Discussion of industry tolerances for aluminum extrusion: http://www.engineersedge.com/extrusion.htm
MakerSlide is a really cool system consisting of:
- 20x40mm aluminum (6105-T5) extrusion profile with a built in V-rail
- Delrin "V" wheels that ride on the V-rail
- Plates and hardware to put it together
Type 2 anodized
Load bearing characteristics
Patrick34 on buildlog.net posted a: theoretical analysis using Solidworks COSMOSWorks on the MakerSlide up to 2000mm in length @ 5#, 2#, and 1# loads in the center of a beam with unfixed ends (worst case). Here are the results:
|Deflection (mm) @ 5lb||0.007||0.024||0.057||0.11||0.191||0.303||0.452||0.644||0.883|
|Deflection (mm) @ 2lb||0.003||0.01||0.023||0.044||0.076||0.121||0.181||0.258||0.353|
|Deflection (mm) @ 1lb||0.001||0.005||0.011||0.022||0.038||0.061||0.09||0.129||0.177|
Forum user samc99us continued the above research, examining the assumptions underlying it, looking at one option for improving rigidity (sistering in a piece of 1/8" weldable steel) and comparing it to a larger piece of extrusion: Re: Working on a custom Shapeoko 2.
Note that one can use side supports to shorten the span at appropriate intervals.
Load bearing per wheel
The maximum load per V-wheel is 6 lbs (2.7 kg) in any direction. Bear in mind that leverage can amplify off-axis forces: a 2 kg spindle 60 mm away from a single X rail would impart a lateral force of 1.5 kgf on each of the four X V-wheels; in addition, the top wheels will have to bear the weight of the spindle, Z axis, X carriage and two motors (say 3.4 kg total, or 1.7 kgf each); the resultant force is very close to 2.7 kgf, even taking into account the fact that the X motor balances a little of the weight of the spindle. Then you have cutting forces on top of that, which have an even larger mechanical advantage over the X V-wheels than the spindle itself.
Roark's Formulas for Stress and Strain
Where To Purchase
MakerSlide is available for purchase from Inventables (North America), Amber Spyglass (Europe), Makerslide Europe or from MakerSlideAsia (Oceania). Accessories for the MakerSlide system are available for purchase either from Inventables or from the MakerSlide store, or the regional vendors listed previously. If you are finding it hard to get MakerSlide shipped to your country you could consider OpenRail which is fully compatible, having completed its Kickstarter campaign. Another option is Vgrooverail.
MakerSlide Tips and Tricks
Here are a few tips and tricks that might help using MakerSlide on your ShapeOko:
Notice that the plates have two different sized holes. On the left is a 5mm hole that perfectly fits a 5mm bolt. The hole on the right is 7.12mm. An eccentric spacer goes in this hole, and a 5mm bolt goes through the eccentric part.
Eccentric spacers have an off-center hole in them. Turning the spacer will allow you to adjust the distance between the wheels up to 1.2mm.
TIP: Use a Sharpie marker to color the side of the spacer on the face closest to hole. This will allow you to see the orientation of the spacer after inserting a bolt and attaching the wheel.
Eccentric spacers are also available in a form which includes threads which allow them to be used w/o a separate nut. Unlike the original spacers which were held in place by a separate hex nut set off by a washer, they serve a dual-purpose of also holding things together. When adjusting, one must be careful not to loosen things --- when adjusting clockwise this is not an issue, but if one must make an adjustment counter-clockwise it may be appropriate to use a hex key to to ensure that the M5 bolt rotates to match.
When you insert the eccentric spacer in the hole, orient it so the marked side of the spacer is pointing away from the other hole.
With the eccentric spacer oriented with the marked side away, the wheels will be as far apart as possible. This will make it easy to slide the v-wheels over the v-rail extrusion.
With the mount plate on the v-rail extrusion, use an 8 mm open end wrench to turn the eccentric spacer to snug the wheels to the v-rail. Tighten the wheels until they are just snug. Do not over-tighten the v-wheels.
Bart, the creator of Makerslide, gave the following advice on tightening the v-wheels: loosen the eccentric spacer until the v-wheel does not rotate when the carriage is moving and then tighten just (and no more!) until the v-wheel rotates when moving the carriage. Overtightening will lead to the v-wheel wearing out.
They should only be snug enough against the rail to take out any play.
Note that when securing the V-wheels, one must be careful to not overtorque or twist, or even bend the bolt.
Note that connecting the stepper motors will result in resistance as the stepper motors interact with the electronics.
Eccentric Nut / Spacer Placement
The circular portion of the eccentric nuts goes all the way into the matching hole: 699px
The Inventables kits comes with the Makerslide untapped. The premium and full kits include an M5 tap and appropriate T-handle. If you purchased the mechanical only kit, you will have to buy an M5x0.8 tap and #0-1/4" T-handle to complete this operation. For those who are unfamiliar with tapping and who have access to a 3D printer, this M5 Tapping Guide for MakerSlide may be useful. Forum user skipmcdonald reported good results in this thread: Avoid tap misalignment for good threads.
Tapping means to cut threads on the inside of a hole. There is an entire industry based around this process, and some people take it very seriously. If you look around the internet you can find 1,000s of site with "drill and tap" charts. These charts tell a person how big of a hole is required to be tapped to a certain thread size. There is a great write-up over at Wikipedia describing Tap and Die.
For instance, if you want to have a finished, threaded hole that will accept a standard M5 bolt (.8 pitch), you'll actually need to start with a hole that is only 4mm. This is because as you're cutting the threads into the hole, you'll obviously need material to remove. Always try to start as straight as you can in respect to the hole, or part, respectively.
Some people use a T-handle (which is my preference) something like this from Amazon.com works well. You would also need a tap like this. Other people just put the tap into a hand drill and set the torque to a low setting (something like 10 on a scale 1-21, where 21 is "drill"). Because Makerslide is made from aluminum, which is a "soft" metal, it's fairly easy to tap. But, you'll need a cutting fluid to make it easier - any kind of lubricant, e.g. WD-40, should work well. And others just grab onto the end of the tap with a pair of vise grips or other pliers. This is obviously not the recommended way, but can get you by in a pinch.
When tapping, it's important to not just torque down and twist as hard as you can.
Remember, as you're cutting the threads into the hole, the tap is removing material. That material has to go someplace. Ideally, the tap will be trying push the material out of the way either by bringing it back up the hole, or pushing it out the bottom. (If you're doing a through hole you can watch the material start coming out the back of the hole.) But if you encounter resistance, it's probably due to chip buildup along the tap. Slowly reverse the tap until it's out of the hole, clear the chips from the tap, and start again. Depending on how deep the hole is you're tapping, it may take several times of cutting/removing to accomplish your depth.
Rule of thumb:
- The deeper the flutes in the tap, the more material it will be able to hold before clogging.
- Cutting fluid (or lubricant) enables debris material to flow more easily up the length of the flutes. Suggestion of Tap Magic
- If there is enough lubricant, it may be enough to back a turn or two to get the chips flowing through the flutes, without the need to remove the tap all the way. A typical suggestion is for every full rotation or so of cutting action, reverse the tap by ¼ turn or so to break off chips.
An alternative is self-tapping bolts: Not tapping Makerslide.
Or use “a sharp spiral tap in an electric drill/driver with torque control and a reverse gear.”
Commentary by a person experienced w/ tapping steel:
Aluminum is a tricky little metal. It woos you in with its softness then bites you when you least expect it.
LUBRICATION IS NOT OPTIONAL. WD-40 works great. And if you're like me, you've got at least six cans of it in varying amounts lying around your garage. Just one spray down the hole before you start should be fine. I sprayed the tap between each attempt as well, to wash out the scraps.
If you don't lubricate (and you're reading this after you've destroyed a bolt hole or two in your MakerSlide), the dry Aluminum will gall your tap. What this means is, the friction of the tap against the chips causes it to weld Aluminum into the threads of the tap, rendering it useless. You'll likely destroy whatever hole you're tapping when this iccurs, as the galled threads will undo all of your work on the way back out. You'll need to tap a bigger hole to reclaim the MakerSlide or buy a new one.
To reclaim your tap, you'll need to get the Aluminum out of the threads. This isn't possible mechanically (as far as I'm capable, anyway). You'll need to chemically remove the Aluminum from the tap. Best way to accomplish this is to buy some generic drain unclogger from your local grocery store. Make sure it has sodium hydroxide as one of the active ingredients. This is the chemical that's going to do our work for us. Using a glass jar with a lid, pour enough to cover the tap, drop the tap in and let it soak overnight. It makes for a really neat show, as you can watch the Aluminum dissolving right before your eyes. Be careful when you open the jar, as it creates a potentially dangerous chemical if you breathe a lot of it. Open it outdoors to be safe.
Please note that it's important to get the chemistry correct. There are multiple products w/ various formulations, and another possibility is a chemical which is able to dissolve steel while leaving aluminum intact (this is one way to deal w/ a broken tap as noted below). Please test on a small sample if there is any uncertainty.
Breaking a Tap
A broken tap is unlikely if one:
- is careful,
- is patient,
- uses lubricant,
- and above all, doesn't force it.
But broken taps do happen. Sometimes removing the broken tap can be tricky, especially if it broke off at, or below, the surface. In these cases one option is to dissolve the tap. Since the tap is ferrous, and the MakerSlide is aluminum, one can do this with kitchen chemistry. If all other methods have failed, follow these steps and use caution: Dissolve a Tap Broken in MakerSlide. Another option is to hook three suitably sized pieces of music wire down the flutes and around the tap, then use a pair of locking pliers to twist them together counter-clockwise until they tighten enough to hold the tap and allow one to remove it.
Specialized tool for removing broken off taps, Walton Tap Extractor: http://waltontools.com/
Alternately, cut out the broken tap, tap the hole past the removed material and get a longer bolt.
- Thread-forming Tap --- Requires that one drill out the holes from 4.2 mm to 4.5 mm. One puff of cutting oil, then zoom all the way in in one go with the cordless drill, back out, done! No chips to worry about, and can easily thread 20-25 mm deep in seconds. Clearly easier than the thread-cutting tap, even though there are two steps. The downside is that the tap costs a little more.
If possible, source a gun or spiral end tap as noted here: http://www.shapeoko.com/forum/viewtopic.php?f=5&t=5743&p=43269#p43269
Dealing with stripped threads
One option for dealing with stripped out threads is to simply tap the threads deeper and use a longer bolt. A more elegant solution is a Perma-Coil Repair Kit, mentioned in the forum thread Thread repairs in aluminum.
It is very important to examine all pieces of aluminum extrusion when opening the kit to check for straightness, squarely cut ends, and intact V-rails.
In the event of any differences, the parts should be arranged so that the straightest/squarest form the X-axis gantry (rotate them until they make the squarest arrangement possible), since it is easier to adjust the Y-axis rails for squareness.
If the V-rails are dinged any raised portion should be carefully filed down w/o creating a low spot and the damaged portion filled in w/ a metal-impregnated epoxy such as J.B. Weld. Another option is Alvin Lab Metal Repair Putty, Dent Filler & Patching Compound Epoxy.
Naturally if any insurmountable non-conformities are encountered one should contact your vendor's customer service for a replacement.
Materials properties: See also: http://www2.dupont.com/Plastics/en_US/assets/downloads/design/DELDGe.pdf
- Elongation at Break - 55%
- Yield Stress - 62Mpa
- Tensile strength - 65Mpa
- Compressive Strength - 63Mpa
- Flexural Strength - 75Mpa
- Shear Strength - 60Mpa
- Rockwell Hardness - M80
- Elastic modulus MPa - 
- compressive: 3105
- tensile: 2601 -- 3202
the elastic modulus, is the most relevant characteristic.
- Openrail --- http://openbuildspartstore.com/openrail-black-anodized/ --- available in 1M and 1.5M lengths
- http://www.zoro.com/pbc-linear-linear-rail-4850-in-l-0187-w-0437-h-vrd1-048500/i/G0753672/ 
- http://woodgears.ca/pantorouter/glides.html