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Step 13: Timing Belts

Hardware required:
3x MXL timing belt
6x 3/16" x 2" eye bolts
12x 3/16" nuts
24x #8 washers
6x 6-32 x 5/8" machine screw
6x 6-32 nuts

The timing belts are what converts the rotary motion of the stepper motors into precise linear motion along the axis. The belts are clamped onto eye bolts and the tension is adjusted by tightening the nuts on the eye bolts.

13.1 The first step to assembling the timing belts is to locate the two holes per end needed to clamp the belts in a loop. Test fit the components and mark where holes should be located if looped around the eye as in Photo  #1. I purchased closed loop belts and simply cut them open using an utility knife.

13.2 Drill/punch the holes into the timing belts at the points marked. Use a 1/8" drill or an awl to form the holes. The material will be flexible and the resulting hole will be smaller than the bit diameter. The holes should be similar to those in Photo #3.

13.3 Assemble the timing belt anchors by looping the ends of the timing belt around the eye bolts and closing the loop using 6-32 machine screws (Photos #2,3). The holes will be smaller than the screws but twisting them while pushing will get them though the hole. The grooves should be on the inside of the loop and clamped shut making sure the grooves are meshed. The completed assembly should look similar to Photo #5.

13.4 For the Y-axis, loop the belts around the pulley and idler bearings and then bolt the eye bolts to the steel belt clamps (Photos #7-9). The Y-axis was designed to be the correct length for the belts used so there is no excess. The slots in the belt clamps are oversized to allow for adjustments in the belt positioning; adjust them so that the belt lines up with the idler bearings and the eye is far enough away from the base that it clears the gantry side when it is at the extent of its travel.

13.5 For the X-axis there is excess length in the belt. Instead of cutting the belt to length I tied the excess out of the way as shown in Photo #10 in case I wanted to make the axis wider in the future. It is a tight squeeze to get the belt around the idler bearings and motor mounting bolts and onto the pulley. Don't try and snake the eye bolt through because it wont fit. Make a loop in the middle of the belt and feed it up past the idler bearings and over the pulley. Position the eye bolts so that the belt is in line with the idler bearings which should also be close to in-line with the X rail. Photos #10,11.

13.6 Finally tension the belts by tightening the outside nuts on the eye bolts. Try to apply equal tension on the belts. Once you are satisfied with set-up, tighten the inner nuts to prevent the eye bolt from rotating.
<p>I am working on a similar project. But it's a laser cutter.</p><p>Neat project! </p>
<p>Hi Tim:</p><p>I am interested in making a cnc laser to cut clothes stacked, I would like to know how it was with the manufacture of this cnc instructive or if you have additional information.</p>
<p>I was planing on building something similar to this but I was using draw-slides. The project was stopped do to high cost if controllers and lasers. </p><p>Tim</p>
<p>Hi Nick, good job.</p><p>I haven't read through all the comments, yet, but since it's been over 4 years since you built this, (assuming the Apr '12 post date isn't long after completion), I wondered if you have done an assessment of the build, evaluated the actual performance vs anticipated/hoped for and how you would change v 3.0? If you have done an assessment, have you written/posted it anywhere?</p><p>Also, depending on where you live, you might be able to scavenge some components for building structure &amp; support for the axis rails, and other parts and pieces which could stiffen up the overall structure, given hard material capabilities.</p><p> I'm not up on CNC terminology, I intend on building a CNC router, which will be my first foray into CNC. It's a way down on my 'to do' list, so all I'm doing at this point is trying to get familiar enough to know what to grab when I'm scavenging. It will not be my first foray into building tools, though. I have built a number of fabricating machines. Most of what I've built have been re-purposed, frankenstein stuff, like the dual belt, 1 x 42&quot; sander I made from an old radial arm saw. I shortened the radial arm, connected to the deck mounts, used a single cogged belt sprocket to drive a custom dual drive for the belts. I used serpentine belt pulleys from a Dodge/Chrysler V6 for the belt rollers, (get the right ones from the wreckin' yard and they have replaceable roller bearings and a choice of lips/no lips on the edges of the face, (a mix works best). The platens, (the surface supporting the belt where the grinding takes place), are a design I 'pinched' from some commercially available narrow belt sanders. The base equipment has a square tube 'socket' like the better trailer hitches have, allowing different platens to be built for different sanding profiles: flat, convex, concave, etc.</p><p>I've been fabricating with wood, metals, stones &amp; plastics for nearly 50 years. For all you young guys, don't bother with grinders, get/build tools using abrasives. Belt sanders, drum sanders, spindle sanders give you better performance, less expense for a variety of grit, and much more accuracy.</p><p>Old table saw motors can be found with dual arbors, 1HP for $40-50. A pair of arbor extension/adaptors to std R &amp; L thread for ~13.00, and some thoughtful protection of the motor internals from grinding dust, and you have the equivalent of 600.00-800.00 industrial grinder buffer. If you have never used a 1hp grinder buffer, better hit the gym and work on your forearms!</p><p>The drum sander mentioned above is a jeweler's tool. Uses a 2.5&quot; by 6&quot; diameter abrasive belt you can buy for ~3.00. They are metal eaters! There's another design, (hard to find), which splits, and uses flat strips of abrasive cloth, (defective belts from a belt sander work great in these, and the gap where it splits is NOT noticeable in use).</p><p>I will never buy/use a bench grinder stone or a puny .25 or .33hp bench grinder, ever again. I put a small, (4-5&quot;) diamond grit saw blade on a Ryobi bench grinder I got at a garage sale a number of years ago, and turned it into a great fab tool.</p><p>The last question I have for you about your router, ( I eventually get back on topic), is have you tried any foam core PVC as a material? I've used it for proof of concept and prototype mock ups for a long time. It's a 'fast' material to work with, will hold threads, and has enough strength to make early stage working prototypes. Recently, though, I've been spending half my time in NY. My apt on LI is right down the street from a sign shop, and I suddenly have a near in-exhaustable supply of foam core PVC. The result has been I've discovered it is tough enough to use for structural material. The dump apt is scary, so rotted and dry-rotted, the 0.125&quot; thick paint on the walls holds up the old 3 story house converted to apts. I built a kitchen base cabinet completely out of foam core, scavenged doors &amp; drawers from street side trash. I mounted the drawer slides and hung the cab doors from the plastic. It won't last as long as particle board or wood, but it's waterproof, didn't need any finish, and is easy to cut &amp; drill. Plus, once you have it fit &amp; squared, you can glue-weld the stuff together with plumbing glue, and it essentially becomes the same as if you machined it from a 2 x 3' x 5' block of foam core PVC, with the added strength of the hard shell on two sides of all the individual pieces.</p><p>I worked at a mobile home factory when I was 18-19, my PVC cabinet is tougher than a lot of stuff put into mobile homes, OR sold by Ikea! Find a sign shop, and see what you can scavenge, they'll be glad to give you what will go in the dumpster, otherwise. A lot of what is made from plywood, could be made with foam core, and gain increased rigidity.</p><p>Again, good job. Would love to see a look back on v.2.0 from a Monday morning QB perspective.</p><p>Thanks,</p><p>GeoD<br></p>
<p>Hi, I've added your project to <em style="">&quot;</em><em style="">The Ultimate Collection of DIY Workshop Tools</em><em style="">&quot; </em>Collection</p><p>Here is the link If you are interested:</p><p><a href="http://www.instructables.com/id/The-Ultimate-Collection-of-DIY-Workshop-Tools/">http://www.instructables.com/id/The-Ultimate-Colle...</a></p>
<p>Wow that spindle is just perfect, I will definetly use that in my cnc :) Do you happen to have any video of the machine running, I am curious about sound levels :) thank you for the excellent instructable :)</p>
<p>fdgfdgerzf</p>
<p>Likewise the Shapeoko3 has beefy aluminum rails and steel plates for the router. I love DIY as much as the next guy, but if the money is the same, I'd rather end up with a more solid result.</p>
<p>I'm looking at the X-Carve from Inventables. It comes with a Dewalt 611 trim router for $1600 delivered to my door in Canada. Nice build but I think I'll but the kit for the X-Carve.</p>
<p>Hola, tienes un dise&ntilde;o del equipo mejorado actualmente?, costo?</p><p>Tiempo de entrega?, costo de env&iacute;o?, requerimientos d hardware y</p><p>software,? etc.Estoy en M&eacute;xico, D.F</p><p>Tel.52- 5555-27-21-21</p><p>movil. 044555-4196924 Gracias.</p><p><br></p>
<p>I see this was made 3 years ago any improvements since then ? and could you use nema 23 with this build </p><p>thankyou</p><p>Richard Westerfield </p>
<p>Anyone know how to size/pick the timing belts and pulleys?</p>
<p>Approximate cost?</p>
<p>What driver board did you use? </p><p>Thanks</p>
<p>Great Job Nick.</p>
<p>I built one, cost $750 and has a cutting area of 3'x3'x4&quot; you can see my videos in Youtube under my name bubalettow</p>
<p>Why you worked in the unit inch?</p>
<p>i wonder where you put the usb or any communication cable to communicate between the CNC machine to the PC *i assume this CNC controller is PC-based. and if there is, where di you pluh that cable on the machine? directly to the stepper motor or add an additional built-in controller. Thanks</p>
<p>Excelent work</p>
Wow!
<p>Hi Nick, this is such a good instructable. I have a little question if you don't mind. I noticed that in the plan of left-right gantry sides one of the holes (where you attached limit switch) is missing. Do you get that hole later after installing everything or you just forget to draw it? Or maybe its position is given different on the plan?</p>
<p>Is this 130 oz-in unipolar rating of the stepper motor? And will the dimensions change if we use any other motors....</p>
<p>Hi everyone, I'm getting a lot of messages asking if I have a 3d model for this project. Unfortunetly I don't. I only have the 2d dimensioned drawings attached in the steps.</p>
<p>amazing work </p>
thanks thanks thanks .... so much... <br>ill try its
great article!!! very informative!!!
Just to let everyone know, i am working on a sketch up of this project (minus the custom sled hardware) to be made with standard length aluminum extrusion, and all 3/4mdf (for ease of construction and rigidity). if you would like a copy let me know <br>
A great project! I would like to have access to your latest mods and CAD drawings. <br> <br>Thank you, <br>
I'm interested in this sketch up. I'm about to rebuild my CNC.
Here is a list of my modifications so far. I have not finished the mock-up so this is not the final list <br> <br>Moved mount for y axis motor up 4 inches <br>changed gantry assembly for moved motor mount <br>replaced bearing block with alernitive gantry sides <br>shortened overall gantry height for added clearence <br>modifed track for easier assembely <br>modified ider bearings for timing belt security <br>modified base for new tracks and timing belt tensioner <br>changed belt tensioner to 3/4 mdf
I'm looking forward to seeing your modifications. My one suggestions would be to avoid using MDF if you can. I used it on my first machine for cost reasons and found it to be less than ideal as is its much heavier and not nearly as stiff as ply.
The reason that I wanted to do this in all mdf is because it is half the price of 3/4&quot; ply. This is also just to be able to have a machine that i can use to cut more sturdy, expensive woods, such as the 3/4&quot; ply or other soft lumber (because a 1by is actually 3/4&quot;). <br> <br>These modifications are only for a first machine to make the better machine, not for a really long term use (put it together, make new parts, replace, repeat) <br> <br>:)
thanks
i would like to know what type of sepper motor make and model you used and is your roter large enough to use on 1/4 steel if not what would you recumend ? <br>thank you <br>richard westerfield
Richard, this machine is not even close to being stiff enough to machine steel. If you want to machine steel you will need to use a proper milling machine such as a Sieg mill. There are a number of tutorials online on how to modify one for CNC use and this website (http://www.littlemachineshop.com/Info/minimill_compare.php) has a great breakdown of the different models sold by distributors.
+1 for Shigley's!! That's my bible.
you are too good man. can i use stepper motor with 80 oz in( 0.6 Nm) .will it work or not. <br>thks
You jump so quickly from hardware to software. Could you give more information how you work to load your designs to the machine. Also which motor drivers do u use? <br>Thank you so much
The Instructable was meant to focus on the hardware as software could vary depending on personal preference. In general I used Rhino 3D for the CAD work, exported as an STL which was loaded into CAMBAM. From there I generated G-code which was read by Mach3 and sent to the Hobby CNC driver board. Let me know if you need any more information.
Thank you for this instructable! I'm planing on building a similar one with some modifications on the Z axle to have a little bit more depth and I will be using a dremel 4000 as the cutting unit. you mentioned metric units...do you, by any chance, have the metric drawings for this? I am converting everything, but I then have to match it with commercial sizes and if had already done that... ;) <br> <br>another question...have you tried to cut either copper or aluminium with this machine? do you recoon it is stable enough for that? <br> <br>once again, thank you for sharing this ;)
It shouldn't have any troubles cutting aluminium using a dremel as long as you get a high quality double fluted, spiral, carbide end mill. I have quickly found that the cheap HSS cutter I have are limiting the machine's performance. As for metric drawings all I have are the imperial ones. As long as everything is sized as the closest metric alternative it should all work out with only a few holes needing to be re-bored larger.
that's what I've been doing ;) maybe i'll just cut all the parts in imperial sizes and make all the holes in metric size because it's easier to match with screws and nuts ;)
I want to built a 50&quot;x50&quot;x@5&quot; high routing capacity,what is yiou recommendation regarding the electronic and motor,i built several composit airplanes 4 passenger and i am designing a twin with Mazda rotary rx-8 engine. <br>First i get quote from several place with a big CNC router and they came up about$11000 to do the fuslage half mould from polystyrene. <br>This is why i started to look building my own from aluminum rectangular structure. <br>i do design with Rheno and any recommendation can be appreciated,my experience in router is very limited but i am learning very fast and i dont see any <br>problem of building the structure

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