I am considering building an epoxy granite cnc with a steel structure as buying one is beyond my budget. I need to factor the cost of tools that I would need to buy also. Appreciate if some one can point me to essential tools that I will require.
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I am considering building an epoxy granite cnc with a steel structure as buying one is beyond my budget. I need to factor the cost of tools that I would need to buy also. Appreciate if some one can point me to essential tools that I will require.
It would be helpful if you posted some pictures of what you're trying to do, so people here could better advise you on how to do it. If you're proposing a welded steel understructure, you'd need welding and metal-cutting tools at a minimum. If you're making a mold out of wood, you'll need woodworking tools. If you need to drill holes in your epoxy-granite casting to mount components, that will require special tooling as well. You'll also need some measuring tools to tell you how you're doing.
The great thing about epoxy granite is that you don't need many special tools.
For casting the epoxy granite machine base you'll need something to make a mold out of and mold release to start with.
You can use a simple mdf mold if you apply the mold release properly. I used Meguiars Mirror Glaze mold release wax plus purple PVA mold release.
If you're going to build something that's worth using then you'll probably want a shop crane too. Epoxy granite is incredibly heavy. I had to buy a 2 ton shop crane from Harbor Freight just to lift my epoxy granite gantry onto the base.
Once it gets above a certain size, forget moving it by hand, even if you have help. Even a relatively modest EG benchtop mill can end up close to 1000lb.
Casting the epoxy granite around a steel skeleton is a good idea. Epoxy granite does not hold screw threads well and you don't want to crack it.
Based on my experience, I'd also suggest buying a bunch of steel or aluminum tubes for wherever you plan to attach other components with screws. Cast the tubes into the machine base. You don't want to be drilling through epoxy granite after it has cured.
It cost me at least one cobalt drill bit for every hole I had to make through my EG gantry. Never again...
Aside from this, most of the rest of the components are the same as what you'd need for any other cnc machine.
I.e. You'll need an actuator for each axis and a spindle etc, plus a good way to mount them to the epoxy granite.
I installed aluminum tooling plates (using long bolts going all the way through the EG gantry) over each mounting surface. These are already flat enough so no extra milling was required. You'll need something like this as you shouldn't attach rails or actuators directly to the EG.
Hi Suspension - The thought that making a machine will cost less then buying a machine needs to be considered carefully. Have you priced second hand machines that do what you want? A refurbished machine is often the least cost option. You may have to wait to find the machine but once you have it the rest is straight forward. Making any CNC machine to a required tolerance can be difficult. There are several machines in the forum that needed much more work to get it to spec then the builder expected... What size machine are you looking at? and what accuracy are you aiming at? Peter
Quote:
Originally Posted by peteeng
I spent a long time agonizing over that myself before going ahead with my build.
Thanks to all the failed small businesses ebay is full of low cost used VMCs and old Bridgeport style mills etc.
Some of them are comparably priced to parts for a decent diy build. If any of the available used machines met my needs I probably would have gone that way.
The problem I found was that there are very few (if any) cnc machines in that high quality benchtop / low cost, decent work envelope hobby category (new or used).
Most off the shelf low cost cnc machines are overpriced aluminum t-slot kits or flimsy mini-mill conversions with tiny work areas.
Most of the used VMCs weigh 5 tons+ and would require complete retro-fitting.
I think Tormach tried to fill that niche of decent (ish) quality, small footprint / low cost VMC but they've become way too expensive (new or used) to be in the hobby space or be competitive with a diy build.
While It's unrealistic to think a first diy build could match up to $100k+ industrial VMC precision, I think that building a Tormach quality epoxy granite machine is a reasonable goal. And you could do it on a typical $3000 hobby build budget with smart shopping.
Ebay is also full of used high quality / low cost components from all the VMC part-outs. You can furnish a diy epoxy granite machine base with some very nice used cast iron milling tables, Cat40 spindles, tool changers, precision linear actuators, servo motors etc.
Still... It's a long learning curve. If I didn't enjoy a diy build project I probably would have given up half way.
Hi Suspension - To lower cost with no impact on performance consider UHPC or CSA concrete. Half the cost of epoxy granite (by volume) and potentially easier to achieve a good modulus. Can point you at a USA available one if you want to consider this. Peter