right of the casting. If there are things you don't want stuck, polypropylene is pretty hard to bond to.
If you mean RTV as in anything that contains silicone, I'd keep it away from your project.
One of those little sandblasters would be nice to prepare the surface, as long as you could keep it away from the ways, and shiny parts.
Last edited by BrendaEM; 03-01-2008 at 08:42 PM.
Thank you BrendaEM!
Hot glue is a good idea. I'm not sure why, but I almost never think to use my hot glue gun rather than the other adhesives. It's much quicker. I also need to put magnets in the hanging hole of about 5 more chip brushes, so I need to get it out anyway.
BTW, very handy to have a chip brush with a magnet. Slap 'em on the side of the machine and they're there the next time you want one.
Best,
BW
Bob,
i did a cnc conversion on my second IH mill and am wondering if the epoxy fill your doing will really help in vibration damping. i agree with the theory behind it but i think you would need to fill the column as well, at least partially. good lcuk with your project.
Runner, I think the base will still matter. There's one heck of a cantilever involved with that column and heavy head. It's going to be even more so if I fill the column to any extent. I also do agree that some column fill could have an even greater effect, and plan to investigate it.
There are two aspects. First is just putting some fill into the column. The challenge is ensuring there is enough clearance for the leadscrew and nut in there after you're done. This is not much of a problem in the lower part of the column because the screw doesn't even go there. Higher up, I will either have to do multiple pours and turn the column each time, or fabricate some sort of a mold that goes in through the open slot to reserve the necessary space. I need to go ahead and assemble the Z-axis leadscrew enough that I can take some measurements and formulate a plan.
The thing is, Epoxy Granite is cheap and easy, so experimenting with it seems a worthwhile risk/reward equation.
Meanwhile, the hot glue didn't work out so I'm trying some RTV. I found a reference that there are no adverse effects with West Marine Epoxy. Biggest issue is I only had enough in the house for one test, so I'll go get more if it cures up okay. I need to do a trial mix of the epoxy outside the mill anyway.
Cheers,
BW
The Epoxy Granite experiment has progressed to the mud pie making stage!
I did a bunch of tests mixing sand and gravel and checking the epoxy required with water as a substitute. Based on the experiences from the big CNCZone E/G thread, I was shooting to find a ratio that had me at a little under 15% Epoxy by weight, and 85% the rest of the aggregate. The real pros can get this down to more like 7% epoxy, but I'm not trying to over optimize the problem.
Once I had my proportions figured out (full details on that on my web page: http://www.cnccookbook.com/CCMillEpoxyFill.htm ), it was time to do a trial batch and see how it came out. FWIW, The mixture I arrived at with the water tests wound up using these proportions by weight with epoxy resin:
62% gravel
23% sand
14% epoxy resin
That worked out pretty darned well if I do say so myself. In terms of volumes, this was 1/8+1/4+1/3 cup of gravel, 1/4 cup of sand, and 1 1/2 pumps each of resin and hardener. I wouldn't over analyze any of these numbers, BTW. Here's what you need to mix up this stuff:
The pumps are real nice. They meter out the right proportions of resin and hardener, and the instructions say just leave 'em on the cans when you put them into storage and they'll be fine. Keep in mind, epoxy builds up a stronger and stronger allergic reaction from exposure, so you don't want to get any on your skin! I wore rubber gloves and eye protection and was really really careful with the stuff.
So, after all that, here is what an Epoxy Granite "Mud Pie" test looks like:
Tomorrow I'll see how it has set up. If it looks good, I'll start doing the pour on the machine base using these proportions. If this turns out to be a useful way to improve a machine, it has to be one of the easiest mods I've done in a long time!
I'll keep ya'll posted...
BW
I just noticed that in Wikipedia, that white vinegar can be be used to clean uncured epoxy from things.
It's also good to wear gloves because some epoxy has a known cancer causing chemical in it.
I am suprised that no one sells the optimal EG recipe of premixed in bags, but that's one for the EG thread, which is hundreds of pages now.
Good to know about the white vinegar.
I argee on the premix. OTOH, the more I look at some of the commercial stuff, the more I wonder "how optimal is optimal"? The procedure to succeed with the optimal E/G mix may also require a lot of other investments in vacuum bagging, vibrating machines, the ability to measure with more precision, and so forth. We're talking about the difference between 14% epoxy and maybe 7% here, and I haven't really tried all that hard to bridge that gap.
If you get 90% of the value really cheaply with gravel and play sand, it's time to rock on and get something done with it.
Speaking of which, I went down to check the test batch this morning and was very pleased:
Some observations:
- The material set up very nicely. The only air bubbles were at the top. The epoxy is clear and I didn't see any embedded with the aggregate. Could be dumb luck, but the West Epoxy seems to wet really well. Vibrating Tables and Vacuum Chambers were not needed here.
- It faithfully reproduces the mold in minute detail. You can see tiny scratches that were in the plastic cup from the sharp gravel edges reproduced in the epoxy. If you have a precision mold, you will get a precision surface back on the epoxy. Imagine making a lathe or mill headstock out of this stuff. Your precision surface is the machined outside cylinder of a cartridge spindle. Just mold it in place and you have a solid epoxy granite headstock that should be pretty darned solid for machine work.
- The finish is very nice where it was in contact with the mold. It looks polished and is definitely clear enough to see inside. I don't know that I'd try to make a window out of it, but it's a nice finish from an aesthetic standpoint. Looking at pix of some finished E/G machines, I'd always wondered how hard it is to get a nice finish. Came for free on this experiment!
I won't have time today to do the base pour, so I'll probably tackle that in the morning.
Runner440 has PM'd me with an important suggestion for others who may be following the same path. To install the IH CNC kit sometimes requires a little grinding on the underside of the casting to clear the ballnut. I understand perhaps 1/8" of material may need to be removed. Once the E/G dams and/or pour are done, you won't have clearance to get an angle grinder in there. You want to make sure you have either done the grinding beforehand, or that you have a way to get in there to do the job with limited clearance.
In my case I will use a long-nosed grinder I have for head porting, or I will put the base up on my other IH mill and mill a little pocket. I can definitely get in there with my 2" face mill to do that if need be.
Another good suggestion I got was to extend the dams so that the base picks up an inch or so of E/G on the bottom. This allows for the addition of considerably more E/G mass, as well as providing an opportunity to tie across the leadscrew cavity more strongly. I'm very tempted to do this, and undecided, but I probably won't go there. It would mean a lot of extra work and delay, and I'm anxious to keep going on this one.
So far, the E/G process has been fun and easy. That probably means a painful screwup is right around the corner. I'll let you know what it is so you can avoid it!
Cheers,
BW
Bob,
how did you remove the epoxy from the cup? what was used as a release agent?
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