[Regnar]

Hey guys I have been searching and I cannot find a good example of a direct belt drive system. I search youtube and it looked like some had it directly connected to the stepper through a gear while others had a pretty elaborate system. Im looking for info on how to calculate power and speed as well a good example of what its suppose to look like.

[grahamshere]

Do you mean like the solsylva plans?

[Regnar]

No more like the Romaxx system. I think I am just going to try it like the romaxx system and then gear it down if it doesnt work out. The machine is only going to be 12x24 so I can imagine it will be that bad.

[CarveOne]

Regnar,

Solsyla plans book shows a belt drive machine that uses direct belt drive for x, y, and z. If you google "Belt drive calculator" you will find online calculators and formulas for what you need.

Look at this video of one of these machines and you will see it zoom in on the y axis drive. It gets in real close the second time it zooms in and you can pause the video to take a look at the details. You can get a rough idea of the pulley ratio by measuring the widest part of each pulley and dividing the two numbers while the video is paused.

[ame="http://www.youtube.com/watch?v=K3vHUw76SGk"]YouTube - Homebuilt CNC[/ame]

CarveOne

[Regnar]

Sorry guys I didnt know David put out a new set of plans I have the older ones with the largest router being the 25x37. I guess I have to go and check out his site again Thanks.

I also have been reading through the linear motion forum and learing a few interesting things.

This is what I am trying to put it on. I finished up the Router mount last night and it was time consuming. 3 Hours just to pocket the hole. Today I am pulling it pretty much apart to start painting.

[grahamshere]

Hey Regnar that's a nice machine, whats the cutting size on that? Like you bearing trucks too, was thinking about getting some my self when I,m ready for build #2. Check out the solsylva plans like Carve one mentions, sure that would work. Graham

[Regnar]

I wanted 12" x 24" but ended up with 14.75" x 25.5" . What has surprised me the most is how rigid everything is and how quickly it gets heavy. I would have to put it weighing in around 175 to maybe 200 as it sits. The 3060 and the 7" steel plate are a good chunk of the weight.

I cant take full credit for the Bearing trucks because they are of Arhens design but they are custom made for the machine. At first I wanted to use a leadscrew and at the time there was no solution on how to get the nut to fit inbetween the Y axis and Z axis so I put my benchtop mill to work. What a pain in the A$$. Dont be fooled what Arhen has listed the bearing at is well worth the price of the amount of heartache that goes into them. Well anyways I made them bigger for the y and x. X is 4.5 x 4.5 so that it will reach behind the 3060 and the Y is 2.5 x 9 so that the 1530 will fit nicely above the 1545.

I have started to read the guide on Spd-si site about the pulleys and how to figure in force and rotation.

[Regnar]

Well here goes nothing. I have most of the parts from my first router build like the belt and pulleys so no lost there and plenty of scrap so this is the first part. I plan on driving the pulley with the extra thread that is sticking out the backside. I need to get a little shorter bolt so that I dont have to use the stack up of washers. It spins freely and is right now and is holding the whole thing together. I plan on adding more bolts to secure it all together. I still have to do some flycutting along with a trip threw the tumbler.Well here is some photos.

[CarveOne]

Hi Regnar,

It's looking good already. Plan your design so that it isn't difficult to replace or adjust the belts. These things are a tinkerer's delight. I'm watching.

CarveOne

[Regnar]

Seeing I have at least one person watching I figured I post my progress. I made the other side today. I ran into sort of a hiccup but on the back side the wall is extremely thin so when clamping together it start so bow and bend. This doesnt effect the function just looks ugly.

All I have left is to figure out how to attach the belt to the axis and how to tension it as well. I have a pretty good ideal of how to go about doing this. I will probably model it up in sketchup and mull over it for awhile. Not that I am going to be able to get anything done here in the next couple of days. The Inlaws should be here later tonight for the weekend.

On a positive note I threw a 1/4 drive pulley that I had left over from another build on the backside of one of the mills stepper motors just to see what it takes to stall it out and was pretty impressed on what it took. I know jogging will not be a problem at all but maybe some deep cuts. Either way gearing it wont be a problem either.

And now for the pictures.

[grahamshere]

I,m watching too bud so you have 2 ppl watching. I just don't have much to say, I,m way out of my league with you guys so what ever I say would probably be wrong or already thought of. But I have been looking into the belt drive thing, there's a guy on here, cant remember who, but he was getting 750 ipm with his no problem, that's fast for a diy . but then there was a another that said he would never do the belt thing again, think he had a stretching problem?
Any way your doing a great job. Graham

[Regnar]

Alright this is what has been in my head for the tensioning and mounting to the x axis. The Green piece will be mounted the the back of the axis while the orange will be floating. There is 2 screws on the side that I will tighten and once I reach the right amount of tension I will tighten the screw on the orange piece to lock it down to the axis to. The belt is actually skinner than the setup but I didnt feel like resizing it but I should be able to fit 3mm screws on either side to lock it down.

So lets get some opinions on this. I think it should work fine. Anyone have a better ideal?

[grahamshere]

Would it not be better to wrap it around an idler that could be adjusted for tension. But like I said I'm still a newbie and could be wrong.

[Regnar]

This was my thought process. I wanted to keep the pulleys down to a minimum so If I can keep it to 2 then I am doing good. Second I wanted to keep the belt length down so that stretching and the amount of error is down even further. Going around a idler could easily add another 6-8 inches of belt. And even though they are on bearings it will add some more resistance to the set up.

[grahamshere]

Oh ok now I see what your doing, sort of lol. So the belt dose not really travel. kind of like a rack and pinon. Any way that's what I,m seeing,if that's the case then that will work and if there's any stretch you just tighten the screws right?sorry if I have you all confused if you dont understand what I,m thinking, like I said a newbie. Graham

[Regnar]

Sorry graham but I dont think you see lol. The part that I made in sketchup will be attached to the x axis slide. This will move my router back and forth. The 2 parts that I have made will be at each end of the axis. The stepper motor will turn the pulley that is on the bigger of the 2 pieces that I made while the other end is free wheeling.

[grahamshere]

Ok I think I see it now, sorry, hope I,m not wasting your time here answering My ?. So you cut the belt a little short so to tighten with the new thing you designed, What are going to call it. I dont know why but I was thinking the belt does a full rotation, guess thats were I got lost. Cant see why that wont work. Should . Should see if any one eles has done that, You may have come up with something new. Graham

[Regnar]

Well just to let everyone know that the project isnt dead. I have been busy working on the house and havent had to much time in the garage. Its kinda amazing how long this little project took and I am only 3/4 of the way done. I need to trim up the traction piece and fly cut all sides and slice it down the middle. But some pictures to hold you guys over.

[Jeremy Harris]

Very nice looking build. I've stumbled on this thread whilst looking for tips on direct belt drive - it seems a rare way to do things as far as I can tell.

I'm planning on using the smallest pitch belt I can easily get hold of in long lengths, HTD 3M, with a 10 tooth pulley directly mounted to the stepper shaft. This gives 30mm of travel for 360 degrees of stepper rotation, or a resolution of just over 0.7 thou at 1/8 step. Speed should be pretty good at this sort of gearing, but it will need a fair bit of drive current to the steppers to get enough torque, I think.

Unlike your set-up, I'm thinking of mounting the steppers to the carriages, with the belt held wrapped around the pulley by a couple of idler rollers. The belt will just be a single length, with the ends fixed to the ends of the rails. That way I can tension it with a tensioning screw at one end. The steppers I have are double ended, so the X axis drive will have two belts, with the second being driven via an extension shaft from the back of the motor to the second pulley.

I have toyed with the idea of a single arm gantry, like that used by some flat bed plotters, or like an old fashioned drawing board. It's a bit radical, perhaps, but would lend itself to a sloping bed design that might take up less space.

I'll be really interested to see how you get on with your build.

Jeremy

[Regnar]

Jeremy, Things have been going really slowly around here. Between the Holiday, Family in town and the worst case of food poisoning I have ever had I haven't had a whole lot of time to spend in the garage.

I was able to get a few hours last week to mach everything up.

The reason I didn't go the traditional method with the idler pulley was because it would introduce more resistance to the system. Also my belt from a former build was longer than what I needed so I came up with this ideal. Work is going to start lightening up with the holidays so Im hoping that around Christmas I have all the axis moving. I just hope I didn't jinx myself.