- September 21, 2017 at 4:09 am #44330
as i already learned much in this forum, i´d like to ask some questions (hope they are not sticky anywhere and i just oversaw them)
so there´s multiple questions 🙂 :
-How fast do you run the machine? (Ryan said he´s cutting 6mm Plywood in one pass with around 15mm/s)
-How fast do you set your plunge Feedrate (Ryan wrote, that not to exceed 5mm/s)
-I tried different bits (2 Flute ones / No-Name / Bosch) and get alot of Tearout and “squeak” noises at 15mm/s Feed and 5mm/s Plunge feed.
-While plunging into material there´s always a little smoke but when i slow down the spindle it simply doesn´t sound right.
-Might it be shitty bits? Where do you get your bits from? – I´ll buy the same and try it out.
-What Settings and how many passes do you use?
And finally :
For a workpiece with 5 Pockets and multiple Cuts (1600mm * 1200mm) how long would you calculate it takes? (picture in attachment)
Hope that aren´t too many questions. I get good results with my lowrider (with some fails), but wanted to hear oppinions.
Attachments:September 21, 2017 at 4:53 am #44332
Your not pocketing that circle, right? Just removing the pieces can save a ton of time on but pockets. I try to limit pockets too places where I’m not going all the way through, or they are very small.
EstlCAM has a little estimate on the preview window. It’s been low by about 25% or so for me, but it gives me an order of magnitude.
What thickness is your material?
For the plunge, do you have the plunge angle set? That helps a lot, because it will drive into a cut instead of trying to just drill into it. The bits (especially ones not designed for milling) don’t remove material in the center when plunging, so you’re just pushing that wood, and it caused a lot of stress. If the bit is moving when plunging, then the sides are cutting and you get a lot less stress. I also had trouble with the plunge with the default pocket strategy, so I use parallel or peel.
For speeds, and DOC, do some tests in the material. I can’t tell you what to use, you have to try it on your material. If it’s anything thicker than 6mm ply, then you’re pushing it at 15mm/s. Deeper and faster are trade off, but deeper uses more of the bit (which makes them wear better). If you’re not using a but designed for milling, then you won’t get as good results as Ryan is.
You’re not just tuning the machine, you’re training yourself. Make some coasters first.September 21, 2017 at 5:19 am #44334
Thanks for the answer 🙂
My estimated settings on this project would be 6mm per Pass (8mm 2 Flute bit) – 10mm/s . 90 degree plunge angle with 5mm/s plunge feedrate. Material is 18mm thick.
The big circle will be a full thickness cut.
Haven´t noticed that time window in preview 🙂 Learned another thing, hehe!
I just tested bits like the bits that come with the makita router.
Cuts through, but leaves some tearout.
Will try with a “more expensive” specially for cnc milling designed bit.
And one more:
Would it make sense to choose the smalles bit possible in terms of mechanical load? I mean..I don´t need to cut away 8mm width, 6mm or less would totally be okay for the parts.
Thank you!September 21, 2017 at 7:52 am #44337
Yeah, a real endmill will work much better with cam software. Woodworking bits are usually very specific to one material or type of cut. Example, most people are trying to mill with really long drywall bits…
Can you find where I said 15mm/s I need to change that for sure. I have been milling 6mm MDF in one pass at 8.3mm/s 15 is not my style at all. A vary all my cuts between 8-12mm/sSeptember 21, 2017 at 8:26 am #44342
On plywood specifically, upcut bits and cheap plywood will create a lot of tearout. A downcut bit leaves a mess on the underside, but it’s a lot less, since the spoil board is pushing against it. The problem with downcut is that they don’t get the chips out as well, so drilling anything is not good, and deep cuts have more load.
Better quality plywood has more glue on the top veneer, so the tearout won’t do as much damage.
I think changing the plunge angle will help. Diving straight down 6mm has some danger to it. The bits don’t have a cutter in the middle, so it’s just pushing that center. IIRC, I used 45 or 30 degrees.September 21, 2017 at 8:50 am #44346
I started trying to write up a milling basics page but dang, there is nothing basic about it….I will try and get something up and maybe I can just keep improving it as we go. These questions come up a lot and I am not doing my part in getting any help up.September 21, 2017 at 9:39 am #44353
What kind of plywood are you cutting? Ive been cutting alot of 1/4 birch, which really measure around 5mm. I cut all the way through into a foam spoilboard at 15mm/s. Ive had the most sucess with
Ive also cut some 12 mm birch plywood, that I cut in 3 cuts, 4.5mm DOC per pass.
The other day I tried some 1/4 underlayment because who doesnt like 1/2 the price of birch plywood and I was just cutting out some simple shapes…..that stuff sucks, ruined a couple bits and I had to bout about 7mm/s.September 21, 2017 at 9:56 am #44358
There are some basic number that sound good to me, 1/4″ MDF 8mm/s, 1/4″ Birch ply 15mm/s. It think that illustrates the differences very well.
Don’t forget always use a finishing pass.September 27, 2017 at 7:14 pm #44867
Compression bits are supposed to help with tearout, but they are no panacea. They are upcut near the tip and downcut for the rest of the bit, … this is why tearout is limited. But these bits are a bit more expensive.
I purchased a few from the maslowcnc project (.25″ diameter, 1″ cut length, about 2″ overall length, but this is from memory). The bits look good to me. You can get some to try from http://www.maslowcnc.com/store … I don’t know where they purchase the bits. I have not used one yet.September 28, 2017 at 3:37 am #44868
I´m cutting birch multiplex with 8+ laminates.
I just bought this one https://www.sorotec.de/shop/Zerspanungswerkzeuge/sorotec-werkzeuge/2-schneider/Schaftfraeser-HOLZ/
It has some good recensions on the Internet. My first “expensive” bit, hehe 🙂
Excited where this will go!
Btw, had a 4 Flute laying around and tried it out, cuts are really clean but it makes a hell of a noise and gets really hot.
(i know, 4 flutes aren´t that good for low feedrates – but it worked well)September 28, 2017 at 4:38 am #44870
DanParticipantThere are some basic number that sound good to me, 1/4″ MDF 8mm/s, 1/4″ Birch ply 15mm/s. It think that illustrates the differences very well. Don’t forget always use a finishing pass.
Are these number for cutting all the way through in one pass?September 28, 2017 at 6:39 am #44871There are some basic number that sound good to me, 1/4″ MDF 8mm/s, 1/4″ Birch ply 15mm/s. It think that illustrates the differences very well. Don’t forget always use a finishing pass.
Are these number for cutting all the way through in one pass?
Yes they are, but we also cut through to a foam spoil board so there is not extra resistance from cutting more wood.September 29, 2017 at 7:03 am #44979
What are you using for your foam spoil board? Something like dollar store foam boards?September 29, 2017 at 12:32 pm #45011
Axel KingsleyParticipantCan you find where I said 15mm/s I need to change that for sure. I have been milling 6mm MDF in one pass at 8.3mm/s 15 is not my style at all. A vary all my cuts between 8-12mm/s
The Estlcam basics text does indeed say 8.5mm *plunge* maximum, but the image of the settings shows a Feedrate of 15mm:
I delete all the default tools and use this as a conservative test speed setting for an 1/8″ flat endmill in wood. Do not exceed 8.5mm/s in the z plunge field.
Does the MPCNC run at 15mm/s well? This may be a symptom of one guide for multiple machines. Growing pains 🙂September 29, 2017 at 12:54 pm #45014September 29, 2017 at 1:09 pm #45018
Yes, yes, yes. This is great. Precise information, conservative settings, some good rules of thumb.
Pictures are great too. I was told by a very effective salesperson that people either read or look at pictures, but not both, so you have to explain your most important things in text and images.September 29, 2017 at 1:17 pm #45020What are you using for your foam spoil board? Something like dollar store foam boards?
Insulation sheathing like in the link.
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