Am I on the right track

Ok I am new to this and have been reading the forum for the past 2 days as a guest and it seams this is the place to go for information…. I am bad at name but I like what the guy did when he made his 2’x4’ machine to do signs… anyway I have been toying around with building one for a couple years and now seams to be the time to do it as my business is starting to take off…as of right now I do fiberglass molds for the Chevy luv truck and will be getting into the early imports as time goes on… I am a one man show and parts some times take 3 days to make one a mold is done and I was thinking there has to be a better way or faster way to do some of the parts I make… I found a part I wanted to make and noticed it looked like it was vacuum formed (a cab visor) for a Chevy luv so it got me thinking maybe I can do this and save time and maybe money in the long run… ill attach some pics of what I want to make… my first thought was to reskin the dashes for the truck but I could never find the materials I was looking for… but here is what I want to build… the machine needs to be a 4’x8 size to accommodate the lager stuff I want to form, I have come up with what I think I will need so correct me if I am wrong… I need 3 60 gallon tanks to do the fast form ( will use 2 to do the fast vacuum and the 3rd to do the hard pull? I need a vacuum pump of at least 21 cfm but would like more in the line of around 30 cfm and about 25 to 27 inches of vacuum. I was going to use nichrome coil heaters for the oven , I figure I need 70 feet was going to space the coils about 3 in apart? Is to close or to far apart? Should I run 1 pump for all 3 tanks or should I run 2 pumps 1 for the fast pull and one for the hard pull? I didn’t want to spend 10k or more on a machine and I think I can build this for around $1500 with I have in the shop laying around already … here are some pics, the first is a vacuum forned visor and the rest are some part I would like to duplicate… also some fender flares I have seen was a thin wall ABS I think…
the blu and white where vacuum formed i was told... the dash is what i would like to recover in the right material
http://ctmandu.smugmug.com/photos/380396384_wWeMM-M.jpg
http://ctmandu.smugmug.com/photos/380393864_7Csvu-M.jpg
http://ctmandu.smugmug.com/photos/401040370_fXBcE-M.jpg
these black flares where vacuum formed with a thin wall i think maybe less then 1/16 the cab visors where i think 1/8
http://ctmandu.smugmug.com/photos/380396395_4xEyv-M.jpg

so i know this can be done from the research i have done the question is am i on the right track what am i missing or what are your thoughts ... thanks , Troy @ Luv Truckin'

Ok Some observations.... First, there is no reason for a 2 stage pull. This process is a crutch around inadequate vacuum sources on smaller home machines. 60 gallons of total tank is a nice size, if you do smaller parts on the machine, and you will, you will find it handy to put a valve on the tanks so you can get 20 or 40 callons as choices. This will make the job go faster when you dont need to pull down a large volume.
The heater needs to be zoned. you need to be able to control the heat in local areas to make complex parts. Its easy, add switches and change the coils to make them.
Reality ssays something different though... Build good tools and job it out.... the money is in sales unless you want to build a lot of plastic parts for a lot of people.....

You may also want to look deeper into the finishing that has to be done after the vacuum forming. I have visited places making items similar to those in your pictures and in many cases the vacuum formed parts went into a CNC router to trim the edges and take out holes. This was something that was difficult and un-economic to do by hand.

In addition some parts were done by the technique that pulls vacuum under the part and applies mild air pressure on the top. The equipment for this is a lot more complex.

I am a real fan for doing everything in-house buy you may be biting off a really big mouthful here doing it alone.

Hey Troy,

I vacuum form fender flares for the jeep cherokee on a 2'x4' machine. "Spektr" knows what he's doing and has given me good advice in the past. Keep in mind that on surfaces close to vertical the plastic thins out as it stretches over the mold. Of course, on horizontal surfaces the plastic stays closer to original thickness.

If you're getting ready to build a machine, especially a large one, I would really suggest using plans. Check here: http://www.build-stuff.com/index.htm The large proto-form machine seems to be carefully thought out and planned. There are lots of sources listed for parts too. I wish I had got the plans in the first place when building my machine.
hth, Doug

thanks, I will look into it

I think you are on the right track. You have no problem building the GRP moulds but your proposed oven (nichrome wire) is a No No!
I suggest you build a gas oven. Use Thermal Block (available from any builders yard) Make your oven over sized so you can accomodate most large size plastic sheet for vac forming your mouldings. I would heat the oven using bottle gas and a few gas impact burners with a heat baffle above each burner.
Install your plastic sheet horizonatal (within frames) and remove when temp is correct and manualy locate sheet onto prepared moulds and evacuate same.

i dont think i have seen the gas ones... any pics anyone?

Quote:

---

Originally Posted by fencer

........ (nichrome wire) is a No No!
...........I suggest you build a gas oven
..........manualy locate sheet onto prepared moulds...

---

I do not believe that any of these suggestions are useful for the larger vac forming (car bumpers) the OP intends.

All the major DIY vac former designs, for plastic this size, on this forum and at the more populated vac former forum, tk560.com use nichrome wire and plastic carriers to control the travel of the hot plastic. I imagine a gas fired system would be doable but I don't know why you would want to. Nichrome wire has proven long-term to be safe, efficient, and inexpensive for heating plastic for the DIYer. Also, since the hot plastic & metal frame are well over 300+f a controlled method for moving the hot plastic from the oven to the mold is important, particularly for something this large.

For the DIYer, consider the TJ design or the Proto-Form. Both long-term, user proven, reliable & safe designs that use nichrome heating systems and plastic carrier systems. Both of these designs are often used by DIYers from this forum and TK560.

I am a relative novice since I've only been doing this a few years. But you can refer to the lengthy experience of other vac formers with proven track records.

Respectfully, DougN

I thermoform for a living. Using a brick style gas oven is NOT the way to do it. If you wish to use gas, and I have, use infared gas panels. They are throttleable, robust and reasonably priced. Electric heat seems to be the industry standard for one reason however. It is easily regulated and zoned. The gas oven described above will not run at an even heat inside. You need to hold a set point plus or minus 5 degrees F in the interior space to get consistant results from oven heated plastic. My electric oven is there, but only after a LOT of tuning, interior recirculation fans, baffles and other nonsense.

If you want gas, fine, just dont look to anyone doing Vac Forming seriously for help if you use a nonregulated oven..

Scott.

FACT: Everyone knows that gas heated ovens work regardless of what ever we decide to put into them -- if this wasnt so then few of us would ever have eaten a hot dinner, roasted a turkey, baked bread and a multitude of cakes and cookies ... all cooked at different temperatures and times. Even the dumbest housewife eventualy learns how to use a gas oven. So why not dispell some myths and use one yourself -- only bigger?
Sure nichcrome wires will heat up an oven (given long enough) On Utube we see kids producing all manner of plastic parts using mums oven and a vacuum cleaner.
So build a gas oven in which to place your valuable plasic and heat it until its ready to form. If you want the details on how to build an oven then open any oven door --and take a look at what is inside, okay!
Now measure the size of the plastic you want to heat and build your oven. You can wreck any old oven and take the parts from within -- including the temperature controller and thermometer if needed. Just construct YOUR oven a little, or a lot, larger. Its as simple as that! No but's no If's. But If -- 'your custom oven' doesnt work, then say goodbye to any more hot dinners as things must be changing very rapidly and there will never be any more roast beef, lamb, chicken and turkey on any menu ever again -- ever!
Construct it -- Use it -- Form it. (No rocket science required )

Hi Troy,
Having been in the GRP (glass reinforced plastic) industry for a little over 30 years I should note that: You could pull 40+ vacuum formed parts by the time your initial gell coat has hardened. Lifes a gas!
Best regards.
Ed

Quote:

---

Originally Posted by spektr

I thermoform for a living. Using a brick style gas oven is NOT the way to do it. If you wish to use gas, and I have, use infared gas panels. They are throttleable, robust and reasonably priced. Electric heat seems to be the industry standard for one reason however. It is easily regulated and zoned. The gas oven described above will not run at an even heat inside. You need to hold a set point plus or minus 5 degrees F in the interior space to get consistant results from oven heated plastic. My electric oven is there, but only after a LOT of tuning, interior recirculation fans, baffles and other nonsense.

If you want gas, fine, just dont look to anyone doing Vac Forming seriously for help if you use a nonregulated oven..

Scott.

---

Hi Scott. Non regulated ovens will work very well indeed in this instance. The guy who intends to make auto panels would be making them one at a time and not on a 'conveyer belt' principle. He would be simply heating a sheet of polyprope or ABS as a single unit measuring about 2foot x 5foot and aprox 3/16ths thick. With this in mind -- he would be placing the plastic upon the buck/mould manualy (within a frame). At this moment the guy is laying-up gell coat and fibreglass that takes at least 24 hours to complete and cure prior to removing the same from his moulds. So what Im suggesting is not in contradiction to what you offer upon the subject -- but to close the gap between what he is currently doing and him moving onto vac-forming. Given this scenerio a gas oven (as outlined) would be a perfect rout providing he closely monitors the heating of the plastic sheet -- do you agree?
Kind regards
Ed

Ed..

A regulated gas oven would work fine. A non-regulated simple gas oven will not get it done... I'm just trying to save the guy some misery..

The first problem is controlling the radiant heat from the flame front out of the burners. THAT is why I suggested radiant panels instead of open burners.

When working with plastic you need predictable even heat on the sheet. Non-uniform temperatures cause non-uniform finished part thicknesses. Warmer spots are thinner than cooler spots. If you dont control the temp inside the oven accurately, each part will come out differently with respect to part thickness. Since Vacuum Forming is a stretch form process, you just have to control that primary variable. Over the years, I've found +/- 5 degrees from a set point to be needed. Remember he's talking in excess of 3 x 5 feet of frame. My small oven I use for drape forming 1/4 lexan for windshields accepts a max blank size of 67 x 45 inches. Its 3 feet tall at the door and took quite a while to get regulated when I started, it would run as far apart as 40 degrees high to low inside the oven depending on where yo umeasured it. Ive got it inside 5 now after quite a bit of fiddling.... It is black art, not science.

FWIW, Lexan gets draped at about 345 f and starts to get iffy at 370. It wont form well below 320. This shows you how narrow the window can be.

Scott.

You know, if the GRP parts are working, he can do it another way..
Use Sunrez UV resins and the existing tooling. Its simple to do.
Release coat the mold. Spraypaint the tool in lieu of gellcoat.
layup the part , expuse to sunlight to cure, or use tanning bed lights
to cure it in about 10 minutes to demoldable. This should really step up his cycle time. Another benefit is that the open time for the layup isnt controlled by the resin promotion percentages.. Its open until you expose it to UVB....... More than 1 way to skin a cat.


Scott..

Whatever size oven you require and whatever the temp needed then you cannot beat a gas oven. You want even-heat then go for gas. Construct a metal box with a hinged-lid. Beneathe the metal floor of the box plase gas burners ( I use two burners and each are ten foot long) My oven is 12foot x 3foot witha depth of 3foot. The gas burners are within 4 inches of the base of box. The whole box is enclosed in thermolite block. The gas burners heat the floor of the box and the heat travels up the sides of the metal. This is an enclosed 'Convection Oven' and everyone knows these units promote even heat throughout the box -- no draughts no hot or cold spots. allow the oven to reach your operating temp and insert the plastic sheet (horizontaly) _______ and never verticle. Lexan sheet will also be happy within this environment as would any other plastic. Make the metal oven out of 2mm steel sheet and rivet the thing together. Provide a metal floor so you can adjust the height by fixing metal angle |_ ______ _| to hold in desired position. This is'nt a black art -- its common sense and its pretty certain you cannot beat this type of oven. Rolls Royce Motors use this 'same set-up' for their "inner-wings." I've been using it for 10 years or more to make just about everything that is formable. By the way I use bottled 'Propane Gas' as its hotter and does not freeze in the winter. No matter what you are vac-forming the answer is in the 'even temperature of the sheet material' and not the brute force of your vac-pump. Lifes a gas!

Quote:

---

Originally Posted by fencer

Hi Troy,
Having been in the GRP (glass reinforced plastic) industry for a little over 30 years I should note that: You could pull 40+ vacuum formed parts by the time your initial gell coat has hardened. Lifes a gas!
Best regards.
Ed

---

yes faster.. it takes me (a small shop) 3 days to pull one part.
1.Gell, wait
2.apply fiberglass, wait
3.pull and trim

that's 3 days could make a lot of parts in that time if needed

How are the flares coming out... to be honest i was thinking of doing same thing.. makeing them for jeeps..cherokees to...so im curious how its working out for you and what they look like..
Thanks
Greg

Quote:

---

Originally Posted by Hommersimpson

How are the flares coming out... to be honest i was thinking of doing same thing.. makeing them for jeeps..cherokees to...so im curious how its working out for you and what they look like..
Thanks
Greg

---

Here's where to find the info on what's happening.
Jeep Cherokee Fender Flare Thread on NAXJA
I'm usually on TK560 since there's a lot more going on with vac forming over there.

Quote:

---

Originally Posted by fencer

FACT: Everyone knows that gas heated ovens work regardless of what ever we decide to put into them -- if this wasnt so then few of us would ever have eaten a hot dinner, roasted a turkey, baked bread and a multitude of cakes and cookies ... all cooked at different temperatures and times. Even the dumbest housewife eventualy learns how to use a gas oven. So why not dispell some myths and use one yourself -- only bigger?
Sure nichcrome wires will heat up an oven (given long enough) On Utube we see kids producing all manner of plastic parts using mums oven and a vacuum cleaner.
So build a gas oven in which to place your valuable plasic and heat it until its ready to form. If you want the details on how to build an oven then open any oven door --and take a look at what is inside, okay!
Now measure the size of the plastic you want to heat and build your oven. You can wreck any old oven and take the parts from within -- including the temperature controller and thermometer if needed. Just construct YOUR oven a little, or a lot, larger. Its as simple as that! No but's no If's. But If -- 'your custom oven' doesnt work, then say goodbye to any more hot dinners as things must be changing very rapidly and there will never be any more roast beef, lamb, chicken and turkey on any menu ever again -- ever!
Construct it -- Use it -- Form it. (No rocket science required )

---

FACT: Despite the condescending tone of this post implying that the answer is obvious and you're an idiot if you don't see it or can't do it, making your own gas oven for thermoforming is a terrible idea.

Nobody is doubting that a gas oven will heat the plastic, nimrod. However, like others have mentioned, it is vital to be able to precisely control the temperature of different zones (for example, the ones we use have 36 independently controlled panels.)

Indeed, no rocket science required, but some basic knowledge of the subject matter is.