X-Project: Right Tumbling Media for Aluminum
The cooperation started from international business is not easy. People cannot physically see and touch each other. The only way of communication is email, WhatsApp/Wechat/skype, phone call or a video chat. As a result, the company and the person to discuss is very important.
1. Start contact from an email:
On September 2014, we receive an inquiry from ZDC company who make aluminum die casting parts for Honda Motor. At present, they use wheel grinding to polish smaller size aluminum die casting parts. However, the process is dust and dirty, time taking. They would consider a way to way to improve the process and save time and labor.
Besides ZDC shows the photo of the parts before and after dies casting in their current wheel grinding process.
The photo of aluminum die casting parts before and after wheel grinding process
The workshop of their existing wheel grinding process
2. Test the right Tumbling media for Aluminum
To better understand sample requirement, I ask Imran to download sample request data sheet to fill in. He fills in all product related information. The technical information and polishing requirement is very important without misunderstanding.
Product request data sheet send together with sample
Besides, he sends me a technical drawing of all workpieces together with production volume in one day. The information of product geometry is important to select media size without lodging problem. The right combination of media and parts is easier for parts and media separation. The production volume together with a shift number is important to decide the machine size.
Production volume report with each size of parts
Product technical drawing
3. Sample received confirmed with customer requirement
The workpieces received one week later. When I open the parcel I found the workpieces have a very large edge and heavy burr which hard to remove by any mass finishing process. I talk with Imran if we can do the process after those big burr removed by wheel grinding machine. Otherwise, if burr removed by mass finishing process, the whole parts completely deformed. Imran agreed with my point.
After a short telephone meeting, we agreed: the parts with heavy casting edge from mold need to remove before the mass finishing process. We use the traditional wheel grinder to remove rough edge and burr in our factory.
4. How we select the machine, tumbling media and polishing compound
How we select the machine
- The workpieces size is medium size with a large production volume. So batch based centrifugal barrel finishing machine cannot be considered.
- The processing time will be long for several hours, so the continuous surface finishing machine is not suitable for the application.
- The part surface requirement is critical so we want to keep parts-on-parts contact to a minimum level. The high energy centrifugal disc machine with speed 150-180rpm will leave surface scratch and hit. As a result, centrifugal disc finishing machine is not considered in this application.
- Vibratory finishing machine with frequency converter (Variable Frequency Drive) is suggested in the application.
How we select Tumbling Media for Aluminum
- Based on surface requirement, the oxidation layer after casting need to remove and grinding mark need move as well, a media with grinding and cutting function is desired
- Because aluminum is a softer metal material, plastic media can make a good balance between smooth surface and effective cutting
- The size of plastic media needs to carefully considered to prevent lodging and make enough surface contact on workpieces surface.
- After smoothing with plastic media, zirconia ball gives the plastic surface a mirror shining function without making the dent on the part surface.
- Holder B1 parts have the hole for screw diameter 2mm, to prevent zirconia ball stuck in the parts, 3-4mm zirconia ball size is suggested
How we select polishing compound
- Grinding compound LC-13 is suggested to make the vibratory deburring process smooth and lubricative, the media and compound protect parts on parts hit and give it a smooth surface
- Polishing compound H-3 in the next step to make product mirror shining, HM-3 is a neutral chemical with a slight acidic property. HX-0 cleaning compound is added in the polishing process to remove dirt on the metal surface
5. Surface finishing result for aluminum die casting parts
The polished aluminum dies casting parts is send back to Imran with express for confirmation. He will receive the sample within 3-5 days.
The mirror shining aluminum die casting parts
6. Sample received with ZDC
Imran received the sample over the weekend. He told me he is very happy with the product personally but they will have a meeting with his team to discuss the outcome.
Two days later, he informed they are very close to making the decision. But to change the process, he needs to have a cost comparison between the current wheel grinding process and the vibratory finishing process. If the long-term operational cost significantly lower than the manual wheel grinding process. That can help they make the decision faster.
So I make a detailed cost knock-down sheet, including electricity, depreciation of machine in 10 years, media and compound as consumable (plastic media and polishing compound) as well as zirconia ball that will never wear out.
Process solution for aluminum die casting parts
Cost per components for aluminum die casting parts, the tumbling media for aluminum is the major cost
When received the cost of details break down, Imran compared with his wheel grinder process and vibratory finishing process. In Pakistan, labor cost is as low as USD 200/month.
He found the cost of the vibratory polishing process have significant cost saving, especially for small and medium-size parts. However, for big size parts, wheel grinding process still cost saving.
After confirming with top management, Imran told me they have decided to purchase the setup.
7. Order prepared
The first order to prepared is 3 machines, including 2 pcs of 600L vibratory finishing machine and 1 pcs of 400L vibratory finishing machine. The 600L machine is for first step smoothing process with plastic media, and the 400L machine is for second step polishing with zirconia ball.
Production time is very important. For ordinary goods, production time about 20-25 days. Some specially customized goods take a much longer time because of mold, raw material, design, etc.
I informed Imran that the goods will be ready for 30 days after payment confirmation.
The shelf life of media and compound is very long. But it not necessary to order big amount at the first time. I suggest Imran make an order for 3-4 month consumption of plastic media and polishing compound.
Imran agreed and an order including vibratory machine, tumbling media and polishing compound is prepared.
Later, when we consider full container loading with 40’ container, Imran wants to put as many goods in the shipment as possible. Because shipping cost is fixed.
Some of the plastic media bags are put inside of the vibratory bowl to save space for polishing compound. Imran is happy with the idea.
8. Payment Term
Because this is the first time to do business, both of us is very careful with the payment term. We usually do the payment 30% in advance. And after goods finished, we will take the photo for confirmation before customer make the final payment.
Imran insists on LC at Sight 100% and he adds us 2% to total amount to change the way of payment. We finally agreed to this term with our bank guarantee. Bank consultant makes a suggestion to correct terms to prevent misunderstanding.
After 1 weeks and over the weekend, we get the formal notification from the bank that LC arrived. Imran send me the draft at almost the same time and he is very eager to see the goods ready soon.
9. Cargo Shipment
During the time we prepare the order, Imran send me a message that he wants us to come to his factory to make installation! He told me this is the first time they do the process. Technical guidance and knowledge are very important to run the machine.
We agreed to come for 3 days training program without additional charge on service. And Imran agreed to afford flight tickets, visa, and accommodation during our stay in Lahore.
After goods arrived in Karachi, Imran prepared me the flight and visa. He informed he the clearance will take about one week.
At the same time all documents required to clearance the goods sent to the bank, and the payment is released in a few days. Besides, Bill of Landing, packing list, and commercial invoice, CO (certificate of origin) or Free Trade Agreement is very important to help the customer reduce import duty.
10. On-site installation
Imran already waiting for us at the airport for 2 hours. At the time we arrive in Lahore, it was in the afternoon. Imran told us to take a rest in the hotel and meet tomorrow at 8 am in the hotel lobby.
When we arrive at the workshop the next day, we found all the machines and goods are unpacked.
Electric control box setting Greasing on motor Waste water drain away
Starting at 10 am in the morning, and we finally finished the work at 4 pm. Imran is very happy about the progress and he is considering to do the media testing on parts.
11. Successful production in site
The next morning, aluminum die casting parts is prepared and send to vibratory finishing machine workshop. The workpieces same with the sample delivered to me a few months ago with large burr and edge removed.
Aluminum die casting parts before vibratory finishing with the edge ground
The process is carried out as expected in vibratory finishing machine, the result is shown below:
The parts after plastic media smoothing The parts after zirconia ball polishing
To make sure the performance of machine and media is stable without change, we stay in ZDC factory for extra one day to inspect and check if anything wrong reported. The production goes 14,000 pcs with a different size as it scheduled in 2 shifts.
Photo with Imran Photo together with the management team