Fisher Build

There were a couple of reasons I decided to try this little delta, firstly since getting my Mendel 3 I've found that I'm become limited by the time it takes to print big stuff and wanted something to print smaller parts, the Fisher stood out not only because of its size, but I realised that the commonality of parts would mean that in times of failure I would have spares... particularity the duet board, which recently feared (incorrectly) Id blown on the Mendel!...also I've spent 30 years working on multi axis CNCs so really liked the idea of playing with a delta!... plus lets face it, once you take out the cost of the 'spare' duet from the price paying the balance for a whole printer is a no brainer!

Because this printer is in beta, before building mine I took the time to review the comments people have made here and did some research into the kinematics of delta machines, even built a kinematic model of a delta in Excel, and also reviewed the RRP design.

For the most part I decided the design concept was pretty good, there are actually very few places where the builder can adversely affect the kinematics, especially if they make sure everything is rigidly assembled and they take some care, compare this to the Mendel and I counted about 50 places where a slapdash builder can have a significantly adverse effect on the final machine performance.

The one place I did identify that the builder can introduce or remove error, and its the one place the instructions gloss over......the position and alignment of the bearing balls.

On the kinematic model I found that small changes in ball positions actually have VERY small effects on the kinematics, which is great, it means they are not so critical.... but they still have an effect, so I decided that during the build I would endevour to position the balls as accurately as I could.

The second weakness that is generally identified by users on this forum is the motors and idler bracket have a tendency to slide up and down the rails, so Ive adopted Bluesign2K's lower motor mount brackets, and have designed my own belt tension bracket that will brace the belt tension force axially along the vertical rods.

A third weakness is with the belt tracking on the idler bearings, some have recommended changing the idler holder to a 4 screw design, which I actually dont like all that much (sorry), I've decided to press ahead with the standard idler arrangement, and if I have issues can see myself trying to do a complete redesign of the idler assembly to incorporate both the tension and tracking modifications.

On getting the parts the first thing I did was assemble the effector and carriages and measured the ball positions, from the drawings I was able to determine that the nominal pitch of the balls was 50mm, which would mean I was looking for an across balls measurement of 56mm, the kinematic theory doesn't care about the actual pitch, but all balls should have the same pitch, and the distance between each set of balls should be the same to ensure the assembly matches the 120degree spacing of an idealised kinematic model.

Carriages

Before adjusting either the carriages or effector its important to look at all dimensions and formulate a plan, its easier to make screws shorter than longer, and using an exacto knife you can make mods to the carriages that effectively make the pitches wider, but this is very limited, its important to have a target dimension in mind before starting, and I settled on 55.7mm

The out the box dimension of the carriage balls was between 55 and 55.6mm, but after some adjustment and fettling of plastic I was able to get them all to 55.6,55.66 and 55.65 which I felt was actually pretty good. Simply adjusting the pitch on its own is not the whole story, I also measured the distance between each ball and the opposite bearing hole (without the bearing in place), this ensured that as well as the bitch being correct it was also central to the carriage

One change I did make was to add a washer between the plastic body and the nylock nut, I found that this kept the screw squarer to the body, as well has having the balls pitched correctly its also good that they are on a flat plane, and I found the washer greatly improved this, if I make a new set of carriages I may modify them to remove the slot that's causing the screws to sit awkwardly.

note, at this stage its not possible to check the distance between carriages, as I hadn't built the frame.

Effector

The carriages were easy..... the effector was a different story

The out the box measurements across the balls were 57.66,56.76,57.3 and the measurements between each set of balls were 20.07,20.86,19.78, in comparison to the carriages its a bit of a horror show!, much of the difference I attributed to the use of different screws, which presumably had much more relaxed tolerances that the screws on the carriages.

After some work on the dremmel I was able to change this to 55.76,56.05,55.75 and 20.99,20.35,20.89... there is one rouge dim in there which I'm going to maybe touch up later, it may just be swarf under the screw.

A tip for anyone attempting to adjust their screws with a dremmel or file this way, get some M3 nuts on put them on the screws between the balls and the nylock nuts, when your grinding down the screws just remove the balls and leave the nut in place, you will find that its handy for cleaning out burrs on the thread end before trying to replace the ball.

To make sure the balls were central I took measurements between the opposite side of the effector body and the balls to try and match them.

Frame

There was little I could do with the frame, and as long as its correct this is a great plus for the design, so it was a case of just assemble and hope, on assembly and mounting the carriages I measured the between positions and got...... 149.39,149.49,149.27.... which frankly I felt was an result well worth celebrating with the beer I had just opened!



The rest of the assembly was pretty straight forward, there are some places where the instructions could be clearer, and my design for the belt tensioner meant that I cant remove the top plate.... but then I didn't really have to, and unlike on my Mendel 3, there was plenty of fasteners of the correct length...

The build took me probably 8 hours, 3 hours of this was spent adjusting the ball positions, and because I printed the plastic parts beforehand I spend some extra time fettling them before I got the hardware kit.

Overall this is a really tidy looking machine, really neat and compact, I've not actually applied power to it yet so wont comment about whether any of my additional work has been worthwhile, but it certainly should not have an adverse effect.

The kit itself came well packaged plenty of fasteners of the correct length with few to spare, and the only defective part I found was a ball without a thread tapped in it!, and frankly I spend more time trying to fit it to a screw before I realised the problem than I would care to admit!, fortunately there was an extra ball, at this time I've not tested the electronics yet so can't comment about errors with the wiring (I found several in my mendel kit!)


some minor gripes.....

- Not keen on the way the fan is held to the effector
- not complaining, but really didn't expect a hardware only kit to include the 3d printed plastic for the extruder.
- logos I printed didn't fit, need to print some downsize ones
- broke a small piece of plastic from the central plate of the effector, one thing that's to be learnt is this plastic needs handling like glass!
- manual adjustment knob for extruder I printed didn't fit, need to print an oversize one.
- Don't like the way the cable routing is too close to the one carriage, I need to do some rework on cable routing before commisioning.
- Have some suspicions about the bed switches, don't like the way different places on the bed require more force to activate than others, I suspect this may contribute to some calibration issues.... may look up DC's IR probe for this one!
- The limit switch wiring sucks, will be fixing that with some solder before commissioning tonight!
- Never use ball end allen keys to tighten tiny grub screws (amateurish error I made and at the time knew I was going to regret...and now do!)
- maybe the design of the ball assemblies could be better so they can be adjusted without using a dremmel, how about threaded rod instead of screws, or just replace the screws with ones that are more consistent.
- whilst I appreciate the cost I think that replacement of the plastics in the arms effector and bed plate will go a long way to improving the durability.
- maybe redesign the carriages to remove that slot where the ball screws go, or include the washer I used into the build instructions.
- no base plate!

Edited 1 time(s). Last edit at 08/26/2015 01:29AM by bgkdavis.

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RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

Commissioned my Fisher last night and the best calibration I got with the 6/10 probe was 0.15, which seams to be the ballpark for a stock Fisher and my efforts may not have reaped much in the way of rewards, but at least I'm fairly confident that the machine is built at least as well as its possible to build this kit, looking forward to improving it further though, Im still learning the ropes witho operating this machine, but Ill post some better data as I understand how to obtain it.

I did run a couple of prints off, the robot was OK, there were a few heat issues with the overhangs, but it looked reasonable, and I made a spigot ring for my filament spool, which works reasonably well.

The prints were frankly meh, but for first prints I guess were good and may of my problems may just be S3D settings.

I had some problems with bed height which I compensated for by changing first layer height.

I opted to not used the buildtack surface yet as Id rather not gouge it whilst I'm playing, so have been using painter tape, which has a great adhesion on this machine.... maybe too much adhesion in fact, but this may be a characteristic of the sun filament, I have other filament that is not so adhesive

Somehow I got one of the side panels on back to front, its the panel without any switches mounted to it, got no idea how I managed to do that as I was sure I took great care to get them the right way round!...FAIL!

nearly lost one of the bed springs, maybe some hotmelt will help keep them in place?


a few points to note

- The calibration needs to recognise that if the switch s open before calibration starts then there is an error, not just blindly proceed with calibration, or at least if there is an option for NO/NC switches, it needs to look for a change in state
- The visible bed temperature is annoying, I notice that ZPL has released a firmware version that hides this.
- DCs calibration instructions needs better visibility, took me way too long to find it
- If we are going to try and collectively resolve calbration issues we need a common process, with common calibration files

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RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

0.15mm sounds high to me. Have you corrected for the different probe trigger heights at different points on the bed?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Indeed. You should be able to get better than 0.15. I'll upload a copy of my SD card when I get to a PC, but essentially I don't set any probe offset when probing the 9 radial points then I set an offset of -0.2 (if I remember correctly) to the centre. This is enough to get the build plane flat, then in my start code I call the setz.g macro from the latest RRP SD. This then sets z=0 at the right height.

I'd install the BuildTak too, I had some pretty heave crashes when I was first getting myself familiar with the machine and Diet macros, but I didn't experiance any significant damage. The feint marks from numerous successful builds have long covered any marks. The important thing is to stick the HillsDale of the flattest side of the bed - ignore the RRP instruction about which side to put the balls and BuiltTak, its way more important to get a flat plane.

Quote
dc42
0.15mm sounds high to me. Have you corrected for the different probe trigger heights at different points on the bed?

nope, just looking into that, saw some info about it earlier, but not entirely sure of the process

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RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

put

G31 Z-0.25

before the last probe and now down to 0.081

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RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

Quote
bgkdavis
put

G31 Z-0.25

before the last probe and now down to 0.081

Using my more recent firmware versions, you don't need to mess with the G31 Z height, you can use the H parameter on the G30 commands instead. I suggest you set the G31 Z height in config.g to be correct at the centre of the bed, then use positive H corrections for the other points. The probe points midway between towers will probably need less correction than the ones next to towers.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

yeah, I was wondering about that....are the H values negative or positive?

---

RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

The H value can be negative or positive. It is the amount that has to be added to the G31 Z parameter to get the actual trigger height at the XY coordinates of that G30 command.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

After a single calibration cycle got down to 0.045



bed.g file

G30 P0 X-65 Y-37.5 Z-99999    		; X tower
G30 P1 X-52 Y30 H-0.15 Z-99999         ; between X and Y towers
G30 P2 X0 Y75 Z-99999     			; Y tower
G30 P3 X52 Y30 H-0.15 Z-99999        	; between Y and Z towers
G30 P4 X65 Y-37.5 Z-99999                  ; Z tower
G30 P5 X0 Y-60 H-0.15 Z-99999       	; between Z and X towers
G30 P6 X-32.5 Y-18.75 H-0.2 Z-99999  ; half way to X tower
G30 P7 X0 Y37.5 H-0.2 Z-99999    	; half way to Y tower
G30 P8 X32.5 Y-18.75 H-0.2 Z-99999   ; half way to Z tower
G30 P9 X0 Y0 Z-99999 H-0.3 S6           ; centre, and auto-calibrate 6 factors

config.g settings

M665 R81.0 L160.0 B75 H180			; set delta radius, diagonal rod length, printable radius and homed height
M666 X0.0 Y0.0 Z0.0  			; put your endstop adjustments here

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RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

Here's my latest SD files along with the matching S3D profile...

Thanks for the S3D files, Ill look at it later, mostly interested in your speed settings

here is the photo gallery, wont bore you with pics of stock fisher parts....




Edited 1 time(s). Last edit at 08/27/2015 06:01AM by bgkdavis.

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RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

I like your method of retaining the top of the rods / belt tensioning. I think I'll do something similar on mine - while grinding the rods and making acrylic stops for my test machine worked, your method seems to require a whole lot less effort.
Can you show some pictures of your spool holder? I don't use the roll holder on the Fisher as I think it risks compromising the geometry too much. I currently just use the box that the roll came in with a Biro stabbed through the side to act as a rudimentary axel... it works, but it's a dirty solution.

I'll post my build log and pics tonight...

The spool holder is really simple, I have a box full of 1/2" balls and made two races, the orange part is deliberately separate so I can make different adapters to suit different spools, and was actually my first Fisher print after the robot

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RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

http://www.thingiverse.com/thing:970132

Here is a 3d printed effector. 2 piece.

Bought Fisher full kit at model engineering exhibition, can't get my head around not having any plans kit still in box ?

Quote
Dave Wellington
Bought Fisher full kit at model engineering exhibition, can't get my head around not having any plans kit still in box ?

Have you looked at the build instructions at [reprappro.com] ?

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
zaccom
http://www.thingiverse.com/thing:970132

Here is a 3d printed effector. 2 piece.

Ive seen your file, but I think if I go down the road of a printed effector I wll be redesigning the ball mounting to make them easier to adjust, and would probably look at incorporating the fan duct parts too.

---

RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

A R M - A G E D D O N

carp!!!!



Fortunately I thought ahead and bought some spares from RRP...wish I bought more!

I've also just bought some carbon rods and 6mm ball end sockets, I'm going to make some better arms!

---

RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

I've made some improvements to my filament holder hand published it

[www.thingiverse.com]

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RepRapPro Mendel 3 Tricolour
RepRapPro Fisher
-Carbon Arms
-Easy adjust Carriage+effector
-axis stiffness mods
HE3D -600 delta
-Duet 0.8.5
-PanelDue
-DC42 Height probe
-RobotDigg metal components
Simplyfy3D
RS Design Spark CAD

Thanks for the holder !