Previous in Forum: Modelling Complex Manufacturing Systems Using the IDEF Modelling Languages   Next in Forum: Discharge Tube Used in CO2 Laser
Close
Close
Close
21 comments
Member

Join Date: May 2020
Posts: 7

Mold Material for Refractory Cement?

05/10/2020 4:24 PM

Hello,
I design molds for years and always made metal and plastic injection molds. Now I got a new work about refractory cement mold. It is a material used for fire bricks and cement will be filled into mold then with vibration, it will reach everywhere.

I just want to ask that, if anyone has experience with this material? What material should I prefer for mold? Cement heats up to 80 degree during process and I want my mold to be in good shape and re-use for many.

Register to Reply
Pathfinder Tags: mold material refractory
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Guru

Join Date: Mar 2007
Location: by the beach in Florida
Posts: 33231
Good Answers: 1807
#1

Re: Mold material for refractory cement?

05/10/2020 4:50 PM

Are you making a mold for firebricks, or a firebrick mold for foundry application?

__________________
All living things seek to control their own destiny....this is the purpose of life
Register to Reply
Guru

Join Date: Mar 2007
Location: by the beach in Florida
Posts: 33231
Good Answers: 1807
#2
In reply to #1

Re: Mold material for refractory cement?

05/10/2020 5:59 PM

Most I've seen used a wood frame... I guess it depends on how many you want to make, and how fast you want to make them...

https://dexterpottery.com/2011/07/02/hand-made-fire-brick/

__________________
All living things seek to control their own destiny....this is the purpose of life
Register to Reply
Member

Join Date: May 2020
Posts: 7
#3
In reply to #1

Re: Mold material for refractory cement?

05/11/2020 1:20 AM

I will make mold for firebricks. Thanks for reply

Register to Reply
Active Contributor

Join Date: Mar 2020
Posts: 12
Good Answers: 1
#7
In reply to #3

Re: Mold material for refractory cement?

05/11/2020 6:40 AM

Fire bricks and blocks usually use a pressure steel mold machine as this is faster and uses a drier mix than used in vibration molds. But have used vibration molds of hard plastic that has release agents or oil in them. Regular bricks are normally made using wooden molds as the bricks are formed and then air dried..where they shrink..

Not sure what newer processes for brick molds are.

Register to Reply Score 1 for Good Answer
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32044
Good Answers: 838
#4

Re: Mold material for refractory cement?

05/11/2020 3:25 AM

Wood, lined with PTFE sheet, would be a good place to start.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Member

Join Date: May 2020
Posts: 7
#5
In reply to #4

Re: Mold material for refractory cement?

05/11/2020 4:11 AM

Thank you, is there any difference about wood types?

Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32044
Good Answers: 838
#6
In reply to #5

Re: Mold material for refractory cement?

05/11/2020 4:51 AM

<...design molds for years...>

https://en.wikipedia.org/wiki/List_of_woods

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru

Join Date: Oct 2006
Location: 44.56024"N 15.307971E
Posts: 7784
Good Answers: 264
#8
In reply to #5

Re: Mold material for refractory cement?

05/11/2020 6:48 AM

Redwood would be a good choice,if you are going to use wood.

It is very resistant to decay and does not shrink with changes in moisture and very stable.

As SE said,a plastic liner is recommended if using wood.

Type UHMW plastic is my recommendation,as it resists abrasion and is very durable,and is almost as slick as Teflon,giving easy release from the mold without the use of release agent.

If you are going to inject under pressure,an external reinforcement is recommended.

Of course,you could construct the entire mold from this material,which I think would prove to be the most durable design.It would not require a liner or a release agent, and eliminate one step in the process versus wood.

Here is a link:

https://www.amazon.com/dp/B000ILG0KA?tag=duckduckgo-ffnt-20&linkCode=osi&th=1&psc=1

__________________
"A man never stands so tall as when he stoops to help a child." "Never argue with a stupid person.They will drag you down to their level and beat you with experience" "Homo homini lupus"
Register to Reply
Member

Join Date: May 2020
Posts: 7
#9
In reply to #8

Re: Mold material for refractory cement?

05/11/2020 7:35 AM

Thank you a lot. There will not be any pressure as injecting. Just casting and vibration. But shape is curvy, as dome so TPFE has been very expensive as my calculations. Polyethylene is kinda cheap but I wasn't sure about heat resistance. I thought maybe 80 celcius degree could have been problem. Even it is not long time, just around 1 hour. Have you used this material around 80 degree?

Thanks a lot for your answer.

Register to Reply
Guru

Join Date: Oct 2006
Location: 44.56024"N 15.307971E
Posts: 7784
Good Answers: 264
#10
In reply to #9

Re: Mold material for refractory cement?

05/11/2020 8:17 AM

UHMW is usually cheaper than the fluorocarbons,and I think better for your applications.I would use an external support frame if this is going to be used in a continuous repetitive high production application.

This material can handle up to 180F temperature continuously.

See spec sheet below.

https://www.curbellplastics.com/Research-Solutions/Technical-Resources/Technical-Resources/UHMW-Data-Sheet

I am sure there are cheaper alternatives but you most consider the reliability,durability and total cost of each option.

__________________
"A man never stands so tall as when he stoops to help a child." "Never argue with a stupid person.They will drag you down to their level and beat you with experience" "Homo homini lupus"
Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32044
Good Answers: 838
#11
In reply to #9

Re: Mold material for refractory cement?

05/11/2020 8:26 AM

<...maybe 80 celcius degree could have been problem...>

That was the reason for suggesting PTFE as it can go readily to 110degC or so without significant effect. In the context of casting <...refractory cement...> from an aqueous slurry, this temperature is above the boiling temperature of the water present, and therefore the setting <...cement...> will suffer first as temperature is increased. PTFE is also very "slippery", meaning that there would be little issue in principle with releasing the <...mold...> from the finished <...fire brick...>.

Were the PTFE to seal the wooden former against water leakage, then the nature of the wood would be of little importance.

Do let the forum know how initial trials went.

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Member

Join Date: May 2020
Posts: 7
#12
In reply to #11

Re: Mold material for refractory cement?

05/11/2020 8:54 AM

Thank you for your attention. I would prefer PTFE but it seems expensive, if I can find a solution for cheaper alternative then I can. I will write here again, which I tried and how it went.

Register to Reply
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32044
Good Answers: 838
#13
In reply to #12

Re: Mold material for refractory cement?

05/11/2020 9:15 AM

That practice is sometimes known as "Value Engineering".

<unsubscribes>

__________________
"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Register to Reply
Guru

Join Date: Oct 2006
Location: 44.56024"N 15.307971E
Posts: 7784
Good Answers: 264
#14
In reply to #12

Re: Mold material for refractory cement?

05/11/2020 9:37 AM

UHMW is usually about 1/4 the price of PTFE for same thickness and square foot, is more durable and second only to Teflon insofar as lowest frictional coefficient;No release agent required.

Check out my previous links,plus these for prices.

UHMW:

https://www.amazon.com/Molecular-Weight-Polyethylene-Standard-Tolerance/dp/B000ILLNIY?th=1

---------------------------------------------------------------------------------------------------

PTFE:

https://www.usplastic.com/catalog/item.aspx?itemid=30887&catid=

You could build the box frame out of your choice of materials,and line it with UHMW sheets.

__________________
"A man never stands so tall as when he stoops to help a child." "Never argue with a stupid person.They will drag you down to their level and beat you with experience" "Homo homini lupus"
Register to Reply
Guru

Join Date: Oct 2006
Location: 44.56024"N 15.307971E
Posts: 7784
Good Answers: 264
#17
In reply to #9

Re: Mold material for refractory cement?

05/11/2020 12:46 PM

The cement only needs to be in the mold until it sets up.

The lower the slump of the concrete,the faster it will firm-set.

This should not result in a very high prolonged temperature.

Matter of fact it should be cooled after setting to prevent weakening of the concrete by excess heat.

It is an exothermic process.

The cement is also a hygroscopic process,and needs moisture after the initial setup to prevent cracking,so it must also be kept moist while curing.

I am sure you are aware of the curing process if you are going to be manufacturing them?

__________________
"A man never stands so tall as when he stoops to help a child." "Never argue with a stupid person.They will drag you down to their level and beat you with experience" "Homo homini lupus"
Register to Reply
Member

Join Date: May 2020
Posts: 7
#18
In reply to #17

Re: Mold material for refractory cement?

05/11/2020 1:01 PM

Yes I know them for my material choice, water absorption and heat resistance are key matters. Need to find a design to manufacture it cheaply.

Register to Reply
Guru

Join Date: Mar 2007
Location: by the beach in Florida
Posts: 33231
Good Answers: 1807
#15

Re: Mold Material for Refractory Cement?

05/11/2020 11:57 AM

I have several concrete molds everything from statues to stepping stones and they are all made out of ABS plastic...

https://www.ebay.com/b/Concrete-Slip-Casting-Molds-Kits/83898/bn_73160526

https://www.creativemechanisms.com/blog/everything-you-need-to-know-about-abs-plastic

__________________
All living things seek to control their own destiny....this is the purpose of life
Register to Reply
Member

Join Date: May 2020
Posts: 7
#16
In reply to #15

Re: Mold Material for Refractory Cement?

05/11/2020 12:08 PM

Is ABS good enough for 80 celcius and chemical reactions? Have you ever used ABS with materials like fire bricks?

Register to Reply
Guru

Join Date: Mar 2007
Location: by the beach in Florida
Posts: 33231
Good Answers: 1807
#19
In reply to #16

Re: Mold Material for Refractory Cement?

05/11/2020 1:28 PM

Yes it's good at 80°C and is chemical and abrasion resistant...firebrick being lighter than concrete should be less demanding...

https://www.creativemechanisms.com/blog/everything-you-need-to-know-about-abs-plastic

__________________
All living things seek to control their own destiny....this is the purpose of life
Register to Reply
Power-User

Join Date: Jul 2010
Location: North Carolina, USA
Posts: 423
Good Answers: 9
#20

Re: Mold Material for Refractory Cement?

05/14/2020 8:16 AM

I worked for a company for a while that used hot forming tools made of refractory cement. The tools were made in low quantities but could weigh around 100 pounds per segment. Our molds were typically made from marine plywood and other common cabinetry woods as well as UHMW or Delrin sheet. Common lumber was used for structure as needed. Sometimes our tools would show the wood grain so I believe they were not always lined or were lined with thin poly sheeting or the wood was sealed with varnish or similar. I believe when pouring the mold a release spray was used as well. I know from another source that common cooking spray can work for that.

Although this seems to concur with other replies, my point is unless you are making large quantities and need a high level of repeatability you basically just need a stout wooden box. A talented cabinet maker could build them for you. Just make sure your brick design has some draft and follows good casting mold design practice.

Register to Reply
Participant

Join Date: Jun 2020
Posts: 2
#21

Re: Mold Material for Refractory Cement?

08/14/2020 4:42 AM

As I know, I think the first thing is that you need to confirm what material of mold is. Then you can figure out those things.

Register to Reply
Register to Reply 21 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.

Comments rated to be "almost" Good Answers:

Check out these comments that don't yet have enough votes to be "official" good answers and, if you agree with them, rate them!
Copy to Clipboard

Users who posted comments:

ahmedsayeed1982 (6); BroAdam (1); HiTekRedNek (4); JRiversW (1); PWSlack (4); SolarEagle (4); songshun (1)

Previous in Forum: Modelling Complex Manufacturing Systems Using the IDEF Modelling Languages   Next in Forum: Discharge Tube Used in CO2 Laser

Advertisement