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alank2
04-03-2012, 06:43 PM
Hi,

I've looked through the forum listing and I don't see one that is a catch all forum for beginners. If this isn't the right one, please feel free to move my post to the correct one.

I've been cutting a plastic enclosure (1599HBK made by hammondmfg, 8"x4"x1") by hand using some wooden forms with drill bushings, but I'd like to get into CNC. I drill 4 5/8" holes in the top and need a 1" x 6" rectangle. But the thing is I also need to cut a rectangle and have a round hole in the bottom edge and left edge as well. The left edge is going to be 8" above the "table" for example and I'm not sure how much of a problem this would be.

Do you guys have any directions I should start looking?

Thanks,

Alan

jckstrthmghty
04-03-2012, 06:51 PM
First thing is budget. How much are you willing to spend? Are there any other projects you have in mind? If it's only the one then cnc is not the way to go. Be far cheaper and perhaps faster to make a few cutting jigs. What size of table, what kind of accuracy are you looking for.

alank2
04-03-2012, 07:23 PM
Hi,


First thing is budget. How much are you willing to spend?

I saw the Zen Toolworks kit over at Amazon which is what peaked my interest in CNC. I've never really looked or read about them too much. To get one that would do the work I need, I can probably go 1K-1.5K, but less is more. One thing that would be important to me is durability.


Are there any other projects you have in mind? If it's only the one then cnc is not the way to go. Be far cheaper and perhaps faster to make a few cutting jigs.

I am a project type of guy and it always seems I'm wanting to work on a new one. So, while something that could machine the cases I need would be a great help, the ability to do machine other things over the long haul is what is exciting. I love a new hobby and CNC looks like an awesome one. One of my existing hobbies is electronics, microcontrollers, designing pcb's, so I am familiar with that already.


What size of table, what kind of accuracy are you looking for.

Don't even know where to begin. I do have wooden forms now that I am using with drill bushings. I use a trim router with these wooden forms to cut out any rectangular openings I need. I'm not sure what type of accuracy I have with these.

Thanks,

Alan

IBBruin
04-03-2012, 10:15 PM
I've done the manual router bushings, templates and such and there is some degree of satisfaction with that. But I LOVE drawing in AutoCAD, exporting a dxf into lazycam, opening up the gcode in Mach3, picking the multilayer wizard in Mach3 and cutting an exact pattern in something using the machine/electronics/software I chose and put together. It's hard to describe it.

flojor10
04-03-2012, 10:28 PM
Hi,



I saw the Zen Toolworks kit over at Amazon which is what peaked my interest in CNC. I've never really looked or read about them too much. To get one that would do the work I need, I can probably go 1K-1.5K, but less is more. One thing that would be important to me is durability.



I am a project type of guy and it always seems I'm wanting to work on a new one. So, while something that could machine the cases I need would be a great help, the ability to do machine other things over the long haul is what is exciting. I love a new hobby and CNC looks like an awesome one. One of my existing hobbies is electronics, microcontrollers, designing pcb's, so I am familiar with that already.



Don't even know where to begin. I do have wooden forms now that I am using with drill bushings. I use a trim router with these wooden forms to cut out any rectangular openings I need. I'm not sure what type of accuracy I have with these.

Thanks,

Alan

So if you are interested in Cnc would you built or buy? You could probably built a better machine than if you buy a kit. If your always working on projects and know a little bit about electronics your at a big advantage and a Cnc router is probably for you. Looking foward to seeing what happens ;)
-George

alank2
04-03-2012, 11:37 PM
Hi George,


So if you are interested in Cnc would you built or buy? You could probably built a better machine than if you buy a kit. If your always working on projects and know a little bit about electronics your at a big advantage and a Cnc router is probably for you. Looking foward to seeing what happens ;)
-George

I am open minded on build vs kit, but leaning slightly towards kit. I think I have so much to learn. I've been doing some reading here and at Wikipedia.

Is G-code something that the computer would send to a control board? Or does a computer interpret G-code and translate it to lower level signals a control board needs?

What does CAD/CAM software do? What is the difference between CAD and CAM?

How does a CNC machine know where it is? Does it have to go home and use limit switches to know?

What is the difference between a stepper and a servo?

Given my needs to cut a plastic box on 3 sides, am I really looking at 3 distinct jobs, each with the surface I want to work up? With one surface up, it will be 8" tall, how can I deal with this?

What is the difference between a CNC mill and a CNC router?

Thanks for the help!

Alan

jckstrthmghty
04-03-2012, 11:43 PM
I definitely think some reading/research is in order. First I think you should look at the joes2006 sub forum. That would fall into your budget and is an excellent machine available in a kit.

A bit higher would be a extrusion build like CNCrouterparts but those will take you out of the stated budget.

Then there's something like what I have. A jgro which can be built with hand tools which will be under your budget if you plan well.

As for a fully built machine, don't think that's feasible unless you are willing to double your budget.

If your cutting area is 8x11" or smaller look at microcarve's thread. Absolutely a smoking value for a super precise kit.

louieatienza
04-04-2012, 07:04 AM
There are not too many routers on this forun that have enough Z travel to cut an object 8" on end. Usually this would be the domain of the mill.

You might want to look into a Taig or Sherline CNC mill, which are very durable and capable of machining hard metals as well. Of course you still need a way of fixturing your box to machine it on end.

As for knowing where the job is, well it is you that must tell (or show) the CNC where the orogin of your job is. You normally locate 0,0,0 whether it be the center or a corner of your wok, depending on how it's set up in your software. You could have the CNC probe the center or edge of your work, but you'd still need to get it in the proximity first.

I would do your job as three separate programs. This way, if you're doing a batch of boxes, you can do one face, before tearing apart your setup/fixture to do the next face.

For stepper vs servo check the mechanical section. Though for most applications here steppers are fine.

Routers and mills come in vavrious forms, and line between the two can blur. I would say routers have a larger table format, than mills. Routers are generally not used for milling hard metals, though there are commercial tables more than capable of doing so. The spindles on mills usually run slower, with more torque, though there are mill with high speed spindles.

flojor10
04-04-2012, 08:22 AM
Hi George,



I am open minded on build vs kit, but leaning slightly towards kit. I think I have so much to learn. I've been doing some reading here and at Wikipedia.

Is G-code something that the computer would send to a control board? Or does a computer interpret G-code and translate it to lower level signals a control board needs?

What does CAD/CAM software do? What is the difference between CAD and CAM?

How does a CNC machine know where it is? Does it have to go home and use limit switches to know?

What is the difference between a stepper and a servo?

Given my needs to cut a plastic box on 3 sides, am I really looking at 3 distinct jobs, each with the surface I want to work up? With one surface up, it will be 8" tall, how can I deal with this?

What is the difference between a CNC mill and a CNC router?

Thanks for the help!

Alan

G code is made in you cam software and then sent to you post processor(mach 3). Then signals are sent to your motor driver board. Your motor driver amplifies the signal so it can moves the motors.


CAD software stands for computer aided design, you use it to make a solid model of what your going to cut. Cam is Computer aided machining, you use this to create toolpaths from the design made in the CAD software.

You don't need limit switches or touch plates, if you don't mind you could visually zero the axis's.

Servos are more expensive and usually aren't used in hobby Cnc. But they are more accurate than stepper motors and more powerful.

To cut a 8" high box you need to have a long and sturdy z axis. You could also make a fixture that held the piece you are cutting below the table so you wouldn't need a long z axis.

A Cnc mill is meant mostly for ferrous metals and its spindle has slower speeds with more torque. A Cnc router is used more for wood, plastics, and aluminum cutting.

Sorry for the bad grammar, I was writing in a rush. If you have any more questions feel free to ask.;)

-George

alank2
04-04-2012, 10:44 AM
Hi,


You could also make a fixture that held the piece you are cutting below the table so you wouldn't need a long z axis.

I was thinking about this direction as well.

Thanks for all the information everyone, I'll get to some reading!!

Alan

arizonavideo
04-05-2012, 02:36 AM
The micro carve would work but for the 6" box if you do a lot of them then you could cut a hole in the table or make the Z travel longer.

What do you put in the box?

alank2
04-05-2012, 08:06 AM
Hi,


The micro carve would work but for the 6" box if you do a lot of them then you could cut a hole in the table or make the Z travel longer.

I emailed John of microcarve and he even send me a BMP of how it could be done!


What do you put in the box?

Here is what I build : SA Development Press Monitor (http://www.pressmonitordevice.com)

It is a monitor for ammunition reloading presses. You can't see the bottom or left machining, but here is the face.

http://www.pressmonitordevice.com/media/pmii.jpg

Can you cut labels with CNC too? What about the 5/16" holes? I usually use a punch for this and it is a pain to clean up the hole with an xacto... I was thinking if you could press a label between two thin wood layers could it be cut with a spindle?

Thanks,

Alan

flojor10
04-05-2012, 02:28 PM
Hi,



I emailed John of microcarve and he even send me a BMP of how it could be done!



Here is what I build : SA Development Press Monitor (http://www.pressmonitordevice.com)

It is a monitor for ammunition reloading presses. You can't see the bottom or left machining, but here is the face.

http://www.pressmonitordevice.com/media/pmii.jpg

Can you cut labels with CNC too? What about the 5/16" holes? I usually use a punch for this and it is a pain to clean up the hole with an xacto... I was thinking if you could press a label between two thin wood layers could it be cut with a spindle?

Thanks,

Alan

You could cut the labels with a drag knife, or possibly even a10-20 degree v bit. A Cnc wouldn't be ideal for this though. I would get a laser cutter that you could mount in place of the router on your Cnc.
-George

alank2
04-05-2012, 02:43 PM
Hi George,

I've been playing with EMC2 a bit and its help mentions software stepping and latency.

Why is latency so important? If the PC is telling the CNC what to do, literally step by step, then if the next step is slightly delayed, then what is the result?

Thanks,

Alan

flojor10
04-05-2012, 06:35 PM
Hi George,

I've been playing with EMC2 a bit and its help mentions software stepping and latency.

Why is latency so important? If the PC is telling the CNC what to do, literally step by step, then if the next step is slightly delayed, then what is the result?

Thanks,

Alan

Latency is how long it takes your pc to send out periodic step pulses to the motors. In simple terms how close your machine runs in accordance with its schedule. Excess latency can contribute to un-smooth stepping(noisy), and can limit your speeds, or your ability use microstepping. Some people have reported losing steps because of this, but there are many other factors that could have caused it. I use mach 3 and I believe there are less latency problems with it, but it most has to do with your pc. Here is some info on testing for latency and recommended amounts.:)

http://wiki.linuxcnc.org/cgi-bin/wiki.pl?Latency-Test

-George

louieatienza
04-05-2012, 07:05 PM
You could cut the labels with a drag knife, or possibly even a10-20 degree v bit. A Cnc wouldn't be ideal for this though. I would get a laser cutter that you could mount in place of the router on your Cnc.
-George

I'd still print the labels... BTW you cannot cut the table on a microcarve machine since the leadscrew runs underneath it.

alank2
04-05-2012, 07:40 PM
Hi,


BTW you cannot cut the table on a microcarve machine since the leadscrew runs underneath it.

I suppose you could partially notch it so long as it didn't run into the leadscrew or a rail. What about mounting something on the underside of the table with part of it extending past the table edge - you could machine the part past the edge right? it might be perhaps an inch below the table I would think.

I've got a few more questions (thank you guys for being so patient while I learn!):

What is microstepping? I've read a few things about it is done electrically, but why do you/would you want to do it? Is this something that the motor drive handles or can handle? Does it let you redefine a step as a smaller unit (than 1.8 deg)? Is that the purpose?

I've done some more reading - Gecko says they have 10 micro steps by default. Does it remember WHICH micro step it was on when you power off? If you want to leave your CNC at a specific location, do you need to make sure you are at a specific step first? What happens when a motor control fires up? How does it know the motor state?

I see there are some USB implementations that get away from the standard parallel type interface. I looked at Planet CNC and it looks like they have moved the high speed latency type stuff to a microcontroller that processes the G-code. Is this a new thing or something that has been going on for awhile? What is the general opinion of this type of interface/control board? Obviously a downside is that it locks you into a specific software where with the parallel port you can choose many.

Is this the difference between a traditional parallel port setup vs something like USB/Planet CNC:
G-Code --> Traditional CNC Control Software --> Parallel Port --> Parallel Breakout --> Motor Drive --> Stepper Motors
G-Code --> Planet CNC Software --> USB --> CNC USB Microcontroller --> Motor Drive --> Stepper Motors

I've played around with LinuxCNC (EMC2?) and also TurboCNC. The latency issue was terrible on one PC I tried but much better on the other. I have to admit I liked the simple DOS console type interface of TurboCNC, but I haven't really gotten into messing with LinuxCNC much yet. Any reason why I shouldn't spend some tme with TurboCNC and should invest that energy into LinuxCNC instead? I didn't see much going on in the forum for TurboCNC...

What is the purpose of the resistor used with a stepper motor? What does it accomplish?




Thanks,

Alan

louieatienza
04-05-2012, 08:03 PM
Hi,



I suppose you could partially notch it so long as it didn't run into the leadscrew or a rail. What about mounting something on the underside of the table with part of it extending past the table edge - you could machine the part past the edge right? it might be perhaps an inch below the table I would think.

I've got a few more questions (thank you guys for being so patient while I learn!):

What is microstepping? I've read a few things about it is done electrically, but why do you/would you want to do it? Is this something that the motor drive handles or can handle? Does it let you redefine a step as a smaller unit (than 1.8 deg)? Is that the purpose?

I see there are some USB implementations that get away from the standard parallel type interface. I looked at Planet CNC and it looks like they have moved the high speed latency type stuff to a microcontroller that processes the G-code. Is this a new thing or something that has been going on for awhile? What is the general opinion of this type of interface/control board? Obviously a downside is that it locks you into a specific software where with the parallel port you can choose many.

I've played around with LinuxCNC (EMC2?) and also TurboCNC. The latency issue was terrible on one PC I tried but much better on the other. I have to admit I liked the simple DOS console type interface of TurboCNC, but I haven't really gotten into messing with LinuxCNC much yet. Any reason why I shouldn't spend some tme with TurboCNC and should invest that energy into LinuxCNC instead? I didn't see much going on in the forum for TurboCNC...

What is the purpose of the resistor used with a stepper motor? What does it accomplish?

Thanks,

Alan

You might be better to ask John who is a member here (handle: microcarve) and there is a huge thread.

Dedicated pulse generators have been around for a long tome, probably as long as CNC itself. The new SmoothStepper is ethernet based, and yo can still run Mach3 with it. Galil has PCI based solution but expensive.

If I'm not mistaken, there are certain limitations with TurboCNC, such as circular interpolation, and pulse generation restrictions as well. But it's cheaper, and for simple tasks like drilling and square holes, may suffice.

I believe in the case of GeckoDrives, the resistor limits the current going to the steppers.

flojor10
04-05-2012, 08:50 PM
Hi,



I suppose you could partially notch it so long as it didn't run into the leadscrew or a rail. What about mounting something on the underside of the table with part of it extending past the table edge - you could machine the part past the edge right? it might be perhaps an inch below the table I would think.

I've got a few more questions (thank you guys for being so patient while I learn!):

What is microstepping? I've read a few things about it is done electrically, but why do you/would you want to do it? Is this something that the motor drive handles or can handle? Does it let you redefine a step as a smaller unit (than 1.8 deg)? Is that the purpose?

I've done some more reading - Gecko says they have 10 micro steps by default. Does it remember WHICH micro step it was on when you power off? If you want to leave your CNC at a specific location, do you need to make sure you are at a specific step first? What happens when a motor control fires up? How does it know the motor state?

I see there are some USB implementations that get away from the standard parallel type interface. I looked at Planet CNC and it looks like they have moved the high speed latency type stuff to a microcontroller that processes the G-code. Is this a new thing or something that has been going on for awhile? What is the general opinion of this type of interface/control board? Obviously a downside is that it locks you into a specific software where with the parallel port you can choose many.

Is this the difference between a traditional parallel port setup vs something like USB/Planet CNC:
G-Code --> Traditional CNC Control Software --> Parallel Port --> Parallel Breakout --> Motor Drive --> Stepper Motors
G-Code --> Planet CNC Software --> USB --> CNC USB Microcontroller --> Motor Drive --> Stepper Motors

I've played around with LinuxCNC (EMC2?) and also TurboCNC. The latency issue was terrible on one PC I tried but much better on the other. I have to admit I liked the simple DOS console type interface of TurboCNC, but I haven't really gotten into messing with LinuxCNC much yet. Any reason why I shouldn't spend some tme with TurboCNC and should invest that energy into LinuxCNC instead? I didn't see much going on in the forum for TurboCNC...

What is the purpose of the resistor used with a stepper motor? What does it accomplish?




Thanks,

Alan

Microstepping moves your motors in steps smaller than 1.8 degrees. This helps to eliminate resonance and jerky motions. Some people with large motors use it to improve resolution, but don't expect it to increase accuracy because microstepping isn't as accurate as stepping.

Untill you get motors and driver I wouldn't invest to much time in Emc2. Try to making g codes with cam then you could run them in a simulator if you don't have the machine, just to get comfortable with software.

When you turn on the stepped motors the will jump to the nearest winding and you might here a jerk. Stepper motors won't remember their position when you turn them off. If you have limit switches you can automatically find a position even after a crash.

-George