Rotocast #25 | How to choose the right mold? | How to choose between aluminum, stainless steel, or carbon steel — LIVE

What you gain by watching

• You learn how to choose between aluminum, carbon steel, and stainless steel by looking at details, thickness, and cost-benefit — not just the price of the sheet.
• You understand how to avoid warped molds, visible seams, and rework with practical criteria for thickness, heating, and closing.
• You see how to move knowledge away from improvisation and dependence on a single person, with a documented process and porosity recovery.

Episode chapters

1. 1

   Choosing the right mold: aluminum, carbon steel, or stainless steel?

   How do you decide between aluminum, carbon steel, and stainless steel when the part you see doesn't always reveal the mold behind it? We tell the story of a mold we swore was aluminum because of its richness of detail — and the manufacturer showed us it was carbon steel, made by hand, without a hydraulic machine, without a brake press, without laser cutting, with a level of finish that impresses and even rivals cast aluminum.

   No, that mold is carbon steel, come here

   ▶ Watch at approximately 7:06
2. 2

   Cast or machined aluminum? What decides the right mold for each part

   When is an aluminum mold really the right choice for your product? We talk about the criteria that weigh in this decision — amount of detail, tooling cost, and even the advancement of 3D printing and CNC machining — and we show why cast aluminum is still the best known, while machined aluminum is starting to gain ground and change the math in the market.

   The finish is the same… that's really a matter of the quality of whoever is providing the service

   ▶ Watch at approximately 12:09
3. 3

   Cast aluminum or carbon steel: what nobody tells you about choosing a mold

   The doubt that stops many people when deciding on a mold is expansion — what happens to the seams when the part heats up? The answer lies in the quality of the tooling work: the machined part can be so perfect that when you join one piece to another, you can't even see the seam. And then came the checklist that was missing: the first criterion is the amount of detail in the part — ridges, grooves, and textures that cast aluminum delivers and carbon steel simply cannot achieve without chemical plating or blasting that make everything more expensive — and the second is cost, which only makes sense to compare after understanding what the part requires.

   The machined part, it can be so perfect that when you join one piece to another, you can't even see the seams

   ▶ Watch at approximately 17:12
4. 4

   Not every part needs the most high-tech machine on the market

   We always come back to this point because it decides investment: buying a fully high-tech machine to make a trash can may not make sense, but a technical part with shrinkage control and fit changes the game. And when the subject turned to thermography, we told how the thermocouple can read 300 degrees while the part is at 200 — and it is precisely this control inside the mold that we will show next week, because relying only on the operator's sensitivity is a risk that leaves the company along with him.

   Your thermocouple was way out of position there, it read 300 degrees and the part was at 200 degrees

   ▶ Watch at approximately 22:37
5. 5

   When labor disappears, the process needs to be in your hands

   The cost of keeping qualified people on the factory floor only grows, and finding someone to press the button has become the biggest challenge for many rotomolders — to the point that we joke that we supply almost everything except labor. The answer we explored is to document the process within the company itself, with SOP and technology closely monitoring production, so that knowledge does not live in the head of an employee who may one day leave.

   The only thing I cannot supply to you today is labor.

   ▶ Watch at approximately 27:43
6. 6

   When knowledge becomes a hostage: the lesson about decentralizing knowledge in the factory

   Imagine arriving at a company and discovering that a single person masters all the technical knowledge and does not accept anyone else's opinion. That is how Júlio César told his story: the mechanic who solved everything was bothered by the arrival of the new manager, but instead of firing him, he chose to talk, recognize the guy's value, and create procedures and train other people. We learned that distributing knowledge does not weaken anyone, on the contrary, it protects the company and also values those who really understand the subject.

   I was not there to give him orders, not only for that. Of course, I went there with that role, but how important he also was to the company, I did not want to dismiss him.

   ▶ Watch at approximately 32:46
7. 7

   Too thin a mold warps from ventilation alone: the right thickness for aluminum and carbon steel

   Who hasn't seen a mold warp in the oven and heard the sheet metal crack as it cools? We share what we learned about sheet thickness: for aluminum, the range that both practice and the scientific method point to is between six and eight millimeters, with eight guaranteeing resistance against impacts and deformations. For carbon steel, the logic flips and cost becomes the first criterion, followed by production lead time, which is usually faster than aluminum — and the choice of thickness always depends on the mold size, the part profile, and the amount of detail, with the range of two point seventy-five to three point ten millimeters prevailing in day-to-day work.

   ▶ Watch at approximately 38:02
8. 8

   Carbon steel mold: when thin sheet metal becomes a headache

   The doubt that stops many people is whether you can mix sheet thicknesses in the same mold — and the answer is that it's not advisable, because each sheet heats at a different rate and that disrupts the material distribution. We also show that the way forward isn't to change the arm settings, which would affect the other molds, but rather to direct the heat with insulation or specific rotomolding techniques.

   If you have one sheet different from the other, it will heat more or less, and that will influence the material distribution.

   ▶ Watch at approximately 43:10
9. 9

   How to handle different sheet thicknesses without touching the mold

   We returned to the point that stops many people in production: when sheet thicknesses are different in the same mold, you can insulate one part or pull more heat to the other with technique, without changing the settings every cycle — and the care needs to be even greater at the closing flange. After a message from our partner CX Contábil, with the case of Ivan Grisolia, we stay firmly on the mold closing hook, which is very valuable for anyone who wants to stop relying on improvisation in production.

   They're less unpredictable, right? Yeah, if you already have a mold, for example, you want to use part of the other mold, they're different sheet thicknesses, you can join the two pieces in the mold there and you insulate one part or pull a little more heat to the other with techniques, without changing the settings.

   ▶ Watch at approximately 48:32
10. 10

    Accounting is not a cost, it's an investment in your mold

    We received a message that made it clear how much accounting can be an investment for the rotomolder — and not a cost. We talked about the episode 'Pix dos Impostos', which even Júlio's wife followed and understood everything, and we kept showing that the right sheet, the thickness of carbon steel or stainless steel and the spacing of the clamps make all the difference in the final result.

    Do you think accounting is a cost or an investment?

    ▶ Watch at approximately 53:33
11. 11

    A mold arrived so full of holes that we sent it back right away

    A mold arrived to us with a gross porosity flaw — the kind you only discover when you start sanding and finishing — and we told the company right away: take this thing back, it's not possible. We showed how that is just the tip of the iceberg, with the blue material inside still releasing gas and piercing the part, until a porosity recovery technique comes into play with an application that fixes the mold and even gains extra protection against wear and demolding.

    ▶ Watch at approximately 58:36
12. 12

    Why the aluminum mold can beat carbon steel — and when that turns into a loss

    We showed why the choice of mold material cannot be decided only by the price of the sheet: a cast aluminum mold can be the cheapest option for parts with many details or curves, while carbon steel requires a hydraulic press brake, machining and highly qualified labor. And we closed with the message that is worth more than any spreadsheet: you don't choose a mold by cost, you choose it by cost-benefit — because we have already seen a client save on the foundry and have to spend again, twice.

    You don't have to think about cost for a mold, you have to think about cost-benefit

    ▶ Watch at approximately 1:04:21
13. 13

    A welder doesn't make a mold — but with guidance, he made it perfectly

    We always hear the same argument: 'I have a trusted welder, he makes the mold.' But a welder is good at gates, not molds — and when we invited one to try, he himself was afraid to take it on. It was only by closely following along, guiding every detail of the outlet, the reinforcement rib, and the weld point, that the mold came out perfect — and we proved that what's missing isn't manpower, it's the experience of someone who knows the process.

    ▶ Watch at approximately 1:09:32
14. 14

    The porosity specialist's challenge: he only comes to RotaCast if the community calls for it

    We invited a specialist in porosity recovery and Teflon application on aluminum and carbon steel molds, but he set a condition: he'll only participate if a real number of people show interest. So we opened the invitation to those who live with this problem — fill out the form, comment on the video, share it with those who suffer from porosity — and the reward is a rare case: 'You can send the mold to me, I'll do it. If the person isn't satisfied with the result, they don't pay,' with impressive results in porosity recovery and the possibility of bringing this technology into our own company.

    You can send the mold to me, I'll do it. If the person isn't satisfied with the result, they don't pay.

    ▶ Watch at approximately 1:14:32
15. 15

    The secret that holds the industry back: why nobody shares solutions in rotomolding

    We often hear that recovering porosity isn't possible, and the answer lies in the very way the industry behaves: each company guards its solution because of trade secrets and competitiveness, and information gets scattered. That's exactly why we created Rotocast — to bring together those who want to bring solutions and useful information to those in the day-to-day, because in our view if you stay hidden, the client won't even reach you, and it's by sharing that the industry grows.

    If you stay hidden, the client won't even reach you either.

    ▶ Watch at approximately 1:19:43
16. 16

    The Portal Rotomoldagem agenda: who's coming to talk about burners, additives, and Rotomax

    The question that sparked the segment was simple: how do we keep the wheel turning with heavyweight guests every Friday at noon? We closed with José Marques from Rotomax on the 27th, lined up Douglas to come talk about burners, and we're still waiting on Mr. Mirai's schedule regarding additives, not to mention the open invitations for heavy machining and molds. And that's what drives the Portal: we go after the people who truly know their stuff, bring the subject to the audience, and even open the doors for the market itself to announce here — because the commitment is Friday, at noon, with content that helps those on the factory floor grow.

    Any topic you'd like us to cover, send it to us, and we'll go after the people who have the knowledge to bring that topic here to you

    ▶ Watch at approximately 1:24:59