The attached indicates a gear which I will cut on 1/4" plywood. Have several similar gear of various size to do and what I don’t particular like on them is that the teeth and the interior of the gear are all on the same chain. I was thinking to modify the geometry and isolate the interior from the teeth. Is this a good/bad idea?
Do you use a contour path to cut gears?
And the interior I guess I should use a pocket path?
Personally, I think the design allows a little flexibility....but the choice of the final design, is yours.
What design of "holes", for your purpose is purely aesthetic.
I work with items that require heavy gearing, so the teeth must be rigid, & made of stronger material,(steel, cast iron etc)
I was not suggesting to alter the design, just to split the chains for cutting.
The plywood teeth for my wooden hobby clock will be strong enough, Since I never cut any gear teeth I wonder if there is/are things I should be looking for.
BTW with the knowledge on chaining I got from you yesterday Superman, I was able to finish a cut yesterday after 2 previous attempts, many thanks.
My mistake... wrong bull, wrong horns...
Yes, split the geometry by all means.
Doing a pocket toolpath requires a closed chain. You might consider having the teeth profile around the perimeter as a full circuit, then the internal pocket opening actually having added geometry to loop out over the tooth profile and then back in to join up the pocket.
My concern is how to secure the material so it won't move while cutting.... a problem that happens with every job.
Its true securing the material looks like a problem and I will experiment on a pc of scrap to find a way. I was thinking since the final material is 1/4" thick to have the cut perhaps down to less than 1/4”, perhaps 0.22”? and use double sided tape? I will also use a screw in the center hole of the gear but this may not prevent it from spinning. Any idea about the feed speed and RPM? I normally use about 40 IPM and 12K RPM but going with 30 IPM may be better?
I assume no vac. table,... if yes, nearly cut thru when doing the inner pockets, & finish the cut with a knife.
Look at leaving "tabs", little bridges to connect piece together with those that hold onto the table
I have used double sided tape, I've seen others use glue (in the right spots, & does require effort to clean up the job).
Next hint.... when contouring with a larger cutter that misses going into some areas. Try the "Remachining" feature in 2D Contour.... if a corner is not reached, it can just do the corners without doing the full profile (depends on tool dia. settings)
Would have loved to have a vac table but too noisy for a residence…
I know about the tabs but my thinking was instead of the tabs to just leave the whole bottom solid (about a few thou) which may provide better surface to hold the pc in place. No problem to clean the mess afterwords.
Your tip, as always, is excellent! Didn’t know about the “Remachining” feature. If needed I will give it a try.
Sorry I forgot these details:
1/8” carbide compression 2 flute spiral end mill (I bought 5 in a pack from SpeTool, $41 shipping included)
3/4" Cut Length
I do 1/32” depth of cut per pass
Use my manual shop vac to clean the chips after every second pass
I haven’t been able to find any 1 flute end mills, most are 2 flute or more. 60 in/min is too fast for me, with my limited experience I’m afraid to push it any faster than 40 in/min.
Always afraid that I may cook the end mill but looks like I don’t burn the wood so far. Have been cutting a lot 1/2" deep and the gears will be on 1/4" ply so it will be much easier/faster
Do you think I may damage the end mill at 12 RPM with 40 in/min? My water cooled spindle can go up to 28 RPM so I can increase/decrease the RPM but going to 60 in/min? Kind of too fast for me but if you say so I will do it.
12k for a 1/8" cbd cutter is perfect speed.... if cutting steel
If cutting aluminium, you go about 4x faster in cutting speed, feedrate is adjusted depending on the material conditions.
Wood, I would place higher above alum.
Now ... your RPMs may be a little low, work your way up, protect your spindle
40 in/min is very slow, try putting the feedrate up, you are only cutting 30 thou deep with a 2 flute which effectively halves your chip load.... do it without the tool, or in areas that don't have sharp cornering, experiment going faster in speed & feed.
I have used a 2½" cbd facemill in alum @5000RPM, F200"/min, 0.08" DOC and that sometimes seems slow.... I'm using a heavier 5 axis cnc machine, fully enclosed with a chip conveyor. But, I have stability built into my machine, We shouldn't expect the same results from every machine.
Will increase my water cooled spindle RPM to 20K, feed rate I’m afraid to go more due to no experience but will give it a try to go up to 60 in/min and perhaps a bit higher.
You were doing F200”/min in aluminum? Wow, can’t even deam about it…
I built my cnc with 3/8” aluminum plate and flatbars and is rock solid. My problem is that I have no experience in cutting and that creates fear. Like driving a car lol, you need experience to go fast….
Due to a family visit I can’t do any work now and neither next week due to an ice storm we had last week which created some damage to my house and I have to do some repairs. Will start working on my cnc around 2nd week in May
Sorry to hear about hailstorm damage. Hope it is an easy fix
And enjoy having family around.
Please, don't feel pressured about upping speeds & feeds.
You do get comfortable turning them up after a while
My F200" is by the book. I'm in Aus running metric specs.
63mm facemill with Al tips with 5 flutes
5000 RPM is around 1000 M/min cutting speed
At F5000.(F200.) is only 0.2mm chip thickness ... that's 0.0080" feed per tooth... I could go up to .3/.35mm per tooth
Once had to put a small skip under the swarf conveyor instead of a 240litre bin.
Somehow I had the impression you are in USA Superman but there are a lot of knowledgeable people in Aus and very happy you answered my post. From the numbers you stated you must also be a heavy user of cnc’s and it must be boring answering my elementary questions especially when I talk Imperial vs metric.
I don’t think I will ever be comfortable upping speeds & feeds because I’m a retired man and my main hobby is to build cnc mills all in aluminum (about 3x4 feet cutting area) which I sell after to recover my cost. It takes me about 1.5 years to build and sell one (using only hand tools) and until I sell it I play around with it to learn how to use it but the learning never last long to grasp, remember and be comfortable since soon or later it will be sold. The one I have now is my 11th machine and takes longer to sell due to covid I guess so in the mean time I decided to build this wooden clock.
The bloody storm we had in Quebec (Quebec 2013 Ice Storm) put 1.4 mil people out of power for some 2 weeks with -10C outside. I was among the lucky ones cause I only lost power for 5 days but had a tree fallen over my roof which punched a hole into it and damaged my 12x12 feet balcony and handrail. A similar storm happened in 1998 but during January when it was -24C outside. Then I lost power in another house I was at the time for 2 weeks and ended up in an army temp. shelter to avoid freezing. You guys must have other natural problems to worry about down there but I don’t think freezing is one.
When you said "ice" storm, I pictured a hail storm, an ice storm (canada style) is serious $hit, just as deadly as a firestorm or flood.
Machinists never retire (I'm not far behind you). Didn’t you know, the elec. cabinets make great caskets... an urn for those with smaller machines.
Yeah, been on the CNCs for more than 40 years, started in '82 thereabouts. Lot of water under the bridge since then. I've lasted better than the companies I was employed at.... they have all gone.
Anyway... keep looking forward, enjoy family, stay healthy.