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First Router And Mill Project

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JimDawson

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I got started on the router project that I mentioned in this thread http://www.hobby-machinist.com/threads/cnc-router-its-alive.38222/

The total run is 208 parts, 104 left and 104 right pieces. These are brackets for a luggage rack for a local outdoor recreational equipment manufacturer. Made from 1.25 thick UHMW, about 13 x 3 inches. Three 1.00 pockets, 0.90 deep, and an outside profile. The top surface is a series of blended arcs and the bottom is straight but will be cut with a 5.0 radius in a second operation. The top edges are also rounded over with a 0.25 radius in a second operation. There will also be two 0.25 mounting holes drilled through the width and counterbored in another operation.

The first operation is to cut the pieces out of a 48 x 96 sheet on the router. I'm using a solid carbide, 0.25, single flute, high helix bit designed for cutting soft plastic. Running 100 IPM feed and 13,000 RPM, 0.375 DOC per pass. Using the 0.25 bit I am able to nest the parts tight to get maximum yield from the sheet. The parts are spaced at about 0.270 all around, so not much wiggle room. I'm leaving 0.020 material thickness at the bottom to maintain the vacuum integrity over the entire sheet. It takes about 10 minutes to cut out one pair, so about 520 minutes of run time for one sheet.

Here is a picture of the first test cuts. Cutting a bit deep on these. I've since made adjustments.

IMG_0429.jpg

Next operation is to round over the edges, 1/4 inch R corner rounding bit on on a Craftsman router table. I attached a scrap piece of UHMW to the table because I found that the aluminum table was scratching the parts. This operation takes about 30 seconds. And watch your fingers. This part already has the 5 inch radius cut on the bottom

IMG_0428.jpg

For the next operation the 5 inch radius needs to be cut on the bottom surface. This is a project for the mill. A fixture needs to be built to hold the parts. Bolt the MDF base to the mill table.

IMG_0412.jpg

Then add two more pieces to the top of that, glue and screw together.

IMG_0414.jpg

Then profile the outside to provide a witness surface to be able to set it up for the next time it's used.

IMG_0417.jpg

Then do the pocketing for the parts and the pockets over the bolt holes so you can get it off of the table.

IMG_0421.jpg

Here is the 5 inch radius bit, it's about 2 inches diameter at the top.

IMG_0426.jpg

This is done in three passes at full depth, once down the center then step over and take the last 1/4 inch or so off of each side. About 3000 RPM, 30 IPM. The clamps are set up to put pressure both down and back on the part to keep it tight to the fixture. A few seconds after this picture was taken, the tool grabbed the part, broke the clamp bolt, and threw the part on the floor. Hmmmm....time for plan B.
IMG_0424.jpg
So the new clamping system, seems to work fine now. I need to make a HF run this morning to get four more 3 inch C-clamps. I was able to finish out the First Article parts for customer inspection. Once I get the go ahead I'll run the rest of them.

IMG_0427.jpg

I haven't built the drill fixture yet because I'm still waiting on the tooling. That will be in the next installment.
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brino

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Thanks Jim!
I always enjoy seeing how you set up these runs of parts.
I really appreciate that you mention your failures as well (the clamping issue above), I learn a bunch from your posts.

Thanks Again,
-brino
 

Fabrickator

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Great write-up Jim. I worked maintenance in a full blown factory (with automation) for a period of time and also as a machinist in a production machine shop. I especially like making fixture, jigss and making anything mass production. I always thought I missed my calling when I watch "How it's Made" on TV. I would really like the opportunity to do something like that again.

Good Job!
 

JimDawson

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Thank you all for the kind words. I enjoy the challenge of figuring out how to hang onto and machine parts. Figuring out the process is the fun part, actually running production not so much. I have only had my CNC mill for a couple of years and found that it has opened up a whole new world of fun stuff. It allows me to build stuff that I may not have tackled before.
 

middle.road

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... Figuring out the process is the fun part, actually running production not so much.
Conceiving the process is always the best part. Performing 'First Article' and hanging around on the production floor is always the downside.
 

countryguy

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Well I think this is a super project! Totally motivates me when Jim gets his CNC on and posts this stuff. We have the 5th axis on order to turn the CandCNC /plasma table into a high speed routing table with rotary 6" too.
What a first article in shop speak guys?
 

JimDawson

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We have the 5th axis on order to turn the CandCNC /plasma table into a high speed routing table with rotary 6" too.
I can't wait to see that setup. Sounds interesting:encourage: I have a 4x8 CNC plasma system, but no room to set it up.

What a first article in shop speak guys?
When making a production run for the first time, many times the customer will want to inspect the first part(s) out to make sure they are in spec or maybe need modification. This is called the First Article Inspection. In this case I'm taking 4 pairs of brackets to them, was going to be 5 but I scrapped one in setting up.
 
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JimDawson

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Well I finished my first run of parts on the router. This is run of parts minus the five pair I took out for the customer first article inspection.

IMG_0442.jpg

All did not go according to plan. I started the run and walked away, not the best plan. :chagrin: Here is the result of a trig error in the G-code compiler in my program. You will probably never run into anything like this. In three years this error has not shown up until now. Very strange! I corrected the error and all is well now. What was worse, the tool path on the graphic screen looked fine, so I didn’t catch it until the run. Had I run an air cut to start with, the error would have been caught there because the actual tool path would not have matched the predicted tool path and would have been displayed as incorrect. I did the top row (bottom in the picture above) as individual parts so the error didn’t show up. When I compiled an entire row the error reared it’s ugly head. :confused:

The parts are NOT suppose to look like this :burned up:
IMG_0443.jpg



But rather like this :encourage:
IMG_0444.jpg


Another small problem, I had two of the pocket locations off in the drawing and didn’t catch it. I hate it when a machine does exactly what you tell it to do rather than what you want it to do. This has been corrected also. :(
IMG_0445.jpg


I need to work on the chip management shoe. It’s still not doing what it’s supposed to do. It gets about 80% of the chips, scattering the rest all over the place. Going to require a bit of redesign when I get time. I suspect it will work fine for sawdust as it is, but UHMW is much more dense thus is a problem. I’m thinking some kind of a floating brush that will stay in contact with the work surface as the Z-axis changes height. I expect that this machine will see a lot more plastic than it will wood.

As a side benefit, it turns out the vacuum on the chip management system makes a reasonable shop heater. :grin: It was a bit cool in the shop this morning and the vacuum did a fine job of taking the chill off. The exhaust air from the vacuum is running 110F and the ambient temp was about 62F. At about 200 CFM out, and a 15,000 CuFt shop, it takes about an hour to theoretically cycle all of the air in the shop through the vacuum.

Over all I'm happy with the result. I have one more sheet to run so I expect things will go more smoothly on that one. I did a bit of measuring and it looks like the machine is holding about 0.002 or better on the target dimensions, and better than 0.001 repeatibility. Not bad for an old worn out router. The specs call for +/- 0.010 for most of the dimensions, so well within spec.
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