Joe's CNC 4x4 to 4x8?

[matt-CNC]

1) Could you build Joe's 4x4 gantry, exactly as is, but install longer acme screws, and longer steel rails to accommodate the longer 8' size?

2) And then get bigger stepper motors. Or could you install dual steppers at each end and have 4 total (two on each end, on each side, is this crazy talk?)?

Mainly I need a 4x8 machine and Joe's seems proven, but my knowledge of CNC's is limited!

[ger21]

I've heard that some people have done it, but not using your methods.

8ft is really too long for acme screws, unless you used really big ones, which would then require really big motors too spin them. I believe that the people who have done it have use rack and pinion. Apparently this info is available on Joe's forum to anyone purchasing plans.

If you link two motors together mechanically, they'll always be fighting each other a small amount and may not give you much better performance at al. Better to use a single larger motor.

[matt-CNC]

Originally Posted by ger21 I've heard that some people have done it, but not using your methods. 8ft is really too long for acme screws, unless you used really big ones, which would then require really big motors too spin them. I believe that the people who have done it have use rack and pinion. Apparently this info is available on Joe's forum to anyone purchasing plans. If you link two motors together mechanically, they'll always be fighting each other a small amount and may not give you much better performance at al. Better to use a single larger motor.

I dont advise anyone using my methods!!! I thought since two steppers on each side work together, why cant four? But, I guess I am researching rack and pinion stuff now. I should just buy the Joe 4x4 plans so I can unlock his forum that is so informational.

[RyanD]

Perhaps you should consider exactly why it is that you need a 4x8 machine in the first place. Some, if not all projects that are 96"x48" can be done on a 4x4 if you consider that half the machining can be done on one side of the sheet and then slide the sheet over to complete the other half. Of course if you are doing something more than just working with 4'x8' sheets of material then that can change your needs.

Just a thought anyways....Anyone can feel free to correct me as my knowledge is somewhat limited to just having lurked around on these forums for a long time haha

[ger21]

Originally Posted by RyanD Perhaps you should consider exactly why it is that you need a 4x8 machine in the first place. Some, if not all projects that are 96"x48" can be done on a 4x4 if you consider that half the machining can be done on one side of the sheet and then slide the sheet over to complete the other half. Of course if you are doing something more than just working with 4'x8' sheets of material then that can change your needs. Just a thought anyways....Anyone can feel free to correct me as my knowledge is somewhat limited to just having lurked around on these forums for a long time haha

It's not quite as easy as you think to move a 4x8 sheet of material 4 ft and have it be aligned within .005 or so. If you have continuous routes that you need to do in two halves, you'll see any error over about .003. But, there are people that'll tell you that .01 is close enough for wood. (not me ) Just depends on your requirements.

A machine capable of cutting full 4x8 sheets needs a LOT of space. But you'll need nearly the same amount of space to cut a 4x8 sheet on a 4x4 machine.

[matt-CNC]

Originally Posted by RyanD Perhaps you should consider exactly why it is that you need a 4x8 machine in the first place. Some, if not all projects that are 96"x48" can be done on a 4x4 if you consider that half the machining can be done on one side of the sheet and then slide the sheet over to complete the other half. Of course if you are doing something more than just working with 4'x8' sheets of material then that can change your needs.

I am coming to the realization that the 4x8 is what I need, so that is where I am now concentrating my research. I need this size because it is standard construction size/sheet, meaning, I don't want to limit myself to someone in the construction field that needs larger wood elements. For instance, if someone wants custom molding/etching on a fireplace, I would have to cut 8' pieces accurately. I have chairs and tables, furniture, etc already thought out using the 4x8 template.

[ger21]

Be sure to give yourself a few extra inches of travel in both directions. I'd recommend at least 52" x 100". You may want to cut around a 4x8 panel with a large diameter bit, and you also need room for homing and limit switches.

[matt-CNC]

Originally Posted by ger21 Be sure to give yourself a few extra inches of travel in both directions. I'd recommend at least 52" x 100". You may want to cut around a 4x8 panel with a large diameter bit, and you also need room for homing and limit switches.

That makes a lot of sense. What do limit switches do/protect against?

[ger21]

Originally Posted by matt-CNC That makes a lot of sense. What do limit switches do/protect against?

The machine over traveling and destroying itself, or the gantry sliding off the end of the machine

[Tonex]

a few years ago I used joe's "basic" ide to build a router for playwood thickeness up to 8mm. what I needed was SPEED and NO extra time for cutting it in half or do "reposition"

The only sheets we could by was 1500 x 3000 mm so I needed a BIG machine - today it is sold to a company that work with it daily,,,

I did the working zone 1620 x 3080 mm with bigger steppers controlers screws and so on...
they still working with mach3 on it.

take a look in other forums ,, i combined JOE's ide with others ...

.

[stoneyreef]

I was the first one to build a hybrid into a 4'X8' machine. My build is completely documented on Joe's Support forum.

The cost was about the same, however, there is increased cost for the table and spoil board. I turned one axis into a rack and pinion set up with the pinion gear pivoted and spring loaded into the rack.

I believe we currently have 2 or 3 other machines that followed my lead and a couple more in the works currently.

[Tonex]

I forgott to say that my build was "only" made in MDF