My custom Cartesian

OBELIKS

Oh, I didn't notice the distance.

wilriker

@obeliks Yeah, the recent images are misleading in this aspect.

stewwy

Just converted to a 2mm lead screw, now I can print at any layer height to 2 significant digits without worrying about height accuracy.

i.e. 0.10, 0.11, 0.12..... etc

Previously, with a 'normal' lead screw, the only accurate heights where , 0.1, 0.15,0.2....etc.

first print is on as I type

oops, meant to mention, you are unlikely to need a reduction ratio because the torque needed is much reduced from an 8mm pitch.

Torque needed should be about 25% of what is needed for an 8mm pitch, the number of steps has changed from 400 to 1600.

wilriker

@stewwy said in My custom Cartesian:

Just converted to a 2mm lead screw, now I can print at any layer height to 2 significant digits without worrying about height accuracy.

i.e. 0.10, 0.11, 0.12..... etc

Just did the same today. Images will follow.

Previously, with a 'normal' lead screw, the only accurate heights where , 0.1, 0.15,0.2....etc.

That seems odd to me. What lead did your lead screw have previously? On 8mm lead it would be 0.04mm increments. To get to 0.05mm increments it would have needed a lead of 10mm. I rarely came across this type of lead.

oops, meant to mention, you are unlikely to need a reduction ratio because the torque needed is much reduced from an 8mm pitch.

Torque needed should be about 25% of what is needed for an 8mm pitch, the number of steps has changed from 400 to 1600.

I never used the reduction ratio because of lack of torque. I only used it to convert a physical 8mm lead into a logical 4mm lead.

stewwy

@wilriker said in My custom Cartesian:

That seems odd to me. What lead did your lead screw have previously? On 8mm lead it would be 0.04mm increments. To get to 0.05mm increments it would have needed a lead of 10mm. I rarely came across this type of lead.

You are right, we had a party last night so still a little hazy!

Note to self: don't press submit without thinking it through lol

deckingman

As well as better resolution, you get other benefits too from using a finer lead. Effectively you get better gearing so can use a smaller motor or a single motor to drive say 3 screws via a single belt. The shallower helix angle also means that if you have a heavy bed, it will be less likely to drop under it's own own weight. I did a bit of a write up on my blog almost two years ago which explains things https://somei3deas.wordpress.com/2017/01/31/z-axis-lead-screws/

stewwy

@deckingman said in My custom Cartesian:

As well as better resolution, you get other benefits too from using a finer lead. Effectively you get better gearing so can use a smaller motor or a single motor to drive say 3 screws via a single belt. The shallower helix angle also means that if you have a heavy bed, it will be less likely to drop under it's own own weight. I did a bit of a write up on my blog almost two years ago which explains things https://somei3deas.wordpress.com/2017/01/31/z-axis-lead-screws/

That write up is one of the things that prompted me to order one, so thanks

deckingman

@stewwy said in My custom Cartesian:

That write up is one of the things that prompted me to order one, so thanks

Blimey - that's 3 people who have read it

wilriker

@deckingman said in My custom Cartesian:

Blimey - that's 3 people who have read it

Does that include me already? Because I read it, too.

Phaedrux

@deckingman I read the whole rag front to back when I was planning out my printer. There must be a few of us with more time than sense.

OBELIKS

Definitely, that is a very helpful blog.

deckingman

Strewth - there are 6 of you who have read it!

wilriker

@deckingman I even have a subscription to your blog added in my feed reader, so I get notified of new entries even if you do not announce them here.

timcurtis67

@deckingman said in My custom Cartesian:

Strewth - there are 6 of you who have read it!

Ian,
Add me to the list. Now it's 7 people

lui2004

Hi

Is it possible that you can Upload your config for the anet am8 ?
Because i have the am8 with duet wifi and i dont know how to beginn

Thanks a lot

wilriker

@lui2004 said in My custom Cartesian:

Is it possible that you can Upload your config for the anet am8 ?

Sadly, I cannot. Except for the extruder and the PSU I more or less changed every single part of the printer for something different and I don't have an old version of my full config.g. The only thing remaining from that time is the excerpt I posted in post #2:

M92 X100 Y100 Z400 E96.939                         ; Set steps per mm (at default 16x microstepping)
M350 X16 Y16 Z16 E16 I1                            ; Configure microstepping with interpolation
M566 X600 Y600 Z24 E300                            ; Set maximum instantaneous speed changes (i.e. jerk) (mm/min)
M203 X6600 Y6600 Z720 E3000                        ; Set maximum speeds (mm/min)
M201 X2000 Y2000 Z100 E10000                       ; Set accelerations (mm/s^2)
M204 P400 T1000                                    ; Lower accelerations when printing though
M906 X500 Y500 Z500 E700 I30                       ; Set motor currents (mA) and motor idle factor in per cent (increments of 100mA, rounded down otherwise)

But what is it that you are missing to get your config completed? I am happy to help you with that part (even though answers on the weekend usually are very slow for me).

wilriker

So, some small updates here:
I am in the progress of switching to 24V. The PSU I already have, the bed heater is ordered from Keenovo (200x200mm, 200W, thermostat 150°C) and should arrive somewhen this decade (currently waiting on 5-6 shippings from China partially for over three months). Also heater cartridge is ordered.

Apart from that I am also switching to standby-hot-dual-PSU mode. I currently use an old USB phone charger to provide 5V to the Duet as well as to a small relay board. The relay then switches on and off via PS_ON and will give or cut power to the (still) 12V PSU. It let's me feel again a little bit safer in therms of failing MOSFETs and uncontrollable heaters.
The phone charger will be replaced by a small Mean Well 5V PSU (RS-15-5) somewhen in the next couple of weeks.

Wyvern

@wilriker
If you are worried about the heating element mosfets on the duet, you can install a mosfet tube, it offloads the board, going straight to the PSU and only uses the boad's mosfet circuit as a signal.

That's what I did with my ramps board with my big 310x310 bed, and since I still had the part, I put it on my duet, it allows the board to better cool the drivers since it's the board itself that is the heatsink.

dc42

@wyvern said in My custom Cartesian:

@wilriker
If you are worried about the heating element mosfets on the duet, you can install a mosfet tube, it offloads the board, going straight to the PSU and only uses the boad's mosfet circuit as a signal.

That's what I did with my ramps board with my big 310x310 bed, and since I still had the part, I put it on my duet, it allows the board to better cool the drivers since it's the board itself that is the heatsink.

The bed heater mosfet on RAMPS is awful, it's a very poor choice for this application. The bed heater mosfet on Duet is far, far better. Also, most RAMPS boards probably use 1oz copper for the top and bottom layers, whereas genuine Duets use 2oz copper. So although there are good reasons to use an external mosfet with RAMPS, the same argument doesn't apply to Duet unless your heater draws an exceptionally high current.

The caveat is that the VIN and bed heater screw terminals must stay tight. Use the ferrules we supply, don't tin the wires first, and do check that the screw terminals are remaining tight during the first few days of use in particular.

wilriker

@wyvern As @dc42 said the MOSFET on the Duet are of superior quality and I trust them much more than I would trust any external MOSFET board. I even do have one laying around here from the times when I used the original Anet board.

Also using such a board doubles your chances for a problem because then you have two MOSFETs that could fail (however likely it is that they fail closed) and in both cases it would lead to uncontrollable heating - whereas cutting VIN via a relay (cutting live wire to the PSU) is a lot safer. Of course unless the relay fails open. But since this relay carries only a rather small current it is rather unlikely to fail.