Tuesday, December 3, 2013

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

This is the fifth part in my series on a delta printer that I designed, which started life as just a few changes from RichRap’s similarly named 3DR RepRap Delta Printer. Here are the previous posts:

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

In my last blog post, I covered printing all the parts and assembling the top and bottom frames. The next step is to disassemble your Printrbot Simple as you’ll need the various vitamins to continue this build.

Finishing the Top Assembly

In this step you’ll mount the Printrboard and end-stop switches. Use two M2.5 x 10 screws and nuts for each micro switch. You’ll want to ensure the free end of the lever is towards the center, as shown here.

Next use two M3 x 10 screws to attach the Printboard to two of the posts. The board will need to be attached next to the wing with the extension for the power connector, as shown at the top-right of the photo above. Plug the end stops into the correct slot of the Printboard as shown above. The center socket is attached to the micro switch in the upper-right corner.

The power connector is designed to be held in place with the nut on the back. Unscrew the nut and slide the wires through the slot, with the nut on the inside. Place the nut into the slot and then turn the power connector to screw it into the nut. Once this is tight you can plug the square power connector into the Printrboard.

Next, each smooth rod is held in place with an M4 x 10 screw and nut. Place one M4 nut into each of the six slots next to the smooth bar holes. Then screw in an M4 x 10 screw so it’s all the way into the nut, but not projecting into the smooth rod hole.

Adding the Carriages

Add one LM8UU bearing to each smooth rod. Then use four zip ties to attach one carriage to each pair of smooth rods. The carriage should be oriented so the rod connections are on the top, like this:

OLYMPUS DIGITAL CAMERA

Make sure the zip ties are very tight.

Installing the Top

Now install the top, with the Printrboard facing down. Carefully slide the parts over the extrusions, and then over the smooth rods. Work it down until 20 mm of extrusion is extending out of the top of each corner. Then lock in place with an M5 x 8 screw and washer that attaches to a T nut in the extrusion. Finally, tighten the six M4 screws on the top corners that hold the rods in place.

Installing the Stepper Motors

The cords on the stepper motors are much shorter than you’ll need. Obtain some 26 gauge stranded wire. You should use the same four colors as on the original motors: red, green, blue, and black. I chose to use new wire and connectors, and also to install connectors on the bottom between the stepper motor and where the wire enters the extrusions. This will make it easy to change stepper motors if I need, but I’m not sure it was that important. In any case, you’ll need to cut the wires on the stepper motors and either splice in new wires, or use a connector like the one shown below.

OLYMPUS DIGITAL CAMERA

The connectors I used are Molex 1625-4PRT .062” 4-pin connectors, although you can use other connectors. These have both a male and female part, and the pins crimp to the wires. To ensure a secure connection, I also soldered the wires to the pins after crimping. Ensure you have the colors matching as shown before you push the pins all the way into the body:

OLYMPUS DIGITAL CAMERA

For the wires that will be attached to the Printrboard, cut wires more than long enough to go through the extrusions and to the Printrboard (you can cut them to length later when you know exactly how long you’ll want them).

Once you have the connector attached to the long wires, fish the cut ends of the wires through the rectangular hole on the bottom part and into the hole in the extrusion. Keep feeding them until they come out the top.

Mounting the Stepper Motors

Cut three lengths of Spectra fishing line. RichRap recommends two meters each. It’s better to have them too long than too short. Thread one end through the holes in the spool so it looks like this:

OLYMPUS DIGITAL CAMERA

The two lengths of string coming out of the spool should be about the same length. Next wrap the string around the  spool in opposite directions. Each one should be wrapped eight times around. Secure in place with a piece of tape. Make sure you wind all spools the same way.

OLYMPUS DIGITAL CAMERA

The nuts and screws can be a little tricky to install on the spools. Using a round object inserted in the hole can help hold the nut while you place the screw, as shown here:

OLYMPUS DIGITAL CAMERA

Now attach the spool to the stepper motor shaft. There should be a small gap of about 1 mm between the spool and the stepper motor. Tighten each of the three set screws in turn so you keep the spool aligned with the shaft. Make sure the set screws are all quite tight. You might wish to place some thread lock on the screws to keep them from coming loose.

Finally, attach the stepper motors to the lower mount and connect the cables. It will look like the following picture once you’ve finished string the fishing line. Remember to install the bottom end cap on each extrusion so you don’t scratch your work surface.

OLYMPUS DIGITAL CAMERA

For now, tape the fishing line to the top surface of the base:

Running the Fishing Line

First create the idler assemblies. Each one consists of an M5 x 20 button head screw, two 625ZZ bearings, one M5 nut, one M5 washer (a wider penny washer would be better, but I didn’t have any handy), and finally an M5 T nut:

OLYMPUS DIGITAL CAMERA

You’ll need three of these assemblies, with one for each extrusion. Insert these into the slot closest to the center, at the top of the extrusion. You can either leave the T nuts loose or tighten them ever so slightly to keep them in place. Make sure the regular M5 nut is very tight against the back of the bearings. If it’s not, the fishing line could work it’s way down between the two bearings and get stuck.

Now tape each carriage so it’s towards the top of the tower, but with enough distance so you can get in there to tie the fishing line to the carriages. You’ll want it to look like this when you’re finished:

OLYMPUS DIGITAL CAMERA

Note: Although this photo shows the rods attached to the carriage, it’s easier to tie the fishing line to the carriages before attaching the rods.

The fishing line shown on the right loops over the top of the idler bearing you installed and then down to tie onto the top hole of the carriage. While the other side of the line coming from the spool ties to the bottom hole in the carriage. Try to make these somewhat tight when you tie them on.

Then push up on the idler bearing as much as you can and tighten them in place. The strings should be fairly tight, but will loosen a little after some movement, so you’ll need to re-tighten every now and then.

At this point you can remove the tape holding the fishing line to the spools and move the carriage up and down to ensure they work smoothly without any binding.

Making the Rods

I found a really nice jig on Thingiverse by ichibey: http://www.thingiverse.com/thing:166605. Print out two of these and add two M3 x 20 screws from the back. Then use two M5 x 10 screws to attach them to one of the extrusions (using two T nuts, of course):

OLYMPUS DIGITAL CAMERA

As you can see, these two printed parts make it really easy to set the length exactly the same for all six rods. If you’re using 200 mm rods, like I am, the carbon fiber tube needs to be cut into six lengths of 160 mm each (the printed adapters and joints add 40 mm to the total length). I used 5-minute epoxy to glue the tubes into the printed adapters (shown in yellow above), and the Traxxas joints into the other end. Do one rod at a time, and before the epoxy sets, fit the assembly onto the jig as shown above and adjust so it’s a loose fit. Also make sure the flat parts of the Traxxas joints line up with each other.

Take your time on this step. It’s very important to have all six rods exactly the same length for the best performance of your printer.

Attaching the Effector

Once you’ve finished all six rods, you can move on to attaching them to the carriages and to the effector platform. First attach them to the platform, as shown here, using M3 x 16 screws and nuts (this is looking at the bottom of the platform):

OLYMPUS DIGITAL CAMERA

Next attach the other ends of the rod to the carriages with M3 x 16 screws and nuts, as shown here (make sure the attachment points on the platform are at the bottom, as shown here):

OLYMPUS DIGITAL CAMERA

I used a tape roll on the print bed to help hold it in place, which made the work a little easier.

Print Bed

To make things a little easier, I designed clips that allow leveling the bed and slight adjustments between the bed and the nozzle, shown in the previous photo. These clamps use three of the bed leveling springs from the Printbot Simple, along with M3 x 20 screws and nuts. The nut slot under the frame is tapered, which allows you to trap the nut firmly in place. Before installing the clip, add the nut to the bottom side of the frame and then screw an M3 screw all the way in, pulling the nut firmly in place. Then remove the M3 screw.

Attach the clips to the print bed and then use an M3 x 20 screw through the clip, and then through the spring, to hold the bed in place.

Next Up, Extruder

There are two more parts I expect to publish. Next up will be building the extruder and hot-end mounts, and finishing up the wiring. The final part (I think), will be on installing new firmware onto the Printrboard and getting the printer running.

Saturday, November 30, 2013

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

OLYMPUS DIGITAL CAMERA

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:

OLYMPUS DIGITAL CAMERA

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:

OLYMPUS DIGITAL CAMERA

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:

OLYMPUS DIGITAL CAMERA

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):

OLYMPUS DIGITAL CAMERA

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):

OLYMPUS DIGITAL CAMERA

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:

OLYMPUS DIGITAL CAMERA

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.

OLYMPUS DIGITAL CAMERA

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.

OLYMPUS DIGITAL CAMERA

And the fully assembled printer:

OLYMPUS DIGITAL CAMERA

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.

OLYMPUS DIGITAL CAMERA

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.

Monday, October 14, 2013

3DR “Simple” Delta Printer Firmware Settings

I’m going to take a brief pause from describing the design and construction of my new Delta printer. I have more I need to write up about my printer. Today, however, I’d like to focus on what values you’ll need to change in Configurtion.h for the Marlin firmware designed for a Delta printer.

It started yesterday when I managed to download the delta version of Marlin into my Printrboard, so I was able to test moving of the effector (the platform in the center). I don’t have a hotend of extruder installed yet, but I really wanted to see it moving. At first things didn’t go well. As it turned out, all my problems were lack of knowledge, and once I figured out what I’ve described below, it worked perfectly.

Setting up Repetier

My first step was to setup Repetier. This is actually very simple once you know what to set, but I stumbled across the right settings through trial-and-error:

Printer Settings

Here are the important settings:

  • Printer Type: Repetier uses Rostock as the printer type. This will turn your preview area into a cylinder
  • Home X and Y: Set both to 0, since the hot end will be above the center of the bed when homed (I had them set to Max at first, and only got motion in one direction)
  • Home Z: Set to Max, as the end stops are at the top of the printer
  • Printable Radius: The 3DR is designed for a 170mm diameter print bed, so I set the radius to half that, or 85mm. This may be a little optimistic, and I’ll reduce this once I find out the useable radius

Using Microswitch Endstops

RichRap modified the Marlin software for his 3DR, which uses Hall-effect sensors as end stops. I had to make two changes from his settings in order to get them to work correctly with the microswitches from the Printrbot Simple donor:

const bool X_ENDSTOPS_INVERTING = false;
const bool Y_ENDSTOPS_INVERTING = false;
const bool Z_ENDSTOPS_INVERTING = false;

These need to be false, so the end stops are triggered when you push on the switch. That was pretty clear. However, the next change wasn’t clear to me at first:

#define ENDSTOPPULLUPS

RichRap had this line commented out (which means he had // at the start of the line). So here’s what happened before I removed the // from the start of the line. When I clicked the home button X (so it would only move one stepper motor), the carriage moved up and hit the stop, and then the motor would keep pushing it for a few seconds before it would finally back off. Once I set this value, everything worked perfectly. It appears the end stop would work after several seconds without the pull-ups.

Delta Measurements

There are a set of values you’ll need to enter in order for your effector to move correctly. These values are all based on the geometry of your printer. The only documentation I could find were comments in the Marlin source code. This blog post is to document what I figured out so others won’t have to do it the hard way.

Diagonal Rod

The first is the length of one diagonal rod, measured from the screw hole to screw hole. I made this 200mm on my printer:

#define DELTA_DIAGONAL_ROD 200.0

Effector Offset

This is the distance from the center of the effector (which holds the hot end) to a line that goes through the two holes on one side. In the picture below, my first effector design has a value of 22.87mm (marked as dY), represented by the green almost horizontal line.

#define DELTA_EFFECTOR_OFFSET 22.87 // mm

Effector Offset 2

Smooth Rod Offset

This is the offset from the smooth rods to a plane that intersects the center (which needs to be parallel to the two smooth rods on either side of a tower). This plane is shown in the picture below with a green outline, and the distance is labeled Center Dist, and has a value of 133.54.

#define DELTA_SMOOTH_ROD_OFFSET 133.54 // mm

Smooth Rod Offset 2

Carriage Offset

This is the distance from the outside of the printer towards the center between the smooth rods and the rod ends. In the picture below, it’s the almost horizontal green line (labeled dY) that extends from the center of the smooth rod (not shown) to the center of the screw hole used to attach the diagonal rod to the carriage.

#define DELTA_CARRIAGE_OFFSET 16.5 // mm

Carriage Offset 2

And the Results

Most printers are not perfectly tuned, so either print the parts a little larger or a little smaller. That means you’ll need to adjust the DELTA_SMOOTH_ROD_OFFSET value up or down a little in order to compensate. When this value is not quite correct, you’ll find that the nozzle moves either up or down between the outside of the print bed and the center.

First adjust the nozzle to be the just above the print surface at the towers. Then if you find the nozzle has moved higher (farther from the print bed) when it’s at the center, increase DELTA_SMOOTH_ROD_OFFSET a little and try again. Likewise, if it pushes into the print bed, decrease the value a little and try again. I found I had to increase my number by about 1 mm to keep the nozzle the same distance between the outside and the center.

Here is a nice blog post: Calibrating a Delta 3D Printer.