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ThomasHeb / 4AxisFoamCutter

Arduino based CNC foam cutter with display and SD-Card
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Slight confusion with modifications and connections to ramps1.4 board #5

Closed goos766 closed 3 years ago

goos766 commented 3 years ago

https://ibb.co/88wLdn4 I am not sure if I understood your connection description correctly. Therefore, I am sending you this diagram to confirm that it is correct. I would be grateful if you could point out the errors in the diagram. I know that I mixed up a bit in the connections to the 100nf capacitors at the ends stops, because I didn't read it carefully. One more question, what should 100nf capacitors look like, what should I really look for? From what I've read, I conclude that I should solder one 100nf capacitor for each of the four ends tops, connecting the signal and ground. Can you provide details, so I don't make a mistake and burn the board when buying wrong parts, can you send a link? Is using an external MOSFET like in 3d printers incompatible with your firmware? The external MOSFET seems to keep the PWM functionality. I am asking you as an expert in this matter because I know little about it. You can answer me in German, Google will surely help me. I am very keen to get ahead with the project. My only regret is that I can't use your software, and I don't have programming skills to convert it to PC. It looks very interesting from your videos.

ThomasHeb commented 3 years ago

First of all, sorry for my late reply. I know that is frustrating, if a project get's sucked.

Your wiring has some errors.

You are the second guy asking for a windows version of the post processor. If someone can do the user interface, I could support with a common/universal class file for the post processing functions.... let's see what happens in future...

I have checked the arduino/ramps and hardware with some files from Keith and all worked correctly. So there is no need for the post processor. Just checkout https://www.rckeith.co.uk for some tools. And google for "foam cutter excel" and you will find some very clever solutions based on standard office tools.

If you have any further question, feel free to ask.

goos766 commented 3 years ago

To begin with, I want to thank you very much for your effort to write such a wonderful description. For now, I am waiting for a few more parts that have been sent to me from China. At the moment I am designing my version of the foam cutter based on the rckeith.co.uk design. I will try to deal with electronics soon.

image

goos766 commented 3 years ago

ramp 16 hot wire

I made corrections to the wiring diagram.

goos766 commented 3 years ago

ramps foam cutter My miniature version of the foam cutter controller

ThomasHeb commented 3 years ago

Hi,

wiring looks much better. I only found Z-/Z+ to be swapped: Z- goes to D4, Z+ to D11. I use two LEDs on D65 (Hotwire) and D66 (Speed). This indicates if the wire is on or if I switched to seek speed (positioning menu). But they are not a must.... you will see it, if the machine goes fast and you will smell it, if the wire is on ;P

It is a very good idea to include the button on the display in your design, If you have any wishes (placing a function like homing on it,...), let me know.

Please be aware, that you select most of the menus by pressing the rotary button. This needs some force, so everything has to be stable and should not tilt.

Overall this is an awesome design! Thanks for sharing.

goos766 commented 3 years ago

The case design is a cluster of models from thingiverse.com. As for the stability of the housing, I am going to add tabs for the screws. The button on the housing of the screen is the reset button, so I think I can select the homing function from the menu. If I have no problems with uploading the software. At the moment, I am still struggling with the mechanics of printing parts and selecting the cheapest and best solutions for it, trying to maintain the functionality and rigidity of the structure. I have a few ideas that I need to verify in reality. Don't just watch them on my computer screen and theorize that the solution will definitely work. In addition, I have to adapt to the availability of materials in two countries (UK and Poland) if I damage something and I need a quick replacement of parts, regardless of the place where the machine works.

ramps foam cutter

ThomasHeb commented 3 years ago

The tabs for screws are a very good idea. Maybe you can separate the green and the yellow button fields a bit and add a raised stabilizer between from top to bottom. Keep the two wires and connectors between displayboard and ramps in mind. I think it is very useful to have a connector between the electronics and the mechanics, so I added a sub-d connector to the housing (walls must be very stable in the area).

The outer design is very compact.... good job.

goos766 commented 3 years ago

The top cover with buttons is quite thick (3.60 mm) on its own. Additionally, underneath, as you can see in the photos above, there are slight bolds around the buttons and lines connected to them, which theoretically could be exported as a separate STL file as surfaces overlapping the printed part in Cura, to apply e.g. a different infill or other density treatments to strengthen this top cover. It seems to me that with such a small area there should be no bending under the influence of pressing the buttons. But I'll do some tests and let you know.

ramps foam x

goos766 commented 3 years ago

After uploading the firmware, it surprised me that the reset button on the screen does not work like on 3d printers. Now I know what you meant by saying that you could assign to this button a function other than its default function, which is reset. One more small thing in the menu with the slicing function, you can not return to the main menu, maybe because I did not change the firmware of the controller operation without buttons or maybe because I haven't connected the stepper motors and end stops yet.

ThomasHeb commented 3 years ago

Hi Goos,

if you use the slicing menu, you select the cutting direction with the buttons, or setting max positions or back travel. you need to have a back button. So slicing makes only sense without the buttons (and the steppers). limit switches are not needed for slicing.

Similar with position menu....

You can quickly define the onboard button as back button inside led.cpp, change

define BTN_ONBOARD 0x00000001

to

define BTN_ONBOARD 0x00000080

I would recommend to follow the next steps:

Congrats that you made this big step!

goos766 commented 3 years ago

I'm glad you answer me at all. I appreciate your willingness to help strangers. I am pleased with your every answer and your time devoted to dealing with my problems.

goos766 commented 3 years ago

A question from a series of unnecessary questions: where did you put the fan? If you used a fan connection only to cool Ramps 1.4 then why not keep it on all the time while the unit is running. You made a separate menu for the fan; does it mean that I should place the fan somewhere else? For example, to cool the hot wire after finishing cutting. Inspired by your video, I made a fan like yours in an electronic's housing. But now I am wondering if the fan should be located only in one place of the device and if it is possible to connect several (e.g. two fans) to a single power connection (D10) without overloading the device.

Do I have to generate all files only with Sketchup? Is your firmware also compatible with devFoam2 (accepts files from it) how much would I have to reconfigure the program (devFoam2), is that even possible? I am asking this because your swift program is not available for windows, and I am not really going to cut wings for RC airplane models, I am thinking of something much simpler.

I should probably ask these questions at the beginning of the project, not in the middle of it. But the excitement in my head reached its zenith and with little thought, I got down to the work without detailed information about what I will do when the device is ready. What are my software selection options, do I have any?

ThomasHeb commented 3 years ago

Hi Goos,

category „afterwards you are smarter“: I saw fans in some other videos, cooling the stepper driver and the powersupply for the hotwire. So I placed some fans, wrote a small interface to test them (fan menu), with the idea that you can control them later on via gcode and found out, that nothing is getting hot...... so they are not used at all in my design.

The foamcutter works fine with devfoam2. Keith gave me some files to test and all of them worked very good. You can use the gcode files on sd card or the usb interface as gcode sender. Check out the page of Keith for some tools. Search the web for foamcutter and excel..... in the end the gcode is very simple. If you want, I can send you some simple files from my post processor for testing.

Software or tools.... you are not limited to my solution. I am just a Mac only user, with no computer in my workshop. So I decided to ADD sd card to the grbl on the arduino - sending gcode via usb is still working. on the other hand I wanted to use SketchUp, so I wrote this tool and the post processor for MacOS. But you can use all other software like devFoam, Jedicut,.... gcode is simple and most of them have the gcode sender already included.

If you want to cut simple shapes, like letters, you only need coordinates around the letters (this I do with Sketchup), add some offset and control commands for the machine (post processor). So you can go for a simple CAD program with Excel post processing.....

May I ask what type of shapes you want to cut?

bye the way.... you can include the power supply to your housing. so you only need to connect on supply with app 30VDC direct to the hotwire. the internal supply is then used to drive the arduino and the stepper with 12VDC. I used https://www.amazon.de/gp/product/B00HV4EPG8/ref=ppx_yo_dt_b_asin_title_o07_s02?ie=UTF8&psc=1

goos766 commented 3 years ago

Initially, I was thinking about cutting letters and vector graphics, but who knows, maybe in the future, when I get to know the operation of the machine and become confident in what I am doing, I will start something more complicated. I prefer to leave myself this margin for expanding the possibilities over time, while keeping the same state of the machine, maybe with some minor modifications / improvements. As for the previous question, I must admit that it is very good news that I can choose the software, to be honest I started to be a bit concerned about the sense of the whole project. I chose your software version mainly because the machine is computer independent. I am not a fan of a connected (dedicated only for this purpose) computer to any type of CNC machine.

ThomasHeb commented 3 years ago

I am pretty sure, that you will be able to do your projects with minor modifications on your machine. I try to make a small video demo with SketchUp / Excel over the weekend.

ThomasHeb commented 3 years ago

simple_sample I added an example for text with SketchUp / Foamcutter.rb, w/o post processor to GitHub. Check out the main section at the lower end and the video https://youtu.be/lMjuI5fZvUQ. Feel free for any further question and have a nice weekend.

goos766 commented 3 years ago

20201009_214918 20201009_215023 I'm making very slow progress and still don't have all the electronics parts. And 3d printing is not one of the fastest parts of this project, especially with the amount of plastic needed to obtain good stiffness of these parts.

ThomasHeb commented 3 years ago

this looks awesome!

goos766 commented 3 years ago

This time, the theoretical question about the power supply: is it necessary 30 volt power supply? Do calculators that can be found on forums related to the topic of selecting hot wire have any positive reflection in reality? Calculators show that the number of amps is more important than the number of volts And what material the wire is made of to obtain the desired resistance at the given cutting distance. The wire thickness is calculated based on the available amps and volts of the power supply, but with Ramps 1.4 we only have 11 amps output available, I believe. I think I can choose the thickness and type of wire to power the entire device from a 12 volt 30 amp power supply, as I mentioned before using a MOSFET to bypass the eleven amp throttling by Ramps 1.4. At least in theory according to the calculator, even the 11 amp output from Ramps 1.4 is sufficient to heat a hot wire at 12 volts.

How did you choose your cutting wire? How thick do you use the power cables for ramps 1.4 and cutting wire to keep it safe and not burn down the house?

I'm not sure if that's all what I wrote makes sense.

ThomasHeb commented 3 years ago

I was worried about the power required for the hotwire, too. I bought a proxxon hotwire from my local workshop to did some tests. I have a wire length of 85...90 cm. With 27....28V DC, power setting 90%, results in 0,6 .... 0,7 Amps. Normal styro (the white one), I can cut with 300 to 500 mm/min. XPS (the good stuff) is working with 100 mm/min. So for my application, 30VDC power supply is perfect and a simple DC/DC converter supplies the arduino and the stepper with 12V at 0,5A to 1A max (measured on the 30V input.... so app 2A on the 12V side).

To heat up the wire, you need power (volt x amps). longer wire needs more power (linear relation). with the voltage you can control the amps (amps = voltage / wire resistance). wire resistance is related to diameter (thiner = more resistance), length (longer = more resistance, linear relation), material. You can control the hotwire with a constant current source (constant amps). But in the end this source must be able to deliver the voltage, too. and with the assumption, that the hotwire resistance is some how constant, you can use a much simpler voltage source to control the hotwire. Simplest voltage source is a power supply with a PWM MOSFET.

The proxxon wire has a relative high resistance and is good for short wire length. I prefer low temperature and slow feed speed for complex shapes. If my proxxon wire length would be 1,6m, I would need 60V..... so not working with my supply. Proxxon hotwire has app. 14 ohms / foot (calculated).

How long is your wire length? Based on that, I can make a calculation.

I would recommend some tests, too: Use XPS foam. Wire length is diagonal length of your machine + some cm. Your powersupply should have less than 60 VDC output (safety), 30V are cheap, 12V, too. Mark a distance of 100mm on the foam. Heat up the wire and put the foam on the wire. the wire should cut the foam with minimal force and nearly no bending of the wire. Adjust the Voltage for the tests between 50% to 90% of our power supply. Test different wires. You should find a wire, which gives gut cutting results at app 80...90% of the selectable voltage of your supply. this leads to minimal currents and a good efficiency.

Hotwire on amazon: https://www.amazon.com/s?k=resistive+wire&__mk_de_DE=ÅMÅŽÕÑ&ref=nb_sb_noss_1

Proxxon Hotwire: https://www.amazon.de/Proxxon-28080-Ersatzschneiddraht-Thermocut-Rolle/dp/B0016ODWWC/ref=sr_1_1?__mk_de_DE=ÅMÅŽÕÑ&dchild=1&keywords=proxxon+28080&qid=1602468872&s=diy&sr=1-1

XPS: https://www.hornbach.de/shop/XPS-Hartschaumplatte-Precit-300-G-1250x600x30mm/5097832/artikel.html

goos766 commented 3 years ago

I checked with online calculators how to choose a power cable and found out I have to buy 14awg / 2 mm2. Choosing a stainless steel as cutting wire, which has lower resistance than, for example, kanthal wire. I wonder about the distance between the towers of about 60-70 cm and a wire thickness of 0.36 mm. At least this is what calculators say, so I can still only theoretically say that I am prepared. The more I think about how the machine should work (I mean motion), the more corrections I can see. Some of these fixes will appear on their own. One thing that puzzles me is that you can't regulate the voltage too much on (hotwire). According to the calculator, when the voltage (V) decreases, the current consumption (A) increases and you can draw more amps very quickly than the power supply can give. I think the purpose of this calculator was to set the fixed voltage and current for a given type of wire and its length. I already have kanthal wire in my house of various thicknesses that I collected during my e-cigarette adventures. https://www.scribd.com/document/442721369/VTDIYHotWireCalculatorVer14bpub-xls

image image I have these two MOSFETs, I don't know if they will work and if I still have to cut pin 10 using one of them. Both models use the same components, the only difference is the larger heat sink in one of them (I have these mosfets for 4 years and only now I noticed that the larger one has the ability to connect the fan on the board itself).

My machine is to be about 120 cm long and 65 cm high. The electrical connections scare me because I'm not sure what I'm doing, I always have to check three times before I plug something in to see if it matches the diagram and sometimes I can't even measure it (I just don't know how). I know how to check the volts, the connection between the wires if there is no short circuit, I can do it with the wire resistance, but I don't know how to check the amps. The amount of small things that I still have to buy or design is also a bit scary, but I try to limit to what is necessary, it still seems to me that there are parts that I do not have or that I need something more. But I set myself a limit to not spend more than £200.

ThomasHeb commented 3 years ago

Hi Goos,

the calculation sounds strange. If you reduce voltage, the current will reduce, too. this is physics (trust me, I studies electronics). stainless steel wire won‘t work, you need NiCr wire. My wire length is about 85...90 cm ( tower distance is 72 cm) and I use the Proxxon 0,2mm NiCr wire with 28V x 90% Powersetting x 0,7A = 18W. easy to control on the ramps! The Excel you are using is trying to keep the Power per inch on the wire constant (W). but this is only for choosing a wire, not for controlling it later on! in my equation above, you can replace the Amps by I = U / R, so Volts x Volts x Powersetting (0....100%) x Powersetting / total wire resistance = actual power in the wire.

On my machine, I get app 35 Ohm total wire resistance (28V x 28V x 90% x 90% / 18 W). With a length of 90 cm, I have 0,39 Ohm/cm or app 1 Ohm/inch or 11,9 Ohm/feet

On your machine: Total wire length is app 1,6m (120 x 65 x 65). with power per length as a constant...... you need 18W x 160cm / 90cm = 32W. assuming you take a 30VDC powersupply, running it on app. 28V. with a powersetting of 90% in the foamcutter (my configuration).... 28V x 28V x 90% x 90% / 32W = 19,85 Ohm total wire resistance. or 19,85 Ohm / 160cm = 0,12 Ohm/cm = 0,315 Ohm/inch = 3,66 Ohm/feet this should work: https://www.amazon.com/Kanthal-A1-Gauge-Resistance-Wire/dp/B07CHYL39X/ref=pd_bxgy_img_2/144-9922268-4104130?_encoding=UTF8&pd_rd_i=B07CHYL39X&pd_rd_r=6c963cc2-a31d-4869-a382-a52f86ecd330&pd_rd_w=iaf9G&pd_rd_wg=S6LD3&pf_rd_p=ce6c479b-ef53-49a6-845b-bbbf35c28dd3&pf_rd_r=GWN8A698W3J3EYBCJQSK&psc=1&refRID=GWN8A698W3J3EYBCJQSK maybe you can find a wire with 0,2mm thickness and a resistance of app 3,5 Ohm / feet.

Current required maximum (30V and Powersetting =100%): 30V/19,85Ohm = 1,5A. The ramps can handle this...no fan is required. you do not need to cut pin 10. Calculation with the recommended wire: total resistance 16,8 Ohm, max current 1,7A @ 30V. No problems.

wires from ramps to hotwire and powersupply to hotwire. I use AWG12 because I had them here... AWG14 is fine.

You should continue with the project. everything looks fine and the details can be solved. If you want, I can support you with the electronics. I have a ramps, all cables, parts and the powersupplys here. Let me know and I can do the modifications, test the board and send it over to you and put some cables and connectors in the box, too. (as always I ordered 5x more than I needed).

goos766 commented 3 years ago

I am looking for the cheapest solution, but as a beginner in this matter I can not verify whether I should buy a laboratory power supply, which, even on aliexpress, is a bit too expensive for my budget. I have also seen people who use a toroidal transformer (230V 250W output voltage 2x30V, 2x4.16A) but here there is another problem that I do not know how to connect it, without burning the entire installation in a few seconds, not to mention PWM voltage control. I cannot avoid the need to connect two independent installations in an easy way. This is getting more complicated and more expensive than I thought.

ThomasHeb commented 3 years ago

Hi Goos,

a laboratory power supply is a good solution, if you will work on similar projects in future. for this project a compact supply works, too. you will need app. 2...2,5A, or 70...80W. check out the LRS-150F-24 or LRS-150F-36 (20...25 EUR) both can be adjusted to app. 28V and have 150W. these are clearly marked how to connect. but never the less, get in contact with an electrical specialist to check right grounding and fusing and protection and ....., to ensure safety.

https://www.meanwell-web.com/en-gb/ac-dc-single-output-enclosed-power-supply-lrs--150f--24

toroidal transformers need additional electronic components to generate DC, so you will not save money nor time.

goos766 commented 3 years ago

So I don't need to look for something that is 10A or even 30A. Even 4.2A is enough. Should I treat this as a separate power supply for the cutting wire only?

I am trying to understand this whole installation and I have one unknown how many amperes are consumed by Ramps 1.4 itself (but it will probably be related to what stepper motors I will use, including the screen, diodes and fan), theoretically I already know how much the hot wire itself consumes (because you wrote about it before). I am writing this because I wonder if the whole connection should not be reduced to your original schematic with one difference, i.e. using a mosfet, but it also seems to be a questionable solution. It would power all of this by one power supply of the model you provided earlier. It all boils down to one question, whether this one power supply will be able to power everything previously mentioned.?

I know that I ask a lot of unnecessary questions and that it seems tiring. You still have to explain the same topic to me ad nauseam. I'll try not to burn anything and calmly analyze your calculations. Thanks again for your help.

goos766 commented 3 years ago

It turns out that this is my fault and my problem with superficial reading of the text. I have re-read everything you wrote and will try to buy the power supply you suggested. Sorry again for not reading carefully. Thank you for your effort in describing everything I ask in such detail, although sometimes I don't understand everything and it's not about the language but about the electrical stuff.

ThomasHeb commented 3 years ago

Bildschirmfoto 2020-10-13 um 22 29 40 Hi Goos,

you don‘t need to worry, theoretical it is really hard do get everything. I go downstairs and check it. 2...2,5A is the complete consumption, including hotwire, ramps, stepper,.... You should choose a bit bigger supply, so that you do not need any fans there. This supply if for everything. Complete setup looks like this. General powersupply: 100...250V AC to 28VDC >4A for general supply and hotwire DC/DC converter from 28VDC to 12VDV for stepper, ramps, fans....

Stepper/Arduino/Ramps will need app 17W (28V x 0,6A, regulated to 12V x 1,4A) Hotwire app. 35W (28V x 1,25W) Total: app. 2A... so a supply with 4...6A or 100 to 150W is perfect. The hotwire works over the ramps, no need for an external MOSFET.

I can build up and wire arduino, ramps (modified with Cs and Pin10), DC/DC converter and all connections, test it and send it to you.

General powersupply: https://www.meanwell-web.com/en-gb/ac-dc-single-output-enclosed-power-supply-lrs--150f--24 DC/DC converter: https://www.amazon.de/gp/product/B00HV4EPG8/ref=ppx_yo_dt_b_asin_title_o01_s01?ie=UTF8&psc=1 IMG_4580

goos766 commented 3 years ago

I am grateful for proposals to send me equipment, but I must politely decline. I respect someone's money and I know that earning money is not easy. I would feel guilty accepting the presents, knowing how much effort it costs. It seems to me that I am able to finance this project myself. Thanks again for this generous offer.

It's not that I don't have ramps 1.4 and Arduino I just wanted to save myself some irreversible changes (like cutting off pin 10). One more change that I made was that I bought the Ramps 1.6 (this board has only one input instead of two (5A, 11A) as in version 1.4) versions instead of ramps 1.4, but not the 1.6 plus. So in this case, cutting pin 10 off probably won't do the job. I still have two old ramps 1.4 SB boards that I would like to use only as a last resort. So I guess the use of this mosfet would be less invasive and I would use the unused parts from the old 3d printer which has been replaced with Ender 3. To be honest I'm a bit afraid of directly plugging ramps 1.4 board over 12 volts unless I order some Chinese rams board 1.4 together with Arduino Mega for testing only. One more question, how can Ramps 1.4 pass that many volts through input 11A and nothing will emit the magic smoke?

ThomasHeb commented 3 years ago

Hi Goos,

my offer is more a exchange.... modified ramps for unmodified, just to help you to get the system running with all the electrical stuff.

ok, now I got your issue. But it is not about the MOSFET on the ramps 1.4/1.6. Its about the voltage regulator on the Arduino and the Stepper. So sorry for my new tipps & tricks..... a bit like crazy new ideas every day.

There is a linear regulator on the Arduino and with more than 12VDC (supplied over the ramps) it is getting overheated. And the stepper should be supplied with 12V, too. But for the hotwire I designed for 28V (in my design to keep the current low) or you reduce the wire resistance to app. 1,6 Ohm / feet. Then you can supply the current from a single 12V source over ramps 1.6 (use hotwire with app 1,6 Ohm / feet) Current will climb to 2,7 A for Hotwire and 1,4A for Arduino/Stepper/..., so total 4,5 A (My supply can only drive 3,5 A, that's why I went for the low current solution).

You can use the LRS-150F-12. https://www.meanwell-web.com/en-gb/ac-dc-single-output-enclosed-power-supply-lrs--150f--12?returnurl=%2fen-gb%2fsearch%3fq%3dlrs-150f-12%23lrs-150f-12 you do not need a DC/DC Converter in this case.

To your question of 28V on the "11A" input. The input is separated from the rest of the circuit on the ramps 1.4 (not on the ramps 1.6), only a common ground. the MOSFET just closes the the hotwire to ground (inner circuit: 28V Input - fuse - connector hotwire - connector hotwire - MOSFET - ground), the MOSFET itself can manage more than 50V and has a very low inner resistance. So low current over the MOSFET means cool MOSFET. but even with 2,7A you are far away from overheating this MOSFET. And ramps 1.6 has a cooling mounted on the MOSFET. Only an onboard LED is in that circuit of "11A" but the preresistor with 1k8 is high enough to prevent any damage.

Cutting and rewiring Pin 10 is only for the fan. you don't need that fan. build the fan in your enclosure but do not wire/connect it. Leave the pin 10 as it is. I do a test with a unmodified ramps 1.4 to check if it is working without the fan and if not, you get a modified firmware. This will work with ramps 1.6, too, when you use the 1,6 Ohm/feet hotwire and a 12V power supply.

goos766 commented 3 years ago

More resistance means thinner cutting wire, or I get it wrong again. I currently have a 12v 30A power supply (at least this is what it says on the sticker), which in the past I was supposed to use for a 3d printer in the ramps 1.4 configuration in case it broke something inadvertently and I needed a quick replacement, but it did not happen so I have a new one / unused.

For now, I am trying to solder cables to use parts lying around unused for several years. The key idea here is to connect DuPont plugs with JST plugs, it could be done probably cheaper using a crimper, but in recent years I have bought a few crimping tools and never suitable for such small things. I have some female to female DuPont cables for which I did not find any use and some JST cables left after the ender 3 cabling modifications. I figured I wouldn't be spending my money again on something that would come in about 2-3 months if at all. So I cut a few cables and solder them now. It turned out that it will probably be a more elegant connection for stepper motors and end stops, and for buttons (with the difference that buttons and end stops do not need JST connection).

ThomasHeb commented 3 years ago

Hi Goos,

more resistance means thinner cutting wire, correct.... but if you go from 28V to 12V you need less resistance, to get the required power on the wire (32W = 28V x 1,4 A = 12V x 2,7A). This may lead to thicker cutting wire. My 12V recommendation is https://www.amazon.com/-/de/dp/B07CHX4MMT/ref=psdc_495310_t2_B07CHSG169 Diameter is 0,64mm..... I remember, that's why I have chosen the proxxon with 0,2mm and played with the voltage, too.

I cutted all connectors, too and I am using standard pin connectors 2,54mm male/female as connectors. Glue them together and where needed some isolation ;)

I finished the test with the unmodified Ramps 1.4 board. Standard firmware without modifications: You do not need to cut Pin 10 as long as you don't use a fan. Appending some screenshots. You see that the internal MOSFET stays very cool (10 minutes, ambient temp. 18°C, no fans active). So Ramps 1.4 and Ramps 1.6 will work fine. I would only recommend to add the Cs for EMC compensation.

28,5V / 0,9A: stepper + Hotwire 28,5V / 0,38A: stepper (10,83W) Values are a bit different because of different ramps/arduino and because I did not do all parameter settings.

Less Voltage means higher current, because power consumption stays almost constant 25,6V / 0,42A: stepper (10,75W) ... only hotwire is not getting hot enough if reduce more.

IMG_4581 IMG_4583 IMG_4584 IMG_4585 IMG_4586 IMG_4587

goos766 commented 3 years ago

ok. I took a step forward with all the stepper motors and their directions checked. Tomorrow and maybe even today endstops soldering. later ... ehh, what the hell, I will cut this pin 10, because without this fan I feel somehow insecure. I have to prepare for testing the cutting wire, because I do not have a power cable of the right length for this whole test to make sense.

Jesus. I did not think / knew you were so involved in it. You go to so much trouble / effort to document it for me. I feel a little embarrassed that you are making such sacrifices for me. by the way, I believe you when you write that nothing gets hot, you don't have to prove it to me.

so at the end, such a novice question, where should I measure the resistance of the cutting wire (from the side of the board at the ends of the two power cables or only at the distance between the two towers (including the hot wire itself in this measurement)?

I must say that after careful calculations, the cost of the device slightly exceeds my initial assumptions, and with such a strict budget, every penny counts. I can't really find an alternative to components that would save money. There are a few more details that I would have to add. I'm really trying to make it as cheap as possible. After the software deduction (devFoam LE) is slightly cheaper than what RcKeith did.

ThomasHeb commented 3 years ago

Hi Goos,

the resistance of the hotwire is measured directly on the hotwire. Between the points, where you connect the cables.... see picture. Bildschirmfoto 2020-10-15 um 06 20 04 Bildschirmfoto 2020-10-15 um 06 19 30

Resistance is the base for choosing the right wire... then follow the fine-tuning: Connect everything. Go to the hotwire menu , select manual and start with a low power setting. Put some foam on it... the foam should not be cut. increase power setting until the foam is cut without putting force/weight on it. this is the setting for slow cutting speed (app 100 mm/min). Check out the video attached in the zip. Put this setting into the parameter ($5 = feed speed and $27 = hotwire power is stored automatically from your last manual setting).

If your wire is not getting hot enough:

If your wire is getting much too hot / cutting is starting below 50% powersetting:

Start fine-tuning again until you are happy with the result.

I keep my fingers crossed for your first cut!

IMG_4588.mov.zip

goos766 commented 3 years ago

So it seemed to me at the beginning. But after reading that the power cable also influences the resistance of the entire installation, I started to doubt a little where this resistance measurement should actually take place. Thanks for that clarification.

ThomasHeb commented 3 years ago

Of course everything has an influence. But to get that baby working, you can focus on the major topics ;o) Cables have less than 1% impact compared to the hotwire/resistive wire.