Guys,

The part is an inline skate frame for speed skates:


The parts require machining solid billet from all four sides and holding reasonable tolerances but nothing crazy hard. You basically need a three axis machine with a tool changer.

A local shop in the area does the anodizing so this RFQ is simply for machining the parts.

I can provide G-CODE, CAD/CAM files, and discuss how I did things when I made them in my own shop. I am sure that someone with experience can come up with a better fixture system and improve the CAM side of things since I am basically self taught and was simply trying to find a way to make the part myself. At this point, making it myself costs me more then having someone else make the item.

Here are some photos and other info from my blog if this helps:
http://gatorbacksports.blogspot.com/...Skate%20Frames

I currently have four designs (basically a family of parts). I use the same fixtures for all four parts.

I can provide design files for all fixtures and if needed can provide G-code and/or other CAM formats.

Each mfg run would be 20-40 items so we are talking small volume. Over time, I hope to increase the volume. Please quote your price for 6061 alloy and for 7075 alloy.

Please email me to discuss the job if you are interested. (mark@gatorbackskate.com).

mrk. What is your email address and how did you get the internal radiused bosses? Mike.

My email address is mark@gatorbackskate.com.

Good eyes for the radius bosses, they are the tricky part but if you have a good 2.5D package the tool paths are not that hard to setup.

The internal radius bosses are cut with a 1/2" ball end mill using XZ arcs to cut half the boss from the top of the frame and when the frame is flipped over the bottom half of the boss is cut with a mirror XZ arc movement. I was using a fairly long 2.5" end mill with HSS but really I think a carbide mill is a better choice since I had more chatter then I would like and as a result had to adjust the programs to take multiple passes and remove only a small amount of material on each pass.

I can provide G code for the parts and fixtures.

I get the material from Clinton Aluminum and sometimes from scrap dealers. I don't exactly remember the per item price.

In terms of making the parts it takes me a LONG time on my equipment. My tool changer is not working correctly so for me all tool changes are manual. My max spindle speed is 3000 rpm and I can rapid at 100ipm. I think a more modern machine could cut way faster and cleaner. I also don't have enough gpm for coolant flow to clear the chips so I am often sitting in front of the machine and clearing chips with air.

Tonight when I get home I will update the thread with information about theoretical cut times from my CAM software and provide info on billet sizes and associated costs. From memory the time is something like 2h per frame for machine time alone.

My target price for this is $75 for the longer frame (brake version) and $65 dollars for the shorter frame (non brake version). Since i want to retail the part at $250 per set my mfg cost needs to be below $150 per set in order to make the numbers work out.

-Mark

I updated the CAD files. The IGS version of the files are HUGE. Most of the other formats are more reasonable in size.

FILES IN EPRT FORMAT
1.3 megs -- http://www.gatorbackskate.com/CAD/Ga...xturesEPRT.zip

FILES IN EPRT, X_T, AND SLDPRT FORMAT
13.6 megs -- http://www.gatorbackskate.com/CAD/Ga...ndFixtures.zip

2 megs -- http://www.gatorbackskate.com/CAD/Ga...0PartsOnly.zip

FILES IN EPRT, X_T, SLDPRT, AND IGS FORMAT
41.3 megs -- http://www.gatorbackskate.com/CAD/Ga...resWithIGS.zip

5.8 megs -- http://www.gatorbackskate.com/CAD/Ga...nlyWithIGS.zip

Thanks very much to all that have responded.

I will decide on a vendor over the weekend and award the RFQ on Monday of next week.

The parts are hard to make so I don't want to waste anyone's time. The first run will be 10 items of each design so 20 items in total. My payment for the first run will be $1400. I can pay for the parts as soon as a proof part is produced. The proof part must match the design and provide finish and tolerances equal to a sample frame that I produced on my own equipment. I will send the sample frame to the vendor.

It's not a lot of money for the work but if your machine cuts well and your shop has reasonably low overhead it is possible to make a profit on the job. If on the other hand your machine has problems with accuracy, XZ arcs, tool digs, and such it would be easy to scrap some parts along the way and since each part is a big expensive billet a few scrapped parts can quickly eat into the profit.

At the end of the day it is a lot of work for a small job but if things work out I hope to release more designs and target selling around 40 of these parts per year. I also have other designs that I think will sell better so if the job works out I think it could build a long term relationship. In addition, I can provide G-Code files, drawings of fixtures, and/or anything else that might help make the job go quicker for you.

I hate to tell you this, but you're going to have to be more realistic with your projected costs. Material alone is $60.88/ea, and that's MY cost. I'm not about to go scouring scrap yards to get better prices either.

Try Clinton Aluminum in Ohio and/or Advanced Metal Supply in NC. Both suppliers usually have fairly reasonable prices. That said I am the first to admit that the margins on this job are not high. The issue is that given the market I simply have to work backwards from my retail price to come up with numbers that work for everyone involved. In truth, most inline skate frames are made in large runs with machining from specific extrusions but for now my volume to keep material costs down. For now my volume is much to small for that so for this project cutting from solid and the associated high material costs are simply part of the problem.

http://advancedmetalsupply.com/products.html
http://www.clintonaluminum.com/

Matt

Metal Supermarkets = APPX $30.00 each for 20 pieces.

A simple I can't do it for that price will work
That's what I had to say for now.
Mike

Maybe, but we all got more information from Mark (he's not a tightwad, just restricted in what he can charge), and I personally learned about 3 metal suppliers I've never heard of. You can call me rough around the edges (or something much less politically correct!), but it worked this time around.

So it looks like these parts will have to be done in roughly 30-35 minutes of cycle time. I like a challenge...

I really like the CAD and CAM side of machining and dove head first into the project but frankly I am a full time software developer and for me doing the part time machining in my garage has not been working out. I like my designs and think at this point it is better to have someone who has more experience on the mfg side of things take over production plus as I mentioned my ebay special machine is currently broken.

I really don't want anyone to get frustrated over the job. God knows the project brought me plenty of frustration (and plenty of joy seeing the designs come to life). I am all about sharing info.

In my shop I made the frames on an very old Acroloc series 10 machine. This machine has problems but the controller is a nice FAGOR 8025M. In any case on my machine with my programs cycle time was 187 minutes PER frame. I was nesting the frames and making four at a time so the 187 number is adjusted to reflect the per frame time. This number largely reflects the limits of my machine 100ipm max speed and 3500 rpm spindle. I often ran at full spindle and in hindsight should have considered doing plunge roughing on the part. Still on my machine getting a 35 minute cycle time simply will not happen. I firmly believe that even if I fixed my machine any "production" of a design is going to require more hardware and/or someone with more patience. I might return to making the frames myself at some point and/or might even get a mini mill or fagor but for right now I need to deliver some frames to customers who have placed backorders and do not like that I am out of stock for my 110mm frame design.

Cycle time is important for the job but so is part finish quality. On my machine I found I needed to take many light passes to get good finish on the parts. This adds to cycle time but since it is a part the customer will handle it needs to look good cosmetically in addition to the mechanical function. On a machine that is more rigid and/or with better cutting tools the job should go faster. Also I really found that when roughing the build up of chips was an issue so a machine with coolant through the spindle would be useful since it would clear the chips better. Like I said someone who really knows the mfg side of things is going to do better on getting the parts made without losing money. Finish on the parts must be good and the parts must be fairly close on tolerances especially in the area of the radius bosses.

I honestly want to protect anyone who is bidding on the job from getting in over their head and/or putting themselves in a place where they lose money on the project.