First post - need some advice

[orion63]

Hello:

I am new to CNC. Been reading the forums and googling and decided to build my first CNC router. I want to be able to cut 3/4" wood and plywood and 0.6 to 1.0 milimeters aluminium. I need the bed to be 4'x4' or slightly more. I am thinking something like this: Mark K's CNC Machine

I like cncrouterparts' 3 Axis Electronis Kit with 380 oz-in steppers and the Gecko G540 driver. This seems to be a winner kit but, been new to this activity, I want to know if it will be able to handle my actual needs. And in the future, if I want to go for 1" hardwood? 5mm aluminium?

Also, what kind of power will I need in the router? is a laminate trimmer like the Makita 3709 enought? Is variable speed a must for cutting metal?

CNCRouterParts

Thanks in advance,

Gonzalo

[brtech]

For 4 x 4, you will need a roller chain design, or rack and pinion. 4' screws are probably too whippy, although people have built them. Most 4 x 4s have double drives on Y, because the gantry is too heavy to drive it with one motor.

I think the real machinists here (which I am not), say that cutting aluminum on an MDF based machine doesn't work so well. 1 mm AL is pretty light, so perhaps you can get away with it.

It does seem a shame to build something as big as 4 x 4 and under power the spindle. I think you want a full sized router, and not a trim router. There is a thread here about "super pid" which is a very cool way to get the lower RPMs you want to cut AL.

I have a 4 x 4 that uses the whole cncrouterparts line - the carriages, R&P drive, etc. It's a Fineline Automation FLA-300. This is an 8020 based design rather than MDF. Costs more, less work, more rigid, probably more accurate, although lots of folks here have very accurate cuts on their MDF based machines.

You might also look at the Joe's Hybrid.

[CarveOne]

The 4'x4' machine is a good size and the kit you mention is ideal for it. If you want to use lead screws and not rack and pinion then use 2 start or 5 start ACME lead screws and anti-backlash nuts. 5 start turns slow enough that you can go a little more than four feet and still get good jog speeds without whipping. Anything over 4'x4' is the size where people usually decide to go to rack and pinion. There are many 4'x4' machines originally built with lead screws that have been upgraded to rack and pinion.

You will use multiple step-downs for wood, MDF, and aluminum cutting anyway, so that's something that you set up in the gcode according to the type and size cutter you are using. You can go deeper than 1" with the cutters that have flutes long enough.

I would recommend the very popular Hitachi M12VC router for this size machine.

CarveOne

[orion63]

Thanks a lot for the answers.

It is not easy to find all the hardware I want here, in Peru. I like lead screws design for it's simplicity, but I just realized that I am not sure I can find good screws of the size I need. Maybe I will have to settle for something smaller, at least for my first machine. That Hitachi router is a lot of machine for the price! but fixed base routers are also uncommon here. Have to do some research....

Thanks for pointing me to the "super pid" thread!

Now, MDF is a material a don't really like. It is heavy and unpleasant to work with. Is there a reason people prefer it against good plywood?

Thanks again and merry Christmas!

[rcheli1]

If you are building a 4' x 4' take a look at MechMate CNC Router - Build your own with our detailed plans

[CarveOne]

Originally Posted by orion63 Thanks a lot for the answers. It is not easy to find all the hardware I want here, in Peru. I like lead screws design for it's simplicity, but I just realized that I am not sure I can find good screws of the size I need. Maybe I will have to settle for something smaller, at least for my first machine. That Hitachi router is a lot of machine for the price! but fixed base routers are also uncommon here. Have to do some research.... Thanks for pointing me to the "super pid" thread! Now, MDF is a material a don't really like. It is heavy and unpleasant to work with. Is there a reason people prefer it against good plywood? Thanks again and merry Christmas!

Routers with a removable base are more popular here. The Hitachi is less noisy at full speed than most others, and at low speed it is fairly quiet with some torque left. The Super-PID will make it even better, and give you the ability to control the speed from within Mach3.

MDF is lower cost than plywood and is easy to cut. It does make a dusty mess if you have to chase behind the cutter with a vacuum cleaner.

If you build a small machine a 1 hp trim router will work well, but you can't be as aggressive with the cuts. You can still cut 1" depths with it. It just takes a little longer.

CarveOne

[orion63]

My budget isn't very high, and to the price of the kit I have to add shipping to Peru and customs. It won't leave me with much to invest in hardware and the router. I am searching for an inexpensive router with speed control, hope to find one soon.
If there is no advantage using MDF, I prefer to use plywood. Curiously, fine plywood here is cheaper than MDF.
One last question: what speed router speed is adecuate for cutting 1mm AL?

[hemsworthlad]

Originally Posted by orion63 One last question: what speed router speed is adecuate for cutting 1mm AL?

Depends on cutter width but any where between 10,000 & 15,000 rpm with the right cutter, single flutes work very good in AL giving good chip clearance.
Twin flutes work ok as well, the less flutes better the chip clearance cooler the tool and longer life.

Al will kill a small weak router very quickly if cutting lots.!

[brtech]

Most of the less expensive routers that have speed controls don't have a closed loop control. That means they don't hold the speed when under load. The Super PID uses a feedback sensor that provides closed loop control - it maintains the speed under load.

If you have a very restricted budget, then the Super PID might be something you can push off, but if you expect to get it eventually, then your router can be a fixed speed model.

I haven't seen anyone using plywood. Lots of MDF machines. One reason is density, another is smoothness. However, I think the real reason is that it's a uniform material, and therefore it machines very well. The layers in the plywood don't machine as well, which would give you a less satisfactory result. You may be able to use plywood on parts that are simple flat plates with through holes only.

If you are set on a wood machine, you might want to look for threads on a Joe's 2006, and the Solsylva designs here in the 'zone, as well as the Blacktoe design you mentioned already.

Have you looked to see if you can locally source 8020 extrusion in Peru?

[orion63]

Cutting aluminium is very high in my priorities, so I am concentrating in a real router, instead of the trimmer. Been in some stores today morning, and started to despair on finding a fixed base at a reasonable price. Can only find high end units in the US$ 300 and up range. I started to think that maybe I can adapt a plunge router. Did somebody do something like this?

Yep, MDF is the material of chice, can't find a machine made out of plywood. Maybe, as suggested, I will end up using both materials. But I'm still not convinced of the advantages of MDF. I've build lots of things with plywood with great results.

Haven't checked 8020 extrusion, maybe it's available here. Any examples of CNC routers made up of this material?

I've seen lots of designs, including Joe's and Solsylva's. I thinks Joe's is a little bit too big and heavy compared to the Blacktoe. The Solsylvas are lightweight and very interesting. I believe I might be able to build something in between.

Thanks again all the help.

Gonzalo

[brtech]

Is your local market a lot more expensive than US? Amazon has the basic M12VC for $103

Amazon.com: Hitachi M12VC 2-1/4-Horsepower Variable-Speed Router: Home Improvement

Amazon.com: Hitachi M12VC 2-1/4-Horsepower Variable-Speed Router: Home Improvement

Take a look at this:
ftp://finelineautomation.com/FLA100-00_rev4.zip

You may need the free viewer
Free eDrawings Viewer for SolidWorks, DWG and DXF files

This one is 2 x 3. There are versions of it that go up to 4 x 4.

[hemsworthlad]

If you plan on machining Alu often then I would consider building from something stronger than MDF or PLY. I'm not saying they wont work but what will happen is the machine will fall apart very quickly.?
The forces when cutting Al are considerably more than wood and will vibrate a weak machine to piece's, it will even kill large routers if you push remotely hard. Router bearings are not designed for the forces and heat created by cutting AL.

Have you considered steel.? dont know how it compares in Puru but in UK steel is a lot cheaper than AL, still more expensive than MDF but not by very much.
I payed £20 for 7.5mtr of 50x50 steel box, 18mm MDf is £15 and to me 18mm is the minimum thickness, I would wont at at least 25mm which is £25.
My machine is not quite 4x4 with a cutting area of 1200x1000 and I used 4 lengths for the complete frame, it does use a piece of AL for the gantry but it could just as easly be made from steel and infact if making again I would use steel for the added strength.
Dont be put off by weight, the extra weight helps when cutting giving a better finish with less chatter.
It will restrict your rapid speeds slightly but IMO high rapids are just for showing off, in actual use very few who quote 1000ipm plus rapids dont actually use them because there machine would tear it's self apart in very short amount of time and even more so with MDF/wood framed machine.!

The plus side to weight is improved cutting speeds due to a massively stronger machine allowing deeper cuts and faster feed rates.
With steel you can have a machine that doesn't cost much more than MDF/wood but allows for wider range of material cutting with far superior finish and will last much much longer than MDF framed machine with less maintenance and cut all day long 7 days a week without complaint. . . . . Try that with an MDF based machine cutting AL and see if you make the week out or even the day before it shook it's self to pieces.!!

I mainly 95% time cut AL with my machine so trust me on this it will kill routers and MDF framed machines very quickly if cutting any thing thicker than 3mm sheet for any length of time, if the odd occasion then yes it will be ok but if you plan on cutting Al often for long periods at a time(4+hrs) then consider stronger materials for the frame and buy dedicated AL cutters designed for DRY high speed cutting this helps take the strain off the router slighty.

Dont be scared off by weight mass helps with cnc and steppers can handle more than you probably realise if correctly matched with other components.
Remember this.! . . . A machine is only as good as it's weakist component and IMO MDF is weak.!

Good luck.!