Matthias Wandel Big Print Program 28
Hanry Moreno
The printing issue is also happening with me and the printing the large boards to multiple pages can be tough to get it printed. I have gone through Epson printer error code e-01 and I want it to be fixed.
matthias wandel big print program 28
Years before that when I still used M$ I sometimes used the print function of the original paint. I never got the hang of that program, but it had a pretty extensive print function and you could specify over how many pieces of paper a picture must be stretched.
Designing this toy definitely took a few tries to get the desired effect. While doing so I researched and collected notes on perfecting printed gears and I thought it was interesting enough to share. This Instructable is intended as a general guide for designing & printing FDM 3D printed plastic gears.
Print all parts minimum 3 perimeters all sides top & bottom, with 15% infill. I recommend 0.3mm layer thickness maximum. Any material will work as long as you can prevent warping, which would devastate this device.
1. Clean up the gear teeth with a razor blade so they will mesh smoothly then place them on the plate in the same rotational orientation they were when you printed them. (The pin on the sun gear is to the right and the handle of the ring gear is top and center.)
3. Apply a smidge of clear drying glue (glue stick works well) to the business end of the wrench then install it from the side so it snaps on the nut. The glue is to keep the wrench attached to the nut. The wrench also holds the sun gear down onto the assembly.
Printed plastic gears are a cheap, quick, and customizable motion transfer solution compared to alternative ways to make gears. Complexity & 3D variations are essentially free. The prototyping & creation process is quick & clean. Best of all, 3D Printers are common enough that a set of STL files can be shared with tons of people eager to use them online.
Of course printing gears using the commonly available plastics is a sacrifice in surface finish and durability compared to injection molded or machined plastic parts. But when designed correctly, printed gears can provide efficient and reasonably high load transfer and are an ideal solution for some applications.
The majority of functional applications take the form of a speed reducer, usually for a small electric motor or hand crank. This is because electric motors do high speeds really well, but they arent naturally good at producing low speed/high torque very well without being geared down. Examples of this done well include:
Center hole shrinkage is a very common issue that occurs even on expensive printers. This is the result of multiple factors. Some to thermal contraction of cooling plastic and some is because the holes are modeled as polygons that have lots of segments cutting short around the perimeter of the hole. (Always export gear STLs with high segment counts.)
Slicing software can also have an effect as different programs may choose different spots for the hole to actually start. If you consider the absolute innermost edge of the extruded plastic to be the inside edges of the hole and shoot to make that the desired hole size, then the hole diameter is easy to stretch out of tolerance by a tiny bit when you press something inside. So a slicer designer may choose to intentionally make holes tighter.
Some software is better than others at automatically fixing this, but one way to manually solve is to increase the layer overlap. RichRap did a great job documenting the problem and various solutions on his 3d printing blog.
3. Standard FDM 3D printing challenges: Thin walled parts are weak, overhanging parts need breakaway scaffolding, part strength is significantly weaker in the Z-axis. All the same, my recommended print settings for gears are no different than for anything else 3d printed. Based on testing I did a while back I recommend that you use the rectilinear infill with a minimum of 3 perimeters. I would recommend as fine of a layer height as you have the ability & patience to print, so as to create smoother teeth.
4. But then again, plastic is cheap and your time isn't. If the application is critical or just cumbersome to replace a broken gear on then you may as well print the gear mostly solid to avoid the chance of any non-wear related failure. The most common failure modes of printed gears are:
Involute (spur) gear teeth are called such because the contour of gear teeth has a special curve inward. This is done in such a way that ensures the rotational speed and angle of contact of the gears stays constant throughout their rotation. A well designed set of gears should transfer motion almost exclusively through a rolling action, with very little sliding involved.
More teeth per gear increases the contact ratio (average number of teeth in contact at any time) and provides smoother rotary motion. But adding more teeth requires that each tooth get smaller to fit on the same diameter of gear. Tiny teeth are weaker and more difficult to print accurately.
3D printing a tiny gear is like trying to use a thick sharpie to color inside the lines of an itty bitty coloring book. (This is 100% a function of nozzle diameter and X-Y resolution of the printer. The Z-resolution has nothing to do with minimum feature size.)
This is information that can be looked up in resources like the Machinery Handbook. 13 is the minimum recommended for gears with a 20 deg pressure angle, and 9 is the minimum recommended for gears with a 25 deg pressure angle.
This is the angle between the normal of the tooth face and the pitch diameter. Teeth with larger pressure angles (more triangular) are stronger but are also less efficient at transferring torque. They are also easier to print, but in use they create larger radial loads on the supporting shafts, are more noisy and prone to backlash and slippage.
Simply making the gear thicker will obviously strengthen the teeth as well. Doubling the width of the gear essentially doubles its strength. A good general rule is for the thickness to be at least three to five times the circular pitch of the gear.
The strength of gear teeth can be approximated by considering each tooth as a small cantilever beam. When viewed this way you can see that adding a solid wall over a face to reduce their unsupported area greatly increases the strength of gear teeth. Depending on the application, this technician can also be used to help reduce finger pinch points.
Press Fit on Knurled Shaft: The easiest method to do but is not seen very often. Watch out for plastic creep which will reduce the torque capacity over time. This also cannot be disassembled without destroying the gears usability.
Set Screw on Shaft with Flat: A setscrew is drive through the gear to contact a flat spot machined on the shaft. The set screw is usually threaded into the plastic gear directly or through a nut that is trapped inside the gear via a square hole. Each method has its own risks.
Directly threading into the plastic runs the risk of stripping the delicate plastic threads. The nut trapping method solves this problem but if not done properly the hub breaks when you apply enough force to secure the shaft with the set screw. Make the hub Beefy!
Recessed Hex- a hexagonal well which traps a hexagonal nut or the head of a hex-head bolt. Make sure to print lots of solid layers around the hex so that a mounted bolt cant strip through the plastic. I've successfully used set screws to secure nuts in place to prevent spinout at high torques.
Integrated Shaft: This design is highly susseptible to torsional failure of the shaft. This is very difficult to do properly with fdm printed gears since you have to print gears oriented normal to the print bed, any shaft integrated with the gear will end up having its weak Z-printed axis subjected to high loads.
By the way, the biodegradability of PLA is an overhyped property. Yes, PLA is biodegradable. But not in a scale that is in any way noticeable for the end user. Do not equate biodegradability with water solubility. To biodegrade this plastic, you need a specialized composting facility with a controlled environment.
Also of note, recently people have been experimenting with annealing PLA for the purpose of increasing stiffness, strength, and heat deflection, at the cost of some slight part shrinkage (possibly non-uniformly). More on annealing PLA gears here.
Helical & Herringbones (double helical): Usually seen on printer extruders, these are annoying to use, but have their merits. They are useful for their ability to increase contact ratio, self-center, and self-retain. (Self-retaining is the annoying property because it makes installation more work.) This type of gear also can't be easily manufactured with conventional machining equipment like a gear hobbing machine. 3D printing is by far the easiest way to make them.
Worm & Worm gear: These can be difficult to 3D model so its very tempting to use a ger template for these. My tip here is that the gear ratio between the worm gear and worm is the number of teeth on the gear divided by the number of flutes in the worm. (Count flutes by looking at the end of the worm and see how many spirals start. Most have 1 to 3 spirals.)
Rack & Pinion: Converts rotary motion into linear motion & vice versa. Rather than rotations, the gear ratio determines the linear distance traveled by the rack with each rotation of the pinion. The tip here is that you can calculate the gear teeth per inch (tpi) of a rack all you do is multiple PI times the pitch diameter of the mating pinion gear. (Alternatively multiplying number of pinion teeth times circular pitch produces the same result.)
You can get away with operating plastic gears without lubrication in light-load low-speed low-frequency applications. But if you have a high stress environment you can try to increase the working life by lubricating the gears to reduce friction and wear. In any case, all gears function more effectively with lubrication and will have a longer service life
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