Author Topic: Homebrew engraver to 3D printer Mod  (Read 12132 times)

Offline BillTodd

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Homebrew engraver to 3D printer Mod
« on: January 24, 2016, 08:53:24 AM »
Inspired by Joules and the other guys with their 3D printers , I have decided to see if I can modify a machine I built toward the end of the last millennium into a 3D printer.

The machine was knocked up in the 80's (many many mods) from bits of an old Repro-Graphic  camera and just about anything I had laying around, with only a drill press and a x-vice.   I had initially hoped it could do light milling but it was only really capable of rather slow engraving.

I'll have to re-jig the X & Y axes : ATM they are driven by M8 screws in backlash free PTFE nuts and will be far too slow for a printer.  Although I have a length of 4mm pitch lead-screw which would be a simple fix . I think I'll just spin the motors around and use timing belts 

I'll have to build a new Z axis but I've plenty of bits that I can use .

The electronics are housed in an old 5 1/4"  external drive box  (the modules were originally  mounted in a PC AT desktop case. With great foresight, I added four stepper drivers.

I have a PC configured with LinuxCNC to drive the thing (the first version ran on DOS based DANCAM ). I think a move to an arduino based REPRAP controller would be the best option , (but are they configurable for step/mm acceleration etc. ?)

Bill

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #1 on: January 30, 2016, 09:11:23 AM »
Not much progress (still recovering from cold/flu) .

I have powered up the LinuxCNC pc which told me it'd been 1475 days since the last update .

Needless to say LinuxCNC would not run  (download latest version ATM)  Given the long print times a stand-alone small controller may be a better option

So,

Of the many  Aduino based controllers on eBay , which would be best for me ? (It will need to be configurable for steps/mm & acceleration etc.)

Any recommendations for extruder/hot end?

Bill

Offline Joules

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Re: Homebrew engraver to 3D printer Mod
« Reply #2 on: January 30, 2016, 10:24:21 AM »
Just go straight for an E3D V6 hotend.  You could machine your own or parts of it as E3D publish the working drawings for the head, so just buy what you don't fancy making.  Extruder, buy in the pinch roller and get someone to print you the rest including the herringbone gears.  I would say go for a Ramps controller as they are so standard and tons of support online for them.  However if you fancy pushing the boat out a bit, look at the Duet controller.  I am totally blown away by this one, however they aren't a cheap option.
Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #3 on: January 30, 2016, 12:04:46 PM »
Thanks Joules, advice noted :-)

what sort of maximum print speed is typical? (mm/s)   swapping leadscrews would be so easy and although it would lack sufficient rapids iit might print ok (?)

linuxcnc is up and running again so I'll see what rpm I can squeeze out the motors.

Bill

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #4 on: January 30, 2016, 04:08:44 PM »
TILT!

 I configured Axis (the linux app)  to run the motors : X and Y fine but no Z...

On investigation I found the z driverr dead and , far worse, the A driver AWOL no chip and even worse, no PIC ( i wrote  a micro step driver running in a pic micro for the z and a power chips)  . I have no idea where the code will be or even if i still have a 16C84 programmer so , game over for these electronics.

I have a cheap three axis stepper driver board which i could use for testing but it looks like I'll be buying a complete driver kit .

Bill

Offline Joules

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Re: Homebrew engraver to 3D printer Mod
« Reply #5 on: January 31, 2016, 04:36:31 AM »
50mm/s would be my idea of max speed.  On small stuff your machine should be running a lot slower than that (controlled by the software) otherwise you start to see poor results.

The speed is very much dependant on the mass you are moving and how accurately you can accelerate and decelerate it.  Any vibration will be ripple and blobs on your model.

Yeah, swop over to belts for X and Y unless you can get 3000rpm out of your stepper motors !!!
Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline PK

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Re: Homebrew engraver to 3D printer Mod
« Reply #6 on: January 31, 2016, 07:36:10 PM »

Yeah, swop over to belts for X and Y unless you can get 3000rpm out of your stepper motors !!!
OK, so this is more of a party trick than a practical application.
In days of yore stepper and servo drives were expensive things, so I spent a couple of years learning how to build them. It turns out, as in all things, there are compromises to be made in tuning simple motor drives.
Here's one I tuned for max RPM.



Offline Joules

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Re: Homebrew engraver to 3D printer Mod
« Reply #7 on: February 01, 2016, 06:35:53 AM »
Wow PK, you even have rpm to spare for those rapids between print.  That should loosen up the PTFE leadscrew nuts !!!


LOL  17khz stepping per axis, so I just need to over clock my LinuxCnc box, a bit
« Last Edit: February 01, 2016, 10:19:10 AM by Joules »
Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #8 on: February 01, 2016, 03:03:59 PM »

OK, so this is more of a party trick than a practical application.
In days of yore stepper and servo drives were expensive things, so I spent a couple of years learning how to build them. It turns out, as in all things, there are compromises to be made in tuning simple motor drives.


Ah-ha ! old school stepper driver (high voltage and tuned !) .
Bill

Offline PK

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Re: Homebrew engraver to 3D printer Mod
« Reply #9 on: February 01, 2016, 05:17:08 PM »
Ah-ha ! old school stepper driver (high voltage and tuned !) .
Not so high actually, an L298 can only handle 46V, I was probably running that around 32V.
Most of the 'trick' is in driving it with a very precise (low jitter) square wave. In this case an $2500 Agilent function generator.

Like I said though, not really relevant in the modern age. Drives now do step morphing, anti resonance dithering and have so much protection it takes skill to let the smoke out. 
Still, I learned a lot about power electronics over that period....

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #10 on: February 07, 2016, 04:21:55 PM »
I'm finding it difficult to find time to do this... However, I did manage to get the belt drive X axis sorted today. I'm getting about 150mm/s &  >2000mm/s/s acc reliably which I hope should be OK.

I'm stil not sure whether to go for a Aduino RAMPS controller  or to try a LinuxCNC version with the bits I have first ,  If it looks like it functions OK,  then I may splash out on a Duet board (if i can find one)

Pictures will follow later
Bill

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #11 on: February 08, 2016, 03:51:35 PM »
OK Bodged converted the X and Y axes to belt and they're working . I've decided to swap the X&Y so the longer axis is Y so that it'll take up a narrower slot on the bench.

ATM I have the 'vice' attached where a bed will go. Somewhere (in some long forgotten place) is a 6mm ally plate that will fit the bolt holes. However....

What is the best material for the bed?  -  I have a selection of ally plate 4-12mm , some perspex ( 5 & 8mm) , a sort-of 'paxolin' fibre plate (~4mm) that maybe too flexible (would need strengtheners)  but is light and would take heat . Ultimately I want a heated glass plate for ABS .
Bill

Offline picclock

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Re: Homebrew engraver to 3D printer Mod
« Reply #12 on: February 09, 2016, 10:11:08 AM »
Hi Bill.

Have you thought of using the glass that you print on as the bed. This is what I have done (see my project log). It is clipped to the bearing carriers with bulldog clips. A clamp holds the glass and connects to the belt. Because this approach minimises weight faster print speeds and acceleration are achievable. I bought an old mirror off of gumtree for 5, which has enough glass for about 6 beds.

Best Regards

picclock
Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #13 on: February 09, 2016, 04:23:27 PM »
Hi Pic,

Yes it will need a glass plate , but I  need to have something under it that will bolt to the two slides. Today I knocked up a piece of 1/4" MDF which looks about the right sort of thickness and is flat-ish.  If I use ally my guess it will conduct the heat away from the plate (did I see you using a cork mat as insulator?)


I've been looking at making the all new Z axis . I have a another piece of type-setter extrusion (same as the slides above) and a few bearing assemblies from old HDDs . I've made nylotron tyres for the bearings and am just in the process of CADing something together.
Bill

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #14 on: February 11, 2016, 04:33:08 PM »
Not too much achieved today.

I managed to take the X axis slide off , cut the excess aluminium off to make it flat , ready to take the new Z axis.

I have decided to mount the Z motor on top of the Z slide so that the screw now goes down with the axis rather than sticking up in the air

Attached is a back view of the latest design idea:  The screw goes into a hole through the back of the mounting plate where it screws into a PTFE nut .  Two of the rollers are mounted on flextures which can be adjusted to close any play to the extrusion.


Still not sure what to do about extruder and hot end  ?   I may have a go at making them   . What are the panls thoughts on Bowen verses direct mounted drive?


Bill

Offline Joules

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Re: Homebrew engraver to 3D printer Mod
« Reply #15 on: February 11, 2016, 05:34:53 PM »
Bill if you just go with PLA you can pick which drive you want.  Bowden is good for speed as your head is lighter and can have better rapids.  If your wanting to print with any springy filament you want direct drive  as ooze and metering are a nighmare with Bowden.
Just get doing and make swarf, you can decide what its going to be later.   :thumbup:

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #16 on: February 12, 2016, 06:50:07 AM »
Thanks Joules,

What sort of speed and force are required for the feed motor?

The ebay hot ends seem to use a 12v 40w heater and what they call a thermistor. Is the thermistor a pt100 typically or is it really a thermocouple?

Bill

Offline picclock

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Re: Homebrew engraver to 3D printer Mod
« Reply #17 on: February 12, 2016, 07:09:31 AM »
Hi bill

Thermistor is usually a glass bead encapsulation resistive element, typically 100k at room temperature, which reduces in value as temp increases. Upper temp limit is normally 300C. Can get head heaters for 24V.

Feed force depends on head temperature/nozzle size/extruded material type. Std 1.75mm filament feeders use 3.5:1 geared reduction driving a toothed 8mm bolt which is about another 8:1. so overall drive ratio is 26:1, driven with a 3-4Kg holding torque stepper.

Best Regards

picclock
Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #18 on: February 12, 2016, 03:25:22 PM »
So just a generic NTC thermistor . How is it calibrated ? I've seen pictures of the control panel showing temp in  degrees F & C .


Hmmm, the force is strong in this one  - looks like I'll have to get hold of some filament and experiment .


Today I mostly made  the Z axis slide  -  turned out OK smooth motion without any play  . I have yet to drill the mounting holes and I stil have a motor plate and nut part to make .
Bill

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #19 on: February 14, 2016, 10:47:36 AM »
Found time to make a motor bracket and mount the Z axis . It moves nicely, albeit at a slow 6mm/s .

The axiz is still too long ATM  but I want to have enough spare movement to raise the X axis to a more useful height should the printer function well ( I would just have to make a pair of new vertical arms)
Bill

Offline picclock

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Re: Homebrew engraver to 3D printer Mod
« Reply #20 on: February 17, 2016, 02:21:16 AM »
Hi Bill

Thermistor measurement is done with a lookup table. It specifies resistance and temperatures at a number of points. Between the table points the graph is assumed linear and the lookup result interpolated. Reprap wiki details this and loads of other stuff.

Try http://reprap.org/wiki/Thermistor

One of the nice things about the whole reprap thing is the freely exchanged information.

FWIW I'm not sure speed in the Z axis is terribly important. Often it may be necessary to wait between layers if making a small item to allow the plastic to harden. Small precise steps are the key here.

Best Regards

picclock
Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #21 on: February 17, 2016, 11:09:23 AM »
Thanks PC,

I've just been designing an extruder.  dual with single motor and auto lift , no idea if it'll work but should be a laugh :-)
Bill

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #22 on: February 20, 2016, 11:57:40 AM »
Extruders get complicated fast !
Bill

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #23 on: March 21, 2016, 07:52:15 AM »
Quick update:

My dual extruder design will not work - had not realised the extruder motor reverses in use  :Doh:
I may as well  just buy an extruder :-(

I have configured and mounted an arduino / ramps board and have the X & Y moving and homing nicely . PSU and Z have stil to be sorted.

Bill

Offline BillTodd

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Re: Homebrew engraver to 3D printer Mod
« Reply #24 on: March 25, 2016, 06:35:15 AM »
ATX supply screwed onto the back of the unit.  BUT...


ATM I have the PS_ON# &  5Vsb going to the PS_ON and 5V  on the ramps board , so the arduino is not powered until I manual enable PS_ON (short it to gnd) . 

Should I link 5V and VCC on the power-control connector to power Marlin when switched on ? (and have PS_DEFAULT_OFF defined in Config.h)  - I am a little concerned at the plethora of 5V rails being shorted together.
Bill