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Forum Index : Microcontroller and PC projects : CNC Milling Front Fascia Panels for TFT displays
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vegipete Guru  Joined: 29/01/2013 Location: CanadaPosts: 1132 |
Polycarbonate seems to be particularly sensitive to chemically induced stress cracking. We found typical machine tool cutting coolant and lock-tite to cause cracks to form. (Air system lubricator bowls are often polycarbonate - the wrong lube oil can result in delightful explosions days, weeks or even months later.) The solution was to use water for tapping, and a continuous jet of compressed air aimed at the actual cutting area. I've never noticed any issues with coolants or lubricants with other plastics, but it would be wise to test on an unimportant sample to ensure there won't be any problems. Visit Vegipete's *Mite Library for cool programs. |
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| MikeO Senior Member  Joined: 11/09/2011 Location: AustraliaPosts: 275 |
I don't have a 3.5" LCD to hand but I do have a 3.2 ILI9341 (from an F4) whose overall dimensions are very near to a 3.5" lcd (except the screen are is larger of course) So I did a few pics sort of hanging in a Deta raised mounting block cover and it looks as though it could fit its just getting the actual visible screen area inside the nice bezel of the cover, it may be easier to make a 3d printed "filler" to hold the display between the bezel cover and the actual mounting block. To mount on the wall the "block" is screwed to the wall board and then the cover, display/electronics would clip on. Power/data cables could also come through the wall as required. .jpg) .jpg) .jpg) If there is real interest I could have a go to make an enclosure using the wall plate, if so what actual display are people using and CPU , Pico I imagine, Anyway let me know. Mike Codenquilts |
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Bill.b Senior Member Joined: 25/06/2011 Location: AustraliaPosts: 235 |
Hi all I not into CNC I 3d print all my enclosures for my projects. Bill In the interests of the environment, this post has been constructed entirely from recycled electrons. |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2642 |
The Silicon Chip magazine website shop has laser cut acrylic bezels to fit various screens including 3.5". |
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| pwillard Guru Joined: 07/06/2022 Location: United StatesPosts: 313 |
I think the issue is how to make them profitable enough for sellers and I think that will likely only come from strict standardization... sort of like EUROCARD PCB standard. |
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Revlac Guru Joined: 31/12/2016 Location: AustraliaPosts: 1154 |
@Mick Thanks, had another look at the NC file and managed to zoom in and see the corner cuts, had to use an external mouse to zoom in because the laptop one was not working. .png) I notice the Command M3 S10000, I take it is to start the spindle, That should be flat out. The M3 command is missing from the Gcode converter program I have been using, will have to sort that out later, often do a test run in a piece of foam, saved me from snapping a new bit.  @Bill.b Yes 3D printed enclosures are great, but will need to consider what it the best type of filament for the particular job. Laser cut enclosures are very fast to cut out.  Some interesting stuff https://www.cnc3d.com.au/ Edited 2022-07-10 20:50 by Revlac Cheers Aaron Off The Grid |
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bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2950 |
Hi MikeO, All, Thank you for that link, I ordered an up cutting 1/8” bit plus a 60degree v-groove cutter from them. I must say I am very impressed with their prices, and unlike many other companies, they are not profiting on the postage either. Their prices were comparable to Chinese prices and they offer some good suggestions for the various cutters and settings and uses etc. One question, Yes I got a 3mm bit melted into a blob of acrylic yesterday, he suggests slowing the cutter RPM and increasing the speed of traverse as well as reducing the depth. I used 200mm/s and fastest speed on my cheapo 3018 cnc. Unfortunately even though I told Easel to cut at 0.25mm depths the gcode it created set 0.5mm depths. I was attempting to cut 2mm acrylic. There seems to be a bug with easel as I tried several times to create the 0.25 cut depth per pass and it persisted with 0.5mm I haven’t seen this before with Easel I don’t know why it decided it knew better. Anyway I will wait for my Adams bits to arrive and try 800mm/s at 0.1mm depths. Now I have a question, or two. The suggestion is to reduce the RPM, would this be applicable to my, already reduced at max 10k or 12k maximum cutter speed? What RPM would you suggest for my 3018 for acrylic. Also, if I double the the diameter of a cutter to say 6mm is this equivalent to double the speed of a 3mm cutter? Regards Mick Edited 2022-07-17 10:31 by bigmik Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2642 |
No experience with CNC but when drilling acrylic a very low speed is needed to prevent melting. Less than 500 RPM. |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
When I went to school, we learnt that circumference = Pi r squared. So, double the radius (or diameter), and the speed at the circumference is 4 times. Somewhere on the 'net there will be cutting speed tables. Jim Edit: I went to a strange school! circumference is 2 Pi R so double radius, double speed. (not having a good day) Edited 2022-07-17 14:49 by TassyJim VK7JH MMedit |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
Oops... Pi R squared is the area of a circle. The circumference is Pi D (or 2 Pi R). Somehow, PI*(R^2), PI*D and 2*PI*R don't look as pretty. :( Edit: Ah... you spotted it. :) My school didn't teach the correct use of spectacles.... . Edited 2022-07-17 16:49 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
OK, we're back to basic geometry. Way back in the hills of East Tennessee there was a family of hillbillies living in such an inaccessible valley that the authorities for many years didn't know they were there. Eventually they were discovered and the parents were told that their teen aged son had to go to school in town next year. Arrangements were made for him to move into town. He returned for a visit at Thanksgiving time and they sat down for an old fashioned Thanksgiving feast. When the feeding frenzy abated and the moonshine came out Pa asked his son to say something edumacated that he had learned. The son thought for a minutes and then said "Pi R square." Pa thought about that for a minutes and replied, "Shucks, you ain't goin back to school! Everybody knows that pie are round, corn bread are square." I'm not even going to sign this one! Edited 2022-07-18 07:20 by Paul_L |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 7937 |
Hehe... Don't blame you. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
A couple of mill cutters spec sheets that know more than me... CNC.zip Jim VK7JH MMedit |
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| Andrew_G Guru Joined: 18/10/2016 Location: AustraliaPosts: 871 |
Hi Jim, I trust you hadn't been on your favourite tipple? (Don't fret, it is an easy mistake - to get circumference and area confused that is. . .) Cheers, Andrew |
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| TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
No Andrew, it wasn't the wrong lubricant, just the wrong gear. Jim VK7JH MMedit |
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| bigmik Guru Joined: 20/06/2011 Location: AustraliaPosts: 2950 |
Hi Jim, All, @Jim, Some interesting data in those spec sheets Jim. I will have to have a good read of them. Unfortunately as much as I like my entry level 3018 cnc mill it really is a bit limited as it has too much flex and slack (even though the anti-backlash nuts and springs are loaded) in retrospect the more solid looking pro version might have been better but the Z axis is still lacking rigidity. The X axis relies on 2 x 8mm rods for stability and they can flex easily by pressing against them. So I think the rule of thumb with this machine is light cuts (0.1mm depths) to reduce the load in the machines weak areas. A few (more) questions if I may, Will stronger springs on the anti backlash nuts help the slackness or create more friction that the steppers have to fight against.? Re. V-groove bits, Do V bits typically leave a flat on the bottom of the cut (due to the carbide blade thickness) or do they cut a sharp point. I used a 90 degree V cutter on my new face panels and it seemed to leave a flat, it was out of a box of router bits I bought from Bunnings (local hardware store). I have ordered a 60 degree but to play with from Adam’s bits so I will have more fun. Last Question, for now, if I buy another, presumably more solid, mill what should I look at? I don’t mind spending some money to buy one but I would like it to be reasonably small, the 3018 does something like 30cm x 16cm x 4cm (even less with the wasteboard) high. Those sizes are fine for most of the work I am likely to do, maybe the z could be 50% more. Regards, Mick Edited 2022-07-18 09:46 by bigmik Mick's uMite Stuff can be found >>> HERE (Kindly hosted by Dontronics) <<< |
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| PeterB Guru Joined: 05/02/2015 Location: AustraliaPosts: 655 |
Good morning Mick. There was a discussion here some time ago about CNC machines and I can't find it. I have a 3040 to engrave PCBs and it works well but it was expensive and I think there are now better ones available. I made my first machine out of MDF, extruded aluminium, ball bearings, scrounged steppers and a Dremel. It did work but the real killer was the noise from the Dremel. Nancye did offer to pay for the 3040 but She never did  Good luck Peter(B) |
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| TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6283 |
https://www.thebackshed.com/forum/ViewTopic.php?TID=8724&PID=95705#95705#94811 There are probably many other discussions. Jim VK7JH MMedit |
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| PeterB Guru Joined: 05/02/2015 Location: AustraliaPosts: 655 |
Back again. I found it! https://www.thebackshed.com/forum/ViewTopic.php?TID=13964&P=2#172125 PeterB |
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| PeterB Guru Joined: 05/02/2015 Location: AustraliaPosts: 655 |
Jim's text is blue, mine is black. I understand that Tassy is very cold but is that the reason?  Peter(B) |
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