Re: Gould Crane
Dennis Storzek
On Sat, Jan 7, 2023 at 04:58 PM, Ted Larson wrote:
On Sun, Jan 8, 2023 at 09:37 AM, Tim O'Connor wrote:
There are two things that can take a tool out of operation; accumulated wear, and a 'crash', where something gets caught in the mold and closed on. Hard steel tooling combats the first, but is not immune from the second. Years ago Accurail lost a boxcar body tool on the second shot; the setup techs hanging the tool made the first shot, didn't notice that the ejector stroke was not long enough to push the part entirely off the core, and let the press close again on the part, mangling the blades that make the Z bar eaves. Luckily it was a quality molder with a good reputation to uphold, and they paid for the repair.
There are lots of materials that injection molds have been made of. Some are cast bronze alloy against plaster masters; the tooling for the intricate City Classics buildings were made this way. The casting process picks up the detail, but holding dimensions is a problem. Firms that had a background in engraving liked to use brass because it cuts well with the traditional form ground cutters engravers use, but it's not very hard. Grandt Line did most of their work in brass, as did Heljan, the Danish building kit manufacturer. Walthers even had them do some car kits in brass tooling, remember the 50 single sheathed automobile car and "beercan" tankcar? Brass tooling. Aluminum was the choice for the early CNC artists because it cuts fast and rarely breaks cutters. Front Range, Intermountain, and Tichy were big users. It's harder than brass and as long as you don't crush it, it's adequate for our industry's run sizes. Years ago many model kit tools were made of P-20 "prehard" steel, steel that was heat treated to a mid-range hardness that could still be cut with common High Speed Steel milling cutters, but the advent of EDM (Electro Discharge Machining, basically spark erosion) pretty much ended that, because now cavities can be sunk in fully hardened tool steel. I'm most comfortable with this process, although we have some aluminum tooling also. The most recent development is "hard milling" coated carbide cutters and toolpath strategies that allow fully hard tool steel to be worked on a CNC milling machine. I understand Brian of Tahoe Model Works is a big fan of this.
In conclusion, all these methods can yield serviceable tools for our industry if they're taken care of.
Dennis Storzek
If the tooling, molds are worn, that is partially good news, indicating that they likely have been used a lot… therefore lots of sales… yes?Back at this now that the traffic has subsided. The problem with the above statement is most of those sales came 5, 10, or 20 years too late to convince the manufacturer to remain in, and keep investing in the business.
On Sun, Jan 8, 2023 at 09:37 AM, Tim O'Connor wrote:
I have heard that aluminum molds don't last nearly as long as steel molds. Maybe Dennis can comment?Fred Becker of Front Range Products made that very same statement to me years ago and you see how that worked out for him. Cutting a new mold cavity is not trivial as far as machining time is concerned. Granted, the design work does not have to be redone, but that's only 10-15% of the total. If the product is past the initial sales "hump", one has to think long and hard whether one wants to commit those resources to a product that's past its prime, earnings wise, or just commit those resources to something new. The best course, to my way of thinking, is to pay a little more up front to get years of trouble free operation to capture years of continuing sales.
Dick Schweiger (C&BT) proudly told me once that his molds were made of steel. The Branchline box cars
mold that I saw was made from aluminum. With CAD files, I guess molds can be recut once they wear out?
There are two things that can take a tool out of operation; accumulated wear, and a 'crash', where something gets caught in the mold and closed on. Hard steel tooling combats the first, but is not immune from the second. Years ago Accurail lost a boxcar body tool on the second shot; the setup techs hanging the tool made the first shot, didn't notice that the ejector stroke was not long enough to push the part entirely off the core, and let the press close again on the part, mangling the blades that make the Z bar eaves. Luckily it was a quality molder with a good reputation to uphold, and they paid for the repair.
There are lots of materials that injection molds have been made of. Some are cast bronze alloy against plaster masters; the tooling for the intricate City Classics buildings were made this way. The casting process picks up the detail, but holding dimensions is a problem. Firms that had a background in engraving liked to use brass because it cuts well with the traditional form ground cutters engravers use, but it's not very hard. Grandt Line did most of their work in brass, as did Heljan, the Danish building kit manufacturer. Walthers even had them do some car kits in brass tooling, remember the 50 single sheathed automobile car and "beercan" tankcar? Brass tooling. Aluminum was the choice for the early CNC artists because it cuts fast and rarely breaks cutters. Front Range, Intermountain, and Tichy were big users. It's harder than brass and as long as you don't crush it, it's adequate for our industry's run sizes. Years ago many model kit tools were made of P-20 "prehard" steel, steel that was heat treated to a mid-range hardness that could still be cut with common High Speed Steel milling cutters, but the advent of EDM (Electro Discharge Machining, basically spark erosion) pretty much ended that, because now cavities can be sunk in fully hardened tool steel. I'm most comfortable with this process, although we have some aluminum tooling also. The most recent development is "hard milling" coated carbide cutters and toolpath strategies that allow fully hard tool steel to be worked on a CNC milling machine. I understand Brian of Tahoe Model Works is a big fan of this.
In conclusion, all these methods can yield serviceable tools for our industry if they're taken care of.
Dennis Storzek