[ger21]

The use of belts would simplify things a bit I'm thinking. Pros and cons??

The problems with belts is they are flexible, and act a little like a spring. You'll notice this more in the middle of the travel. And as you move towards the ends, it'll be easier to flex toward the middle, where the belt is longer. The tighter you can pull the belt, the better.

One member here did a lot of belt research a few years back, and determined that you need to use a 4" wide belt to get stiffness approaching screw drive.

[fretman_2]

Thanks Gerry. I've decided to stick with lead screws as I had in my original design. I was worried about lead screw whip but I think I can keep it to a minimum with proper design.

The problems with belts is they are flexible, and act a little like a spring. You'll notice this more in the middle of the travel. And as you move towards the ends, it'll be easier to flex toward the middle, where the belt is longer. The tighter you can pull the belt, the better.

One member here did a lot of belt research a few years back, and determined that you need to use a 4" wide belt to get stiffness approaching screw drive.

[fretman_2]

A question regarding hook up cable from the drivers to the motors. I saw a Youtube vid of someone using 18-4 alarm cable to run from the drivers to the motors. I can get that easily enough from Home Depot. That ok for my application?

[wizard]

The problems with belts is they are flexible, and act a little like a spring. You'll notice this more in the middle of the travel. And as you move towards the ends, it'll be easier to flex toward the middle, where the belt is longer. The tighter you can pull the belt, the better.

It helps a great deal to keep the belt supported. This acts to damp slap or vibrations in the belt so it acts somewhat like a rack and pinion drive.

One member here did a lot of belt research a few years back, and determined that you need to use a 4" wide belt to get stiffness approaching screw drive.

Of the machines I've seen using belts almost everyone of them is using grossly undersized belts. While not directly related to machining we use a lot of belt drive slides in the automation industry. Often speed is the reason but we at the same time need relatively tight positioning. These machines have very wide belts even for light weight axis, often 50 mm or more wide. On some of our injection molding machines the belts are extremely wide or doubled up from two narrower belts, if I remember correctly one is six inches wide.

I'm not one to dismiss a belt drive router, at least not a smaller one. I just don't think anyone has really implemented one correctly, at least not that I've seen. This includes a few low end (very) commercial machines. I've actually flirted with the idea in my head but I don't have the resources to realize such a machine.

[fretman_2]

Thanks! I've already received my two 48 inch 1/2-10 5 start lead screws for the Y axis. They'll be supported on both ends by double bearings...and possibly pillow block bearings too if need be. I won't use quite all of the 48 inches, but most of it.

The Shapeoko2 that I was using was belt driven, but each axis was very light weight compared to the machine I'm building. I'm hoping that I'll have this machine working by the end of summer.

It helps a great deal to keep the belt supported. This acts to damp slap or vibrations in the belt so it acts somewhat like a rack and pinion drive.


Of the machines I've seen using belts almost everyone of them is using grossly undersized belts. While not directly related to machining we use a lot of belt drive slides in the automation industry. Often speed is the reason but we at the same time need relatively tight positioning. These machines have very wide belts even for light weight axis, often 50 mm or more wide. On some of our injection molding machines the belts are extremely wide or doubled up from two narrower belts, if I remember correctly one is six inches wide.

I'm not one to dismiss a belt drive router, at least not a smaller one. I just don't think anyone has really implemented one correctly, at least not that I've seen. This includes a few low end (very) commercial machines. I've actually flirted with the idea in my head but I don't have the resources to realize such a machine.

[fretman_2]

Got another short video of an X axis test with the drill. Stepper motor mounts will arrive next week I hope and I can get the gantry finished. Then on to the lead screws for the Y axis.

https://youtu.be/zEg_-nmreOg

[wizard]

Got another short video of an X axis test with the drill. Stepper motor mounts will arrive next week I hope and I can get the gantry finished. Then on to the lead screws for the Y axis.

Nice looking machine!

As for Shapeoko, that is one of the machines that I see as having grossly undersized belts. I think a pencil is wider. The rest of the machine isn't that great but it is being built for a price. With a little work it could be a nice laser cutter.

[fretman_2]

Thanks Wizard!!

I agree...the Shapeoko could be a nice laser cutter and I did half way entertain configuring it that way. But ultimately I no room to keep it stored until I could work on it and I decided to donate it to the local Makerspace. The Shapeoko did what I wanted it to do...get me into CNC.

Nice looking machine!

As for Shapeoko, that is one of the machines that I see as having grossly undersized belts. I think a pencil is wider. The rest of the machine isn't that great but it is being built for a price. With a little work it could be a nice laser cutter.

[louieatienza]

A question regarding hook up cable from the drivers to the motors. I saw a Youtube vid of someone using 18-4 alarm cable to run from the drivers to the motors. I can get that easily enough from Home Depot. That ok for my application?

I would at the very least make sure the wire is stranded, and better yet rated for continuous bending (you can get these at places like McMaster-Carr.) Reason being all the repetitive movements can eventually fatigue the wires. Even so, it's a good idea to use cable chain or other support for the wires, and immobilize them wherever possible, especially coming out of the motor housing, where it would be nearly impossible to repair.

[fretman_2]

Good to know about continuous bending wire Louie! Cable chain...definitely.

I would at the very least make sure the wire is stranded, and better yet rated for continuous bending (you can get these at places like McMaster-Carr.) Reason being all the repetitive movements can eventually fatigue the wires. Even so, it's a good idea to use cable chain or other support for the wires, and immobilize them wherever possible, especially coming out of the motor housing, where it would be nearly impossible to repair.

[fretman_2]

Got the X axis motor mounted. Will hook up my temp motor driver tomorrow (I hope) to test it out.

Attachment 325260

[fretman_2]

Maybe you guys get tired of seeing this stuff. Got the stepper motor going on the X axis. Seems to work great...everything aligned so far. I have to cut the far end of the lead screw off, then reassemble. I kept the gShield that was used to power the Shapeoko2 to test things out. It's only rated at 2.5A max, but I do have a cooling fan on it. I'll likely build a smaller NEMA17 machine to do the engraving work on neck and control plates and will use the gShield for that.

I got the X movement steps per mm in the ball park...one inch of jog equaled one inch of movement, but I'm going to need help configuring the rest of GRBL when I get my drivers. I'll also need some help wiring the output of the Arduino Uno to the drivers.

Sorry for the shake in the video...it was hand held.

https://youtu.be/qIdj4THGlw8

[fretman_2]

Well...I screwed up. I thought I was purchasing L bracket motor mounts for NEMA23, but I actually purchased motor mounts for NEMA17's. So I have 4 unusable brackets. Anyone want to trade? Maybe I should just keep them as I do plan on building a smaller machine. It sets me back though as new mounts take a while to get here from China.

[wizard]

Well...I screwed up. I thought I was purchasing L bracket motor mounts for NEMA23, but I actually purchased motor mounts for NEMA17's. So I have 4 unusable brackets. Anyone want to trade? Maybe I should just keep them as I do plan on building a smaller machine. It sets me back though as new mounts take a while to get here from China.

You could consider making your own mounts, even temporary ones would keep your build moving forward.

[fretman_2]

Yes...you're right. I hesitated doing that because I no longer have my other CNC machine. I'll order some correct mounts this weekend. Maybe they'll get here fast.

You could consider making your own mounts, even temporary ones would keep your build moving forward.

[fretman_2]

My calculated work area for this build is X 23.75", Y 28.5". I'll be able to cut out guitar necks and bodies in that area, and even bass necks when they're cut on a diagonal. I can probably eek out another couple of inches in the X by making the Z axis plate smaller in the X direction.

[fretman_2]

What's everyone using as connectors to the CNC control box? I used the screw on 4 pin DIN (I think) connectors from Radio Shack on my Shapeoko, but they don't appear to be available at Radio Shack anymore.

[wizard]

What's everyone using as connectors to the CNC control box? I used the screw on 4 pin DIN (I think) connectors from Radio Shack on my Shapeoko, but they don't appear to be available at Radio Shack anymore.

Try catalog houses like DIgiKey, Newark, Mouser and the like. DIN connectors can be had in all sorts of configurations and frankly it is best to keep on configuration only for the steppers. Beyond that there are all sorts of other connectors that can be leveraged for use in a CNC machine from the cheap to the fairly expensive. It really depends upon your controls setup. Generally with servos and steppers you are better off to avoid connectors as much as possible. In fact some manufactures suggest no connectors at all preferring to run cables directly to the amps. That in part is due to electrical noise but other issues crop up.

For examples of other issues here are a couple that I've experienced over the years at work. A synchronous 3 phase 1/2HP motor wasn't maintaining speed even though the 3 phase driver appeared to be working well. In this case the engineer decided to run the motor power through a standard 3 phase twist lock connector. Apparently the connector wasn't in as good a shape as you would expect from newish hardware because the machine was loosing a phase intermittently. This caused instability in the RPM of the motor. Replacing the plug and socket got things on track. Another issue was with a Name brand stepper drive that had performance problems. That issue was traced down to a pin and socket plug that plugged into the face of the drive. Mind you this is a fairly common arrangement in industrial drives. The point is bad connections due to plugs and sockets are a reality that don't debug easily. None of the above where fixed instantly.

So what would I suggest if you have to use plugs and sockets. AT the cheap end probably AMP plastic circular connectors if the idea is to transition through a panel box of some sort. They are relatively cheap but do require the purchase of a pair of crimpers. In many cases DB connectors are very good and can be cheap if you don't mind soldering, the per pin current ratings though are low so only good for smallish motors/steppers.

There are actually all sorts of low cost pin and socket connectors are used in the electronics industry, the problem is most of them are not designed to keep things clean and often having no strain reliefs. Most of the DIN connectors are actually pretty good for small (low) current stepper drives, so don't dismiss them but they might not be cost effective if you need to by many parts for say a four axis machine.

[fretman_2]

Cool. I bought some of the 4 pin aircraft connectors off of eBay. But... it would simplify things greatly to make all the connections without connectors. After all, my control box is going to be mounted permanently and I won't need to disconnect anything. Something to think about!

Try catalog houses like DIgiKey, Newark, Mouser and the like. DIN connectors can be had in all sorts of configurations and frankly it is best to keep on configuration only for the steppers. Beyond that there are all sorts of other connectors that can be leveraged for use in a CNC machine from the cheap to the fairly expensive. It really depends upon your controls setup. Generally with servos and steppers you are better off to avoid connectors as much as possible. In fact some manufactures suggest no connectors at all preferring to run cables directly to the amps. That in part is due to electrical noise but other issues crop up.

For examples of other issues here are a couple that I've experienced over the years at work. A synchronous 3 phase 1/2HP motor wasn't maintaining speed even though the 3 phase driver appeared to be working well. In this case the engineer decided to run the motor power through a standard 3 phase twist lock connector. Apparently the connector wasn't in as good a shape as you would expect from newish hardware because the machine was loosing a phase intermittently. This caused instability in the RPM of the motor. Replacing the plug and socket got things on track. Another issue was with a Name brand stepper drive that had performance problems. That issue was traced down to a pin and socket plug that plugged into the face of the drive. Mind you this is a fairly common arrangement in industrial drives. The point is bad connections due to plugs and sockets are a reality that don't debug easily. None of the above where fixed instantly.

So what would I suggest if you have to use plugs and sockets. AT the cheap end probably AMP plastic circular connectors if the idea is to transition through a panel box of some sort. They are relatively cheap but do require the purchase of a pair of crimpers. In many cases DB connectors are very good and can be cheap if you don't mind soldering, the per pin current ratings though are low so only good for smallish motors/steppers.

There are actually all sorts of low cost pin and socket connectors are used in the electronics industry, the problem is most of them are not designed to keep things clean and often having no strain reliefs. Most of the DIN connectors are actually pretty good for small (low) current stepper drives, so don't dismiss them but they might not be cost effective if you need to by many parts for say a four axis machine.

[grumpygeek]

I used the 4 pin aviation connectors from ebay on my last build and I think they are great, they screw together so they won't accidentally get disconnected and short of getting them wet I think they should be no issue with contamination. Being able to easily swap to different controllers to see if it is a wiring/motor issue or a controller issue is nice. There have been times when I have moved my machines around and having everything hard wired was a bit of a pain, if you control box is part of you machine and you just need to disconnect a usb or serial cable I guess this is less an issue. I have 3 different controllers, I am planning on wiring the other 2 in the same configuration so I can swap them out if needed.