Mechanical CNC NOT Laser CNC - Questions - Panels

[shearder]

Hey all

HAPPY NEW YEAR from Sunny South Africa!

Well I have been off the "radar" for some time. Between work and family time has really played it's hand and left me with not mucg to hold. However, with that said, I started my 737 build about 4 years ago. I decided on FSBUS - may change that now as it seems to be acting up - BUT be that as it may I used to have to "outsource" my panel making requirements to a small hobby company that had a laser CNC. I got as far as the MCP built and working and the EFIS cut, painted and engraved.

Now a few years down the line I am thinking of chaging a few things. I now have a nice CNC machine with 1200mmx1200mm bed, 200mm high gantry and a 4th axis.

Considering there are folk on here i.e Wendy ;) who have done their own work I would like to know what speeds, i.e. spindle speed and feed speeds, are being used? I have some perspex laying around from the previous years but thinking of moving to acrylic or plexi?

Also i am looking for some GOOD files for a throttle quadrant for 737. I have one but it is foreign and I dont see, logically how it would all fit together.

Any advice will be Most welcome.

73907391

[shearder]

AH another question - I see some are making their own circuit boards. I have a bunch of circuit board mills - what do yuo use to design and generate the g-code for these boards?

Thanks again.

[jonesthesoftware]

AH another question - I see some are making their own circuit boards. I have a bunch of circuit board mills - what do yuo use to design and generate the g-code for these boards?

Thanks again.
Hi
I use Autocad to design the lightplate along with the pcb so as to get all the holes for mounting and switches etc. to line up correctly. I save the file as a "dxf"" then use an Eagle file "dxftoscr" to convert that file to a script which I then run in Eagle software to layout the pcb. Add your components and draw tracks. No need to make a schematic, only position the components and draw the pcb tracks yourself. After all, backlighting circuits are only + and - to the resistor/leds. Then use PCBGcode to convert the eagle file into a cnc file. You can get "dxftoscr.exe" and "pcb-gcode.exe" free on the internet.
Hardest part is getting the pcb to lay flat on a flat surface as the copper is only 50 microns thick (I think) so even a little dust under the pcb wil cause problems.
I use 30 degree V bits to cut the pcb
regards
geoff

[shearder]

Hey Geoff

Thanks for that response. I don't have autocad but i have Rhino 4. Now if i understand you correctly you design the light plate and PC board in autocad then convert for eagle is there no problem with the lightpanel detail being in there too? is it as simple as deleting the lightpanel lines OR do yuo create and export the PCB dxf from a separate layer?


Hi
I use Autocad to design the lightplate along with the pcb so as to get all the holes for mounting and switches etc. to line up correctly. I save the file as a "dxf"" then use an Eagle file "dxftoscr" to convert that file to a script which I then run in Eagle software to layout the pcb. Add your components and draw tracks. No need to make a schematic, only position the components and draw the pcb tracks yourself. After all, backlighting circuits are only + and - to the resistor/leds. Then use PCBGcode to convert the eagle file into a cnc file. You can get "dxftoscr.exe" and "pcb-gcode.exe" free on the internet.
Hardest part is getting the pcb to lay flat on a flat surface as the copper is only 50 microns thick (I think) so even a little dust under the pcb wil cause problems.
I use 30 degree V bits to cut the pcb
regards
geoff

[jonesthesoftware]

Can Rhino export a "dxf"file? You need a file type which Eagle can open that's why I use the dxftoscr to get a script file that produces effectively a line drawing in Eagle which gives the positions of edges, holes, cutouts, text etc. I then use the component libraries in Eagle and place the components in the required positions e.g. LEDs and resistors. Then I draw the tracks where I need them on the bottom layer. Then I use the pcb-gcode to produce the cnc Gcode file. Having all the positions on the "board" in Eagle ensures that I don't put components in the wrong place(mostly anyway hehehe). The secret is in the fact that the pcb-Gcode program only converts the tracks on the bottom layer and the drill holes from the components and ignores all of the lines you imported. Using the Autocad file as the master makes sure that everything lines up when it comes to assembly time.
For cutting perspex/acrylic I find a single or double flute cutter with a continuous jet of air or vacuum to keep it clear works ok. I can't quote traverse speeds but I use 14000 rpm spindle. Plastics melt very easily so slow and cool does it.
Regards
geoff

[shearder]

Hey Geoff

Yes Rhino can export DXF. I have eagle and i have downloaded those little conversion programs. I have a set of circuit board end mills. How do you drill the holes? OR do you use a separate drill bit? i haven't used the end mills yet OH MAN they are TINY!! Like these:

10 Carbide Micro Drill Set 0 25 0 8mm PCB CNC Dremel Press Bits New 1 8 Shank | eBay (http://www.ebay.com/itm/10-Carbide-Micro-Drill-Set-0-25-0-8mm-Pcb-Cnc-Dremel-Press-Bits-New-1-8-Shank-/140612640828?_trksid=p2045573.m2102&_trkparms=aid%3D555001%26algo%3DPW.CURRENT%26ao%3D1%26asc%3D146%26meid%3D4640174174924420203%26pid%3D100034%26prg%3D1079%26rk%3D4%26sd%3D170865789639%26)

I used to drill these holes myself with a dremel and a pile of expensive drill bits that didn't last too long LOL - i was using fiberglass based boards. I can't find any others.

Note: Thought these say Dremel bits this is just an example - The ones I have are actual PCB end mills for CNC router :)

[jonesthesoftware]

Pcb-Gcode generates several files from your Eagle "board"drawing. One of which is a"drill" file. So first I run the "etch" file to do the isolation routing of the tracks using the 30 deg V bit, then I mount a 0.8 mm pcb drill bit in the spindle and run the "drill" file to drill the holes. The pcbgcode programme caters for all the correct drill sizes but my cnc machine does not support tool changes so sometimes I manually edit the cnc code and sometimes I just drill all the holes at 0.8mm as this is ok for resistors and LEDs
regards
geoff

[shearder]

Maybe oneday when i am big my CNC will have a tool changer LOL

Thanks for all your help Geoff! It has been a GREAT help and I understand 100% what you have said and am ready to try my hand hehehe thanks again.


Pcb-Gcode generates several files from your Eagle "board"drawing. One of which is a"drill" file. So first I run the "etch" file to do the isolation routing of the tracks using the 30 deg V bit, then I mount a 0.8 mm pcb drill bit in the spindle and run the "drill" file to drill the holes. The pcbgcode programme caters for all the correct drill sizes but my cnc machine does not support tool changes so sometimes I manually edit the cnc code and sometimes I just drill all the holes at 0.8mm as this is ok for resistors and LEDs
regards
geoff

[Masterploxis]

Hi,

i also do the basic panel layout with auto cad. If you need dxf rhino should also be fine. The pcb layout is done in Sprint Layout. This program allows to prepare the toll path for the the holes and the isolation milling. Then the program creates 1 excellon drill file for the drilling holes and another file for the isolation millings. These files are converted in Lazy Cam ( comes with Mach 3) to cnc readable program. The program is loaded into mach3 and you are ready to go. I use 0,7 mm end mills (no V shape) as the pcb board is not 100% flat on the surface of the cnc machine. If you use V shape a slight difference in height will give you different widths of the isolation channels. So i prefer end mills with cylindrical shape. Feedrate is 150mm/min, 16.000 rpm, and 0,2 mm cutting depth.

Sprint layout cannot use dxf as input so i need to make a manual input of the drilling hole positions which i get out of autocad.

If needed check my threat for some pics here:
<http://www.mycockpit.org/forums/my-cockpit-update/19967-start-b737-ng-project-2.html>
(http://www.mycockpit.org/forums/my-cockpit-update/19967-start-b737-ng-project-2.html)

Good luck.
Andy

[shearder]

OK I am planning to go and buy some white acrylic today for some panels for a King Air B200. I have an idea of what i will do BUT i thought let me pass it via the forum first:

I have the designs for the panels and they are almost ready for cutting. Plan is to cut all the holes and pockets etc THEN spray as necessary and THEN engrave the lettering.

Now: my question is: how are yuo doing the engraving after cut and paint? DO you put it back into the "cutout" and use shims the size of the end mill i.e. 3mm or 1/8" and the machine would have kept the 0 settings for XYZ OR do you reset the center pont and engrave?

OR how do you do it? I am hoping Gwyn can answer ;)

[Masterploxis]

Hello,

what i do to get the correct position for engraving: I do not cut out all the holes. I just mark the position of one or two holes with the mill (just move the top of the end mill a little bit into the material) . The position of the center of the hole is clearly defined in Autocad, or Rhino.
I select usually holes for encoder or switches, as the diameter is 6 mm and i can drill them later - so not need to cut them with CNC.

When the spray paint has dried, i just put the panel onto the work table of the CNC machine. Then i position the end mill exactly over the marked spot. As i know the relative position of these marking from autocad (or rhino), i just make the input of the related X and Y values into Mach 3. This way Mach 3 now knows whery my mill is positionen and i can start the engraving.

For painting: Please make sure that you use some scotch brite or metal wool to apply a roughness onto the acryl surface. Then use some primer before painting. AND IMPORTANT: Give the painted panels minimum 3 - 4 days drying time. The color spay hardens in that time. If you try to engrave earlier, you will pull away the color layer when engraving small letters.

This method (positioning of the panels after painting) works very good for me. I am able to position engraving mill with a accuracy of 0.3 mm and this is very sufficient for engraving....

Cheers
Andy !

[shearder]

Hey Andy

Thanks a ton for that helpful info. Do you simply use some standard plastic primer? I will be using Rustoleum spray - but the primer I would recon most plastic primers would be ok?

[shearder]

OH i nearly forgot does anyone know the font type for King Air 200 etc panels?

Thanks.

[jonesthesoftware]

I approach this differently. I spray the large sheet of acrylic first then allow to dry for at least a week to allow the acrylic paint to harden. Then I cut the holes and engrave at the same session, because then you don't have to lose your XY zero point. When engraving I re-zero the Z axis for every word and sometimes for individual letters. The reason for this is the acrylic sheet thickness can vary by as much as +- 1mm! The paint also is only perhaps 0.050 mm thick so just your finger pressure can change the engraving from "not deep enough" to OK. I then mask off the top surface completely, cut out the holes and then spray the cut edges, sometimes I hand paint the edges if it is going to be hidden areas.
Remember of course if you cut out with CNC accuracy and then paint the edges, the holes will be smaller by 2x the thickness of paint. Not a lot but if you design accurately, your CNC cuts accurately and then your components don't fit. When all dry spray with acrylic clear matt laquer. I've found that if you rough up the surface using 400 grit wet and dry paper then spray 6-7 very thin coats of acrylic paint (to get opacity)you don't even need primer. This is only for acrylic though not other plastics, Usethe 400 grit with slightly soapy water as this prevents static electricity which tends to hold the dust on the acrylic. I dry each sprayed coat with an infra red heater as this gives very fast drying and also hardens the layers.

regards
geoff

[shearder]

AH GREAT ideas there Geoff. Appreciated. I will try different techniques on a couple of panels and see which works best for me.

[Westozy]

OK I am planning to go and buy some white acrylic today for some panels for a King Air B200. I have an idea of what i will do BUT i thought let me pass it via the forum first:

I have the designs for the panels and they are almost ready for cutting. Plan is to cut all the holes and pockets etc THEN spray as necessary and THEN engrave the lettering.

Now: my question is: how are yuo doing the engraving after cut and paint? DO you put it back into the "cutout" and use shims the size of the end mill i.e. 3mm or 1/8" and the machine would have kept the 0 settings for XYZ OR do you reset the center pont and engrave?

OR how do you do it? I am hoping Gwyn can answer ;)

Hi Shearder,
I'll pass on my simple method of realigning the panels after painting, it's quite easy. Let say you have cut out the electrical panel for a 737 overhead. It is white 3mm acrylic and has all the necessary square cut outs, switch holes and small holes for the mounting screws etc. It's finished and you have removed the panel from the machine for painting. After light sanding with 400 wet and dry I paint the acrylic in etch primer before the top coat of RAL7033, (I think that's the right code!). When it is ready for engraving, I generally fit a waste piece of MDF or plastic to the machine bed and plane it flat, it is most important to have an accurate flat surface to work on for engraving as you probably already know. From your original drawing, create a tool path file that spot drills the mounting holes of the panel, you probably only need two holes across diagonal corners to hold the panel down as engraving creates next to no load at all on the work piece. When you have spot drilled them about 2mm in diameter, you will have your locating holes ready to remount the panel with a couple of small screws. Use countersunk head screws as they tend to pull the panel into correct alignment and they are less likey to damage they paint. Don't do them up too tightly, just slight pressure is enough to hold the panel in place. X & Y axis are now set at zero and you will only have to zero the Z axis with your engraving bit. I usually engrave to a depth of 0.1mm, if it doesn't cut all the way through the paint just go a bit more but try not to cut into the acrylic too much as this can cause quality issues. This method is especially good when I'm making multiple copies of the same panels.

Cheers, Gwyn

[shearder]

AH GREAT!! Thanks for that Gwyn. I will try that this weekend. Well I may only get to cutting and sanding and spraying and sometimes in next week do the engraving. All this feedback is a GREAT help!

Thanks all!

[shearder]

I will post the samples here - also doing an annunciator panel for the King Air B200

[shearder]

Hey Guys

Ok so I gave the paint over a week - cos i was busy :) - and then started to engrave. OK i think i need to change the text type to true type. I am Using Aspire and it looks great in the preview but actual engraving is BAD! I have some scrap MDF which I machines a pocket out of so that the panel fits into it and then I screwed it down. I was using a 45* 3mm with a 0.2 (i think) tip and i lost a lot of definition. SO perhaps i need a different font and a 10* or something engraving bit?

Will need to redo the panel. What tip are you guys using??

Thanks in advance.

[shearder]

OK this weekend i am going to try engrave with a 3mm (1/8") 10degree 0.2mm tip and see how it works out. Also I changed the text to a TTF rather than a 3 line text type and use a fill engraving rather than on-the-line engraving.

I am using Aspire.