[runcyclexcski]

Hi all--I've been lurking at this forum for years. I am now putting together a plan for a router to cut EPS foam. I do not need much precision (+- 0.1 mm == +- 0.004 in), but I am looking for good accuracy over a very long X (6 feet). The Y is much shorter -- 12" is all I need. I am thinking to use Al extrusions, 90x90 mm (we have an excellent local supplier), a 2HP router for spindle, youtube-tested Chines rails, bearings, and lead screws.I am a bit at an impasse with the plates, angle brackets, motor mounts, etc., as I would need to make them myself from scratch. Most videos I've seen gave me the impression that one needs a CNC to make a CNC! Al is the first choice, of course, and I've done plenty of Al milling on a Bridgeport when I access to one (had it for years), but now the only mill I've got is a DRO Sherline (some may know...). That thing is fine for indexing holes on 6x6" pieces, I can sure keep my pieces at 6x6 limits, but drilling and milling 1/4 and 1/2 thick Al Plates -- forget it. I do have a 1 HP Grizzly-like drill press, so I could index on the sherline and finish them off on the press. But slots, cutouts etc for adjustments -- forget it. My Sherline handles plastics *acrylic), and wood just fine. I would like to avoid plywood: I am in the UK, it's humid and temperatures fluctuate all over the place.Is there a good machinable plastic that would not absorb humidity like wood, not crack like acrylic, provide the rigidity to drag the 2HP router in XYZ, and available in flat sheets (like the 0.500" mirror-finish Al pieces one can get at McMaster)? I.e. a material that would be closer to Al than wood in strength, closer to wood in costs and machinability E.g. I have seen tabletops in my chemistry labs, made of some badass material... heavy as hell (>>much heavier than particle board), gives off a deadly smell once you drill it (and drilling it is a *****), gray dull powder once drilled, no visible fibers. So I could recycle some of these table tops. Never seen one crack or break, and I tried hard...

[wizard]

Welcome aboard!

Hi all--I've been lurking at this forum for years. I am now putting together a plan for a router to cut EPS foam. I do not need much precision (+- 0.1 mm == +- 0.004 in), but I am looking for good accuracy over a very long X (6 feet). The Y is much shorter -- 12" is all I need.

This sounds like a specialized application with the short Y and long X, can you describe the application further?

I am thinking to use Al extrusions, 90x90 mm (we have an excellent local supplier), a 2HP router for spindle, youtube-tested Chines rails, bearings, and lead screws.I am a bit at an impasse with the plates, angle brackets, motor mounts, etc., as I would need to make them myself from scratch.

A lot of stuff can be purchased if you shop around a bit. To be perfectly honest I have mixed feeling about using aluminum in a machines main structure though it can be fine for brackets, mounts and so forth. Aluminum isn't that hard to work with and frankly after you get the machine built you can always remake any pieces that offend your sensibilities. However when it comes right down to it steel isn't that hard to work with either.

For parts you can't purchase on line your best bet is to become familiar with local metal working and fab shops. For example a decent sheet metal shop will likely have a large press for bending metal and a shear and or band saw for cutting stock. They would be able to knock out some of the parts you need fairly quickly. Some of the parts might be considered temporary as sheet metal work isn't the most precise of activities. If not a sheet metal shop maybe a local jobber type machine shop that can make some of the components for you.

It should be noted that the one place where extruded aluminum T-slots makes sense to me is for someone without a shop and the unwillingness to seek out job shops for his parts requirements. I don't know if there are kit suppliers in the UK but it is worth looking into if local support is thin or you don't have the time to deal with job shops.

Oh one more thing not all T-Slooted extrusions are created equal, some are so thin or light as to be nearly useless in a machine tools structure.

Most videos I've seen gave me the impression that one needs a CNC to make a CNC! Al is the first choice, of course, and I've done plenty of Al milling on a Bridgeport when I access to one (had it for years), but now the only mill I've got is a DRO Sherline (some may know...). That thing is fine for indexing holes on 6x6" pieces, I can sure keep my pieces at 6x6 limits, but drilling and milling 1/4 and 1/2 thick Al Plates -- forget it. I do have a 1 HP Grizzly-like drill press, so I could index on the sherline and finish them off on the press. But slots, cutouts etc for adjustments -- forget it. My Sherline handles plastics *acrylic), and wood just fine. I would like to avoid plywood: I am in the UK, it's humid and temperatures fluctuate all over the place.

Good quality wood products are very viable for machine builds. IF nothing else you can get crude solutions until your machine is functional enough to make proper components.

As for tooling to make the parts you can make everything by hand if you really want too. You would need to learn manual layout techniques and develop skills with the use of hand tools. It might be a bit "old time" but all machinery was built this way at one time.

Is there a good machinable plastic that would not absorb humidity like wood, not crack like acrylic, provide the rigidity to drag the 2HP router in XYZ, and available in flat sheets (like the 0.500" mirror-finish Al pieces one can get at McMaster)?

You can get all sorts of plastic sheets from McMaster. However you can also get aluminum and steel sheets. So why not go metal first?

I.e. a material that would be closer to Al than wood in strength, closer to wood in costs and machinability E.g. I have seen tabletops in my chemistry labs, made of some badass material... heavy as hell (>>much heavier than particle board), gives off a deadly smell once you drill it (and drilling it is a *****), gray dull powder once drilled, no visible fibers. So I could recycle some of these table tops. Never seen one crack or break, and I tried hard...

Recycled, especially free recycle, is often the best approach. However if you have a McMaster - Carr catalog there are all sorts of plastics and composite material listed including phenolics, PVC sheets, fiber glass sheets and so forth. I'd seriously consider though building your machine with temporary solutions to make the final solutions or enlist a local machine shop.

By the way just because a part is made out of wood or plastic does not imply that you can get away with less precision in layout. Your parts still need to be accurate and square where required, to prevent binding and interference issues. This is why I'm not convinced that using easier to work materials will leave you that much farther ahead. You send up suffering though a lot of screwing around (literally turning sees to force parts in alignment) when a part could have been made up square and to dimension in a machine shop.

[runcyclexcski]

Many thanks for writing back!

The temporary solution idea as a proof of principle, followed by gradual upgrades, is a good one... Out of the plastics you've listed -- would Phenolic be your first choice? Does it absorb moisture, like wood does? I have also heard of this stuff calld Trespa...

My application is to make and wind-test different EPS moulds. The moulds generally are shaped like elongated ellipsoids, about 6 feet long and 3 feet in diameter. (I mistyped in my OP -- I meant 36" for Y and 72" in X). The moulds would be used for carbon fiber layout for a human powered vehicle shell. They may also be squished in Z. This means that Z needs to be quite deep (36/2 = 18"). Not sure what the state of the art in DIY is, in terms of making deep Z cuts. I am thinking to attach a thick-wall pipe (say, 1" ID, 2" OD) with bearings on both ends, and run a shaft between the router and the chuck. The chuck will be just a shaft coupler, as I will be using mills of standard shanks (1/2") for foam.

I am exploring the CNC route, b.c. I would like to try different shapes of moulds before committing to a given CF layout. HPVs are narrow and long, hence the long X and short Y.

The Aluminum extrusions I have in mind are 90x90 mm, I have previously used them to make laser rights, and they were rock solid (at least Throlabs ones). I have a good feeling on how beefy they should be. Obviously, 20x20 and 20x40 is not a starter. Another reason I like the Al extrusion idea is that, if I am not successful (90% of the time), I can recycle the extrusions for my laser lab and to make furniture. If, on the other hand, I go the steel/weld path, the kit will end up mostly irreversible, and I won't find any use for the parts.

The idea not to go metal to make brackets was that the mill and the drill press I have are underpowered..

[1Jumper10]

Cast Nylon would probably work. I have a couple sheets that are 1" thick that I bought off Craigslist and the stuff is incredibly strong! I've made a few small parts with it; Sensor mounts and end caps for steel tubes. It cuts great on a CNC router with single flute bits. It drills good to. But if you try and cut it on a table saw it will melt.

[ger21]

Trespa is a type of phenolic. The problem with phenolic is that it's probably not much cheaper than aluminum. It's considerably more expensive than wood.

[wizard]

Many thanks for writing back!

The temporary solution idea as a proof of principle, followed by gradual upgrades, is a good one... Out of the plastics you've listed -- would Phenolic be your first choice? Does it absorb moisture, like wood does? I have also heard of this stuff calld Trespa...

I'm not sure if I would go the wood or synthetics route in your shoes. Note that I'm not against the constructions of machines out of wood, especially if the machine is focused on wood working. In your case though you seem to already have good reasons to avoid wood or wood based products.

The act of going through successive gradual upgrades only makes sense if you are without any machinery at all and don't have any locally.

My application is to make and wind-test different EPS moulds. The moulds generally are shaped like elongated ellipsoids, about 6 feet long and 3 feet in diameter. (I mistyped in my OP -- I meant 36" for Y and 72" in X). The moulds would be used for carbon fiber layout for a human powered vehicle shell. They may also be squished in Z. This means that Z needs to be quite deep (36/2 = 18"). Not sure what the state of the art in DIY is, in terms of making deep Z cuts. I am thinking to attach a thick-wall pipe (say, 1" ID, 2" OD) with bearings on both ends, and run a shaft between the router and the chuck. The chuck will be just a shaft coupler, as I will be using mills of standard shanks (1/2") for foam.

Interesting, I can't really comment upon a long Z shaft like you are describing as I've not done such. What I can say is that generally you don't want cantilevers shafts like the tin machine design. The qualification here is your focus on EPS (assuming Expanded Poly Styrene foam of some sort. I'm really thinking a 2" OD would be a little thin over 18". Ideally the shaft would tape down to the working end to give you as much clearance as possible. Ultimately though you may need a machine with more than 3 axis. Before you build this machine it might be a good idea to model the design and various cutters to see if you will even be successful.

I am exploring the CNC route, b.c. I would like to try different shapes of moulds before committing to a given CF layout. HPVs are narrow and long, hence the long X and short Y.

Make perfectly good sense.

The Aluminum extrusions I have in mind are 90x90 mm, I have previously used them to make laser rights, and they were rock solid (at least Throlabs ones). I have a good feeling on how beefy they should be. Obviously, 20x20 and 20x40 is not a starter. Another reason I like the Al extrusion idea is that, if I am not successful (90% of the time), I can recycle the extrusions for my laser lab and to make furniture. If, on the other hand, I go the steel/weld path, the kit will end up mostly irreversible, and I won't find any use for the parts.

As long as one has a 4.5" right angle grinder welded structures can be reversed!!!!!

Generally I don't like Aluminum extrusions for a few reasons:
1. Builds end up being very expensive.
2. Bolted together extrusions generally are not the most reliable connections one can imagine. This results the need to use plenty of gussets and other reinforcing components to keep the machine together.
3. The way most T-Slotted extrusions are designed means that the linear rials bolted to them are not well supported.
4. Generally DIY designs have compromised on the gantry part of the machine, that includes the structures holding the beam up.

This isn't to so say you can't be successful with extruded aluminum in machine builds, just that there are costs and performance compromises. For the gantry beam it really pays to go beyond the norm for DIY routers as that is often the weakest link in the whole machine.

As for being successful make it a point to be so or don't waste your time.

The idea not to go metal to make brackets was that the mill and the drill press I have are underpowered..

This is the part that really bothers me, you say you have a Sherline and a 1HP dill press, that is far more than many have that are building these machines. This is why I'm really wondering why you are even considering wood for the structural parts of the machine. While I may consider most to the Grizzly like drill presses to be half assed, they can drill holes in anything you are likely to have in the home shop. The Sherline might take for ever to clean up an edge or mill a slot but it can be done. From my perspective it looks like you are dismissing what many would give an arm and a leg to have in their shops. Think about it, you have a Sherline that can layout parts by your own admission so why not use it even if you have to transfer parts to the larger drill press? The Sherline can spot holes or even drill pilot holes in most materials so there is no excuse here. Your machine doesn't need to be a work or art it just needs to be functional.

Maybe I'm missing something here, maybe others have a different opinion, but if you really want this machine and you don't want to pay somebody else to make everything for you, then you will need to put a little elbow grease into the project. By paying somebody else I mean employing the services of a local machine shop, though paying somebody else could mean finding a supplier of said parts. Using a local machine shop is a perfectly rational approach to solving your parts problems too. If you read some of the build threads you will find that guys have started out with less and ended up with very useful machines.

[Goemon]

I've just been through a different but somewhat similar process of shopping for parts to build my CNC machine.

I decided to go with an epoxy granite machine base. It seemed to be the best option for me to achieve quality results from a limited budget and similarly limited metal-working equipment.

If done right, epoxy granite machine bases are apparently superior to steel and aluminum alone in terms of vibration dampening and thermal stability without compromising any stiffness (if the base is thick enough).

I was was initially disappointed with the aluminum extrusions and brackets I bought but that was mainly my fault for trusting a low end CNC hobby store. My observation with al extrusions was that buying high quality brackets is at least as important as buying good extrusions. A Frame made with cheap L brackets from the Open Builds part store was about as stable as the Ethiopian stock exchange. With good brackets it was a different story.

I am building my gantry out of carbon fiber with embedded steel plates to hold screw threads. The only power tools I am using are a router, angle grinder, drill press and dremel.

If the goal is to not sacrifice any strength compared to steel and aluminum then it is more about adjusting part thickness to compensate for the differences in material strength, regardless of what you use. My epoxy granite base will be stiffer than my aluminum extrusions because the walls are at least twice as thick.

google "epoxy granite machine base" and look at the pics. Should give you some ideas. I have mostly eliminated the need for brackets with my current design.