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>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>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>I am working on a similar project. But it's a laser cutter.</p><p>Neat project! </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>
<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>:)
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
The motors will depend on the weight of the gantry. Cutting polystyrene won't give much resistance at all so as long as the motors can move the machine it will be able to cut. The folks over at gecko drives have a good write up on how to estimate the size motors required (http://www.geckodrive.com/support/choosing-a-drive.html).
I was going to build this over the summer with my father, he used to sell CNC machines and he has always wanted to own one. We were wondering if this CNC Control Board would work with your instructable. <br>( http://www.ebay.co.uk/itm/CNC-Kit-3-Axis-Stepper-Motor-Driver-Nema17-12V10A-220V-/270900965305?pt=UK_BOI_Industrial_Automation_Control_ET&amp;hash=item3f12f4afb9 )
The only issue I see with the board is the 62 oz-in steppers. The motors I used are 130 oz-in and I have never noticed them stalling or loosing steps but compared to other builds I have seen, they are on the small side. The axes have a little resistance to overcome but not enough that I wouldn't expect those motors to be able to move the machine so the question is how much torque is left over to do the cutting. If you want to cut platic and wood I don't think it would work but if you're interested in cutting foam and milling PCB's I reckon you could get away with it. <br> <br>On another note, it is the first time I've seen a diver board being run off of a switch mode power supply without a few hefty caps to smooth things out. I'm not terribly knowledgeable on the electronics side of things but I would imagine that performance would be reduced compared to that if it was run on a beefier linear supply.

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Bio: Engineering is more than a job, its a lifestyle.
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