Tuesday, July 17, 2012
Friday, June 8, 2012
K1-Rap
I'd like to introduce a new printer mainly of my own design but heavily influenced/inspired by dkennel's Pocket Printer. I call it the K1-Rap.
This is a work in progress. I'll be updating this as things progress.
Background:
I really liked the idea of using aluminum extrusions for the main structural components of a reprap. My Prusa i2, constructed mostly of threaded rods, worked flawlessly but I wanted something a little more sturdy.
I saw Dkennel's Pocket Printer on Thingiverse and actually started out attempting to replicated his. I didn't have any PLA available and ABS did not make for a good slide material. ABS was too soft and did not "slide" reliably. Since I had smooth rods and lm8uu linear bearings on my Prusa, I decided to cannibalize it and start a "new" design. It should be noted that this is really Dkennel's basic design adapted for 8mm smooth rods. They really deserve the credit for the initial idea.
I attempted to design the printer around a few constraints (much like dkennel's original idea).
1. I wanted to keep the moving mass low (arguably didn't do a very good job)
2. I wanted to keep the amount of hardware (screws, bolts, nuts, etc.) to a minimum. I loved the simplicity of the Prusa i2 design.
3. Like the Pocket Printer, the extruder had to move only in the Z direction. Eventually, I want to add a second Plastruder to the printer and the added weight would make a "mobile" extruder hard to accomplish.
4. I wanted roughly the same build envelope as I had on my Prusa.
Keeping these ideas in mind, I started off by mimicking Dkennel's basic design. I then added the smooth bars to the exterior of the 2060 extrusions. All axes slide on 8mm smooth rods with lm8uu linear bearings. In doing so, I had to then redesign the basic structural components on the printer.
You'll notice the smooth rods sticking out on all the axes. This was done purposely so I didn't have to cut the rods to length. Mainly I was afraid this design wouldn't work properly and I didn't want to cut my prusa smooth rods and then not have a single working printer. In the final designs, I will enclose all rod brackets and cut the smooth rods to length.
The smooth bar "brackets" fit within the interior of the Al extrusion. This is a pretty snug fit and friction is the only thing holding the majority of the printed parts in place. The X axis connects to the Y axis with lm8uu bearing fittings reminiscent of the Zip-Tie bearing holders used on the Y axis of a Prusa. Connected to the X to Y bearing holders are the 2020 Al extrusions that make up the X axis. .
I'm using a NEMA 14 on the X axis. This is the only real deviation in electronics from the Prusa. I had this laying around and its lighter than a '17. I would highly highly recommend using a '14 instead of a '17 simply because of the added mass a '17 would give to the X axis assembly. (As a matter of fact, my '14 is a little bigger than I really need, Dkennel lists a better motor for use with the Pocket Printer).
Once again smooth rod brackets fit into the extrusions. The build plate then sits on top of the X axis smooth bars using Prusa's i2 lm8uu Y bearing holders.
I'm using a thin sheet of plywood with Prusa's Mk1 PCB heated build plate on top. I will likely swap this out for a sheet of aluminum.
The Z axis consists of a vertical 2060 extrusion with 8mm smooth rods on either side. The cantilever extends out over the build plate and rides up and down on the smooth bars.
I used 2 Z motors only because I wanted to maintain speed when I eventually add a second extruder. I'm sure you could get away with a single Z if you wanted.
I'm using my Plastruder Clone and it sits on a printed extension off of the Z cantilever. The Pocket Printer used a nice aluminum plate for this, I would recommend that instead of the printed part. Unfortunately I didn't have access to equipment to make that plate, so I designed a printed part instead.
My RAMPS 1.4 sits on the back using Dkennel's RAMPS box. My X ends are essentially printed versions of his. The Y motor bracket is once again Dkennel's design. I'm using the T5 belts/pulleys I had on my Prusa.
Current Build Envelope: X-200, Y-120, Z-180.
Actual Build Envelope: X- 200, Y-200, Z-180. (Once my replacement Y Al Extrusion comes in)
Actual Build Envelope: X- 200, Y-200, Z-180. (Once my replacement Y Al Extrusion comes in)
To Do List:
Brace the vertical Z axis. Currently I'm using 90 degree brackets and they still allow the Z to wobble very very slightly. Bracing the more will allow for faster printing speeds.
Replace the ZipTie brackets on both the X and Y. These seem to work fine, but I just want something a bit more sturdy.
Make a single X carriage. I will eventually design an X carriage that is all inclusive. Currently I have a belt clamp bracket mounted onto the plywood between the X bearing holders. I want to integrate all of these into one bracket like the Pocket Printer design has.
Extend my Y! A miscalculation resulted in a Y extrusion that was 80mm too short. This is an easy fix just a longer belt is needed.
Enclose all smooth rod brackets.
Integrate cross bar (The bars on the bottom the feet are attached to) brackets into the Y axis end brackets. -I've already actually done this, I just haven't printed out replacements.
Pro's:
Allows the extruder to remain mostly stationary. Except Z travel.
Entire assembly is very rigid even at travel speeds speeds of 200mm/s.
Other than the a few 5mm bolts and the associated aluminum extrusion nuts, there isn't much in the way of hardware, as everything push fits into the aluminum extrusions.
Will likely allow for some light milling, if so inclined. ( I probably never will attempt this)
Can easily be built out of a retired Prusa. -Motors, smooth bars, bearings, HBP, etc
I designed and built it myself! (Ok, this one really just applies to me, but none the less, it's a good feeling to see something you imagined come to life.)
Con's:
Entire alignment of each axis relies on perfectly aligned printed parts and straight aluminum extrusions. If the parts aren't printed correctly and fitted correctly, then the axes won't be squared and level to each other.
There isn't an easy way to fix misaligned parts.
Requires both aluminum extrusions and smooth bars. This adds to the cost slightly.
There is still a significant amount of mass being moved by the Y motor. I don't know the exact weight but its higher than I hoped for. This means a fair amount of vibration at higher print speeds. This is where the bracing between the Y and Z extrusions comes into play. Without proper bracing, the extruder end of the cantilever can bounce up and down causing ugly prints. I'm printing reliably around 70 to 80mm/s depending on the part being printed.
I’d like to thank DKennel for the Pocket Printer design and Prusa for his design, allowing me to steal parts of both for this design. All of the parts are on Thingiverse if anyone is interested. I will post a BOM including lengths of extrusions and smooth rods shortly. Feel free to leave feedback in the comments!
Friday, May 18, 2012
Mark II
I printed a Mark II robot friend today from Thingiverse. I made mine for my nephew, and I'm sure the rest of my nephews will want one as soon as they see it. Pablo did a great job on this one. Printed full size, Mark II stands about 9 inches high. I would recommend printing the "pins" and "joints" slightly smaller so they fit without trimming.
Plastruder Clone Update
I've been using my Plastruder Clone for a number of prints and I am very happy with it. I print between 70 and 80mm/s with out any problem. The increased weight on the X carriage from the larger geared stepper means I can't print much higher without crazy vibration.
I did notice an issue that I never experienced with the hobbled bold on my Wade's - clogging. I have had an issue multiple times where the drive pulley's teeth will clog. This has always been my fault. It always happens if I set my Z height too low. As long as I avoid this, I am completely fine.
I never had this problem before with my wades, it would just squash out the abs and make the first layer look like hell, but never clogged.
Now if my drive pulley clogs, I'll get a very weak infill on my first layer and subsequent layers will lack in density once the pulley spins around to the clogged position.
Moral of the story: be precise with your Z heights. Other than that, everything is going well, even with the incorrect stepper.
I did notice an issue that I never experienced with the hobbled bold on my Wade's - clogging. I have had an issue multiple times where the drive pulley's teeth will clog. This has always been my fault. It always happens if I set my Z height too low. As long as I avoid this, I am completely fine.
I never had this problem before with my wades, it would just squash out the abs and make the first layer look like hell, but never clogged.
Now if my drive pulley clogs, I'll get a very weak infill on my first layer and subsequent layers will lack in density once the pulley spins around to the clogged position.
Moral of the story: be precise with your Z heights. Other than that, everything is going well, even with the incorrect stepper.
Tuesday, May 15, 2012
New Printer Build!
I'm in the process of obtaining all of the required parts to build my Pocket Printer derivative. As stated previously, I am building mine with the standard 9x9"(ish) build area associated with a Prusa. This way I can use the Prusa Mk1 PCB heated bed.
I purchased the 8020 extrusions from Misumi. You can get it cut to specific lengths and have them tap the ends for you too. I will post more information as it progresses.
Monday, May 14, 2012
Webstore
Be sure to check out the webstore for RepRap Printer Parts. Different colors available. If you have any questions/requests, let me know.
Thursday, May 10, 2012
Plastruder Clone
I have read many posts and reviews complimenting Makergear's Plastruder. They charge $170 for the whole kit. I already had my J-Head hotend and could print the parts myself so I decided to try and build a clone. I put this Plastruder clone on my Prusa Mendel i2. Here is the build process. Hopefully this saves someone some time/money.
Drive Gear: ($12 + $20 for machining = $32)
I purchased a replacement mk6/mk7 drive pulley from a seller on eBay. (Makerbot sells them here too, but they weren't in stock when I started this project.) The gear had a 5mm for a standard Nema17 motor shaft. It needed to be 8mm to fit the geared stepper I used for this (see below), so I took it to a small machine shop around the corner and they opened it up for me. It cost me $20 but its perfect and I know I would have screwed it up if I did it on my own. It's 305 Stainless, so it wouldn't be the easiest thing to do on your own.
Geared Stepper: ($34 + shipping = ~$60)
I kind of screwed up here. I really should have done a little more research before I bought this stepper. I noticed after I already had this stepper in my possession that Makergear provides the manufacturer and model number on their website for the exact motor they use.
You can find the "correct" motors here. These motors are a bit more expensive and I have no idea how much shipping would cost.
I didn't notice this and decided to pick out my own geared stepper blindly. I chose this geared stepper by Phidgets. (RobotShop.com sells these as well, and they may have cheaper shipping). It has a 5:1 gear ratio and a respectable 20 kg-cm torque rating (16kg-cm holding torque). In hindsight, it's torque is slightly less than the 26kg-cm that the "correct" Kysan stepper has. (See below).
Printed Parts: (Self Printed = $0)
I found this on thingiverse, and used it for my filament drive body. I liked the rear facing motor because it didn't decrease my X distance at all. (The size of the x carriage, driver body/motor is still shorter than my Wades on my normal x carriage so my Z clearance actually increased by a few mm.)
I used this for my new X carriage. I already had linear bearings so this worked perfectly.
Both of these objects absolutely need to be printed with support. So be patient and clean them properly after printing.
I had to make my own J-Head mounting plate. You can see in the pictures its the white block with the split in the middle directly under the blue filament drive body. Its basically a collar that fits around the groove on the J-Head body. While it works flawlessly, its not the best solution since it requires me to remove the entire extruder from the X carriage to change hotends. (I can upload the design to thingiverse if anyone is actually interested in using it, just let me know.)
Hardware: (Stuff laying around = $0)
5x 5mm bolts - 2 to connect motor to drive body, 2 to hold everything to the X carriage, 1 to hold the idler bearing block
2x long bolts w/nuts - used to hold idler bearing block closed. Probably should use springs, I didn't but I make sure they are tight often.
1x 608 bearing - idler
8mm smooth rod - idler
Total: ~$92
End Result:
Drive Gear: ($12 + $20 for machining = $32)
I purchased a replacement mk6/mk7 drive pulley from a seller on eBay. (Makerbot sells them here too, but they weren't in stock when I started this project.) The gear had a 5mm for a standard Nema17 motor shaft. It needed to be 8mm to fit the geared stepper I used for this (see below), so I took it to a small machine shop around the corner and they opened it up for me. It cost me $20 but its perfect and I know I would have screwed it up if I did it on my own. It's 305 Stainless, so it wouldn't be the easiest thing to do on your own.
Geared Stepper: ($34 + shipping = ~$60)
I kind of screwed up here. I really should have done a little more research before I bought this stepper. I noticed after I already had this stepper in my possession that Makergear provides the manufacturer and model number on their website for the exact motor they use.
Side note: Makergear has two different motors listed for their plastruders. One is a 14:1 gear ratio and the other is a 5:1 ratio. I assume the difference here is it's intended use. The 14:1 has more torque, therefore I have to imagine when a plastruder is used with 3mm filament and a 0.35mm nozzle, this is the motor of choice. (Although I don't know that for sure, but check below for my reasoning.)
You can find the "correct" motors here. These motors are a bit more expensive and I have no idea how much shipping would cost.
I didn't notice this and decided to pick out my own geared stepper blindly. I chose this geared stepper by Phidgets. (RobotShop.com sells these as well, and they may have cheaper shipping). It has a 5:1 gear ratio and a respectable 20 kg-cm torque rating (16kg-cm holding torque). In hindsight, it's torque is slightly less than the 26kg-cm that the "correct" Kysan stepper has. (See below).
Printed Parts: (Self Printed = $0)
I found this on thingiverse, and used it for my filament drive body. I liked the rear facing motor because it didn't decrease my X distance at all. (The size of the x carriage, driver body/motor is still shorter than my Wades on my normal x carriage so my Z clearance actually increased by a few mm.)
I used this for my new X carriage. I already had linear bearings so this worked perfectly.
Both of these objects absolutely need to be printed with support. So be patient and clean them properly after printing.
I had to make my own J-Head mounting plate. You can see in the pictures its the white block with the split in the middle directly under the blue filament drive body. Its basically a collar that fits around the groove on the J-Head body. While it works flawlessly, its not the best solution since it requires me to remove the entire extruder from the X carriage to change hotends. (I can upload the design to thingiverse if anyone is actually interested in using it, just let me know.)
Hardware: (Stuff laying around = $0)
5x 5mm bolts - 2 to connect motor to drive body, 2 to hold everything to the X carriage, 1 to hold the idler bearing block
2x long bolts w/nuts - used to hold idler bearing block closed. Probably should use springs, I didn't but I make sure they are tight often.
1x 608 bearing - idler
8mm smooth rod - idler
Total: ~$92
End Result:
This is made for 3mm abs filament with a 0.5mm nozzle. It works perfectly as long as the bolts holding the idler body closed are tight.
Side Note: I originally tried this with my new 0.35 J-Head hot end. I couldn't get it to work correctly. I don't think the motor has enough torque to push the large 3mm filament into the smaller 0.35mm nozzle. If I tightened down the bolts to a point where it would push the filament, the motor was skipping steps. Increasing the current to the motor eventually resulting in even more missed steps. I imagine this may work better for 1.75mm with the 0.35mm nozzle but I haven't tried it. The Kysan 14:1 ratio model has a holding torque of 26kg-cm. (compared to the Phidgets' ~16kg-cm) I may purchase one of these in the future and see if they helps my problem.
Conclusion:
My Plastruder Clone works and works well (as long as I stick with the 0.5mm nozzle.) I do notice a slight increase in print quality over my previous Wades ( but I may just be bias). It was definitely cheaper than buying a full kit from Makergear, since I didn't need the majority of the parts included in the kit. I'm not sure if you priced it all out separately if you would end up saving any money, maybe? But its always fun to do things yourself! Let me know if anyone has any questions/concerns.
Side Note: I originally tried this with my new 0.35 J-Head hot end. I couldn't get it to work correctly. I don't think the motor has enough torque to push the large 3mm filament into the smaller 0.35mm nozzle. If I tightened down the bolts to a point where it would push the filament, the motor was skipping steps. Increasing the current to the motor eventually resulting in even more missed steps. I imagine this may work better for 1.75mm with the 0.35mm nozzle but I haven't tried it. The Kysan 14:1 ratio model has a holding torque of 26kg-cm. (compared to the Phidgets' ~16kg-cm) I may purchase one of these in the future and see if they helps my problem.
Conclusion:
My Plastruder Clone works and works well (as long as I stick with the 0.5mm nozzle.) I do notice a slight increase in print quality over my previous Wades ( but I may just be bias). It was definitely cheaper than buying a full kit from Makergear, since I didn't need the majority of the parts included in the kit. I'm not sure if you priced it all out separately if you would end up saving any money, maybe? But its always fun to do things yourself! Let me know if anyone has any questions/concerns.
Subscribe to:
Posts (Atom)