Saturday, November 30, 2013

Building the 3DR “Simple” Delta Printer, Part I

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The previous three posts provide background information about this printer. This is the first part of how to build the “final” version of this printer.

3DR “Simple” Delta Printer, Part I
3DR “Simple” Delta Printer, Part II
3DR “Simple” Delta Printer, Part III
Building the 3DR “Simple” Delta Printer, Part I
Building the 3DR “Simple” Delta Printer, Part II
Building the 3DR “Simple” Delta Printer, Part III

Since my last post, I’ve redesigned almost every part of my 3DR “Simple” Delta printer. Yesterday I got it printing, and it works really well. I have one final parts I’m working on, which is a combination fan and ring LED mount. Once these are done, I’m going to declare this complete.

Sourcing Parts

The idea of this project is that you can start with a Printrbot Simple, which is a very low cost printer. You can use the Simple to print all the printed parts required for this build and then start the build. You won’t need to disassemble the Printrbot Simple until you’ve assembled the printed parts. Then, and only then, you can disassemble the Printrbot Simple and use it’s “vitamins” to finish the build. Even so, you’ll need to purchase some additional parts, such as the smooth rod and extruded aluminum.

You’ll need to decide how tall you want to make your printer. My printer has a maximum print height of about 80mm, which works very well for me. However, you’ll most likely want a little more height. The first version of my design had the same dimensions as RichRap’s 3DR RepRap Delta Printer and had a larger maximum height. However, when I discovered I couldn’t use the full diameter, I widened the printer, which resulted in longer rods, and therefore reduced my maximum print height. So, here is what I would recommend:

Smooth Rods: 500 mm
Extrusions: 550 mm

This will give you a maximum print height of about 150mm. You can, of course, choose different lengths. Just make sure the smooth rods are 50mm shorter than the extrusions. Here are some links on Msiumi’s US sight for these parts:

Note: The 400mm long smooth rod is about $12 per rod. But as soon as you increase this to even 401 mm, the price goes up to $19 a rod. So if you’re happy with 80 mm maximum print height, go with 400 mm rods. Otherwise, you can go up to the maximum of 500 mm length for the smooth rods. I’ve also listed T nuts that have a spring to hold them in place, and can be inserted after the fact, which is really handy. When I added the above to my shopping cart, the total came to $147.

There are some other supplies I got from tridprinting.com:

If you purchase 180 mm rods, you won’t be able to get the full 170 mm diameter—it will probably be closer to 160 mm. If you plan to assemble your own rods instead, you’ll need to purchase some carbon fiber rod:

Electrical Connectors

The following electrical connectors are optional, and you’ll only need them if you choose to use new connectors instead of simply splicing new wires into the stepper motors (covered in the next installment):

  • (optional) Molex 1625-4PRT .062” 4-pin connectors (to connect the steppers to the wires that go up the extrusions)
  • (optional) Molex WMLX-102 .100 4-pin connectors (to replace the stepper-motor to Printrboard connections)
  • (required) 26 gauge stranded wire in red, blue, green, and black

Screws and Nuts

I’m still working on updating the list of all the screws required. Here’s what I have so far:

  • M3 x 6 button head (9)
  • M3 x 16 screws (12)
  • M4 x 10 screws (39)
  • M4 x 20 screws (18)
  • M4 nuts (57)
  • M5 x 8 (6)
  • M5 x 20 button head (5)
  • M5 Washers (9)
  • M5 Nuts (3)

Extruder Parts

The extruder needs some parts that don’t come with more recent Printrbots, and perhaps the easiest (and even most cost effective) way to get these might be to order the hard-ware only kit from Makerfarm (they call it the No Printed Parts option, which is $15 at the time I’m writing this): http://www.makerfarm.com/index.php/3d-printer-kits/greg-s-hinged-accessible-extruder.html

  • M3 x 50 (2) for extruder
  • M8 x 20 (1) smooth or threaded rod (no head)
  • Hobbed bolt and other extruder parts (not included in direct-drive Printbot Simple kits)

There are various M3 nuts and screws. However, I believe all of these can be reused from the Printrbot Simple.

Printrbot Simple Parts

Here is a list of parts I reused from the Printbot simple (so you won’t have to buy them)

  • Stepper motors (4)
  • Hot end
  • Printrboard
  • Power supply
  • LM8UU bearings (6)
  • Hobbed bolt and other extruder parts (not included in direct-drive Printbot Simple kits)
  • M3 x 10 screws (12)
  • M3 nuts (24)

If you have a Printrbot Simple V2 with the direct-drive extruder, you’ll also need a hobbed bolt (which is what my V1 came with): http://printrbot.com/shop/hobbed-bolt/. Alternatively, you can purchase the hard-ware only kit from Makerfarm (link in previous section)

While you’re there, you might choose to use their injection-molded gears instead of 3D printing the gears: http://printrbot.com/shop/injection-molded-large-and-small-gear-set/

Other Parts

You’ll need a 170 mm diameter print bed. I purchased a 170 mm round Borosilicate plate from Trinity Labs: http://trinitylabs.com/products/borosilicate-glass-170mm-round. Without a heated bed, you don't really need Borosilicate glass. So you might be able to get a glass place to cut one for you.

Assembling the Lower Frame

As I’ve mentioned before, all the printed parts are designed to be printable on a Printrbot Simple, with a 100mm x 100m print bed. That means you should be able to print all the printable parts on just about any printer.

For most of the parts, I print with 0.2 mm layers, 20% infill and either two or three perimeters (I’m not sure it makes much difference).

Print 3 of 3DR Bottom Motor Mount Simple.stl:

3DR Bottom Motor Mount Simple

Print 3 of Wings.STL:

Wings

Print 3 of Wing Mirror Long.STL:

Wing Mirror Long

Connect the base pieces with M4 x 10 and M4 x 20 screws and nuts. The wings connect to each other with four sets of M4 x 10 screws and nuts. While the wings connect to the motor mount with a pair of M4 x 10 and another pair of M4 x 20 screws. Assemble these on a flat surface and ensure the screws are tight:

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Milling the Extrusions

There is enough room inside the extrusion to run wires for the stepper motors. You’ll need to mill a slot on each end of each extrusion in order to accommodate the wires. Here is what the slot looks like on the bottom:

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You can see that the slot is toward the middle of the printer. On the top, the slot should be to the side shown here:

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Take your time to ensure the slots are milled in the correct location, and that they’re smooth so they won’t cut into the wires.

Insert a T nut into the extrusion and then insert the extrusion into the base. Fasten in place with an M5 x 8 screw and washer. You’ll need to make sure the T nut is aligned with the hole first, of course. Once you have the screw started in the T nut, and before you tighten, make sure the extrusion is flush with the bottom of the base, as shown in the first image of this section.

Print three of these end caps and install them on the bottom of the extrusions (so you don’t scratch your work surface):

misumi_2020_extrusion_cap two Ts

I modified these end caps from this Thingiverse part: http://www.thingiverse.com/thing:45339.

Once you’re finished, the base will look something like this (without the carriages, stepper motors, and bed):

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Assembling the Upper Frame

The upper frame, like the lower frame, is made from 9 printed parts. Note that the three parts for the top all have the same file names as the corresponding bottom parts, but they’re in a folder named Top on Github. In case you’re curious, both the top and bottom files are contained in the same Solidworks file, which is why the STL files have the same name.

Print 3 of 3DR Bottom Motor Mount.STL:

3DR Top Motor Mount Simple

Note that this has the same file name as the bottom motor mount, but it’s a different file (it’s in the Top folder in Github).

Print 2 (note, only two)  of Wings.STL:

Wings Top

Print 3 of Wing Mirror Long Top.STL:

Wing Mirror Long Top

Print 1 of Wings with Power.STL

Wings Top with Power

Assemble on a flat surface using M4 x 10 and M4 x 20 screws and nuts, just like you did for the base. Once assembled, it will look like this (without the electronics, of course):

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Printing the Remaining Parts

Before you can complete assembly, you’ll need to print some more parts (while your Printrbot Simple is still assembled and working):

Print 3 of Spool.STL:

Spool

Print 3 of Carriage for LM8UU.STL:

 

Carriage for LM8UU

Print 12 of Bearing Shaft Coupler.STL (assuming you’re going to make your own rods with 3 mm inside diameter carbon fiber rods):

Bearing Shaft Coupler

Print one of Platform.STL:

Platform

Print one of Hot End Holder.STL:

Hot End Holder

Print one of Hot End Holder Tabs.STL:

Hot End Holder Tabs

Print one of Hot End Plate.STL:

Hot End Plate

Print one of Extruder Spacer.STL:

Extruder Spacer

Print Extruder Parts

For the extruder, I used RichRap’s parts without change:

Print one of 3DR_Extruder_body_V2_Test_001_RTP.stl

Print one of RichRap_Greg_style_Guidler_Modified_with_grab_lever_For_1_RTP.stl:

Print one of herringbone-gear-large.stl:

Print one of herringbone-gear-small.stl:

Next Steps

In the part II, I’ll continue with the assembly instructions. You’ll need to ensure you have all the parts printed and they’re of good quality before you continue, as the next step will be to disassemble your Printrbot Simple so you can reuse parts form it.

Saturday, November 2, 2013

3DR “Simple” Delta Printer, Part III

I finished assembling my printer and actually got it printing…but only for a short while. Before I get into what I learned and the problems I encountered, here are are some in-progress photos of the build.

First is the base with the stepper motors mounted and the spools wrapped with the Spectra fishing line:

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Assembly is nearing completion. Still to be installed are two of the carriages, the hot end effector and rods, the extruder, and the end stops. At this point the wiring looks pretty neat—but that changed later once I had all the wiring in place.

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I ended up designing a new hot end mount. This is made from two halves that bolt together and clamp both the hot end and the pneumatic fitting securely in place. The two-part mount is easier to make because it requires less precision than if you needed tight-fitting holes.

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And the fully assembled printer:

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You can see from the last photo that there are wires all over the place. I discovered I didn’t have any place where I could use zip ties to hold the wires in place. Something I’ll fix with in the next version.

For the extruder, I downloaded RichRap’s 3DR files and built the extruder without any modifications. I was able to reuse most of the extruder hardware from my Printrbot Simple.

Problems

My main problem was with the Spectra spools attached to the stepper motors. First, the set screws kept coming loose and falling out. So it would print fine for a while, and then start to do odd things because one of the spools had come loose. Tightening the screws was also difficult because they were hard to get to. And when I did get the screws tight again, sometimes the spool was a little off axis, which then caused it to rub against the base piece, and therefore not move correctly.

After fighting the spool problems, I decided I could either make new spools that were shorter. Or I could modify the base pieces to provide more clearance between the spools and the base.

I also discovered that I couldn’t use the full 170mm diameter of the print area. When I asked on the RepRap forums, I found out that others plan for about 110mm as the usable diameter for printing. Hmmm. In looking at the Kossel Mini, I noticed the extrusions were quite a bit farther away from the center bed.

Finally, the entire printer wasn’t quite as sturdy as I would like. I could wiggle the top of the printer back and forth too easily for my liking.

So with all of these problems, I decided to start on version 2.

First I tackled the sturdiness. In my original design, each part had three walls and one row of screws. Adding the fourth wall and a second row of screws made the assembly much stiffer than the old design. Here you can see a test with a new set of parts.

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Next I extended each wing section (the green and yellow below) by 20mm. This increased the side-to-side distance between the extrusions by 40mm, which will allow a larger print area. The printable diameter increases by about 35mm, so I should end up with a useable print diameter of about 145mm, which is about the same as the printable height.

Larger Base

I also modified the base parts that hold the stepper motors to provide much more clearance between the spool and the base (can’t really see here). And I redesigned the upper parts so each one has a slot for zip ties that will help hold the wires in place.

Right now I’m busy printing a new set of parts, and we’ll see how the new design turns out.