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Old 12th January 2012, 11:03 PM   #131
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I've also been given the option to have an open legged design with the electronics in a metal locker rather than built into the frame.

From a reliability point of view is any option better than the other?

Here's a shot of the open frame version:

Click the image to open in full size.
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Old 12th January 2012, 11:22 PM   #132
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Quote:
Originally Posted by sploo View Post
Rails: I paid a bit extra for decent rails on mine (they have internal wipers for dust). Very important to try to not let cr*p get into your slider blocks.
This is a worry for me. I might get some thin sheet alu to box in the parts or is that a bad idea because then you can't see how bad things are in there?

How often do you lubricate the rails?

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Kress: I'd be very interested to see how well it works.
Yes well the manufacturers sales blurb and the real world results are often two different things. I'll let you know how effective the electronics are at keeping a constant torque at lower rpm. If its stalling out or your having to crawl along to prevent that then your initial assessment of the Kress would be correct

Its German engineered so I'm hoping...

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Bits: Upcut spirals are very efficient at material clearing.
During the learning phase I plan to use my regular router bits in case I break them due to doing something stupid, but eventually I'll move up to the better cutters.

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Look into chip load and feedrate calculators. I understand the goal is to create chips not dust (as it's more efficient at wicking away cutter heat). Hot cutter = dead cutter.
Is that including MDF? Because in my experience it doesn't really chip in the same way wood does. You might get a few shavings here and there but its mostly dust. I guess this is another reason MDF is harder on cutters.

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Two sided cutting:
Thanks for the dumbed down explanation I now understand what your getting at now. That seems like the easiest solution to me so I'll probably use the method to ensure things line up between the front and back of the part.

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Meeting up: Is your email address still zeroex_15...? I'll email off line.
That's the one yes.

Last edited by ShinOBIWAN; 12th January 2012 at 11:47 PM.
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Old 12th January 2012, 11:26 PM   #133
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Thanks for all the info Mark, very helpful indeed.

At the moment I'm trying to soak up as much as I can so I don't feel completely overwhelmed and clueless once it arrives. I can hope eh
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Old 12th January 2012, 11:44 PM   #134
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Couple more tips:

- You really shouldn't use HSS milling cutters with MDF, they will cook. You need Carbide. I got a 1/4" Solid Carbide spiral ballnose milling cutter for $10 shipped (ebay).
Other than that I use standard 1/4" straightcut router bits - they may not be perfect, but they work.

Length is usually the biggest issue.

You are right, MDF makes dust, at least at router spindle speeds.

- Double sided tape, in combination with a few screws, is great for holding parts down on a board, then you clamp the board - particularly for parts that will bow. After the first part, you end up with a "setup" board for that particular job.
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Old 12th January 2012, 11:48 PM   #135
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Quote:
Originally Posted by ShinOBIWAN View Post
Thanks for all the info Mark, very helpful indeed.

At the moment I'm trying to soak up as much as I can so I don't feel completely overwhelmed and clueless once it arrives. I can hope eh
If you are running Mach 3 I have a few sample programs you can test with.

Name plates for kids, and speaker baffles


One thing you need in your CAM software is a post-processor for Mach3 - the code must match. Luckily Mach3 works with pretty generic code.
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Old 12th January 2012, 11:53 PM   #136
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Excellent, thanks again Mark for your very useful insights!

Quote:
- You really shouldn't use HSS milling cutters with MDF, they will cook. You need Carbide. I got a 1/4" Solid Carbide spiral ballnose milling cutter for $10 shipped (ebay).
Ah mine are virtually all HSS. I do know the Trend bits are but I believe the Freud one's are carbide tipped.

Sod it, I'll order some proper bits as I don't want to make this any harder than it as to be. Use the right tool for the job and all that.

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- Double sided tape, in combination with a few screws, is great for holding parts down on a board, then you clamp the board - particularly for parts that will bow. After the first part, you end up with a "setup" board for that particular job.
I was looking at probe video's on utube and I really like what he's done with his table for clamping. Again I can see issues where great care need to be taken not to crash the cutter into clamps but it does seem flexible and suited to holding down large mdf board.

touch.probes.mp4 - YouTube

Last edited by ShinOBIWAN; 12th January 2012 at 11:57 PM.
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Old 12th January 2012, 11:56 PM   #137
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Quote:
Originally Posted by Mark_A_W View Post
If you are running Mach 3 I have a few sample programs you can test with.

Name plates for kids, and speaker baffles
Thanks Mark,

PM sent with my email.

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One thing you need in your CAM software is a post-processor for Mach3 - the code must match. Luckily Mach3 works with pretty generic code.
Yes I picked this up from reading cnczone but as you state, mach3 is widely supported.
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Old 13th January 2012, 12:53 AM   #138
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Quote:
Originally Posted by ShinOBIWAN View Post
Excellent, thanks again Mark for your very useful insights!



Ah mine are virtually all HSS. I do know the Trend bits are but I believe the Freud one's are carbide tipped.

Sod it, I'll order some proper bits as I don't want to make this any harder than it as to be. Use the right tool for the job and all that.



I was looking at probe video's on utube and I really like what he's done with his table for clamping. Again I can see issues where great care need to be taken not to crash the cutter into clamps but it does seem flexible and suited to holding down large mdf board.

touch.probes.mp4 - YouTube
Don't go and replace all your bits - see how you go.

The difference between CNC and a hand router is the time cutting. It can be hours with CNC, so the risk of burn is higher.

I think you'll find you'll end up cutting the outside of speaker panels/baffles, as the CNC is more accurate than a tablesaw. I cut 3-5mm oversize in the saw, then CNC back.
This makes clamps problematic. I do have some for other types of jobs - but usually I end up clamping a baseboard, rather than the job, because I'm cutting the outside.

I don't think you need to buy anything really. Get started with paper-zeroing and your current cutters (consider them expendable anyway...).
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Old 13th January 2012, 11:39 AM   #139
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Good news regarding the beefed up gantry.

Open legged design + metal locker: Couldn't make a call on the reliability, but anything enclosed is good. I built a large (solid faced) cabinet that sits under the machine for the computer + electronics. An LCD monitor is mounted up on the wall behind the machine. An open legged design may allow you to store stuff under the machine, albiet not protected from dust.

BTW One consideration - I built my cabinet to make the router table surface at roughly desktop working height. Seems sensible, but due to bowing issues when clamping some materials I have to press down on sheets to keep them flat when machining - not easy with a high surface. Also, I have a hose coming down from the ceiling to the head for dust extraction. You really need at least as much ceiling-to-router distance as the maximum travel of the machine (to allow enough slack on the hose). My ceiling height is really low - hence I had to rig up a sliding roller system along the ceiling to allow the hose to slide. If I built a new table I'd have the machine much lower. Perhaps even with the surface well under waist height (I'm ~5' 11").

Lube: Always keep your parts lubed . After every job I wipe down the rails and use a little lube - as well as using a gun to inject lube into the ball screw mechanisms. That is because I may only do a job on the machine once a month though. If I were using it every day I'd probably only do it a couple of times a week. Ask for advice on suitable products. I use a food grade clear/white 'goo' on advice from the manufacturer. Our 'wonderful' climate is a rust creator too - a killer for steel rails.

Chip load: At lower rpm/higher linear speed you can get chips from MDF. That's the problem with DIY machines - too high rpm, too low linear speed. I occasionally get chips, but mainly dust.

Quote:
Originally Posted by Mark_A_W View Post
You really shouldn't use HSS milling cutters with MDF, they will cook. You need Carbide.
+1

On the subject of oversize - CAM software generates paths based on the radius of the bit. I.e. for a 6mm dia bit, it'll have to cut 3mm away from the part edge to make it the right size. You can usually do what's called a finishing pass - whereby you tell the CAM software to, say, take three 1/4" DOC passes to cut through a 3/4" sheet, but leaving the part 1mm oversize. You then add a second cutting path, which cuts the same part, but without any oversize, and at 3/4" DOC in one go. That way you don't overload the cutter, but end up with a fairly smooth edge. If you look at the dust shoe I posted earlier in the thread, that wasn't done using a finishing pass - so was just three 1/4" DOC passes at the finished size. As a result you can see slight changes in the cut sides.

When loading a cutter (due hard material/high DOC/high speed), there will be some flex, so think of it as dragging the cutter, with the tip possibly deflecting slightly. That's why a low load finishing pass can be useful for really important edges.

That's fairly irrelevant for 2.5D cutting though, and when making speaker boxes I'll usually design panels 1-2mm over size at the CAD stage, such that when the box is glued together I get 1mm overhang, which I clean with a trimming bit on the router table. Ensures you get a nice clean edge that exactly matches the rest of the box.
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Old 13th January 2012, 01:51 PM   #140
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In case the Kress turns out to be junk I've been looking at the VFD route and found this:

WATER-COOLED SPINDLE MOTOR 2.2KW INVERTER VFD 2.2KW VARIABLE FREQUENCY DRIVE l5 | eBay

UK stock, 2.2kw watercooled spindle and the VFD. That doesn't seem bad at all for the money.
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