Posted by: Conrad ® 11/20/2006, 23:49:52 Author Profile eMail author Edit

Hi, I am designing and building a fiber glass body for a formula-style race car (approximately 4' x 6' foot print). I am using Chavant I-307 sulphur based hard styling clay. I have found a machine shop with a 5-axis mill; however, they are inexperienced with clay. Question: does anyone have any information on what type of cutters to use, the desired feed rates, quill speeds, how to deal with the excess chips and how to protect/clean the mill during/after the process? Thanks for the help. Formula UVic FSAE Race Car Team University of Victoria British Columbia, Canada

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Re: Specifications for Milling Clay
Re: Specifications for Milling Clay -- Conrad	Post Reply	Top of thread	Forum

Posted by: gkemp ® 11/22/2006, 05:25:20 Author Profile eMail author Edit

I think you should talk to the Chavant guys to make sure you are using the best grade of clay for milling. They should be able to help you the most. Gary

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Re: Specifications for Milling Clay
Re: Specifications for Milling Clay -- Conrad	Post Reply	Top of thread	Forum

Posted by: randykimball ® 11/21/2006, 00:27:23 Author Profile eMail author Edit

..in a nut shell.. Carbide, dry, lots of RPM, and vacuum up ALL the dust and particles. The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them.

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Re: Re: Specifications for Milling Clay
Re: Re: Specifications for Milling Clay -- randykimball	Post Reply	Top of thread	Forum

Posted by: Conrad ® 11/21/2006, 16:29:12 Author Profile eMail author Edit

if you run the cutter too fast it will "burn" the clay (the sulphuric content will crystalize and these hard particles will make it impossible to get a smooth finish). what I am wondering is actual rpm values to run the cutter at and feed rates. does anyone have any experience with this type of work? Formula UVic FSAE Race Car Team University of Victoria British Columbia, Canada

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Re: Re: Re: Specifications for Milling Clay
Re: Re: Re: Specifications for Milling Clay -- Conrad	Post Reply	Top of thread	Forum

Posted by: randykimball ® 11/21/2006, 23:55:19 Author Profile eMail author Edit

Please don't discount my comments quite so quickly, they are the results and wisdom from learned expert experiences you will have to search far and wide to match. I'm sorry for being what may have seemed blunt. To a highly experienced machinest my "nut shell" was fair data for attacking the problem. From there a quick bracketed feed rate, RPM, and depth of cut control group would find the best results in a few minutes. To avoid "burning" you must feed through the material fast enough to out run the heat. Keeping fresh material in the cutter flutes chases the heat out the chips. What you must do is find an RPM and feed rate that performs these functions best. If you use too slow an RPM at the wrong feedrate you will break out clay. I've cut many kinds of materials with several kinds of machines. You are chatting with over 30 years of experience. Unless someone steps forward with actual experience machining clay you will have to do a control group and discover the best combination. I would expect the clay to be abrasive, much like the carbon phenloic I figured out to machine years ago for missle exhaust tubes. "They" were having a devil of a time and scraped the majority of the exhaust rings before that. In the case of the carbon phenloic we had to go to polycrystaline diamond DVJNL's, and required high surface footage. Because they maintained a sharp edge and were sharper to begin with, they did not over heat nor break out the carbon and pulled the heat of work out the chips. The product never even got warm to the touch. The poly-diamonds were expensive to purchase but much more economic to operate. Another method for removing the heat in the chip is to use a positive raked tool edge, this reduces cutter pressures, reducing heat by placing less stress on the product and more on the displacement of the curling chip form. I feel strongly you are going to want all the RPM you can achieve without burning the clay. This is to keep down the flute load to prevent chipping out chunks of clay and to provide a decent finish. A very sharp tool is going to be a requirement, unless I totally miss the cue. Perhaps cermic cutters, they have evolved much since I was involved. Also, I have cut many hours of hard high duro rubber, hard like a bowling ball. I'm thinking this is going to be very similar to hard clay. All the above applied to that application using carbide with an extreemly positive rake, ground a bit like a wood turning gouge. I hope you find someone experienced in clay, if not you have just received input acquired by many thousands of hours in shops machining a vast number of difficult special projects of who knows how many of different materials. I have solved numerous cutting problems for several manufacturers. I hope this experience is of some value to you towards sovlving this problem. Please be kind enough to post your findings when you figure it out, I for one, would love to know how wrong I was. Thank you, The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them. Modified by randykimball at Wed, Nov 22, 2006, 00:35:25

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Re: Re: Re: Re: Specifications for Milling Clay
Re: Re: Re: Re: Specifications for Milling Clay -- randykimball	Post Reply	Top of thread	Forum

Posted by: Conrad ® 11/26/2006, 04:38:50 Author Profile eMail author Edit

That is essentially what I have just been told by a member of the industry. The issues are, exact rates depend on the machine and numerous cutters may be used to obtain the desired result. A test piece is pretty much essential for first timers. The desired setup would be a cutter with a high helix, a lot of relief milled into the flutes, a large diameter and to use a lower rpm (typically it is not neccessary to exceed than 5000 rpm unless high feed rates are required). There will be a significant amount of chatter using this setup which so the operator should make adjustments until they are comfortable with the amount of vibration. Thank you for your post. I did not mean to offend, I simply pointed out a potential problem which can be avoided with neccessary precautions. Formula UVic FSAE Race Car Team University of Victoria British Columbia, Canada

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Re: Re: Re: Re: Re: Specifications for Milling Clay
Re: Re: Re: Re: Re: Specifications for Milling Clay -- Conrad	Post Reply	Top of thread	Forum

Posted by: randykimball ® 11/26/2006, 21:57:51 Author Profile eMail author Edit

Absolutely no offense taken. and.. by plenty of RPM, I was thinking older machines in which 5000 RPM would be an awlful lot of RPM... wink.. I'm thinking your surface footage across the flute tip should be in the 300 feet area.. this is my best guess. ... I'm thinking of as feed rate per flute of about .0045 to .007". One concern I have is the effects the clay will have on the machine ways (actually I'm more concerned about clay getting between the mate surfaces of the ways) and the coolant system. I think... again just taking a best guess.. that a strong vaccum nozzle at the cutter may be the best way to control most of the waste. This is what had to be done in the case of the carbon phenolic, and worked reasonably well, but still left a mess to clean up at the machine. One thing we did was to cover the bed and exposed ways with plastic sheets, they helped clean up intensely and protected the mate surfaces from being clogged with abrasive product. Additionally, the vaccum handled the air pollutant problem, I would expect the cut dry clay to be heavily airborn, but again I must admit, I'm guessing. FYI.. I realize this is not so close.. but I'm live in Texas and will in Canada on business a fair part of this next week. I will be in Toronto, .. well, it is closer than Texas. For some reason, I expect in the spirit of international relations, that felt worth mentioning. again.... good luck.. and please share your findings with us (the world). The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them. Modified by randykimball at Sun, Nov 26, 2006, 22:26:19

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Re: Re: Re: Re: Re: Re: Specifications for Milling Clay
Re: Re: Re: Re: Re: Re: Specifications for Milling Clay -- randykimball	Post Reply	Top of thread	Forum

Posted by: Conrad ® 11/28/2006, 12:44:36 Author Profile eMail author Edit

The machine we will be using is a gantry style machine where the part sits on the ground and the cutter moves around the part, so there are no ways. Jobs that require coolant aren't milled on this machine either. To collect the clay chips we are laying poly on the ground under the part and setting up welding curtains to catch the "flying" chips. Toronto is a nice place, but a little cold this time of year so I hope you're bringing a large jacket and some snow pants! Coincidently, I had an internship in Phoenix over the summer. Formula UVic FSAE Race Car Team University of Victoria British Columbia, Canada

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